[amsat-bb] Re: L and S band antennas

Greg D. ko6th_greg at hotmail.com
Sat Apr 18 15:07:32 PDT 2009

Hi James,

The current mode L/US on AO-51 is really fantastic.  Having the dual downlink lets you confirm on 70cm that you're getting through on the L-band uplink, while you are madly fishing around the 2.4 ghz band to find your signal there.  There's nothing more maddening than having to deal with a whole pile of unknowns, any (and all) of which will prevent success.  Then next week (now that you've got the hang of 13cm), it switches to V/S.  (Kudos to the AO-51 command team!)

But, I think you're still going to have a hard time with the L uplink.  Your 23cm HT is going to need a lot of antenna in order to get into AO-51, except under the best conditions.  I run 10 watts from my Yaesu 736R into an 18 turn helix.  There's a lot of cable in between the two, but most of it is 1/2" hardline.  At low elevations, it takes all of that 10 watts to get through, though when the satellite is overhead I can turn it down a bunch.  Fortunately, helix antennas are easy to make, and pretty forgiving in the exactness of construction.  

For 13cm receive, nothing beats a dish.  But if you want to go portable, you might bank on the fact that AO-51 is a lot closer than the other (in)famous S-band bird, AO-40 (RIP).  Where a dish was required for AO-40, I believe some have received AO-51 with just a helix.  You might Google around or search the BB Archives for references (or others - chime in!).

Good luck!

Greg  KO6TH

> From: davenbeck.engineering at gmail.com
> To: amsat-bb at amsat.org
> Date: Sat, 18 Apr 2009 20:05:11 +1200
> Subject: [amsat-bb]  L and S band antennas
> As a relative "newbie" to satellites, all this talk about the current L/u mode on AO51, and next weeks V/s mode, looks like a lot of fun. I have 23cm tx and 13cm rx capability, but no antennas at present for either band. My current operating conditions are limited to portable operations only, and I wonder if any other list members can suggest/reccomend any hand held/portable/easily packed away designs that work well? (commercial or homebrew) As well as my 910H, I have a Kenwood TH-59 23cm HT, and I can confirm that 700 milliwatts into the HT's ducky won't cut it! (tried last night) Any suggestions welcome                        
> regards and 73
> James - ZL4JM
> QRPARCI #13307
> AMSAT #36899
> RF70bs
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