Dish Systems that I have Built or Helped Build

I have been building dish systems for use on AO-40 and EME for the last 3 years, all based on ideas published on this webpage. These dish systems are listed in order of tested receive gain. I have included pictures of these dish systems, especially when they represented a great idea that you might want to include in your dish system. Click on a picture to get a full sized version of the picture.

3' x 2' BBQ grill dish with standard linear feed

This is the most common and probably the least effective AO-40 receive system. It is available from a number of sources. It was in common use a number of years ago on the terrestrial MMDS 2400 MHz system for local distrubution of programming like a mini cable TV system. The polarization is linear (horizontal or vertical depending on how the dish is mounted). When used on AO-40 which is circular polarized it immediately results in a signal that is 3 db down. Additionally the grill is spaced a bit wide to be optimal, resulting in more loss.BBQ prices vary from free at the local hamfest to $130 for a new one. Often they are supplied with a converted MMDS downconverter that is already mounted. It is generally easy to tell those hams listening to AO-40 with a BBQ grill dish...they can't hear you well enough to get your call correct!

18" Direct TV dish with 5 1/2 turn helix feed on Christmas tree mount

The 18" dish has been very common recently for picking up commercial satellite TV, and recently there is a push to replace the simple dh a slight larger one with multiple pickups for several rooms. The dish has an offset feed and is not a short focal length device. Sometimes it may have DirectTV painted on the front; sometimes Dish Network. Same thing, though. If you pay more than $0 you got taken. I wound up a simple 5 1/2 turn helix over a piece of 1 1/4" PVC, spacing the turns about 3/4" between turns. To get the desired right circular polarization from the dish, you need to wind a left circular helix (like a mirror, the dish reflection inverts the polarization ). Holding the PVC form facing away from yourself, start at the top of the PVC form with about 3' of #6 copper ground wire and wind the helix to the left and outward to achive the correct polarization. Cut a 3 1/2" reflector from 1/16" aluminum,etc. and drill 5 holes to mount a type N male chassis connector about 3/4" out from the center so the center of the helix winds up at the center of the reflector. Mount the helix and downconverter so the helix is looking at the center of the dish with the middle of the helix at the focal point of the dish where the old feed system was located. The dish has about 1/2 the area of the BBQ, but the feed is circular, and the dish is solid, resulting in an output level about 1 db stronger than the BBQ.

The Christmas tree mount was modified to accept the azimuth rotator system for one of the bowling ball mounts described below. The elevation arm was made from a 12" length of 1/4-20 threaded rod pushing against a 1/4-20 nut. The DC motor came from an old dot matrix printer. The adjustable Xmas tree mount was very handy as I can set it down on any unlevel surface and plumb the mount in a few seconds.

3' x 2' BBQ grill dish with 1/4" screening and a 2401 MHz patch feed

You can gain about 4db if you spend an evening covering the BBQ with 1/4" screening or fence wire and replace the original linear feed with a circular patch. Cut the 1/4" screening so you can make the 1/4" screening conform to the original curvature of the BBQ dish. I tied the screen with about 50 ties made from #22 insulated solid copper hookup wire. Start from the center, working outwards.

The patch feed is described in the Feed Systems section of this webpage. The resulting antenna will be a bit heavier than the original but the 4 db gain is an evening well spent.

30" x 20" DirectPC dish on big gear and mini tracker arm mount

I was given a DirectPC dish by a local satellite shop which looked like an excellent way to built a small AO-40 receive station. JMI had a telescope project some years ago that utilized a thin 16" aluminum gear. The owner, Jim Burr, gave me a spare gear and a miniature tracker arm with about 10" of throw. I utilized a small DC motor from an old dot matrix printer to drive the azimuth gear. Puting all of this together with the usual 5 1/2 turn helix, a downconverter, and a couple of precision potentiometers driving a Satellite Tracker Junior resulted in a nice portable setup for listening to AO-40 at minimum cost. The gain with the larger dish was about 4 db more than the BBQ dish.

 

24" (60 cm) Direct TV dish with 5 1/2 turn Helix feed into AIDC 3731 downconverter on Bowling Ball mount, made for AO-40 mobile operation

I picked up a 24" DirectTV dish from a RadioShack.Com store going out of business sale for $20. It is very similar to the 18" model except with twice the surface area, the signal is 3 db stronger than the 18" hubcap size, making it about equal in gain to the screened BBQ.

