At 11:17 AM 3/27/2008, Bill Dzurilla wrote:
I have just been involved with the sats since February and also wanted an omni for base station use. I started with a simple 1/4 wave ground plane (19" for 2m, 6 1/2" for 70 cm), later tried homebrewing Jerry's Eggbeater II, and then bought a second-hand M2 eggbeater and the ARR preamp. I noticed little or no difference between the 3 antennas, certainly not enough to justify the relatively high price of a new M2 eggbeater. The preamp helps a lot but, as Jeff says, SO-50 is still quite weak.
For a simple omni the 19-inch ground plane works as a 1/4 or 3/4 wavelength vertical on either 2m or 70cm respectively. I used one with a P432 ARR preamp ($79.95) to record AO-51 telemetry very well. This is a plain GasFet preamp with 0.5 dB NF so do not transmit into it. The 25w switching ARR preamp is worth the piece of mind in that respect. I think you get much better low noise performance with ARR over the cheaper preamps.
Have not tried the Lindenblad. Not many are using it or talking about it, so I doubt it is all that great. Same for the turnstile.
I am thinking to build a set of these antennas for non-tracking use. Tony AA2TX design looks good. (http://www.arrl.org/qst/2007/08/monteiro.pdf).
I do far better with a 5w HT and a handheld Arrow than I do with an IC-7000, ARR preamp, and any of the omnis I have tried. However, unlike some people, I don't really enjoy standing in the yard holding the Arrow antenna for 15 minutes. So I usually work from inside.
If you do go omni, get it high enough to be in the clear. And unless you get a preamp, use very good coax and keep the line as short as possible. You can get a 70cm receive-only preamp from Ramsey Electronics for $17, but with that you'll need a separate coax line for the 2m uplink, or a duplexer. The ARR is the cheapest RF switching preamp and it's over $125.
I also homebrewed one of Kent's dual band LEO cheap yagis, see http://www.wa5vjb.com/references/Cheap%20Antennas-LEOs.pdf. It can be built for $10 and it works as good or better than the far more expensive expensive Arrow, although it's not quite as portable. As Jeff mentioned, the Arrow unscrews into very small pieces and fits in a suitcase, very nice for air travel. The cheap yagi elements are glued to the wood boom, will fit into a car trunk but is not suitable for air travel, unless someone comes up with a different way to attach the elements to the boom that allows easy removal.
Have not tried this, but I'm almost certain that a cheap yagi mounted at a fixed 20-30 degree elevation and rotated with an old TV rotator will be less expensive and give substantially better results than any omni, even an omni with a preamp.
For couple years I had the 2m portion of my Arrow installed on az-el rotator and it worked well. I would recommend the fixed elevation short yagi as next better than an omni for simplicity with Leo sats. Either an Arrow or home-built will work.
I have the full AO-10/13 long x-yagi's on az-el rotator for the next Heo, but for simpler Leo operation the small fixed rotator or Lindenblad are fine.
***************************************************** 73, Ed - KL7UW BP40iq, 6m - 3cm 144-EME: FT-847, mgf-1801, 4x-xp20, 185w http://www.kl7uw.com AK VHF-Up Group NA Rep. for DUBUS: dubususa@hotmail.com *****************************************************