Eggbeaters are ideal antennas for omnidirectional coverage with dual polarization for strong signals with minimum fades....
But like any antenna, to get gain somewhere, you have to give up gain elsewhere. Here are all the issues and my opinions.
1) Satellites on the horizon are 10 dB farther away than ones above 22 degrees (2000 miles vs 700 miles). 2) Splitting gain into circular polarization (Eggbeaters) loses 3 dB compared to incoming linear polarization 3) Small sats usually have linear antennas or, if they have cross polarization then even if they are RHCP when approaching, they may be LHCP going away, thus you still have a 50/50 chance of having a polarization mismatch, though having both polarizations will minimize most fades. 4) Most small Amateur sateliltes have less than 1W transmitters and simply cannot be heard on the horizon without several dB gain.
My Conslusions are: 1) An Egg beater is ideal for STRONG satellites (Think ISS with 10 Watts). It will minimize fades horizon to horizon. 2) But there are NO, NONE, NADA current amateur satellites (not even the ISS right now) at that power level. 4) Hence an eggbeater even with a dB or so gain on the horizon simply is not going to hear anything until the satellite gets above about 20 degrees (when it is 10 dB closer) 5) So, why even bother with an eggbeater. 6) Use a simple 19.5" quarter wave vertical over a ground plane (for 2m). It will have 5 dBi gain above about 15 degrees (several dB better than an eggbeater). 7) and it will ALSO WORK even better as a 7 dBi gain UHF antenna (3/4 wave vertical) above about 25 degrees up to 70 degrees (6 dB better than an Eggbeater)...
AND it is DUAL band as well! (on the same coax!)
BUT, what about the donut hole overhead for these vertical antennas?
Forgetaboutit.!.... The satellite is only above 70 degrees about 1% of the total pass times per day! And then for less than about 30 seconds!
To visualize the orbit actual geometry see the scale plot on: http://aprs.org/LEO-tracking.html
So, in my humble opinion, a 19.5" vertical whip antenna in the middle of a car roof (neat ground plane) will give pretty good satellite coverage. It will have some fades due to only one polarization, but the strong part of the cycle will be 3 dB stronger than it would be on a dual polarizatiaon antenna. And you don't have to be parked on a mountain. Since again, no omni antenna can hear these weak satellites on the horizon anyway, so as long as the trees are far enough away to give you sky above about 20 degrees, you will have about the best coverage you can get for about a 20" of copper wire and a nice ground plane..
In my opinion anyway.
AND*** If you want to hear them all the way horizon to horizon, buy a $65 TV rotator and attach a small 5 to 6 element beam tilted up at about 15 degrees and hear them all! See above web page...
Bob, Wb4APR
-----Original Message----- From: AMSAT-BB amsat-bb-bounces@amsat.org On Behalf Of Devin L. Ganger via AMSAT-BB Sent: Friday, May 3, 2019 4:19 PM To: AMSAT-BB@amsat.org Subject: [amsat-bb] ARRL Antenna book, eggbeater antenna designs
Greetings, programs!
I'm looking to work with my son (who will be studying to get his Technician license later this month) on building a UHF/VHF pair of eggbeater antennas. I've found a few papers online, but does anyone have a good reference to a detailed design?
Does the ARRL Antenna book latest edition have any significant coverage of eggbeaters at all? I have an older version that has nothing.
Also, most of the designs I see are for a single band. If you're deploying a pair for satellite operations, do you simply attach them through a duplexer? I have a Diamond MX-72N that I picked up a while ago for using with dual Baofengs, but it's been sitting in my drawer since I picked up my TH-D72A. It has a 1.6~150MHz lead and a 350~460MHz lead.
Thanks in advance for any pointers you might have.
-- Devin L. Ganger (WA7DLG) email: devin@thecabal.orgmailto:devin@thecabal.org web: Devin on Earthhttp://www.devinonearth.com/ cell: +1 425.239.2575
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