[TowerTalk] HELP - Hy-Gain TH-3JRS

[Bill Cotter]

Gary,

Attached is the manual for the TH-3 MK3 that shows the (grounded) 
beta-match dimensions, and the coax choke. I think the hairpin may 
be the problem (inductor vs transmission line). I think I would 
construct the beta match as designed. It should be easy to make up 
from available materials. And, thoroughly inspecting the traps for 
electrical integrity and correct location is a must.

73 es GL Bill N4LG


At 09:19 AM 5/18/2025, Gary Mayfield wrote:
>Thanks Jim,
>
>         We did test with the long coax on the ground, and your 
> point is well taken about the balun vs a choke. We will take a 
> fine tooth comb to our hairpin recreation. I suspect that may be 
> a contributing factor.
>
>73,
>Joe n0sd
>
>-----Original Message-----
>From: TowerTalk <towertalk-bounces at contesting.com> On Behalf Of 
>Jim Brown
>Sent: Saturday, May 17, 2025 11:18 PM
>To: towertalk at contesting.com
>Subject: Re: [TowerTalk] HELP - Hy-Gain TH-3JRS
>
>On 5/17/2025 6:04 PM, Gary Mayfield wrote:
> > We have also added a balun made from type 31 ferrite material.
>
>Hi Gary,
>
>Don't know anything about that antenna or have a solution for your 
>problem, BUT -- if that #31 is a lot of turns of transmission line 
>wound around a 2.4-in o.d. core, it is a Common Mode Choke, NOT a 
>"balun."
>Antennas like yours are designed for specific matching networks or 
>feeding methods. A choke is used between the transmission line and 
>that matching system, whatever it is. These matching systems are 
>often called baluns.
>
>And with respect to your problem and on-the-ground testing -- did 
>you have a long length of coax on it when testing on the ground, 
>or just the analyzer connected with a few feet of coax?  Their 
>matching networks often want to be driven by that coax.
>
>Also, study carefully as you can what the original matching system 
>was.
>With gamma and hairpin matching, both the length and the diameter 
>of the
>rod(s) matter.
>
>73, Jim K9YC
>
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