[TowerTalk] RG-8/RG-213 as C in gamma match

Jan Erik Holm sm2ekm at telia.com
Sun Dec 30 01:38:04 EST 2007

Yes this works excellent. For very high power you can use
RG217 or even RG17.
Right now I have about 10 Yagis using this type of gamma.

I´ve measured this and for me it gave much better
return loss compared to a gamma match using an inner
piece of tubing and teflon tube dielectric, that set up
also used a small machined housing for the connector,
probably that set up introduced more stray L.
I´ve measured return loss down to 40 dB or so, with the
gamma Al tube and housing it usually was around 25 dB or so.
Not that a 40 dB return loss is needed but still it´s nice.

73 Jim SM2EKM

donovanf at starpower.net wrote:
> Peter,
> RG-8 will work very as a gamma match capacitor on a 40 meter Yagi.  If
> you can get the correct size aluminum tubing, you can simply insert the RG-8 dielectric into the gamma tube.  I did this for many years
> with my full size 40 meter Yagis, until I converted the matching to
> T-matches.  I still have three 20M Yagis that a gamma match fed, and
> they work very well.
> 73
> Frank
> ---- Original message ----
>> Date: Sat, 29 Dec 2007 20:13:24 +0000
>> From: Peter <pc2a at pi4cc.nl>  
>> Subject: [TowerTalk] RG-8/RG-213 as C in gamma match  
>> To: Towertalk List <towertalk at contesting.com>
>> Hi
>> In preparation to build a new 40 meter beam, I'am searching 
>> possibilities to make the matching C
>> Normally in a smaller beam We using 2 different diameter of aluminum 
>> tube with an isolated tape between them
>> But a gamma match for 40 meter will be in the 2-3 meter range. Due wind 
>> the match will be slight moving in and out and for long term  will this 
>> be a  point of failure.
>> I was thinking if it was possible to make the C from RG-8 With the 
>> 100pf/meter it will be 3-5 meters long.
>> I can make first with a air varible C the match to find the exact value 
>> of the C.
>> Is this done before?
>> Peter
>> PC2A

More information about the TowerTalk mailing list