[amsat-bb] Re: Antenna Opinions?

Bob- W7LRD w7lrd at comcast.net
Tue Sep 21 23:32:52 PDT 2010

Hi Greg et al 

I have been partial with the helix for satellites.  I run 10W to a 16 turn helix through 40 feet of LMR-400.  I rarely have an issue getting into AO-51.  I believe AO -51 is our only L band bird, I try to "exercise" my gear when the opportunity is there.  I experience very little fading with the L band uplink, input to the satellite is quite solid down to fairly low elevations.  The yagi would as you mentioned would better for  terrestial 1.2ghz stuff. 

73 Bob W7LRD 
----- Original Message ----- 
From: "Greg D." <ko6th_greg at hotmail.com> 
To: amsat-bb at amsat.org 
Sent: Tuesday, September 21, 2010 10:03:31 PM 
Subject: [amsat-bb]  Antenna Opinions? 

Hi folks, 

So, we had a swap meet a couple of weekends ago, and I found a bargain I couldn't refuse.  Of course, now I need to decide what to do with it...   

The Find was a 35 element 1296mHz antenna, well built and in excellent condition.  Linearly polarized, horizontal; supposed to be 23dBi gain.  Manufacturer, of course, is unknown.  No markings, but it does not look home-built.  By the mounting hardware, it looks like it was part of some sort of stacked array. 

The problem is that I already have a 1296mHz antenna.  Home-made, circularly polarized, 18 turns Helix.  Should be something like 17dBic, if the calculations are correct. 

In the shack, which is at the wrong end of 60' of 1/2" hardline and a total of about 15' of RG-213 or something like it, I have my Yaesu 736R and its 10 watts of screaming RF power.  No preamps. 

Which antenna should I keep up on the rotor assembly? 

Last weekend I put up the new antenna.  I've made one AO-51 LU pass with the new antenna, and I was not impressed.  Several times I couldn't get into the bird, presumably because of the crossed polarization.  But when I did get in, it was full quieting, even at low elevations.  I don't recall having this much trouble with the Helix.  I think AO-51 is the only current satellite on L-band, right? 

For other uses, there's nothing terrestrial to aim at, repeaters-wise; they're all hiding behind one or more hills, or went off the air years ago.  That leaves Weak Signal work (hence the horizontal mounting).  I do have one shot into the valley, to the North West, but probably slim pickings for contacts.  I haven't tried EME. 

I'm leaning towards putting the Helix back up, and passing the new one on to someone more able to use it.  What are your thoughts? 


Greg  KO6TH 

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