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Re: Suggestions for Mode L antenna




Hi Ron,

I built the helix because they are fairly tolerant of slight differences in materials and assembly dimensions.  I am by no means a precision builder, so this seemed right for me.

I have an ICOM 1271A in the shack, which is supposed to put out about 10 watts.  This goes to about 5 feet of RG-214 (I think - it's the 50 ohm stuff that looks like RG-8, but has better shielding), to a box outside where there's supposed to be a lightning arrestor.  That's on my list of things-to-buy-soon...  Right now the arrester is just an N-N barrel connector.  That feeds about 60' of Andrew hardline (LDF4-50A) up to the roof, where there is another barrel connector and another about 5' of that RG-214 to go around the antenna rotor to the antenna itself.

At 1.2 ghz and 50-odd feet, I expect that hardline is going to be a requirement.  Or you could mount a power amp and pre-amp at the other end of the coax, along with power and sequencing logic.  The hardline I got was a trade from another ham who worked, I'm guessing, in the CATV, Telephone, or similar industry.  I got something like 180 feet of it in trade for a short 70cm antenna, enough for 3 runs to the roof.  There was a bit of a kink in the middle, so that run is on a lower band :-).  Ask around, you might be able to scrounge up something.

Good luck,

Greg  KO6TH


----------------------------------------
> Date: Mon, 12 May 2008 07:50:44 -0500
> From: rnutter@networkref.com
> To: ko6th_greg@hotmail.com
> CC: amsat-bb@amsat.org
> Subject: Re: [amsat-bb] Re: Suggestions for Mode L antenna
>
> Greg:
>
> Thanks for your option.  My antenna building abilities havent been the
> best, so I am looking at commercially made antennas.
>
> What type of coax/feedline should I use  ?  I will probably have the run
>   under 50 ft.  I would hope I dont have to use hardline as that will
> probably be very expensive with the price of copper.  As I get close to
> the antenna, should I shift over to a different type of coax/feedline so
> that I can rotate the antenna to track AO-51 ?
>
> Ron
> KA4KYI
>
> Greg D. wrote:
>> Hi Ron,
>>
>> I've done ok on AO-51 with a homemade helix.  See http://home.wavecable.com/~ko6th at the bottom of the page.  I also have watts in the shack, but a full az/el rotor system.  I don't know how sharp the pattern is for the helix, so I don't know how effective a fixed elevation system will be.  But from the reports I've received, the 10 watts and my 60' of hardline with about 7 feet of RG-214 at each end seems to be quite adequate.
>>
>> Good luck,
>>
>> Greg  KO6TH
>>
>> ----------------------------------------
>>> Date: Sun, 11 May 2008 20:49:23 -0500
>>> From: rnutter@networkref.com
>>> To: amsat-bb@amsat.org
>>> Subject: [amsat-bb]  Suggestions for Mode L antenna
>>>
>>> I am considering purchasing the 1.2 ghz module for my IC-910H.  For my
>>> satellite work, I have my antennas angled at about 20 degrees since I
>>> dont have an az/el rotor.  This setup worked reasonably well with Mode S
>>> this weekend.  What are my chances to be able to work Mode L with this
>>> kind of setup ?  Also, I would appreciate any suggestions for an antenna
>>> that I could use.  With only 10 watts, I am not expecting a great signal
>>> but I would hope to have at least a readable signal.  Also, would
>>> appreciate any suggestions as to coax/feedline that I should look at
>>> buying ?
>>>
>>> Thanks,
>>>
>>> Ron
>>> KA4KYI
>>> _______________________________________________
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