[amsat-bb] Re: UHF antenna help

John Heath g7hia at btinternet.com
Tue Nov 30 04:28:26 PST 2010

Hi Larry,

Just a thought about your problem.
I don't know the antenna but with a 30 in the code number I expect it is a high 
gain/narrow bandwidth antenna. 

If so your experience may be like mine.

I had a 2x21 element for a while and it was just too narrow beam. Its not the 
3dB lobe thats the problem. Its the incredibly deep null on either side.
reception goes from good to nil with just a small pointing error. Eventually I 
took a hack saw to mine and made it about 1/3 shorter and it was much better.  
Since the system worked before, could it be that you have an alignment problem 
which means that the you are tracking with the null and not the main lobe. 

73 John G7HIA


From: Anthony Monteiro <aa2tx at comcast.net>
To: zm1267 at gmail.com; amsat-bb at amsat.org
Sent: Tuesday, 30 November, 2010 11:55:44
Subject: [amsat-bb] Re: UHF antenna help

Hi Larry,

Did you check your new QTH's magnetic declination?


Tony AA2TX
At 08:14 PM 11/29/2010, larry wrote:
>Good evening,
>    Name here is Larry, N1MIW. I recently moved to a better (higher) QTH and
>finally got around to setting up the satellite station "almost" like it used
>to be, but am experiencing some reception difficulties on UHF. I'm hoping
>someone out here can help me diagnose what I'm doing wrong, or what the
>problem is. I am using a Yaesu FT-847 which is computer controlled, as well
>as the Yaesu G-5400 rotator. The antennas are mounted on a solid fiberglass
>mast only ~17 feet off the ground, and fed with LMR-400. The frequencies are
>correct for the satellite I want to use.
>    My problem is with the 436CP30 antenna. I cannot seem to find good
>results with it since my move - terrestrial or sat related. My SWR is around
>1.5:1 at 435MHz, and the polarity switch is working. I tried changing
>feedlines and removing the pre-amp, but I still cannot seem to make it work
>correctly. I am trying to receive SO-50 D/L, and VO-52 U/L, but both are
>just not working like I remember it being before the move. I don't have any
>broken or mis-aligned elements (that I noticed - I'll look again). The only
>thing I was looking into was instead of having it placed on the boom in a
>"+" pattern was making it an "x" pattern - would that make a difference? I
>don't remember hearing or reading about that anywhere, so I was looking for
>your opinion.
>    On a side note, what's your opinion of this antenna? Like I said, I used
>to have good luck with it, but I'm not sure what's different, except the new
>home. Should I get "horizon" to "horizon" coverage (plus or minus a few
>degrees)? Oh, I also looped the coax off the back like the manual states,
>but the improvement is very minimal. I checked the "jumpers" at the tuning
>box, and they seem OK too.
>    I'm running out of ideas, and any guidance would be appreciated. Thanks &
>looking forward to working the birds again!
>73's... Larry N1MIW
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