OFF TOPIC blog

About five years ago or more I bought a used ICOM-737 for less than half the price of a new one. It has worked fine for over four years and I would consider it the best of any transceiver I have ever had the privilege of operating.

About a year ago it began to demonstrate a nasty habit of shifting frequency by about 50 hz or so. It usually happened when I was transmitting. The shift was not serious enough to loose contact. It merely changed the pitch of my voice on SSB and it did not occur all the time. Only on very rare occasions. At first. Recently it has become more and more frequent.

Then, the other day, it began to have trouble with 160, 80, and 40 meters. It just quit working on those three bands. It still worked on 20 meters and up but the lower three bands were dead. No signals, just noise. The condition went away when the radio was powered down and left overnight. The next morning all bands worked as they should for about fifteen minutes, then the lower three bands would fade off into never never land.

I was convinced that it was a power level problem. The 8 volt regulator was a little low running at 7.25 volts. Or so I thought. Turns out that my voltmeter was off but before I discovered that, I replaced the regulator with a new LM7808. A standard LM7808.
The regulator that ICOM used had the mounting tab insulated. The standard LM7808 had an uninsulated mounting tab. No problem. Tab goes to ground anyway, so I just mounted the new regulator with the uninsulated tab to ground. When power was applied the display remained dark. I re-installed the old regulator, powered up and everything returned to normal. I still had the problem of loosing the lower three bands but at least the display was lit and everything seemed to be working on the bands that were still active.

That is when I decided to see if there were any service notes on ICOM on the internet. Yup, sure were. Most had to do with frequency instability caused by defective plastic trimmer capacitors. The notes recommended they be replace with ceramic trimmer capacitors.

I have not done that yet but I am sure that when I do, the problems will be solved. The parts involved are primarily C294 and C205.

I vaguely recall that the ICOM-735 suffered similar problems which were also caused by plastic trimmer capacitors. My guess is that the difference in price between plastic trimmers and ceramic trimmers might be as much a 5 cents, maybe. You would think that the manufacturer would have learned a lesson about trimmer capacitors from the problems with the 735 model, but noooooo… they needed the those 5 cents far worse than they needed satisfied customers. Well, they better find some part that gives them more than just a 5 cent boost in profit because I am not buying anymore ICOM junk.

I figure if they cannot do the right thing and build in the quality that I deserve in an expensive radio, then I don’t need to do business with them anymore. Besides, I don’t want to find out the hard way the trimmer capacitors were not the only parts they cheaped out on.

By the way if you have one of those trashy ICOM transceivers, I can replace the faulty trimmers for you for a flat fee of $100 plus shipping (both ways, of course).

Finally got the tube sockets ordered for the new 811 amp.

Soon there will be a pair of 4-400s with sockets and blower available for more serious amplifier duty in someone else’s shack.

We will be using four 811s along with our 1500vdc one amp HV supply.

The linear will still be larger than it needs to be and rack mounted but it will also be a little better behaved without the noise from the blower to modulate the airwaves.

The conversion should be fairly easy. Just pull the tubes, sockets, blower, build a bias supply, add a low speed fan, and find a 16 amp 6.3vac filament transformer. Need to check that again but the last time I looked an 811 needed 4 amps at 6.3vac for the filament. Man!, that is 100 watts just to light the tubes!

No way am I going to buy that kind of iron new or used. Good thing I saved those 24vac 4 amp utility transformers. Looks like one of them is going to have its secondary rewound for 6.3vac. Shouldn’t be too hard. About six turns is all it will take.

Resonance is the condition where the antenna displays a resistive load of predictable value at the frequency of interest. You get there by cutting a dipole to a half wavelength, breaking it at the center and attaching a feedline there. Then raising the whole mess in a flat top configuration a certain distance above electrical ground.

This is what is called a resonant antenna. Its resistive load is generally 75 ohms. Its height is at least one quarter wavelength above ground (or multiple thereof). Under those conditions its SWR is very close to 1:1. It will absorb all the power you feed it as long as the feedline is also 75 ohms and your radio has a 75 ohm output. Such an antenna will also provide the maximum in signal on receive.

A non-resonant antenna requires an antenna tuner. The antenna tuner adjusts the antenna system and brings the non-resonant antenna into a resonant condition. That resonant condition may or may not be 75 ohms resistive. Most commonly it will be higher than 75 ohms and that condition will be handled with open wire line, window line, or twinlead down to the antenna tuner. The SWR on the feedline may be much higher than 1:1 but that is okay because there is very little loss in open wire line. SWRs as high as 10:1 can be allowed without adverse effects as long as open wire line is used.

The antenna tuner will match the higher, resonant impedance to the radio. It will also ensure that the non-resonant antenna behaves as a resonant device in combination with the tuner to form a resonant antenna system.

Depending on the choice of antenna and tuner this is a nice way of providing coverage over the entire HF bands with one antenna system. You end up with a true multiband system where the system only works on one frequency at a time. The frequency to which it is tuned. Untuned multiband systems are tuned to multiple bands at the same time and may result in undesired radiation of harmonics. Such complications are avoided in tuned systems at the cost of requireing tuning.

I went from antenna tuner to resonant dipole fed with coax and now back to non-resonant dipole with antenna tuner again.

Getting the thing tuned up on 75 meters this morning I re-discovered a neat property of non-resonant antennas. They are completely deaf except for the frequency to which they are tuned.

I had this thing tuned to 40 meters. I switched to 75 meters and the receiver went dead. I mean dead as a door nail. Nothing whatsoever. Not even that reassuring crackle of static that you hear when connecting an antenna to the input. It was nearly as though I had pulled the speaker plug. In fact, I did check the speaker plug just to make sure that had not happened.

Once I got the antenna tuned to 75 meters and the receiver peaked for that band, all was well again. Lots of signals and some noise.

So once again I am appreciating the frequency discriminating aspects of an antenna system that requires tuning. All those possibly interfering signals on unused bands that were present with the all band antenna system are gone now. I now have a very selective tuned circuit right at the antenna. In fact, it is the antenna and provides a very nice preselector function.

This got me thinking about resonance and what it means.

Some people swear by it. I am more inclined to swear at it. QRP is not an option I can consider when I have equipment that is QRO.

Going QRP now would be like trading in my SUV for a moped. I am just not the kind of person that thinks that would be sensible.

I was QRP when I first started in ham radio. I had a 6V6 crystal oscillator for a transmitter, a 6SN7 regen for a receiver, and a long wire antenna that evidently was not long enough because it was difficult to make contacts outside the confines of my town.

All that changed when I got some real equipment and a decent antenna. It never occurred to me to investigate my previous rig to see if it was the transmitter, receiver, or antenna that was the problem. I was having too much fun the with real stuff.

It is not that I think QRP is a bad thing. It is just that I have bad memories about it.

Would I try it again? Probably not. When I first started, QRP was the only thing I could afford. Today QRP is no longer affordable. I think I had all of 50 dollars in my first station. That included antenna, receiver, transmitter, and all the accessories I needed to make them work. Today a basic QRP station is going to run at least 100 dollars. Not that such a price is unaffordable but for 100 dollars I can buy a used QRO rig.

