OFF TOPIC blog

Three lines of code, a flickr account, user_id, and tags, all stuffed between a couple of iframe tags and you have a slide show of selected pictures.

The actual program that does all the work is at the flicker site. This code merely uploads some variables and provides a local iframe.

It makes a call to www.flickr.com/slideShow/index.gne?user_id=xxxxxxxx@N00&tags=yyy

All iframe options are available. Width and Height being the more significant.

I suppose you could use someone else’s user_id and tags. I am a little reluctant to try that. Certainly not without permission.

The header is working really well now. Got too many header pictures. Probably need to select a few that are more specific to the blog and rotate between a maximum of half a dozen or so.

Everytime a new post is loaded the header is updated. Try it. Reload this page and see what happens. If nothing happened, try it again. Sometimes it reloads the same header or maybe does not load anything at all. I have not figured out which is at work here, but it does bring up a new header between log-ons.

Turns out that functions.php is just header related. Before functions.php was disabled there was an additional option under ‘Presentation’ that dealt with changing header top and bottom colors. Those options don’t appear anymore now that functions.php has been disabled.

Also added a contact form. It is shown below. It sends me an email with the information you typed in as well as your IP address.

I have been playing with this thing for days now. Not because it is fun but because I don’t want to have to admit that the computer is smarter than me.

Well, of course! I googled everything I could think of regarding the header and I got lots of information. Unfortunately it was all for a previous version of WordPress.

I tried taking my graphic image (720×200) and renaming it kubrickheader.jpg. I also was careful to make sure it really was a .jpg file. When the header came up I could see bits of the new graphic behind the big blue screen that still came up in front of the graphic. Okay, some more investigating and I discovered that all I really needed to do was name it personalheader.jpg. That did not work either.

Then I found out about Kubrickr. A neat tool that makes graphic headers. That did not work either because I had a display problem, not a graphics creation problem. Oh, I got a nicely formated header graphic for Kubrick but it still hid behind the original blue header. I got distracted with flickr trying to figure out why my own flickr pictures would not get displayed.

I finally got my flickr problem resolved, uploaded a bunch of pictures, then started making header graphics using Kubrickr. Most of them turned out a nice shade of black. I have not figured it out completely yet but it has something to do with the size of the image. The image has to be larger than what ends up appearing in the nicely framed Kubrick header graphic else it gets replaced with a big black banner to replace the blue one.

Just for fun I uploaded a 400kb+ file to my server, a closeup of a red rose. That displayed okay except for being wider than the blog page by just a little on each side. It also took forever and year to load.

I finally discovered a Wordpress Tutorial:Replace Header Graphic Kubrick Template.

Toward the end of that tutorial under PROLBEMS: (no, that is the they way they spelled it ) it was suggested to delete the functions.php file from my wp-content/themes/default/ directory on the server.

Not being one to throw anything away, I renamed the file to functions.php.tst. I reloaded everything and behold!, the graphic displayed as expected. Only problem was it had the title of the blog across it.

Reading a little further, I discovered that I could get rid of the unwanted verbage by adding ‘display:none;’ at the beginning of h1 and #header .description{ sections of the style.css file.

So now I have a page that has no header except for the graphic that is loaded. All the nice border and fancy formatting is gone. The place where the header was is now just a blank part of the page except for the graphic. That is okay. I suspect all the fancy stuff was part of the default graphic anyway and it can be restored with a little creative manipulation of my new graphic.

My only concern is the disabling of functions.php. The name implies it was doing more than just preventing me from displaying a custom header.

Those folks at www.siteoodles.com may not know how to spell ‘problems’ , but they do know how to solve problems. At least I am closer now than I have been all week to making my custom header work.

Now to see if I can get rotator.php to do its magic and display a new graphic in the header each time the page is reloaded.

Got that done too. Everything is easy when you know how. I found the details for the code changes at the WordPress Codex Site.

As usual, when everything else fails, read the instructions. In this case the WordPress Docs.