The mount for this dish was obtained from Surplus Center (800) 488-3407 in Lincoln, Nebraska for $89. It was originally designed for an 18" dish mounted on an RV. The control unit spun the dish around in a search pattern when the RV was parked, stopping when the signal was found. Neat idea, but at cost of $3000 each, it never sold. Surplus Sales also offers it without the control unit, (ball only) for $50. But with a handheld remote even, it's gotta be the ultimate toy for the AO-40 couch potato! Much of the 24" mount was discarded, and the dish brackets were mounted as close and low to the ball as possible to better balance the elevation axis. The helix feed system is held to the original feed arm by two 6" long 1/4-20 bolts with a couple of 1/4" thick aluminum plates making up the downconverter sandwich.

Since the unit was designed for hooking onto the RV's 12 VDC sytem, it is a natural for mobile use. The dish and bowling ball easily fits into my Toyota Camry's trunk or backseat. Worldwide AO-40 communication from a rest stop! Use a several element yagi for the 435 MHz uplink. Not shown is my twin 5 element 435 MHz yagis in a circular polarized configuration that mounts to the bottom of the dish.

39" x 32" PrimeStar dish with 5 1/2 turn helix feed into UEK-3000 downconverter mounted on Yaesu G-5500

PrimeStar was a neat up and coming company bought out and disbanded by the 18" companies to eliminate the competition. They must have made thousands of these fiberglass wonders because they seem to show up everywhere. They are offset fed, so a 5 1/2 turn helix (described above) really works great. There are a number of different versions of this dish, but this oval sized one is the biggest, so it works the best. It has 4 times the area of the 18" hubcap, so you can expect about 7 db better signal from this bad boy compared with a 3' BBQ dish.

The downconverter shown is a UEK-3000 top of the line ($460) unit from SSB Electronics. Its best receiving downconverter of them all until you transmit. Then it is the worst desensing unit unless you widely separate the transmit and receive antennas or mount a filter on the frontend of the UEK-3000 which degrades the noise figure. A couple of type N adapters are used so that when the feed arm comes off the top the UEK case is upright to prevent the case collecting water and drowning the downconverter.

The PrimeStar is much heavier and larger than the previous dishes. I mount mine just as close to the azimuth axis as I can to prevent damage to my Yaesu G-5500 rotator in a storm. If I mount the dish so that the feed arm comes off the top, I can get the dish about 2"-3" closer to the rotator at 0 degrees elevation where I normally park this dish when done operating.

A couple of long cross yagis for 435 MHz and 145 MHz are also pointed by the G-5500. It makes an all satellite system that works not only AO-40 but also the various LEOs. I have this system on the top of a 50' foldover Rohn tower because this lets it see over my house and the surrounding 50' trees on our property. Some directions it sees AO-40 when my bigger but lower dishes can't.

I suggest you consider a two dish system, a high small dish and a low big dish.. The furthest DX occurs when the dish is on the horizon, and the big dish is blocked by houses and trees. Switching to my PrimeStar to avoid the pine attenuators has made many rare contacts for me.

4' TVRO counterbalanced dish with triband patch feed rotated by a Yaesu G-5500 on an R2D2 Jr PVC quadpod

If you want to run with the big dogs, it's going to take a big dish. This 4' dish has 4 times the area of the 2' dish or the PrimeStar dish above, so it has another 6 db of gain, making it about 10 db stronger than the linear fed 3' BBQ used by those not interested in hearing stations they want to contact. This dish was originally designed as a ground mounted C band (4 GHz) TVRO dish for use in areas which had a strong C band satellite signal. It is made of steel, so it is less prone to deformations unless soundly bashed, and it's heavy (~20 lbs). If you mounted it directly to your G-5500, you can count on losing the elevation rotator gears in the next storm. I mounted it on a special framework straddling the rotator made out of 1 1/2" PVC pipe and Tees from the local ACE Hardware. The pipe through the center is 1 1/4" galvanized, at least 2' long. For a permanent installation use 1 1/4" galvanized steel pipe throughout. Adjust the dish to rotator clearance to minumum distance at any elevation angle. The counterweights came from an old weightlifting set, or you can get new weights at the local sporting goods store or Walmart. I adjust the weights so that the dish with feed is about 1 lb nose heavy. The rotator doesn't even know it's there!