Today QRP just does not make sense to me. Going back to the automobile analogy, QRP is like paying an SUV price for a moped.
Now why would anyone want to do that?

You don’t know what frustration is until you have tried to use a marginally functioning regenerative receiver as a communications receiver. Then I guess marginally functioning equipment of any type would frustrate the user. It is just that regenerative receivers have so much more to become frustrating.

Drift, hand capacity effects, flakey regeneration control, dial setting jumps when you touch it, headphones are uncomfortable, not sensitive enough normally and when you increase sensitivity, you can’t keep the signal tuned in. Those are just a few of the ‘fun’ experiences you are opening yourself up to.

Here are a few tips on how to deal with these frustrations.

Choose your tuning capacitors and dials very carefully. Ball bearing capacitors and zero backlash dials are best. If it is good enough to be used in building a VFO, it will probably work fine in a regen.

Wooden cabinets are fine but the front panel needs to be made of metal and connected to ground to prevent hand capacitance effects to the circuitry. Any part of the circuit could be effected by hand capacitance, not just the coil.

You don’t need RF amplification but you could benefit from RF isolation from the antenna. A grounded grid triode amp at the input will prevent the antenna from loading down the oscillator.

A triode makes a decent regenerative detector but a pentode makes an even better detector and allows smooth control of the regeneration threshold by varying the screen grid voltage.

The screen grid voltage to the detector needs to be well regulated. Using a VR tube here is a good idea.

Although a pentode detector has good output, it is not good enough to drive a headset under all conditions. Follow the detector with at least one audio stage before the headphones.

If you want speaker volume, then add another audio stage (maybe a 6V6) after the first.

If you have kept up with the tube count we are now up to five tubes. We might want to re-evaluate the design. Maybe go with a single conversion heterodyne.

Run the radio off batteries or a separate AC power supply. With the high sensitivity of the detector it will be nearly impossible to keep hum out of the radio if the power supply is built into the radio case.

You probably decided on a regenerative receiver thinking it would be a simple project. It can be simple but to get decent performance the regen becomes as big a project as a simple heterodyne.

Also, the same problems you experience using a single conversion heterodyne at higher frequencies also plague the regenerative receiver. At the very least, stability will suffer. Even so, both of these receivers can do very well on 80 and 40 meters. There is absolutely nothing wrong with using a crystal controlled converter, making the system a dual conversion, regardless of whether you decide on a single conversion heterodyne or regenerative.

Is it worth screwing with used ham radio equipment? YES! Most definately, but be careful.

Hams are a cantankerous lot. They don’t get rid of stuff that is useful unless they are dealers. Now it could be that the equipment is just old and they are tired of it. If the stuff is new to you and works, it might take you longer to tire of using it.

On the other hand, the stuff could be junk that has been hosed down and dried off so that it becomes presentable.

Unless you can have the equipment demonstrated under actual operating conditions, maybe make a few contacts and get some signal reports, don’t pay more than salvage value.

Even before you make an offer, pay attention to the conditions under which the item is being offered. Don’t make an offer on the stuff if you are confronted with any of the following:

‘I am selling this for a friend’
Could be his ‘friend’ does not even know he has it.

‘It worked the last time I used it’
That might have been 30 years ago when he first bought it new. Chances are good that if it was working, he would not be trying sell it.

‘It is in mint condition’
If he is not a dealer presenting you with brand new equipment with factory manual, box, and warrantee, he is lying to your face.

‘Complete with copy of the original manual’
If it does not have the original manual, it has been orphaned and probably more than once.

‘Power supply and mike are not included’
Might only have had time enough to steal the rig itself.

‘Very rare collectible’
If you are looking for collectibles at a hamfest, you are out of your mind!

You will just not find highly desirable equipment on the bargain table at a flea market or hamfest. That does not mean it cannot be useful but its usefulness will vary from person to person. It all depends on what their needs are.

Lots of old equipment began life in kit form. Make sure if that is the case for the item you are considering that it had life after assembly. An unusually frequent problem is that kits that never worked are being offered as valuable collectibles. Unless you are a junk collector, you may not be interested in such equipment.

The 811 has to be the most useful of all higher power transmitting tubes.

I got started in ham radio in 1959. That year the December issue QST had an article on the use of four 811s to build a medium power linear. The basic idea was to have one RF deck with the four 811s, one power supply, and five separate, switch selectable, pi-net output circuits covering 80 thru 10 meters.

Now, nearly 50 years later, that is still the most logical, economical, and reasonable approach to high power.

The 811 is still in production. At least in China and it is one of the tubes the Chinese know how to make.

Used to be you could get NOS, American made, 811s for five bucks each. Today they cost you fifteen bucks each and are made in China.

Over the years I have homebrewed linears, used linears made from kits, and also owned commercial amps. This equipment used 813s, 811s, 4-400s, 572Bs, 4CX300s, and 4CX1000s. Out of all of these choices the amps using the 811s were the most reliable, most inexpensive, and easiest to operate. Here is why.

811s are perfectly happy running at 1500 volts on the plate. The lower plate voltage reduces power supply cost and allows less capable components to be used in the pi-network of the plate circuit.

Filament requirements are easily met. 6.3vac at 10 amps is more than sufficient to power a quad set of 811s. You don’t need to wind a special filament transformer or buy a special 5.0 volt high current transformer.

Each tube requires a 4-pin socket which is a fairly inexpensive and standard item, mounts with two screws, and does not require any special sized chassis hole.

Cooling 811s is easily done using simple fans. No need for high volume blowers. Some applications (like the Tiny Tim) can be implemented without need for any forced air cooling at all.

A set of four 811s will easily run a 1KW input without need for a special 220vac line connection.

811 linears are easy to homebrew because low cost parts are still readily available.

Of the commercial 811 linears the Collins 30L-1 is the best by far. Quiet and strong it is a marvel of good engineering and reliability. It is also very fairly priced and can be purchased, used, in good condition for as little as $600.

In contrast all the 4-xxxx series of tube linears fall far short of the 811s benefits by requiring higher plate voltages, higher voltage components, special cooling considerations, expensive hardware and sockets, and special biasing and driving circuits. In short all the things that make the 811 so desirable are missing in the 4-xxxx series of tube linears.

Probably the most significant thing is the missing lower cost. While four 811s will set you back about sixty bucks, you could easily spend ten times that on a 4-xxxx tube equivalency.

I still have four linears. One is a dual 811 Tiny Tim. Another is a Yeasu FL-2000B running a pair of 572Bs. A third is an underpowered pair of 4-400s in a short rack mount cabinet. A fourth is a desktop pair of 813s. All four of these are all-band, band switching linears. I am seriously considering turning the Tiny Tim into a 75 meter only amp, converting the 4-400 amp to a quad of 811s, and setting up the 813 on 20 meters permanently.

That still leaves me with one all-band amp and allows me a higher degree of operating convenience. At least on 75 and 20 meters.

Last weekend I was keeping my weekly sched on 75 meters using reduced power and a non resonant dipole match with an antenna tuner.

The reduced power was being used because on 75 meters the non resonant antenna was presenting an impedance that was developing too high a voltage for the Z-match and I was getting arcing between one of the main coils and the pickup loop wound around it.