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:

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 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 you find in most hardware stores. The brass tubing is very light weight, readily available, and comparatively strong for its size. The bottom section of brass tubing is chosen to be a little larger in diameter than the inside diameter of the fiberglass spreader. The brass is slit lengthwise, compressed, and pushed into the spreader for a length of about nine inches. The wire is soldered to the brass tubing. The brass sections are also soldered together. We now have an assembly that is 31 feet in length, very close to the 32 feet required for a quarter wavelength on 40 meters. The additional electrical length is provided by the winding of wire onto the spreader until the entire assembly is resonant. Note that we do not have to worry with sliding tubing or base loading to shift the resonant frequency of the antenna. We merely change the length and number of turns of wire around the spreader. This thing would also make a very good center- loaded whip for use on 75 meters. Notice I said ‘whip’. That is exactly what we have here. A very large, light-weight, whip that is not ‘floppy’ when extended horizontally. The total weight of my vertical was less than 25 lbs. More than half of that weight was in the steel base section and the unnecessarily long length of PVC pipe. I wanted it base heavy for stability. The additional PVC pipe allows me to mount a small VHF/UHF beam at it’s base. The vertical droop when the assembly was extended horizontally was about five feet.

There is no reason why this antenna cannot be made shorter and still work. I chose not to do that because I wanted as much bandwidth as possible, as high a radiation resistance as possible and as a close match to the full sized vertical I was trying to phase. As it turned out, the new vertical rose to a height almost equal with the tower. The vertical is roof mounted to an eave located 35 feet from the tower. I’m still tempted to mount it on top of the tower, but then I couldn’t phase it the way I want to for 40 meters. Anyone for a full sized quarter wave 75 meter vertical? Wonder how that arrangement would work on 160 meters. With a ten foot insulated, fiberglass section at the middle of this thing, we could wind enough wire on it to make it resonant on 160 meters without the tower extension. A mast mounted switching arrangement could tie it to the tower for 75 meter operation. It could then also be used as a vertically polarized dipole coax feed for 40 meters or balanced feed for multi-band operation. Even then, with the insulation provided by the PVC pipe, we could still mount our triband beam. Or, maybe, a 40 meter beam made from four more spreaders and aluminum tubing.

I couldn’t possibly raise a 40 meter beam at my QTH. My trees are not the only ones that have grown over the past fifteen years. I can just barely clear a two meter beam without having it mangled by the large oak in my neighbor’s front yard. However, if that were not the case, here is how I would build it.

Four sections similar to the one described above would be made, but I would substitute aluminum tubing for the steel in the base. I would also shorten the brass extensions by a few feet adding additional turns of wire to compensate for the shorter length. The driven element halves would be connected using a slotted length of PVC pipe. Four muffler clamps (two per element halve) would hold the element to a six foot section of sturdy aluminum angle stock. Each element halve would have been inserted into the six foot length of slotted PVC pipe taking care to leave a gap between them in the exact center. Electrical connection to the elements would be made by drilling through PVC and tubing, then installing self tapping screws. I would probably try using an inductive hair-pin match taking care to make sure the driven element sections were electrically shortened enough to provide the required capacitive reactance. I would mount the parasitic element the same way in order to ensure each full element had very close to the same weight for balance. The boom would need to be at least 2 inch aluminum. A good application for the tired and true irrigation pipe. I would most likely opt for close spacing (.15 wavelength) and use a director. Even at .15 wavelength we need a 20 foot boom capable of supporting about 35 lbs at each end. Remember, one wavelength at 40 is 136 feet. Muffler clamps would also be used to hold the elements to the boom. I would opt for using four clamps per element.

Tuning an almost 60 foot element would be feat in itself. I can envision it suspended at the ends of the spreaders, but I think it would be more reasonable to tune each of the four sections separately as quarterwave verticals. This would require some very careful planing and careful work. Checking resonance with a dip meter verified by a frequency counter or communications receiver would be a minimum requirement. Remember to allow for the 100 to 200 khz upward shift in frequency when this monster is raised.

Getting it up onto the tower could best be accomplished using the PRCV mount for a stationary tower. A tiltover would allow you install the boom, install one element, raise it, rotate it 180 degrees, and lower it so you can install the other element all from ground level. Well, at least nothing more dizzying than a stepladder, anyway. Note that if your tower is not at least 40 feet high, you may not be able to install this antenna at all unless you DO have a tiltover tower. Of course, we would like to get it up to at least 60 feet, with 70 feet preferred.

