Bazooka Dipole

Some two or three decades ago I built a bazooka dipole for 40 meters. I chose 40 meters because I had just enough old RG8 coax to do the job.

The antenna worked fine and the coax was heavy enough to serve as two of the guys for the push-up mast I was using for my 15 meter quad.

Time marches on and the bazooka fell into disrepair and was abandoned in favor of a 40 meter loop.

Recently I took another look at the bazooka design and finally built one for 40 meters out of RG8X coax. Again, I chose 40 meters because I had just enough coax to do the job. The coaxial center section was 53 feet, 8 inches long and the insulated wire ends extended another 4.5 feet on each leg. The end result was 1.2:1 SWR bandwidth from 7.000 to 7.400 with relatively low static noise. Considerably better than my 80/40 meter trap dipole.

After that experience I just had to try a bazooka on 75 meters. I used a 100 foot length of RG8X for the two 1/4 wave stubs and added 12 feet of insulated wire to each leg to get the dipole to resonate in the 75 meter band. The result was a 2:1 SWR bandwidth from 3.600 to 4.040 and the same relative quiet I experienced with the 40 meter bazooka.

Each antenna was close to 300khz bandwidth with the 40 meter version being somewhat better and each displayed a static noise level reminiscent of a loop. Both bazookas and the trap dipole are up on the tower installed as inverted vees. The 80 meter versions are at 45 feet apex and the 40 meter bazooka is at the 30foot level. The trap dipole runs SW to NE. The 40 meter runs E to W. The 75 meter bazooka runs NW to SE. They are not all at 90 degrees to eachother but I did not want them to all line up in the same direction.

Antenna selection is through a homebrew antenna switch which grounds the unused antennas. Only one antenna is allowed to go active at a time. I am running power levels up to 1000 watts. That is 1kw output to the antenna.

The dipoles share space with a KT-34M2 beam, a 40 meter loop, and a 20 meter j-pole.

Spam

Desperate times call for desperate measures. Spammers are in desperate times. It appears no one wants to buy their stuff. Now most intelligent people would recognize that fact and try to find other stuff to sell. Stuff that people might want to buy. Spammers don’t understand that and believe that by making people mad folks will buy stuff they don’t need or want.

Does that sound like the reasoning of a sane person? It does not sound sane to me. I would rather not deal with insane people even if they don’t make me mad or are selling stuff I need.

It is hard to shake a bad reputation. Once you step in it the smell lingers on even after you wash up.

Antenna Switches

While it is possible to have one antenna for all bands I find single band antennas are better, more convenient performers. Their main problem is changing out feedlines when changing bands. Well, we use band switches on our equipment, why not use them to switch antennas too?

A decent antenna switch does not need to be any more heavy duty that the bandswitch in your amp or transmitter. It does not need to be coaxial. Short runs of coax braid used for hook-up material inside a metal box is more than adequate and will not adversely effect antenna matching.

Light to heavy duty ceramic switches are adequate for handling powers up to the legal limit in the USofA. Even with 1000 watts of RF we are only experiencing 4.5 amps through the contacts and 220 volts across the contacts when we are dealing with 50 ohm transmission line.

This assumes we are feeding an antenna that is matched to 50 ohms at the transmitter end as well as at the antenna end. The SWR needs to be 1.5:1 or less at all points on the transmission line from the transmitter to the switch to the antenna.

Antenna tuners and transmatches may end up destroying the antenna switch depending on how badly is the mismatch the tuner is compensating. Tuners will match to the transmitter only. They will not match to the feedline and antenna where the antenna switch is located.

So, antenna switches are best applied to systems that use 50 ohm resonant antennas and feedlines.

This may not be common knowledge. Suspected improper use of antenna switches ends up killing the used market for these devices. The boxes may still have use but the welded switch contacts may need replacing.

Software Updates

Software vendors who offer periodic updates for security reasons are admitting that they distribute software that is not secure.

What reason do I have to expect that software to be any more secure after the update. What other problems have these fools created.

No, frequent updates are an indication the software is flawed and produced by a flawed vendor. Time to find something better. Time to make sure we are not invested in flawed vendors.

In fact, some of these hackers are so incompetent they want 24/7 access to your computer. I have a real problem doing that. I need to know what the update does and why. Especially when I pay good money for what I believed was quality software.

I am not interested in providing a beta test site for free and paying for the privilege.

On-line time on my computers bills out at $500 an hour.

G5RV ANTENNA

Not a week goes by that I hear someone on 75 meter SSB proudly announce he is using a G5RV antenna. I resist the urge to ask if he really knows what a G5RV antenna is because if he knew he would not be so proud of using it on 75 meters. The G5RV is a 20 meter antenna!! If you really have a G5RV you would be better off trying to load your triband beam on 75 metres!

G5RV invented his antenna because he wanted a simple and cheap wire antenna for 20 meters that also had some gain. You can increase the gain of a half wave dipole by making the legs longer. In the case of the G5RV each leg is 3/4 wavelength long on 20 meters and provides about 3db gain. It also provides a high input impedance.