Signal reports were dissapointing. Somewhere between s-6 and s-9 even though I was running close to 200 watts output to the antenna. I was beginning to suspect that the new 88 foot non resonant dipole was just not going to cut it.

I got he arcing problem solved by using rg-58 coax for the pickup loop. The insulation on the coax allowed me to run a full 500 watts out to the tuner as I had done with the 80/40 meter trap dipole.

This weeks sched on 75 resulted in a 20 over 9 report. I guess the new non resonant antenna is working after all.

I would not have thought that increasing the power from 200 watts output to 500 watts output would make that much of a difference. I am still not convinced that is all that is at work here. For the last two days we have had continuous rain and the ground is about as soaked as it will ever get. I think that might have some effect on antenna efficiency.

Unfortunately it never occured to me to reduce the power to the 200 watt output level and get a report. Oh well.

The present setup is a 44 foot dipole (44 feet, non-resonant, per leg). A 27 foot vertical (also non-resonant). A tri-band beam and a two meter antenna.

Both non-resonant antennas are fed with 300 ohm twin lead and matched with an antenna tuner. A Johnson KW matchbox for the vertical, a homebrew Z-match for the dipole.

Evidently the dipole is a high impedance antenna when used on 75 meters. I can get a very good match but the tuner arcs at the 200 watt power level. Arcing is not at the capacitors but between the high impedance coil and its pickup loop. Better spacing or insulated wire should solve the problem.

Actual experience while running on 75 meters at the 200 watt level indicate a signal level from s-6 to s-9 with a contact 200 miles to the north. This contact is an old friend and we have had a weekly schedule on 75 meters for the last 15+ years.

Prior to using the non-resonant dipole, I was running about 500 watts to an 80/40 meter trap dipole and the signal was mostly 10db over 9. It cannot just be the reduced power. Appears the non-resonant dipole is not as good as the previous antenna on 75 meters.

I like the non-resonant dipole because it can cover any frequency from 80 thru 10 meters. Okay, so it is not a super good antenna, but it does work and I want to keep it.

So now the plan is to install a special, full sized, resonant dipole for 75 meters. Also, a special full sized, resonant dipole will be installed for 40 meters. The feed lines are already in place. It will simply be a matter of connecting enough wire to the insulators to get to resonance.

Once that is done, I will have all the antenna capability I think I will need for some time to come. Five feedlines to five antennas, three of them multi-band. Looks like I just might have enough to service the three rigs I have available. Now to figure out how to use all three rigs at the same time. Will probably end up with two rigs monitoring seperate bands while using the third rig to work a different band.

I finally got a chance to check out my two new antennas. The vertical works fine using 300 twin lead to a Johnson KW matchbox. Good performance on 30 meters and up.

The homebrew Z-Match also works great on the 88 foot dipole using 300 ohm twin lead for feedline. Works great on all bands including WARC from 80 thru 10. This particular Z-match will handle up to 500 watts.

I was running out of room for all the equipment and it seemed that the Z-match might be better off sitting on a different part of the station shelf. The relocation was going to mean I would have to swap out the Z-match with the Johnson Matchbox but either tuner should work with either antenna.

Not so. Seems the Johnson Matchbox is not at all happy with the 88 foot dipole. 75 meters, 20 meters, and 10 meters seem to work just fine but it did not do well on the other bands. I am sure I could have corrected the situation by trimming the feedline but I have never been one to start cutting (or adding to) feedlines. I figure if they reach from antenna to rig they must be just the right length. Any matching issues need to be taken care of in the tuner.

So, it is back to the vertical with the Johnson Matchbox and the Z-match will be used on the 88 foot dipole.

I have always been of the mind that you cannot have too many antennas. This is particularly true if you have more than one radio. The happy ham has antennas to serve all his radios.

I have three radios so I guess that means I am not completely happy yet but I did progress toward that end this weekend.

Back to ATUs and balanced line. One ATU is attached to a vertical L style antenna with 300 ohm twin lead. This particular vertical works well on all bands from 20 meters up. After next weekend it should also work well on 40.

A second ATU is attached to an 88 foot non-resonant dipole. This dipole has its center up at 50 feet with one end at 30 feet and the other end at 20 feet. Not exactly an inverted vee but starting to approximate that shape. This antenna is driven with 300 ohm twin lead too and works well on all bands 80 thru 10 meters.

A third antenna is the beam up at 55 feet. It is a KLM KT-34. A nice triband four element affair that works wonders on 20, 15, and 10 meters.

A fourth antenna is a simple 40 meter inverted vee. Center up about 40 feet. Ends at 15 feet. This thing will soon be converted to a two element wire beam with switchable directivity favoring either east or west.

A fifth antenna is a two meter full wave vertical. Useful for local repeaters all the way to Fort Worth.

That leaves two coaxial transmission lines unused.

All these antennas are managed through a five position coaxial antenna switch that quickly selects beam, vertical, dipole, dummy load, or 40 meter inverted vee. This will not be the final setup but it is useful in evaluating the various antennas. Now I can get some useful comparisons between the vertical, beam, and dipole.

Later the all band dipole will be used with the TS-120 and homebrew 811 amp primarily on 75 meters.

The vertical and the beam will be used with the ICOM 737 and a Yeasu FL 2000B linear.

The 40 meter antenna will be used with a Drake C-line primarily for CW work.

This entry is more a note to myself an anything else but it should be of interest to anyone interested in antennas. Realize that all of these comparisons are heavily influenced by what I can do physically with the yard I have and the effort I want to invest. Your situation may be different.

This is a comparison of several antenna types both single band and multiple band listing disadvantages of each approach.

The main disadvantage with a ATU free multiband antenna approach is lack of harmonic filtering. Normally a single band dipole is the equivalent of a very narrow tuned filter. This is not the case for dipoles that have been tweaked to perform on multiple bands. Not that I am particularly concerned about harmonics from the commercial gear, but I also have homebrew stuff that may not be as harmonic free.

A secondary disadvantage of ATU free multiband antenna systems is a lack of adjustment in the shack and relatively narrow bandwidth compared to operating with an ATU. Antenna systems characteristics change when it rains and snows as compared to when it is dry. If you can’t tune out those changes, you have to live with the mismatches. Besides, it always seems that I want to operate on a frequency that will not give me a decent swr when I use a no-tune antenna system.

DIPOLE - This is an excellent antenna all by itself but it requires proper installation. Meaning it should be installed as a flat topped antenna at a height not less than 1/4wavelength. I can do that on 20 meters but I have a four element beam for 20 so I am not about to rush outside and put up a 20 meter dipole.

INVERTED VEE - This is a dipole that has a high center support and is allowed to have its ends droop. I can manage a center support of about 50 feet and allow the ends to be up at around 15 feet. Not good for 80 and barely sufficient for 40. Also, with those dimensions, the included angle between legs is such that the antenna ends up being a cloud burner on ALL bands. Take off angle at 90 degrees.

G5RV - This is a 20 meter antenna. I already have and excellent beam for that band. I am not sure what form of mythology considers this to be an all band antenna. Oh sure, it could be all band with an ATU but then nearly anything could be all band with an ATU.

