A 10 foot yagi design that delivers an impressive 16dbi gain at 440mhz. Fits perfectly into a 10′ PVC pipe that you can buy dirt cheap at any building supply store.

Recipe:

$3.00: 1 10′ PVC pipe, 1″ diameter for best support.
$7.00: 7 aluminum welding rods, 1/16″ x 36″ Go to a welding supply shop they sell them by the lb.
$2.00: SO-239 Connector
$1.00: Silicone sealant in a tube
$1.00: Hot glue stick
$2.00: Paint
$0.10: A scrap of coax for your balun

$16.10 or so for mine.

Construction:

Measure out all elements very very carefully down to the mm according to the plan below. I used a chalk line to then make a straight line down the middle and followed up by drilling the element holes. Use the tightest fit you can manage, use the right size bit for your elements. The best way to do this is to use a drill with a level bubble on the top so you can make sure all your elements are in line. You can always re-drill if you get any odd ones though.

Cut each element very carefully to the exact length, and feed them through. You should use some sort of box or brick to keep it suspended above ground to avoid bending the fragile aluminum elements.

Once the elements measure up evenly (same amount of aluminum rod sticking out each side) fix them in place with a generous dollop of hot glue, all around and out across the rods to get a good surface area binding. Or use silicone if you want to wait.

The folded dipole requires a little special attention to bend it around and get it just right. An ASCII illustration is included. On my antenna I aligned the center of the oval with the elements so that it looks symmetrical and that seems to be the way most builders make them also.

You’ll also need to make a balun to get the impedance down to 50 ohms. I simply used a scrap of coax that I strapped to the antenna. Here is a good website to tell you about making one for yourself: http://www.n-lemma.com/calcs/dipole/balun.htm

The software used to calculate this is described in the following output that I have modified to include a little extra info, and can be freely downloaded from many places online. Google is your friend on that.

Strapped it to my mast and I’m hitting far away repeaters that I never even could hear before. Highly recommended and a nice cheap weekend project.

VK5DJ's YAGI CALCULATOR

Yagi design frequency =444.00 MHz
Wavelength =675 mm
Elements using a non-metallic or separated boom
Director/reflector diam =2.50 mm
Radiator diam =2.50 mm

ELEMENT LENGTHS AND SPACING
Reflector
330 mm long at boom position = 30 mm

Radiator
Single dipole 319 mm tip to tip at boom posn =165 mm
Folded dipole 325 mm tip to tip at boom posn =165 mm

Dir	Length	Spaced	Boom position	Gain	Gain
(no.)	( mm )	( mm )	( mm )		(dBd)	(dBi)
1	300	51	216		5.3	7.4
2	297	122	337		6.8	8.9
3	294	145	482		8.0	10.2
4	291	169	651		9.0	11.2
5	289	189	840		9.9	12.0
6	287	203	1043		10.6	12.8
7	285	213	1256		11.3	13.4
8	283	223	1478		11.8	14.0
9	281	233	1711		12.3	14.5
10	279	243	1954		12.8	14.9
11	278	253	2208		13.2	15.3
12	276	260	2467		13.5	15.7
13	275	263	2731		13.9	16.0
14	274	267	2998		14.2	16.4

Director spacings are measured from the previous element
Tolerance for element lengths is +/- 2 mm

Boom position is the mounting point for each element as measured
from the rear of the boom and includes the 30 mm overhang.The total boom length is 3028 mm including two overhangs  (9.93ft)

The beam's estimated 3dB beamwidth is 31 deg

A half wave 4:1 balun uses 0.80 velocity factor RG-8 (foam PE)  and is 270 mm long plus leads
-----------------------------------------------------------------------------------------------------
A half wave 4:1 balun uses 0.66 velocity factor RG-8U (foam PE)  and is 223 mm long plus leads

Here are some construction details for a folded dipole

Measurements are taken from the inside of bends
Folded dipole length measured tip to tip = 325mm
Total rod length =669mm
Centre of rod=335mm		   FOLDED DIPOLE
Distance HI=GF=145mm		B========C========D
Distance HA=GE=165mm	       A(		   )E
Distance HB=GD=185mm		I=======H G=======F
Distance HC=GC=335mm                   (gap)         
Gap at HG=10mm
Bend diameter BI=DF=25mm

If the dipole is considered as a flat plane (see ARRL Antenna Handbook) then its resonant frequency is 427.9MHz and K is 0.929

Today I discovered the FLdigi program which is a swiss army knife of digital modes. Formerly I was resigned to running ham software only on Windows which was a depressing prospect. Now I look forward to using this along with Klog or Xlog to do some digital contesting!