The high input impedance is handled by a 1/4 wave section of open wire line. It is about 33 feet long, 1/4 wave on 20 meters and transforms the high antenna impedance to close to 50 ohms for a match to normal coax.

All this trickery only works on 20 meters making this a single band antenna.

This did not prevent hams from trying the antenna on other bands. When they discovered it did not work well on other bands, they extended the ladder line to an antenna tuner and tuned the antenna system to allow it to work on other bands. Only now it is no longer a G5RV. It has become a non-resonant dipole with 50 foot legs.

Unique Linear GG Amplifier Input Circuit

The ideal input circuit needs to be able to handle 100 watts of RF, present a 50 ohm impedance to the exciter over the desired frequencies, and prevent the driving power from being wasted in the filament transformer.

The conventional solution is to use a ferrite loaded filament choke and band switched individual low Q tuned circuits – one for each desired band.

Recently there have been several articles offering an alternate solution using a homemade coaxial line composed of copper tubing into which a length of #12 copper wire is inserted as the center conductor. The copper tubinged coax is then wound into a 1 inch diameter coil. At one end the shield and center conductor are wired to the filament transformer. At the other end the center conductor and shield are wired to the tube filament.

A 1000pf variable capacitor is wired across the copper tubing and a 2.5k ohm 2 watt resistor is wired across the capacitor to lower the Q of the circuit. The input RF is applied to the third turn from the filament pins through a .01mf ceramic capacitor.

With the tubing coiled to 15 turns around a 1 inch diameter form and the variable capacitor value at 1000pf we can tune 80 through 10 meters. The tap at 3 turns from the pins at the tube socket provide a 50 ohm impedance to the exciter over the same frequency range.

This alternate method requires the addition of a variable capacitor to the input circuit and burdens the operator with an additional adjustment. It also eliminates the need for seperate individual circuits, an input bandswitch, and a ferrite cored filament choke.

This alternate method is both effective and inexpensive.

The most troublesome part of the alternate method is the uninsulated copper tubing used to create the homemade coax shield. This brings up an obvious question, why not use real coax. Well, for two reasons. Most coax you can wind onto a 1 inch diameter form will have too much voltage drop across it at the current levels required by the filaments.

So the first step is to reduce the filament current. As an example, assume the use of four 811 tubes. If you wire all the filaments in parallel the power requirement will be 16 amps at 6.3 volts. If you wire two tubes in series and parallel their seriesed connections, the power requirement will be 12.6 volts but the current will only be 8 amps. Wire all four filaments in series and you can power the filaments with 4 amps at 25.2 volts.

With the filament current reduced we can now use RG8X to build our input coil. This further reduces the cost of this input circuit solution by eliminating the copper tubing.

Double Bazooka Dipole

There is a lot of information about this antenna on the internet. Lots of offers to sell. Lots of construction information with formulas to calculate lengths for various bands. Very little information on why it works, how it works, and where best to use it.

The bazooka is a dipole made up of two quarter wave transmission lines connected in series and wire tails connected to the ends of the transmission lines to resonate the antenna to the desired frequency.

As the transmitter frequency is varied the antenna impedance (real and reactive) also begins to vary. The impedance of the quarter wave sections will also vary but in the opposite direction of the antenna impedance. So the variation in quarter wave impedance offsets the variation in antenna impedance and we have an antenna that maintains an overall impedance over a larger span of the band. We have a broadbanded antenna. About twice as broad as a normal dipole for the same band.

Now, where is more bandwidth really needed? Although more bandwidth would be welcome everywhere it is most useful on 80 meters and 2 meters. Lets take a look at the 80 meter version.

First, the quarter wave sections. The two quarter wave sections are constructed from coax. Most of the construction articles on the internet assume that solid dielectric RG58 will be used. This coax has a velocity factor of .66 and is not suitable for high power levels. We could substitute RG8 but it is expensive and heavy. So lets use RG8X instead. But wait. RG8X has a velocity factor of .84 so the formulas designed for RG58 will not work. They will not get us the quarter wave sections we need and without those quarter wave sections we do not get a broader banded dipole. We still get a dipole, it will just not be broader bended.

Something else to notice is that quarter wave sections for 80 will be quarter wave only for 80 ( and odd multiples of the 80 meter frequency they are cut for i.e x3, x5 etc.). This makes the bazooka a single band antenna. Those claims of multiband bazooka dipoles do not tell the whole story. Yes, you can have a multiband antenna that incorporates a bazooka dipole but it will be a broadband bazooka only on one band. Acually, that is probably okay if the bazooka effect is on 80 meters. You don’t need a broadbamd antenna on 40. A normal dipole is plenty good on 40 meters.

If we want to construct a bazooka dipole for 80 from RG8X, we can use the formula for a half wave wire dipole and apply the .84 velocity factor. 468/Fmhz X .84. This comes out to a little over 100 feet. Good deals on RG8X are available for lengths of 100 feet ($40 on Amazon). 100 feet of RG8X will make two quarter wave sections for 3.932mhz. This should allow 1.5:1 SWR from 3.78 to 4.082 mhz or the entire 75 meter band.

