Using a small satellite dish as an 11 meter antenna

[dudmuck]

to have a gain of 10, a dish size needs to be the same as the wavelength.
and if you wanted a 20dB gain dish for 11 meters, it would need to be 35 meters (115 feet) in diameter.
For 30dB gain, it would need to be 110 meters or 360 feet in diameter, for 11 meters.

if you dont believe me:
gain = (9.87 * diameter*diameter) / wavelength*wavelength
diameter = sqrt((gain * wavelength*wavelength) / 9.87)

but the dish doesnt need to be solid metal, could be a wire mesh with no more than 3 foot gaps in the mesh. Still would be a monster.

 

[baublitz]

I took the receiver module off of the small satellite dish and mounted a small center loaded mobile antenna on the existing bracket by drilling a 3/8" straight down.

It works so well around Carson City, Nevada that everybody wants me to build them one.

Dick Baublitz KI7YF
blitz@pyramid.net

 

[Marconi]

No pictures from King Mudduck or Baublitz (an extra class no less) = more CB bullsh*t.

 

[RatsoW8]

I took the receiver module off of the small satellite dish and mounted a small center loaded mobile antenna on the existing bracket by drilling a 3/8" straight down.

It works so well around Carson City, Nevada that everybody wants me to build them one.

Dick Baublitz KI7YF
blitz@pyramid.net

Only in the bizarro world of CB radio could this happen...very amusing.

 

[Shockwave]

Just because you see some directional characteristics and a good SWR does not mean the antenna is working well. As has been already said any directional effect is due to shielding from the dish and has nothing to do with the dish acting like a parabolic reflector that would add forward gain. The dish is about 100 times too small. But more important is the orientation of the driven element (4 foot whip) with respect to the dish. First of all for the dish to be able to reflect energy back onto the driven element, the driven element should be parallel to the dish, not perpendicular. Second the driven element must be properly spaced out in front of the dish so that it's placed in the focal point of the dish. Not with it's feedpoint on the dish.

I won't argue that it doesn't work, it just doesn't work well and the dish is doing little more then acting like an insufficient ground plane. The signal would also be horizontally polarized and tend to talk broadside of the driven element. It could have some rejection on the back because it's not a balanced dipole and the ground plane would shield some signal from the back. Whatever signal you could produce with this dish would easily be surpassed by even the cheapest base ground plane. It's a 4 foot loaded 1/4 wave ground plane with a ground plane that's too small. That places it more then 2 db behind a simple half wave. That's not even including the major loss in cross polarization. This could be as much as a 20 db loss!

 

[BOOTY MONSTER]

i would not have thought a 2 foot or less diameter ground plane would be capable of tuning to 1.2 vswr on 11 meters with a 1/4 wave verticle radiator .

i also cant understand why the 1/4 wave firestick would have more gain out the top than off to the sides . i can see it on a full wave length verticle since the strongest lobes come out the end of the top of it .

i certanly have a lot left to learn about antennas though .

ill add another request for pics .

 

[Shockwave]

i would not have thought a 2 foot or less diameter ground plane would be capable of tuning to 1.2 vswr on 11 meters with a 1/4 wave verticle radiator .

i also cant understand why the 1/4 wave firestick would have more gain out the top than off to the sides . i can see it on a full wave length verticle since the strongest lobes come out the end of the top of it .

i certanly have a lot left to learn about antennas though .

ill add another request for pics .

The dish is not big enough to mimic a ground plane and produce the 1.2:1 SWR. You can be sure the coax and or the mast is acting as the counterpoise to reach the match. I would also expect maximum signal to occur off to the sides and not the dead front of this dish. The back may be the weakest signal but the front is not going to be the strongest. Check it again and you'll find there are two spots, one on each side that show the highest signal. Not one high spot right in front.

 

[Marconi]

I have been playing around with this thing to today and i actually got it to work. What i did was drill out the center of a direct TV dish and mounted a 4 foot fire stick antenna there. I have it up about 10 feet right now as i am still working the bugs out but after figureing out the ground for this antenna i have the SWR down to 1.2. It's seems to receive and transmit very well and it is very directional with great rejection which is what i wanted from the start of this little project. The only reason i tried this was out of boredom but i was wondering if any of you have tried something like this.

The reason i posted this here was because most hams like to experiment and i thought that some of you may have tried this in the past.

King Mudduck, based on the experimental aspect of your claim, can you tell us what you figured out regarding the ground, and then how or what did you do to the ground to get the SWR down to 1.2 as noted.