80/40 TRAP DIPOLE - Nearly all band but narrow (100khz) bandwidth on 80 meters. For my location it can only be installed as a cloud burning inverted vee. A poor solution.

WINDOM - Actually just an off-center fed dipole for 80 meters. The idea is to find a feed point that remains fairly constant over frequency, match to it, and enjoy ATU free operation. The main problem with this is that I can’t get this thing up high enough to do any good on 80 and 40 meters. Also, the low swr points shift when it rains.

DELTA LOOP - Works great on 40 meters but does not make a very good all band antenna even with an ATU.

INVERTED L - I can run a wire 50 feet up and 60 feet out but the end will only be 15 feet off the ground. Height problem.

SLOPING DIPOLES - Not enough yard to accomodate them on 40. Forget using them on 80.

SHUNT FEEDING TOWER - I did that for a while. It worked. Did an EZNEC analysis on the setup and found it had a -2.0 DBi gain. Close-in signal strength to a weekly sked dropped from 10 over 9 to 9.

88 FOOT NON-RESONANT DIPOLE - This needs an ATU to be able to work and requires open wire line of sorts to be able to run high swr with low loss, but it can be installed here as an almost flat-topped dipole, can be tuned for very low swr on nearly every ham band from 80 to 10 meters, will not limit me to any range of frequencies. I have been avoiding this antenna because it requires open wire line and there are installation requirements that I cannot meet. However, it can also be made to work with 300 twin lead and I can meet the installation requirements for twin lead.

So now I am back to the 88 foot dipole I was using back in November of 2006. Since then I have also added an L antenna. A 27 foot vertical with 27 foot counterpoise also driven with 300 ohm twin lead and a second balanced antenna tuner. All balanced line and tuners. No baluns. Seems to work fine. It is at least as good as what I was using before and has the advantage of offering operation at any frequency on any band.

If you have the ATUs, use them. If you don’t have the ATUs get some.

When last addressed, my approach was to use a three band trap dipole to cover 75, 40 and 30 meters and rely on the triband beam for 20,15 and 10 meters.

Since then I have discovered that trap dipoles exhibit reduced bandwidth. The bandwidth gets narrower and narrower as more bands are added. Therefore I have settled on two bands per dipole and two dipoles to cover 75, 40 and 30 meters.

One dipole takes care of 75 meters and the 40 meter CW band. The other dipole takes care of 30 meters and the 40 meter PHONE band.

Both dipoles are mounted as inverted-vees one below the other and at right angles to each other.
Seems to work fine. There is no real directionality. Each antenna appears to be omnidirectional on all bands.

Some time ago I realized that I could make a multiband vertical by simply taking half of my 80/40 meter trap dipole and turning it on end.

There is another way to do this by using a tapped, switched, loading coil at the base.

I recently saw a design that covered four bands with a 27 foot vertical radiator. A quarter wavelength on 40 meters is 33 feet. That 27 feet is a mite short for a quarter wavelength on 40 but add a little inductance and you have a quarter wave resonant radiator for 40 meters

With considerably more inductance you can force the thing to be an electrical quarter wavelength on 80 meters.

Other bands can be covered by forcing them to be resonant as 3/4 wavelength and 1/2 wavelength radiators on the bands of interest.

The main difference in utility between the trap vertical and this is the need to change taps on the coil for this design. A trap vertical will cover multiple bands without need for tap changes.

There is also a large functional difference between the two designs. In a trap vertical, each trap acts as an automatic switch disconnecting sections of the antenna that are not needed at the higher frequencies. For instance, a trap vertical will disconnect all but about an 8 foot section to obtain resonance on 10 meters. When you consider that the live section remaining might only be a few feet above ground, you may well fear some problems getting the smaller antenna to radiate effectively.

By using 3/4 wavelength and 1/2 wavelength sections you use more of the the full length of the vertical. It has always been assumed if not written that an effective antenna presents as much metal as high as possible into the sky.

The disadvantage of having to change taps can be solved by providing a remote switch to do the job.

One additional factor to consider is bandwidth.  The higher frequency bands usually have plenty of bandwidth, but the lower frequency bands ten to suffer with bandwidths as low as 100khz on 40 and 50khz on 80.

This situation can be improved by not trying to cover all bands with traps.  A dual band, 80/40 meter antenna using a pair of traps will have a bandwidth more than twice what was quoted above.  Better but still not capable of covering the entire band on 80 meters.

Depending on your operating habits, there may not be any need to improve bandwidth.  Just center what bandwidth you have on the frequency that interests you.

After kicking this subject around for decades, I have finally decided on the best solution for my purposes.

I already have a multiband beam which covers 20, 15, and 10 meters. All I really need now is a multiband dipole (inverted-vee) for 80, 75, 40, and 30 meters.

Since I already have the 40 meter traps, all I need to build is the 30 meter traps to cover that additional band.

It is going to be a cloud burner on 80 and 75 because the apex is only going to be about 50 feet high, but on 40 it might do better and it will be close to a flattop dipole on 30 at a decent height.

My only concern is that the bandwidth will suffer because of the traps. Then that is no big deal. I don’t do much frequency hopping now and don’t intend to change my operating habits.

Although I am not considering the remaining two WARC bands at all for now, it will be possible to include them in a two band beam mounted on the second mast which now holds a vertical antenna.

Or, I might just modify the 40 meter vertical to cover those two bands.

Phase Shift Keying, thirty-one style, came out some time ago. Shortly after it appeared, I began using it.  The requirements were PCs running DOS or Windows and using sound cards as a poor mans dsp. One application I had used a real dsp. A TI 50dsp thing that used a DOS driver to develop the signals.

PSK31 is different from other phase shift keying systems in that it is a very narrow shift. That allows it to fit into a very small spectrum giving it a very good signal to noise factor, making it a very reliable means of communication. You do not need much power, much antenna, or much patience to work lots and lots of good DX when using PSK.

Perhaps that is why I became bored with it very quickly. No challenge.

A few days ago I decided to see if my PSK setup was still usable. It was. Had a 30 minute chat with a ham in Tucson around noon.

My standard setup is an ICOM-737, homemade sound card interface, athlon +1800 computer running windowsXP and Digipan 2.0. With that setup the QSO worked flawlessly for about 25 minutes before XP locked up with that stupid screen asking if I wanted to send a note to its maker so it could report how screwed up XP was. Honestly, if I had known what a nuisance XP was going to be I would never have tried it.

I never had any Linux distribution lock up like that. So I decided to try Linux.

Having already had considerable success with Debian-Etch, KDE 3.5, and a few multimedia applications I decided to use that same setup and see if I could get KPSK working. It took the better part of an afternoon to get it to work right but it does work once the alsa mixer is setup correctly and all the right setup and configuration files are complete.

KPSK looks very much like the old version of Digipan. Same sort of display as old Digipan but KPSK can copy four QSOs at the same time. Now, new Digipan 2.0 can copy 26 plus QSO’s at the same time but it has a tendancy to lock up on my computer. I figured that four QSO’s and no lockup was better than all the QSO’s on the band if the thing locked up.

So now I am running Linux and KPSK on one machine.

Over the years I have had a variety of communications equipment. Some of the gear was all tube type, other gear was all solid state. There has always been some controversy regarding performance when tube gear is compared to solid state. Tube gear is supposed to have a much better signal to noise ratio when compared to solid state.