I have a RigBlaster Plug and Play for keying and ptt control on my Icom IC-735 rig as well as a simple looking USB rig control cable that works perfectly well with hamlib.

I have so far managed to tune CW and watch Fldigi decode it successfully, and Fldigi can activate PTT on my rig but it seems it is designed to send an audio signal directly to the sound input on the rig rather than through a keyer like the RigBlaster. What I need to get it to do is to activate RTS for PTT and use DTR for keying CW instead. While a few searches on the related Yahoo groups for this software indicated that such support may exist I have not been able to find out how to activate it as yet.

I posed this riddle to Joe, a classmate of mine: “Last night I built a full wave 40 meter antenna. It cost me about $2 to build, has a 1:1 SWR, pulls in signal like nothing else I’ve tried and is virtually invisible.”

Being a new ham he didn’t guess, but some of the more experienced hams knew. I had lit up my rain gutter system.

I got the crazy idea yesterday that three sections of the perimeter of my house actually added up to just under 40 meters in length, so I went out and measured and found that sure enough, it was. An hour later I had electrically joined my gutters into a ~41 meter long (including the downspouts) U shaped “random wire” antenna.

I found that others around the net had done similar things and here are a few pointers I gathered on this. Of course, if you try this at home your installation is your own responsibility/liability so do your own homework first!

1. Make sure all metal to metal connections are sound. Gutters are often missing screws and any gaps will allow arcing of the transmission and thus broadband interference. This includes gaps where two sections are joined on long runs, I just drove some small screws through every joint.
2. Use an antenna tuner with a very good ground.
3. Don’t use it to transmit when it’s raining. The water will disrupt the signal and additionally if you transmit while it is wet you may have some serious electrical hazards.
4. Did I mention a good ground? Both the radio and antenna tuner should be connected to the ground by the shortest length of ground strap possible. If you can’t do a good ground, do not try this antenna.
5. Take measures to ensure nobody can touch the metal parts of the gutters when you are transmitting or they may be burned. One easy way to do this is to replace the metal downspouts with vinyl ones.

Another idea I had along this line since my house has gutters only on the longest sides of the rectangle is to use one gutter as a driven element and the other as a reflector or director. A whole-house 80 meter yagi might be possible though I would likely not get a strong directionality since the height of the gutters are only 1/8 wave high on that band. The gutter setup already seems to have a certain amount of north-south directionality though due to the U shape as it is, I worked and heard mainly stations south (TX) and north (Canada) last night. If I try the yagi idea I will talk about it here so stay tuned.

Update Jan 2008- I have ditched the gutter setup and opted for a long wire sloper instead after modeling the gutter on 4nec2. The rain gutter was so-so for local contacts but it was a serious cloud burner- all the signal went straight up instead of out and there was at least 13dbi of attenuation at any reasonable elevation level. The sloper is quite a bit better at least on computer models, will post about it when I have tuned it up.

Update Mar 2008- The sloper as I designed it was nearly useless in practice, it really needs a yagi or some sort of “hat” to work when top fed evidently. The rain gutters were actually better. I’ve since reallocated the rain gutters to perform as part of my radial system for my MFJ-1793 20/40/80 vertical however which beats all previous attempts as expected.

In the last few weeks I have tried a number of new things in Ham Radio.

