My 2 cents:

The problem with Eggbeaters is that their design goal (omni coverage) sounds good but also means, by definition, equally poor in all directions. There is no such thing as "gain" for an omni. The closer its gain approaches 3D omni, in all directions, then the closer its gain approaches 0 dBi. Of course, placed over a ground plane, then they can achieve 3 dBi...

Now, on the other hand, satellites are nowhere near omni located. They are 10dB or more farther away on the horizon than when they are overhead. So you don't need as much gain at all overhead as you need on the horizon.

Further, satellites spend more than 70% of all pass times below 22 degrees! (where they are weak) and only 5% of their time above 45 degrees where they are 10 dB stronger.

The last thing then that you need for "omni" coverage for a non-pointing antenna, then, is gain that is UP (where the satellite is 10 times stronger).

See the scale drawings of a LEO pass: http://aprs.org/LEO-tracking.html

BUT on the other hand, most cubesats simply do not have the power to close the link to an OMNI antenna when it is on the horizon. It just cannot happen due to the distance and the omni only being at best 3 dB gain.

So the BEST "omni" in my opinion is a 19" whip over a large metal ground plane. Not only does it provide 5 dBi gain above 15 degrees or so on VHF, it also provides almost 7 dBi gain on UHF above about 30 degrees where it acts as a 3/4 wave vertical..

Yes, it has a null overhead, but the satellite is 10 times stronger then. And the satleilte is only in that null less than 2% of all pass times.

So the 19" vertical gives good gain from above the horizon in all directions and sacrificaes some gain overhead wehre it is not needed. And no omni antenna is going to hear these weak satellites all the way down on the horizon where they are 10 times weaker.

And a 19.25" vertical piece of wire over some chicken wire is pretty easy to construct, AND it does not need to be on the top of a tower, since it cannot hear to the horizon anyway. So jjust put it where it can see most of the sky above abouit 15 degrees and you will hear about all you can on an Omni. And it is not bad...

The value of a true circular hemispherical antenna is only when the satelile is strong (ISS) and it can be heard even on the horizon. Then the circula hemispherical antenna has the advantage of fewer nulls in its pattern. But you give up gain where it is most needed to get that.

And a low noise preamp is essential...

Just my 2 cents... Bob, WB4APR

-----Original Message----- From: AMSAT-BB [mailto:[email protected]] On Behalf Of Paul Stoetzer Sent: Tuesday, March 15, 2016 1:12 PM To: [email protected] Cc: [email protected] Subject: Re: [amsat-bb] Homebrew Up-Dated Eggbeater Antenna

Jim,

The key words here are "noise floor." Omnidirectional antennas can work for satellites when you have a low noise floor and short runs of very good coax (and/or a preamp).

As an example, I've listened for SO-50 a couple of times from here in Washington, DC with my Baofeng UV-3R+ and Nagoya NA-774 telescopic whip. I can hear the satellite a bit, but still quite nosily, above 45 degrees. Back in August, I was in a field in the middle of nowhere and heard it very well from 5-7 degrees above the horizon.

Another example is that some people report decent telemetry success from AO-73 (when in high power mode) using nothing more than 1/4 wave whip. I've never been able to decode a single packet with that type of setup here in the city.

Most people live somewhere between the two extremes I've presented here of "field in the middle of nowhere" and "apartment building in a major urban center" so your mileage may vary. Just keep in mind that in any receiving system, you are looking for an optimal signal to noise ratio. If you have no noise, you don't need much signal and omnidirectional antennas might work fine. If you have a ton of noise, you are going to need a lot of signal from the satellite, which means a beam with decent gain.

73,

Paul, N8HM

On Tue, Mar 15, 2016 at 12:46 PM, Jim Walls [email protected] wrote:

I built one about a decade or so ago and was grossly underwhelmed with

it.

I built it to use for a sat igate. I was able to decode maybe one or two packets per day. Everything else was lost in the noise floor.. Only had about 20 feet of RG-214 cable to the receiver.

Jim - K6CCC

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From: "Joe" [email protected] Sent: Tuesday, March 15, 2016 9:37 AM To: "amsat-bb@amsat org" [email protected] Subject: [amsat-bb] Homebrew Up-Dated Eggbeater Antenna Has anyone built this antenna, and what are your opinions? Meet all the claims being made?

http://wb5rmg.somenet.net/k5oe/Eggbeater_2.html

Joe WB9SBD

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Sent via [email protected]. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect

the official views of AMSAT-NA.

Not an AMSAT-NA member? Join now to support the amateur satellite

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Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb

_______________________________________________ Sent via [email protected]. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb

NO84 is only 300 mW compared to 2W for the original PCSAT and 5W for the ISS (currently). You need gain to hear it...

If you want a non-moving fixed antenna to hear NO84, I'd try a 58" vertical whip over a large metal ground plane. This would give you up to 7 dBi above about 30 degrees. Then you would hear it every day, but only for the better passes above 25 degrees. But you would hear it then.

And I modeled it in EZNEC and just a vertical over say 4 radials is not the same thing. That helps matching, but does not block the 3db part of the pattern into the ground. You need a real "ground plane" of a metal roof, or about 6 feet or more of chicken wire.

Easy for me to say, because I have not built one yet...

Bob, WB4APR

-----Original Message-----

Bummer! I'm looking for some sort of an Omni ant to use with NO-84