As you can see, a 40 meter, rotatable beam is a major undertaking even with low cost, light weight materials. My method of constructing the 40 meter monopole is offered as a cost effective way to achieve good performance with a minimum of effort. It could make the job of constructing a 40 meter beam less formidable and at a lower cost. I feel it is definitely the way to go when multiple verticals are required. My next antenna project will most probably be a four element 40 meter beam. A vertical beam, of course!

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These devices are called Traps, but they are actually more like frequency sensitive switches. They are parallel resonant, high Q, tuned circuits which provide a very high impedance at their frequency of resonance.

An example of their use can best explain their operation. Take, for example an 80/40 meter trap dipole. The center section of this antenna is a normal 40 meter dipole of conventional length. One end of each trap is connected to the ends of this dipole. The other end of the trap is connected to additional lengths of wire (typically 21 feet) to allow the complete antenna to resonate on 80 meters.

The resonant frequency of the traps should be the frequency you wish to use in the 40 meter band. The additional 21 foot lengths of wire should be adjusted so that the antenna resonates at your choice of frequency for the 80 meter band. Note that each leg of the dipole is only a little over 50 feet long making it about 20 percent shorter than a full sized 80 meter dipole.

On 40 meters, the traps have a very high impedance, effectively disconnecting the two 21 foot lengths of wire needed for 80. On 80 meters, the traps act as loading coils permitting the antenna to be shorter than a conventional 80 meter dipole.

The 80/40 meter trap dipole example will work on all bands (80, 40, 20, 15, and 10), but will work most efficiently on 80 and 40. If this sounds to good to be true (shorter antenna with multiple band performance), there are some compromises to be considered. On 80 meters even a full sized dipole cannot provide an SWR of less than 2:1 across the entire band. On 40 meters, we have the same problem to a lesser extent. A trap dipole exhibits an even narrower bandwidth than a full sized antenna. Still, if your use of these bands can be served with a 200khz to 250khz bandwidth, a trap dipole can be a good solution.

Another compromise of a trap dipole is the requirement for the traps. Conventional traps are constructed of high voltage transmitting type capacitors and heavy B&W miniductor stock. They are not particularly difficult to make, but the parts are expensive and they are subject to drift in frequency when exposed to adverse weather conditions. However, there is a method of building traps that is very inexpensive, can withstand full legal power limits, and is relatively stable under even the most adverse weather conditions.

The 1988 ARRL Handbook alludes to this method of trap construction but does not give any specific data. I have built a set of traps using this method and would like to share the information with anyone interested in homebrewing a trap dipole.

My traps were built to be used in an 80/40 meter dipole as in the example given. The same method of construction can be used for other frequencies with the turns reduced to cover the higher frequencies.

The method of construction alluded to in the handbook uses a coil of coax to form the tuned circuit of the trap. The shield of the coax forms the coil. The center conductor of the coax on one end of this coil is connected to the shield at the opposite end. This allows the capacitance between the center conductor and the shield to act as the capacitance that resonates the assembly.

Aside from the low cost, this method reduces resistive losses in the coils to an absolute minimum. The shield portion of the RG62AU coax I used is electrically equivalent to using quarter inch copper tubing. The capacitor formed by this assembly is capable of withstanding several thousand volts of RF allowing the use of high power on 40 meters. Although I used RG62AU, RG58 or RG59 would serve as well. RG8 may also be usable, but it’s stiffness might require a larger diameter coil form and may result in a heavier assembly.

My traps were wound on two 6.5 inch long pieces of schedule 40 PVC pipe 1.25 inches O.D. I found that 20.5 turns would resonate at 7.285 mhz, my chosen 40 meter frequency.

Each end of the PVC pipe was prepared by drilling two opposing holes in it about 0.25 inches in from each end. Solid number 12 copper wire was inserted through these holes and bent around the PVC to form a loop with the wire inside the pipe. These terminations were used to attach the antenna wire as well as provide a tie point for the coil of coax.