Let’s start with power. I have a good old 12v 12A ATX power supply that I have converted for use with the ham radios, see my previous article for the details. One weakness that I noticed with this setup was that there was not enough current being supplied to my 100 watt HF rig; the lights would dim whenever it was putting out more than 75 watts or so. So this week I checked it over with a multimeter to make sure all of the yellow wires were connected to the same circuit and all the blacks to the same, then I just joined all of them into one big wire per color. After a quick test with the HF rig it was clear that there was enough power after all, it now dims almost imperceptibly indicating it could maybe use a few more amps but I don’t think it is suffering any.

I had previously tried hooking everything up to a 12v marine battery which supplied plenty of amps to the radios. However I didn’t want to deal with two problems related to that. First is keeping the battery topped off. I could pretty easily make a relay circuit that would kick in whenever the voltage dropped below a certain threshold. But the second problem is that the battery charger is loud, really loud. And I can’t stand a lot of loud whirring and beeping. So I reverted to using the computer PSU and I think it will handle the job fine. Here are a few photos of my setup now.

I bought what turned out to be a necessary piece of equipment for HF, an antenna tuner. I also thought it would be worthwhile to buy a nice one that includes a dummy load, an antenna switcher, and a built in power/SWR meter. So I chose the MFJ Deluxe Versatuner II. I have also picked up a VHF SWR/Watt meter that is very handy for my antenna building. My HF rig is an old Icom IC-735 which works very nicely, and my 2 meter/440 dual band radio is a Yaesu FT7800.

Neither of these radios is well supported under Linux for rig control or memory management. I’m hoping to get some time to learn more about this and write some software to allow using these with the computer. In that interest I have bought a Rigblaster PNP which is a device that uses your computer sound card as a TNC to get you on the digital modes. I have used it for some CW work but nothing serious yet since I have to wait for the next testing date to get my General (or if I’m lucky, Extra) class license.

In the antenna department I have constructed a Bobtail Beam. This replaces my Slim Jim 2 meter antenna. It has substantial gain and very tight directionality. I have mounted it atop my antenna mast with another antenna I recently constructed, a 440mhz yagi. The rotator is an old Radio Shack Archerotor that I picked up on ebay wire and all for $41. It works great. The bobtail has a very low SWR curve along 2m which is just great for getting me into some of those fringe stations I had trouble with before.

The same can’t be said for the yagi-uda which has a wildly bouncy SWR curve all across the 440 band. Unfortunately some of the frequencies I like to use are in the higher SWR areas. I’ve picked up an older edition of the ARRL Antenna book on Amazon for $10 and I’m going to study antenna theory as time permits and see if I can’t design a “flatter” yagi. Perhaps I just need to add a half dozen more elements!

It turns out that the FBI has been data mining middle eastern food stores to discover terrorists with the alleged assistance of the major credit card lords.

I imagine they were sorely disappointed when they discovered that their list of terrorists was full of gourmets, expat Israelis, and vegetarians along with plenty of good flag waving Arab-Americans.

Hit em where they eat. Yep. I would hope that they both get sued for painful amounts of money by some of the importers of these foods if this proves to be true.

It’s true. I, Matthew Steven, have solved the abortion issue with a compromise that should suit all parties, and no law needs to be drawn up to implement it.

If a member of the Roman Catholic Church has an abortion, then by church rules they should suffer the consequences. They should have to go to prison for murder.

But the rest of the people who do not believe that it is murder should not have to pay for it.

Therefore the answer is to have churches exercise the power to imprison their own members, but with a few stipulations that already exist in law.

First, should the member publicly renounce their faith and agree to permanently be expelled from the church community, they will no longer be under the church jurisdiction and shall be free to leave whatever punishment has been imposed on them by their congregation.

Second, no permanent harm may be done- no executions, no torture, no repeat of the Spanish Inquisition. The churches are only imprisoning voluntary prisoners and are not allowed to break any laws, period. Nor do they have the authority of the state to execute people. The state will have the right to inspect these prisons at any time.

Finally of course the churches shall have to pay for their prisons on their own. Since their prisoners are only there for breaking church law but not national law, the rest of the nation who may not agree with the criminality of the act should not have to pay for it.