Currently I can play with three rigs. One is an ICOM 737, one is a Kenwood TS-120, and the last is a Drake C-line. The 737 is the more capable of the three and thus, it gets used almost without consideration to the other equipment. At least that has been the situation here for the better part of the last few years.

Ham activity here has been reduced somewhat to weekends and evenings. The only sure activity is on 75 meters on Sunday mornings where I have been keeping a schedule for the last 20 years. This evening I decided to change out antennas and fire up the Drake C-line on 75 meters. At the same time I also fired up the old 737 on the same band for comparison but had to use the 40 meter dipole as the antenna.

The first thing I noticed was that the S-meter was messed up again. Well I don’t ever remember an S-meter that was able to provide better copy, so I ignored it. I left the R4C on while I continued to work on the new mythtv installation on the computer.

It was getting into early evening and 75 meter activity was beginning to pick up. Signals were starting to come in, some with a fair amount of strength. I continued monitoring the band for about three hours and noticed how remarkably quiet the band was. That rushing, frying, noise I had become accustomed to on the 737 was much subdued.

I don’t have the equipment to measure the difference in performance, but my ears tell me there is a significant advantage to receiving signals on the Drake R4C. Now I am happy about not selling the Drake C-line after all.

Ha! If you believe there is such a thing as an all band antenna, you might also believe there is a pot of gold at the end of each rainbow. To build a really good all band antenna system you will need a pot of gold.

After experimenting with radios and antennas since 1959, I have come to the conclusion that most of us in suburbia living on average sized lots in averaged sized houses do not have a prayer of achieving a really good all band antenna system.

All band in this case is everything from 160 meters to 10 meters.

My solution to the antenna problem is pretty simple. A four element tri-band beam for 20, 15, and 10 meters. I use a KLM KT-34 up at 55 feet. Now there is a very good multiband antenna. For 80, 40, and 30 meters I use resonant dipoles, all three fed from a common coaxial feedline. I have given up on 160 meters entirely.

At one time I used a non-resonant dipole, open wire line, and an antenna tuner. I changed because I wanted an antenna system that did not require tuning. I wanted to be able to merely flip a switch and be ready to go on any band I wished to operate. So the open wire line and antenna tuner were retired.

Then there was a period where I did some extensive computer modeling of 80 and 40 meter antenna systems. In nearly every case the results were less than spectacular. Perhaps the best was the full wave delta loop, but all the other dipole configurations had take-off angles pointing straight up.

Since there was no way I was going to be able to flat-top a dipole at 136 feet, I decided to settle for what could be done. So far I have not been disappointed in the performance of my three resonant inverted vee dipoles on a common coax feedline, but then I have never used a flat-top dipole at 136 feet so I may not realize what I am missing.

Here we go again. One of these days I will end up with a simple all band antenna system that works well enough, is easy to use, is effective, efficient, mechanically sound, and all those things we like to see in an antenna system. A setup soooooo goooood that I won’t be tempted to mess with it.

Yeah, I am not there yet. Lucky guess.

I do have a system up now that is unique, and works, but it does not work well enough to give up on trying something new.

Actually, all-band is guilding the lily somewhat. All I need it to cover is 80,75,40,and 30 meters. I could do it with traps but I want to cover ALL of the frequencies in those bands and I want to do it with SWRs of less than 1.5:1. Okay, I know SWR is not everything. Some antennas with high SWR are very good performers. True, but my radios don’t like high SWR so I need some way of tuning things so that SWR does not become a factor.

My Main rig includes an automatic antenna tuner, so the job should be easy. It would be if I was satisfied to endure the loss in coaxial cable that I would get with SWRs higher than 3:1 on the line from the tuner to the antenna. I don’t want to do that. I figure if am going to go to the trouble of matching feedline to radio so I get a maximum power output, the least I can do is show enough respect for that power by not wasting it as heat in the feedline.

Also, I don’t like baluns. I don’t like building them, using them, or worrying about possible losses in them. At the same time I would also like to keep my radiation pattern as balanced as possible.

When you put all those ‘wants’ together, they point to the use of open wire line, a balanced tuner, and a non resonant dipole.

I have come full circle. That is what I had five years ago, before I began experimenting with antennas. Back then I wanted to get rid of the antenna tuner. I guess I still could by using transmission line matching transformers but just my luck I would find a frequency that I would want to try and the transformers did not want to match. No, got to be adjustable from inside the shack AND cover all frequencies in all bands from 80 to 30 meters. Hmmm….wonder if I should include the 60 meter section as well? Why not!

Predictable radiation patterns are a good thing. An 88 foot dipole will provide predictable patterns for all the bands being considered. It will not be super efficient on 80 or 75 but I am not going to be interested in low band DXing anyway. The 88 footer should be fine for locals out to 300 miles or so. That 88 footer is 44 feet per side. That will work out fairly well. My center support is at 50 feet. My end supports are high enough so that the 44 foot horizontal distance will still be elevated at 35 feet. Not exactly flat-topped, but better than a full sized inverted vee on 80.

I will use what is left of all that surplus RG62 coax. 88 feet for the antenna and two lengths of 100 feet to make some ‘open wire line’. Use the sheet PVC to make insulators. Always wanted to try that. The old 450 ohm ladder line is pretty old and beat up and I don’t want to buy any more of that stuff. I just don’t want to spend the money when I already have the materials for an alternate solution.

So here is hoping that this is going to work out well.

It is not at all unusual for a radio amateur who has had more than a few decades invested in the hobby to own all the kinds of equipment he ever had. On the other hand, it is rare for someone to have held on to every piece of equipment they ever acquired. A certain amount of that stuff was bought back after it was discovered that it still had value.

Most of us don’t realize what we have until it is gone. Then we attempt to get it back and end up paying more than it is worth.

I am sure this is true of many things but I know for a fact that is the case with old radios. Whatever the reason for selling, the most common reason is that you found something better. So you should not be offended if buyers don’t want to pay a lot for your old stuff. Makes no difference what the condition. Working or not. Clean or dirty. All beat up or in like-new condition. It is old. You obviously don’t want it or you would not be selling it. Most of us are reluctant to pay a premium for something old and unwanted.

Unless you are a dealer in new radios, there is not much money to be made. You wont get rich selling radios regardless of how many you have. At least that is my experience.

Here is a collection of keys and paddles. The keys are standard J-38s. The paddles are homemade. The iambic paddle is made from two J-38 style keys. Lots of companies make, market and sell keys and keyers. Vibroplex, Whiterook, Junker, Ramsey, Nye Viking, Morse Express, MFJKeyers, K1EL, Jackson Harbor, Hensley Paddles, and now K5DKZ as well.

There must have been millions of these keys made. Old ads in QST have them priced as low as one dollar. Then that was some time ago. A nice, clean, complete, J-38 should bring anywhere from 10 to 50 dollars in todays market.

These keys are quality materials and construction without any frills. They have been duplicated and improved upon. I recently saw a cheap oriental knockoff of the J-38 where bearings had been added to make the keying action smoother. Should have worked but the implementation of the bearings was so poor that it made the keying action worse instead of better.