Each trap will require 80.5 inches (6.7 feet) of coax. Start with seven feet and trim it up to the frequency you want in the 40 meter band. Each length of coax is prepared by stripping about 2 inches of outer insulation from each end. The shield is unbraided and twisted at each end. The center conductor at one end is stripped of insulation for a length of about 1 inch.

Start your winding by drilling a hole just large enough to pass the coax through the PVC pipe. This hole should be located about 0.5 inches in from the end of the pipe. A close fit of the coax through this hole will help secure the winding until the holes are filled with epoxy.

Insert the end of the coax that has the center conductor stripped through the hole and wrap the shield of the coax around the number 12 wire at this end. Solder the shield to the wire. Use a 50 to 100 watt iron and do it quickly so that the heat will not travel up the braid to melt the insulation to the center conductor. Let the soldered connection cool completely before starting the winding.

Now wind about 22 turns of coax onto the pipe. I estimate that 22 turns will resonate at the low end of the 40 meter band. If you are interested in the higher portion of the band, stop at 21 turns. Remember, you can always cut off coax to raise the frequency, but if you get too high in frequency, your best bet is to start over with a new length of coax.

Mark the pipe at the end of the winding and drill another hole in the pipe at this location to pass the coax. The close fit of the coax into this hole will keep the windings in place.

Prepare a length of wire. Hookup wire #20, #18, #12, is adequate. Cut the wire to 6.5 inches in length. Strip off 1.5 inches of insulation from each end of the wire. Solder one end of the wire to the center conductor of the coax at the end where you started your winding. Pass the wire down through the center of the pipe and twist it’s bare end to the coax braid where you finished the winding.

Pull the hookup wire through the center of the pipe so that the soldered bare end of the coax center conductor is pulled down away from the soldered coaxial braid at the end of the coil where you started the winding.

Now you will need a grid dip meter to check the resonant frequency of the trap. Don’t rely on the grid dip meter’s calibration. Use a frequency counter or your communications receiver to verify the frequency. (My homebrew grid dip meter doesn’t even have a calibrated dial. Only it’s coils are marked as to frequency range covered.) I found that by inserting the coil of the grid dip meter about 1/8th inch into the end of the PVC pipe an easily recognizable dip could be obtained. For your final frequency check you may want to reduce the coupling between the dip meter’s coil and the trap. In my case I found a 50khz shift in frequency as I reduced the coupling. The dip obtained at the reduced coupling is the more accurate one. Also, make certain that your dip meter is on the right frequency range and that you have the receiver tuned to the fundamental frequency and not a harmonic. My grid dip meter had enough output to register an S9 +20db at the receiver with the receiver’s antenna disconnected. Use the receiver’s S-meter to zero in on the dip meter’s output when determining frequency or zero beat as you would on an AM signal.

Your first frequency measurement should fall somewhere in the low end of the 40 meter band. If it doesn’t, and if you did get a dip on the meter, you may be too low in frequency. If so, cut off about two inches from your winding and try again. In my case, I found that a one inch reduction in coax length resulted in an approximate 50khz frequency shift.

As you cut more and more coax from the winding, you will need to drill additional holes in the PVC for proper termination of the winding. The PVC is easily drilled. This cut-and-try method requires a little patience, but it is very repeatable. My first trap took me two hours to build. The second was done in 15 minutes.

The coax winding is tight and close spaced onto the PVC form. After your final frequency check, trim the finished end of the coax winding and solder the braid and the short length of hookup wire to the #12 copper wire termination that you installed in the pipe at that end.

That completes the trap. Now all you have to do is build another one and solder the antenna wires to the copper wire terminations at each end of each trap.

Note that the number of turns required will only hold true for RG62AU coax. Other types of coax may well be used, but the turns required may vary.

Initially, I was a little concerned as to whether or not the end terminations I used would hold the strain of supporting the traps. The terminations have held through the weather conditions we have experienced in the last two months. However, I would not recommend using anything less than schedule 40 PVC pipe.

If you would like to purchase a set of traps to buid this antenna, click on the paypal button below. For a flat fee of $40 I will send you a matched set of traps. This offer is good for buyers in the continental U.S. only. Others inquire via e-mail.

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