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@contesting.com> On Behalf Of
Jim Brown
Sent: Saturday, May 17, 2025 11:18 PM
To: towertalk@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
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|