There is more time invested in this key than it is worth. I like sideswipers over iambic keyers because I dont know how to use iambic keyers and have no interest in learning how. I know some will disagree perhaps even to the point of becoming disagreeable but there are some things, skills, and subjects that just do not interest me. Squeesing two paddles against each other to make CW is one of those things.

Sideswipers act more like bugs. Push paddle to one side get dits. Push paddle to other side get dahs. This one has a fancy self-centering spring mechanism that is as ingenous as it is old. The design was lifted from an old QST article. Construction is brass and pvc and ceramic. The ceramic spacers were just the perfect length. If you look closely at the contacts, you might be able to see the silver inlaid in the square brass center beam. That silver came from cutting down an old silver dime. The brass beam was undercut with a dremel tool and the silver section was soldered to the brass. Next a file was used to remove excess solder. What you see it the finished result.

Does it need silver contacts? No. The sideswiper without silver contacts works just as well, but having silver contacts on a homemade key makes me feel special.

Here is another labor magnet. Took lots of work and time. This was the first serious attempt at rolling my own. The biggest challenge was supporting the square brass bar on a single bolt and still letting is swing freely from side to side. It is a little touchy to use. There is some bounce back that can cause errors but overall it does the job if you are careful. Still, it is not as easy to use as the old QST design.

I never thought I would ever say this about anything I built but I have to admit this is the ugliest contraption I ever saw anywhere. The only reason it has not been disposed of is that it works. It works pretty well and is the only iambic paddle I have now that I have sold my Bencher paddle to someone who can appreciate it.

Two j-38s bolted together back to back. This idea also came out of an old QST. When I first saw it I figured that it was written by someone selling old j-38 keys. After all such a paddle used two of them. So I was not expecting much. Turns out I was wrong. When properly adjusted this thing is every bit as good as a nice Bencher. I have not yet figured out how to convert it to a sideswiper without ruining it for iambic operation. I have decided to leave well enough alone for now.

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 Last updated Sep-2006
All pages ©1996-2006, by Frank Kamp, all rights reserved.
 

This unit is all original and in pristine condition. Not a scratch on the original finish anywhere. Electrically, mechanically, and cosmetically, it rates a 10 on a scale of 1 to 10.

The unit sits on a specially constructed hardwood, four wheel, dolly allowing its 160 pound mass to be easily moved around the room. The dolly is included in this sale.

It is currently set up for 120vac operation. It is recommended that be changed to 230vac operation. A power cord, with plug, for 230vac operation is included.

Comes complete with original manual and the military version of the manual.

Accessories include a special 20.5 foot RF input cable, fuses, ALC matching transformer spares and 230vac, 10 foot line cord.

The output coax connector has been replaced with a standard SO-259 but the original connector is included. It uses solid state 3B28 rectifiers in the power supply. Otherwise everything is factory original except for the 4CX-1000. The 4CX-1000 is esentially new with only 100 hours of use.

As nice as this equipment is, it belongs in a Collins station. This amp is the only Collins equipment at this location.

Price is $2000 cash with buyer responsible for pickup in Richardson, Texas. Serious buyers may also, see, operate, and test this amp at its Richardson location prior to purchase. SOLD.

I am keeping this page on the 30S1 to remind me of what a really clean and decent amp looks like.

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 Last updated Sep-2006

These antennas are larger versions of the small loop antennas that were part of the cardboard back panel of older AC/DC five tube AM radios. Loop antennas of this type were popular in the very early days of radio. They are still useful today for long distance reception of AM radio stations found in the range of frequencies between 550 and 1700 Khz. Some AM DX listeners consider the loop superior to outside antennas because of its ability to null out unwanted stations. A well designed loop will allow azimuth and elevation adjustment to take full advantage of the nulling feature.

rn pickup loop is centered on the 13 turn loop and is held just inside the main loop. A 400pf capacitor is wired in series with one side of the pickup loop to permit a better match to coaxial cable. Six feet of coaxial cable connect the pickup loop to the radio. The cable used here is RG62. It was chosen for its low internal capacitance rather than its 92 ohm impedance.

The spreader arms and wire combs are made from 1 X 5/8 inch clear, knot-free cedar. Redwood or pine would work as well but cedar is aromatic and lighter in weight. Some builders use PVC pipe which also works, but I find PVC pipe is significantly heavier than wood and tends to flex more. Reinforcing PVC with wood to prevent flexing makes the PVC completely unecessary. Just use the wood and don’t worry about PVC.

The vertical base support is made from a 6 inch length of 1-7/16 inch diameter dowel and a 3 foot length of fir 1 X 2. Use either fir or pine. Weight is not a factor here. What we need is something strong with little chance of bending. Note that the 1 X 2 actually measures 5/8 X 1-3/8. This allows for a better fit into the slot that is cut into the 6 inch length of dowel. A metal collar made from 1-7/16 I.D. galvanized pipe is slipped over the connection between dowel and 1 x 2 to keep the joint from seperating. Only glue is used to hold the parts together. The collar also acts as a stop for the bottom support

The bottom support is made from a single cell cinder block and a 9 inch length of 1-7/16 I.D. pipe. The pipe is centered in the cinder block, aligned so that it is perfectly vertical, and the hole in the block is filled with mortar. Once the mortar sets we have a nice weighted base capable of holding the loop antenna. The dowel slip fits into the pipe allowing the loop to be rotated 360 degrees. The dowel is treated with lindseed oil to allow smoother rotation. A carpet sample is glued to the bottom of the cinder block to protect the floor. The pipe and block look better if painted.

A couple of coats of clear polyurethane give the loop a finished look but this is only necessary if the antenna is going to be used outside.

FINISHED LOOP READY FOR USE

The indoor performance of this loop is just short of sensational. Radio stations that are not heard otherwise come up to full volume when using the loop. This is particularly dramatic when using a small battery powered radio. The battery powered radio is simply placed inside the loop, close to the wires. The loop is tuned and the stations are received. Remove the radio from the loop and the stations dissappear. I have not tried using the loop outdoors but would expect even better results.

I have tried using the loop with a simple crystal radio and found it picks up three local DWF stations with comfortable headphone volume. While not spectacular, this degree of performance is more than adaquate considering a full wavelength 40 meter loop outside only picks up five local DFW radio stations with the same crystal radio.

THE CINDER BLOCK BASE

THE WIRE COMBS

TUNING CAPACITOR

TILT MECHANISM DETAIL

SUPPORT SHAFT DETAIL

TESTING WITH A BATTERY OPERATED RADIO

IN MAXIMUM ELEVATION ADJUSTMENT

I AM OFFERING A BASIC KIT TO BUILD A 3 FOOT LOOP LIKE THE ONE DESCRIBED HERE.

BASIC 3 FOOT LOOP KIT

Included are:
4 - PRE-CUT WIRE COMBS
2 - PRE-CUT SPREADERS
1 - PRE-CUT 6 INCH WOOD DOWEL FOR THE MAIN VERTICAL SUPPORT
1 - 3 FOOT 1 x 2 VERTICAL SUPPORT
2 - ELEVATION MOUNT SIDES
1 - SET OF DETAILED ASSEMBLY INSTRUCTIOINS AND USE TIPS.
1 - SET OF BRASS HARDWARE INCLUDING ALL THE BOLTS AND SCREWS NEEDED FOR ASSEMBLY.
1 - X - frame wooden base

This offer makes use of a wooden X frame base instead of the cinderblock base.