 

[Lazybones1222]

There aren't any pics cause it probably does not exist except in someones imagination.

 

[baublitz]

baublitz

Not to start a pissing war here but i used it last night on a 25 foot push up pole with a small TV antenna rotor and talked all over.....And yes i did my research on this while working out the bugs so i kinda understand why it should not work but i also know that it does work..... The rejection is killer and the damn thing talks great. It is very derectionail and if i put a 9+ signal on someone ( 10 miles from me ) while pointed in their direction then turn away the signal drops to under 2 s units.


Oh and i will get pics on here soon but it's really nothing to it. Drill the center out of a round Direct dish. Put your antenna stud and antenna in the center just as you would a mirror mount. Put it on a pole and play around with the ground until you get your swr down and have at it!


Will it out do a moonraker beam,no. But it was something fun to mess with at no coast to me and taking only a short time to build it was well worth it and it was fun...ain't that what this hobby is all about?

10/1/10
Hi this is Baublitz again Radio KI7YF....I think you will find that a small satellite dish is a good reflector and thats about all you need to worry about.
Just make sure that the small center loaded or base loaded antennas you are using are tuned up well.

Then you will see the directionability of the dish.

My test took a (2) meter signal on 146.520 with 45 watts all the way to Fallon from Carson City, Nevada. Some: (60) miles simplex to KC7ORU.

(11) meters was a lot shorter and I was able to make it to Gardnerville, Nevada some (30) miles away.

Regards: Dick Baublitz xpi

 

[Captain Kilowatt]

Somebody needs to study parabolic gain figures versus frequency of operation and then rethink this thread. FWIW a 6 foot dish is all but useless for even 2m.Rejection is simply a lack of coverage and not a display of forward gain.

 

[baublitz]

xpi

Just for your information my antenna is mounted in the center of a 22 inch Dish 500 system. This puts the center at 11 inches and it does make it very directional.

I use a rotator and it pounds a good signal downtown from my high up North side Radio Station. I did no tuning on the dish and it has no matching system or tuner in line. The only check I ever made was a (1.5) to (1) match with a Radio Shack swr meter and then disconnected it.

I will not argue the fact that you math-heads say it will not work...because the book shows it won't...but it does!

It is good enough to use locally and it sure gets rid of the strong static and skip we are used to in the Sierra Mountain area. I can tune in distant stations by just homeing in on them and have actually gotten a response out of the Orange County area of California.

I don't want to beat a dead horse to death...but if you don't believe how good it works...you could always build one and try it yourself.

By the way...the antenna I use is for a radio-telephone and that should not even work on 27 mhz at all...but...it does. Perhaps it just works because I am high above the city and although using just a 4 watt Navaho Radio with lots of modulation.

The output is similar to my magnetic loop antenna. Lots of magnet energy and not so much in the way of watts.

Dick Baublitz xpi
KI7YF
:bdh:

Not to start a pissing war here but i used it last night on a 25 foot push up pole with a small TV antenna rotor and talked all over.....And yes i did my research on this while working out the bugs so i kinda understand why it should not work but i also know that it does work..... The rejection is killer and the damn thing talks great. It is very derectionail and if i put a 9+ signal on someone ( 10 miles from me ) while pointed in their direction then turn away the signal drops to under 2 s units.


Oh and i will get pics on here soon but it's really nothing to it. Drill the center out of a round Direct dish. Put your antenna stud and antenna in the center just as you would a mirror mount. Put it on a pole and play around with the ground until you get your swr down and have at it!


Will it out do a moonraker beam,no. But it was something fun to mess with at no coast to me and taking only a short time to build it was well worth it and it was fun...ain't that what this hobby is all about?

 

[C2]

I had a 10-foot C-band dish on 23 cm that worked GREAT! Close to 30 dB gain.

The diameter of a dish needs to be multiples of the wavelength for which it is used.

 

[W5LZ]

I can see why this ancient thread was resurrected on 'St. Pat's day. I think it has to do with 'blarney'...
- 'Doc

 

[towerdog]

Low SWR and your claim it works well is just circumstantial. You ought to mount a 1/4" wave horizontally and I bet you it work just as well.

Dude, it is not acting as a parabolic dish, the coax is doing part of the radiating and when shit other than the antenna starts radiating, that 1.2 swr might change tomorrow when a bird takes a crap on it.

Besides, parabolic dishes are fed by a signal from an antenna that is in line with the dish, not 90degrees opposed.

I think for 11m you need something like this http://www.redicecreations.com/ul_img/9832seti.jpg