Take that 100 feet of RG8X, Short each end of the coax, center to shield, find the center at 50 feet and cut the outter covering and shield being careful NOT to cut the center conductor, fray the cut ends of shield to make two pigtails for connection to the feedline to the rig.

(The 100 foot roll of rg8X from Amazon comes with coax connectors attached to both ends. You can avoid cutting these off by terminating them into female coax connectors and shorting them at the new connector ends.)

The part of the bazooka that does the radiating is the shield of the coax we used to build the quarter wave sections. The quarter wave sections are a quarter wave due to their relationship to the center conductor and the insulation in between that conductor and the shield. The shields are too short to be a quarter wave alone. They are too short by the velocity factor of .84. To make this a resonant dipole we have to add wire to the ends of the coax. The overall length of the antenna should be a half wavelength or 468/Fmhz. Some articles show 300 ohm twinlead added to the ends. This may help the broadbandedness but ordinarry wire will do too.

The bazooka has an additional advantage over a standard dipole. It is quieter. No static buildup because the antenna is a short circuit to DC and can be grounded at the feedline. Use a 1:1 balun at the feedline to prevent radiation from the feedline.

Universal Boatanchor Power Supply

Collins, Heathkit, and Drake all produced transmitters and transceivers that require external power supplies. These supplies were usually housed in speaker cabinets but could also be used as stand alones. Collins also had provision to house its 516-F2 supply on a shelf inside the 30S-1 amplifier.

Heathkit provided the 23B supply and Drake provided the AC3 and AC4 supplies. All three manufacturers supplies were designed to power tube style transmitters and transceivers in the 100 watt class.

Filament voltages of 6.3 and 12.6 volts at up to 8 amps, low voltage B+ around 300 volts at under 200 milliamps, high voltage B+ of 600 to 800 volts at up to 250 milliamps, And -40 to -80 volts bias at 10 to 20 milliamps.

By using two transformers, solid state rectifiers, and modern filter capacitors, I have been able to incorporate all the components needed to supply the various voltages an currents required by the various brands of transmitters and transceivers into the 516-F2 foot print. This 7X9X2 inch chassis is equipped with three output cables each terminated in the required connector for the target equipment. Eleven pin female for Heathkit, 11 pin female for Collins, and special 12 pin female for Drake. Each cable is terminated inside the supply to provide the voltages needed by the various equipment supported.

The only compromise is the high voltage. Both heathkit and collins provide 800 volts. Drake provides 650 volts. My supply provides 570 volts. This means, that at 65 percent linear operation, the finals will only deliver 74 watts output with this supply. Both heathkit and collins offer 104 watts output under these conditions with 800 volts to the finals. Drake will deliver 84 watts output.

The lower output with this power supply should not effect the ability to drive a linear amp to full output and it allows the finals in the exciters to loaf along, extending their useful life.

Plumbing

I hate doing plumbing work but I hate to have a running toilet even more. It wastes water and makes noise.

I always blamed poor quality fill valves and recently discovered that the fill valves are not causing the problem. They are merely functioning as they should to keep the water level in the tank at a flushing level. The real culprit is the flapper valve.

Flapper valves are made of rubber and chemicals in the water designed to kill germs also kill the rubber in the flapper valves. Over time, the rubber in the flapper valves becomes hard, brittle and no longer is able to keep water from flowing past it.

A recent toilet problem was solved by replacing the flapper.

Selecting Lawn Grass

Take a walk through your neighborhood. Look for cracks in the sidewalks. Do you see grass growing in the sidewalk cracks? That is the kind of grass you want for your lawn.
In my area that happens to be Bermuda.

Kentucky blue grass is fine if you are in Kentucky. I live in Texas and I think grass should be green.

St. Augustine grass does not like the sun, or the heat, or lack of water. It does not like the area where I live so I don’t use it. Grass abuse is a terrible thing.

When you decide on the grass you want, buy it in seed form. If you can’t grow it from seed, (assuming it propogates from seed), it will probably not survive anyway. Grass that propogates from seed is particularly low maintenance. Just let it go to seed a few times a season to replenish any weak spots in the lawn.

Sod is expensive to buy and install. Sod guarantees a finished lawn almost immediately and is the best way of establishing non-native grasses quickly. That might last a year or two but eventually you will find out why those grasses are not native.

If you are looking for Bermuda seed, then buy Bermuda seed. The bad should read Bermuda Seed on its face. Grass Mix, Sun and Shade, Quick Grow Grass Patch, these are all examples of products to avoid. If it does not say Bermuda, it is not Bermuda. In fact , generic platitudes are an indication the vendor does not want you to know what is in the bag because if you knew, you probably would not buy it.

Just because it is not approved for use in parts of California does not mean it is bad grass. California is run by people of low intellect and low morals. Being banned there may be a good thing.

Expect to pay at least $3 a pound for real bermuda grass seed.

Scotts products are usually overpriced and underperforming.