The wood provided in the kit is clear, knot-free, cedar. All wood parts are cut to size, slotted and drilled where required. A light sanding is all that may be required.

PRICE IS $85. Includes shipping to addresses within the continental U.S.A.

email for details or order below:

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This link will take you back to the K5DKZ home page. You can also get there by selecting K5DKZ under the Pages heading in the green sidebar.

The best antenna to have is a rotatable, multi-element beam mounted to a tower that is at least a half wavelength in heigth at the lowest frequency of interest. Such a system is commonly used at frequencies of 14 mHz and higher, but poses mechanical problems at 40, 80 and 160 meters.

The majority of installations end up with a beam of sorts on a 50 foot tower with dipoles installed as inverted vees hanging below the beam. The inverted vees will radiate and receive signals, unfortunately they will not perform as well as a properly installed dipole.

STANDARD DIPOLE

A standard dipole has a 75 ohm balanced feedpoint, and about 2.7 db gain over an isotropic radiator and is one of the less expensive antenna choices. Those are some nice features but there are conditions which must be met in the installation to take advantage of these features. Proper installation is not always inexpensive.

The dipole must be installed as a horizontal wire at an even height of at least one half wavelength. If it is installed at greater height, it must be in multiples of half wavelengths.

Such an installation will result in a 75 ohm feedpoint. It will also get us most of the 2.7 db gain as the ground reflects radiated energy skyward to combine with the energy being radiated upward by the antenna. How much gain we get depends on the quality of the ground and its ability to reflect RF energy. The half wavelength spacing of the antenna above ground will ensure that the reflected energy will be in phase with other energy radiated by the antenna so that there will be an addative affect rather than a cancellation.

Half wavelenght at 40 meter is 65 feet. Half wavelength at 80 meters is 130 feet. Half wavelength at 160 meters is 260 feet. Standard dipole installations cannot be made for these three bands if the suport structure is a 50 foot tower.

COMPROMISES

One of the more common compromises is to install the lower band dipoles as inverted vees using the peak tower height of 50 feet to support the apex of the inverted vee. This works fairly well, probably because it raises the high current feedpoint as high as possible. The result is an antenna that is more or less omnidirectional and pretty much vertically polarized. Sort of a high angle vertical radiator without the need for ground radials.

LARGE LOOP ANTENNAS

A sometimes overlooked solution is the delta loop and right angle loop. This is a full wavelength of wire at the lowest frequency of interest, typically mounted apex up with base around 15 feet off the ground. It can be fed with open wire line and makes a good all band antenna if used with a good antenna tuner. If it is fed at the center of the base, it becomes a horizontally polarized, cloud burner. Sort of like the inverted-vee but with lots more gain (up to 6db depending on frequency).

It can be fed at a point about 25 percent up from one corner to transform the loop onto a very effective vertically polarized radiator. Low angle radiation, no need for radials, and a 50 ohm match to coax for a single band SWR of less than 1.5 to 1.

A SUPERIOR SOLUTION

If we go back and study our beam atop the 50 foot tower we might notice that it has a good sized boom. My KLM-34 has a three inch diameter 20 foot long boom and all the elements are insulated from the boom. Normally the boom merely supports the elements of the beam, but there is no reason the boom could not be used as an antenna. Perhaps a rotatable dipole. Twenty feet is a little short for 40 meters but it is in the clear and the boom is a good bit larger in diameter than any of the elements of the beam. Large elements can be shorter and still reach resonance. Add ten feet on either end of the boom, use capacitive and linear loading to get to resonance and you could have a decent rotatable dipole for 40 meters. Why stop there? A little more effort could turn the boom into a 40/30 meter rotatable dipole nicely elevated and in the clear. The boom can remain grounded in the center. Feed it with a gamma match.

More on this later when I get a chance to try it. If it works well I will include it as a project with enough data to duplicate the effort.

I recently found this….http://lists.contesting.com/_towertalk/199710/0676.html

It presents a way of using a yagi boom directly, without modifications, by relying on the reflector and director of the beam to load the ends of the boom. Then an omega match is used to match to coax on the desired frequency. In the case of an antenna like the KLM-34 where all elements are isulated from the boom, the two elements closest the ends of the boom may need to be electrically tied to the boom to make this work.

The following link will take you back to the main antenna page.

This link will take you back to the K5DKZ home page. You can also get there by selecting K5DKZ under the Pages heading in the green sidebar.

The best and most complete source of information on shunt feeding a tower is the ON4UN’s book, Low Band DXing. It contains a wealth of information, several shunt feed matching methods, and verifies that a vertical needs to be at least an electrical quarter wave in length at the lowest frequency being used.

After contemplating these requirements, I decided to take the easy way out. I added a drop wire to a cross spacer at the bottom of the rotator plate. You can see the cross spacer, drop wire, and extra halyard in the picture of my antenna installation. The drop wire is actually three lengths of RG62 coax twisted together. This drop wire is cut about 15 feet above ground and attached to 450 ohm ladder line. The ladder line is routed to a homemade tuner.

The system works well on all bands and is more effective than the inverted vee I was using before.

MORE ON THE SHUNT FEED FIASCO
EZNEC is a neat program. It allows you to compare antenna performance on a computer. It also requires you know what you are doing. Looking at radiation patterns alone can be misleading. I thought that I had the perfect vertical radiation pattern for my shunt feed tower. It was a perfect pattern with launch angle at about 27 degrees but on closer examination the gain was down to -2.5dbi! Maybe I just wanted to believe that it worked better than the old inverted vee.

Luckily I installed three drop wires which were all bundled together for the first shunt feed attempt. Using EZNEC I remodeled the system with one of the drop wires acting as a top load. The top load wire is attached to the tower at the 45 foot level. I lengthened the top load wire to be 69 feet long and ran it to a tree in the side yard. The end of the wire was about 12 feet off the ground. With this setup EZNEC reported a takeoff angle of 90 degrees, but at 27 degrees the gain had gone from -2.5dbi to 1.5dbi. A 4dbi improvement!

I always thought that if you could get power into an antenna it would radiate regardless of what you were using for an antenna. That is still true but some radiators are more efficient than others. Getting the antenna to take power is just half the battle. The rest of the problem is making sure that the antenna makes effcient use of the power that is fed to it. Oh sure, the original shunt fed tower worked. Signal reports were as good or better than any I had received while using the inverted vee. The problem was that it was not working a well as it could. The new top loading wire brings the system to resonance at 3.9mHz. With an antenna tuner you don’t need a system to be in resonance to take power and radiate, but if you want maximum efficiency, a resonant condition is the best solution.

True the new system with top load wire is a cloud burner with 5dbi launched at 90 degrees. However, it has 1.5dbi to offer at 27 degree launch angle where the original setup only delivered -2.5dbi.

So for transmitting it should be better than the previous setup. For receiving it may not be as good because now it is going to much more sensitive to noise coming in at 90 degrees with a gain of 5dbi.