The feed system is a triband patch feed system described in the Feed section of this webpage. The 16 1/2" 435 MHz reflector gives about a 10% blockage which will be an insignificant signal loss in db, but will result in sidelobe degradation, a nuisance factor if bothered by 2400 MHz computer and telephone QRM. But it is a great all in one chunk ham antenna system for AO-40. The transmitting gain of a 4' dish at 435 MHz and 1269 MHz is not high enough to use the dish barefoot with a TS-2000 or an IC 910H. A 100 watt brick amplifier on 435 MHz and an 80 watt brick or a 2C39 / GS-7 / GS-15 cavity amplifier on 1269 MHz will do the trick.

The quadpod construction is described in the Mounts section of this webpage. It is extremely sturdy, lightweight, and can be disassembled to lie flat in the back of an SUV with the 4' dish on the top of the PVC. The Yaesu G-5500 dual axis rotator costs about $600 friendly price, and by adding a Satellite Tracker Junior and an old Laptop (I recently purchased a used Toshiba Laptop with a 150 MHz Pentium for $90) running NOVA, you come out with a very capable portable AO-40 antenna for less than $1000.

Four 7 1/2' TVRO dishes with triband patch feeds using motorcycle sprockets, pulleys & gearmotor rotators

This my choice for the ideal AO-40 antenna system. Smaller antennas are ideal for those who made the mistake of living in an area with antenna covenants. But small antennas are weak! A 7 1/2' dish + a triband patch lets you run barefoot for most of your operation on AO-40. Most of the 7 1/2' dishes I have been given are made of aluminum mesh which I can assemble and lift all by myself. But make sure you get one that did not come off second best in a hailstorm. The surface of a dish on 2401 MHz should be a parabola to within 3/8". A bunch of 1/4" hail or rock dings won't look pretty, but the dish will still work like one right out of the box. See the Mounts section of this webpage for more details on the drive system.

A 7 1/2' to 8' dish has about twice the area of the 4' dish above, so we can anticipate about 6 db more gain on both transmit and receive making it about 16 db stronger than the good old BBQ dish you used to think was great.

I use a Satellite Tracker Senior to drive all my 7 1/2' and larger dishes. It keeps them pointing at AO-40 within 1/2 degree all day long. The larger the dish the more accurate your pointing has to be as the gain is obtained by narrowing the beamwidth. A 7 1/2' dish has about 5 degrees beamwidth, a 10' has about 2 1/2 degrees beamwidth and the 16' dish below has about 1 1/2 degrees beamwidth on 2401 MHz.

7 1/2' TVRO dish with dual band patch feed rotated in elevation and azimuth by three tracker arms

I recently built up this mount system just to prove it can be done. Well, it does very well. The tracker arms can be found anywhere, and with a little luck you can get some free to almost free ones. The elevation tracker arm is like the sprocket and pulley mounts above, but the azimuth rotation is much different. A tracker arm is a linear device, and we are trying to make it move in an arc. Without too much effort it will provide 90 degrees of arc, and with some care maybe 120 degrees. But it's push goes to pot when it is at the end of travel points. By using two tracker arms, each pushing for 90 to 120 degrees against a common floating idler arm between them, you can achieve 180 to 240 degrees of arc, more than enough for AO-40's orbital movement, and enough even for EME using JT44 or JT65 (see webpage).

10' Janeil TVRO dish with triband patch feed

Another 3 db of gain is available for transmit and receive if you use a 10' dish with your triband patch. A 10' dish is a good 3 S units improvemet over the 3' BBQ dish. The 10' dish was very common in the early days of TVRO when the preamps were not so good, so 10' dishes tend to be older than the 7 1/2' dishes. The 10' dishes were generally made of steel or fiberglass, both much heavier than the newer aluminum mesh dishes. So figure that extra 3 db of gain is going to cost you 10 db of more effort. But the price is usually right (free) so go with the flow. I had to use a gin pole system to get the 10 steel dish off the mount to put on the motorcycle sprocket on the top cap and lazy Susan bearing on the ground post for azimuath control. I can lift a 7 1/2' aluminum mesh dish with one hand. More about this 10' dish and mount can be found elsewhere on a this webpage.