The following link will take you back to the main antenna page.

This link will take you back to the K5DKZ home page. You can also get there by selecting K5DKZ under the Pages heading in the green sidebar.

This project started as a result of renewed interest in 40 meters coupled with the desire for an antenna system that would be more effective than the simple dipole.

Over the last several years I have concentrated on VHF. Experimentation with VHF antennas had me retiring the HF beam and quad to the garage for storage. This made it a lot easier to crank my homemade, tiltover, drill stem, tower down to mount various VHF antenna designs. It also gave me a large inventory of telescoping aluminum tubing and fiberglass spreaders. Making sure I had the parts set aside for at least one triband beam, I used some of the other materials in this project.

Before starting this project I was using an 80/40 meter, inverted vee, trap dipole as an all band antenna, and a 40 meter broadband dipole flat topped at 35 feet for 40. Those antennas are still up and in use, but most of my serious 40 meter operating is now done on a pair of full sized, phased, quarter wave verticals spaced 35 feet apart.

Implementing the first vertical was a simple matter of shunt feeding my grounded tower. I used the Gamma match. A ten foot section of one inch diameter tubing was spaced ten inches from the fixed section of the tower. Braid from a length of RG8 was used to ensure a good electrical connection between the fixed and tiltable portions of the tower. An old ARC-5 variable capacitor (approximately 275pfd) was used to cancel the reactive portion of the Gamma stub.

Your probably wondering where the 40 meter beam comes in. I guess I could squeeze out of this by implying that two phased verticals do qualify as a two element beam. Don’t laugh. VK9NS uses four quarter wave phased verticals on 40 for about 7 db gain and does a pretty good job of working into the states. I won’t disappoint you though. My design for the additional full sized quarter wave vertical could easily be used to build a real full sized two element Yagi should you desire to do so.

A slightly heavier construction is used for the vertical application and will be covered first. By ‘heavier’ I’m referring to weight, not necessarily increased structural strength. A base heavy vertical lowers it’s center of gravity giving it stability. Using this design I was able to securely mount my 31 foot vertical by securing the base and providing a sturdy mounting bracket only three feet up from the base.

To provide the weight, I used a 44.5 inch section of 1-1/4 inch steel TV mast. This is driven into the end of a 70 inch long section of 1-3/8 inch aluminum tubing. The steel mast presses into the tubing a distance of 1.5 inches. A ten foot section of 1-1/4 inch, schedule 40 PVC pipe was cut to a length of 105 inches. There is nothing critical about the length of the PVC pipe as long as it is shorter than the steel mast/tubing assembly. Moreover, there is nothing critical about any of these dimensions. They are given in inches because that is the way I took them. The only ‘critical’ thing is to make sure your finished assembly is less than 32 feet long or you will have less leeway in tuning it to resonance. The pipe is used to electrically insulate the lower section of the vertical. I had originally planed to mount the vertical on top of the tower by clamping it’s base into the rotator coupling. That was before I decided to make it full sized and use it in phase with the tower. The extended section of PVC pipe allows additional beams to be mounted on the base of the vertical. The PVC also adds strength to the press fit between the first two sections.

The inside diameter of the PVC is too small to slip over the 1-3/8 inch aluminum tubing and is a loose fit for the 1-1/4 steel mast. By cutting a 1/8 inch wide slot through 65 inches of the PVC pipe the inside diameter can be enlarged to fit snugly around the aluminum tubing. The first two sections are pressed into the PVC pipe until the pipe is almost flush with the base. A 9 inch long shim is used in the base to take up the slack between the steel tubing and PVC pipe. The shim is made by cutting a length of 1 inch diameter aluminum tubing in half lengthwise and using one half of it for the shim. The slot in the PVC extends down the tubing assembly a few inches past the 1.5 inch pressed overlap. Drill a hole sized for a self tapping stainless steel screw through the overlap and centered on the 1/8 inch slot in the PVC pipe. The screw will prevent the press fit from working loose and also help ensure a good electrical connection between the two sections of tubing. Install another self tapping screw at the base of the assembly. This second screw should pass through the shim and into the steel pipe. Cut off the head of this second screw and wrap a couple of layers of electrical tape over it (just in case even though this is a high current/low voltage portion of the antenna). Electrical connection to the base is made by drilling a through hole for 6-32 stainless steel hardware. Use a solder lug or simply make provision for clamping the feedline between two washers mounted on the bolt.

The 1/8 inch slot in the PVC pipe was cut on a table saw using a carbide metal cutting blade. The same tool was used to split the 1 inch aluminum tubing in making the shims. If you don’t have access to a table saw, a hand held, rotary skill saw will do the job if you clamp the pipe to a table. However, for safety I would recommend using a hack saw in making the shims.

The next extension is a 72 inch length of 1-3/8 inch aluminum tubing. Since both of these tubing sections were salvaged from my quad, it was a simple matter to slide the second piece onto the coupling and secure it with a self tapping screw.

The next section is a 129 inch long fiberglass spreader. In my case the spreader end had already been fitted with a length of aluminum stock that was a snug slip fit into a nine inch length of 1 inch diameter tubing. The length of 1 inch diameter tubing is mounted into the inside of the 1-3/8 inch tubing using shims and self tapping screws. The objective here is to have all junctions tight and wiggle free so they will not work loose when the antenna is subjected to wind stress.

We now have an assembly that is 26 feet in length and have a few options to consider. The first is to run a wire straight down the hollow tube of the fiberglass spreader, bring it out through a hole drilled in the spreader at the bottom and secure it to under the head of one of the self tapping screws. The other end of the wire can be bent over the far end of the spreader and secured with electrical tape. Number 12 or 14 solid or stranded copper wire will do. We now have one leg of a self supporting dipole that can be mounted vertically on top of a tower and feed with balanced transmission line (300 ohm twin lead or open wire line). The other leg of the dipole can be made from wire and strung at an angle way from the tower. This second wire should also be 26 feet long and insulated at the end. Now we have a balanced feed, multi band, vertical dipole that can be used on 40 through 10 meters with an antenna tuner. On 10 meters it is 3/4 wavelength and should provide a radiation angle of 7 to 30 degrees as well as some gain over a dipole. On 15 meters, it is 5/8 wavelength, with a slightly lower angle of radiation and the ‘3db gain’ we have come to expect from a 5/8 wave vertical. On 20 it is about 0.4 wavelength and should have radiation angles lower than what can be experienced with a quarter wave ground plane. On 40 it is equivalent to a base loaded vertical. Even though this antenna qualifies as a vertical, note that it does NOT require any radials. It is a balanced vertical dipole.

Another option is to cut a 14 foot length of wire and spiral wrap it onto the outside of the fiberglass spreader. This coil will then need to be pruned until the antenna is resonant at 40 meters. This could then be used either as a vertical or as a vertically mounted dipole with a 32 foot counterpoise as suggested above. It’s performance should be very good on 40, 20, and 15 meters.

The third option, the one I chose, was to add another five feet of tubing to the end of the fiberglass spreader. This tubing is electrically connected with wire loosely wound over the outside of the spreader to connect to the sections of aluminum and steel tubing. The additional tubing was made from three telescoping sections of brass hobby stock. The kind