14' TVRO dish with dual circularity triband patch feed for AO-40 and EME use 

                                   

Here's a question for you. How big in diameter is a 14' dish? Answer: 12' rim to rim. The TVRO industry measured the size of a dish not by the rim straight across to the opposite rim but size was measured from rim through the concave center to the opposite rim. That way the dish specs made it sound bigger. The 14' fiberglass TVRO dish was free. To put it into service working AO-40 took 6 months and $3000. It took 20 db of effort to gain 3 db.

The mount for the 14' dish is completely different from the previous mounts. The basic problem is weight. The 14' fiberglass alone weighs about 400 lbs. So I assembled the 14' dish face down on the ground. The clothesline pole design azimuth axis is built inside a section of Rohn 45 tower, and lowered to dish. After attaching the dish, the assembly is winched to vertical. Was it worth it? 3 db for $3000 and 6 months? Probably not. But the devil made me do it!

15' WWII surplus dish and 200 lb counterbalance, with dual circularity triband patch feed for AO-40 and EME use, built for W9NTP

20 years ago, Don obtained a WW2 dish from Purdue University for $1. It sat propped up behind his barn for many years. I designed a large sized counterweighted clothesline pole mount for the dish, and 2 months later the dish was turning. Although Don estimated that the dish weighed about 300 lbs, it took 200 lbs of counterwights on a 4 to 1 lever arm to balance the dish, meaning the dish alone weighs 800 lbs.

The 6" ground tube is not buried in the concrete. Instead, the ground tube and braces are butt welded to a thick steel plate. 3/4" threaded rods are buried in the concrete, and the 6" tube can be plumbed by adjusting the 3/4" top and bottom holding nuts on the threaded rod. Good thing, because when I checked the post for plumb, it was off by 2 degrees due to concrete pad settling. This much offset will make make horizon to horizon tracking impossible for a narrow beamwidth big dish like this.

16' Paraclipse TVRO dish with dual circularity triband patch feed for AO-40 and EME use, designed for and built by W4SM

Stacey was given a 16' dish a few years ago after the mount's elevation arm was destroyed in an East Coast ice storm. After viewing pictures of the damage, it was obvious what the design flaw was and how it could be simply corrected. But Stacey wanted to build the ultimate mount for this 16' Paraclipse dish. So with my experience of designing the counter balanced mount for W9NTP and the tower mounted 14' for myself, Stacey and I designed a magnificent mount for his 16' dish. Shortly after it was erected, even before it was finished, it survived a hurricane. The dish rebuild and mount took Stacey about a year to complete. The resulting dish is almost 4 S units (22 db) stronger than Stacey's BBQ grill dish.

30' dish offer

I was offered a free commercial Scientific Atlanta 30' dish last year. Tongue in cheek, I told the wife about the offer. She said, "No way!" The next morning she came up to me and said, "I know if you want it, you'll get it. But if you get it, I get a new computerized sewing machine with all the software." ($10K). The Scientific Atlanta mount would need a new azimuth axis to work AO-40 and EME (at least $10K). Cost of the "free dish": At least $20K and a year of work. I turned down the offer. And 5 S units over a BBQ grill dish.

60' dish

Really. There is a 45 year old 60' dish sitting unused and unmaintained in Eastern Colorado at a site suitable only for rattlesnakes and sand fleas. It was built in 1957 by a bridge company from Brooklyn, NY for the US government to test scatter propagation potential. But Sputnik showed that satellites had more potential. It was sold at a government auction 10 years ago for $17K to $33K, depending on whom you talk to, a very small fraction of its original cost. The current owner is advertising it in QST for $375,000. But no takers. So it's your chance to get 6 S units over a BBQ grill dish. Plan to spend several $10K to restore and upgrade.

Two identical dishes were also built 200 yards apart at a government site North of Boulder, Colorado. K0DJV put one of my dual circularity 1296 MHz patches and a low noise preamp at the focal point and copied signals from a recent EME contest at S7. But the site doesn't allow transmissions, a definite deterrent to ham operators.