The characteristics of the doorknob are unknown. It's a junk box
special, with all of the lettering faded. Found an interesting article
on the web by I0IJ on RF vs. HF capacitors. I'll have to try
experimenting with more caps from the junk box.
Thanks for the suggestions.
73,
Steve, N2IC
On 03/12/2017 11:01 PM, Jim Kennedy wrote:
Garys suggestion is right on. I assume from the the cap you describe that its a
doorknob type. If so be sure it is RF rated and not a HV type used in power
supplies, Total different characteristics.
Jim
W7ouu
----- Original Message -----
From: "Gary Schafer" <garyschafer@largeriver.net>
To: n2ic@arrl.net, "Topband" <topband@contesting.com>, towertalk@contesting.com
Sent: Monday, March 13, 2017 4:00:42 AM
Subject: Re: [TowerTalk] What's heating up ?
Probably the capacitor. Try 2 or 3 smaller values in parallel to make your
2200pf. Then see if the drift is the same.
Or the coil wire size is too small.
73
Gary K4FMX
-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of
Steve London
Sent: Sunday, March 12, 2017 10:42 PM
To: Topband; towertalk@contesting.com
Subject: [TowerTalk] What's heating up ?
I am experimenting with the N4KG reverse feed method for 160 meters on a
tower with a lot of stuff already on it. I like the possibility that
elevated radials will be an improvement over my terrible, dry,
mountaintop ground characteristics.
As I transmit, the SWR creeps up, pretty significantly. Something is
clearly getting warm.
Possibilities:
- I am matching the 160 feedline with an L-network (series L, shunt C).
TLW says 7 amps through the capacitor, with 3 watts of dissipation. The
capacitor measures 2200 pf, the usual transmitting capacitor,
cylindrical, about 3/4" in diameter.
- The M2 balun feeding the 40 meter beam on the same tower. I monitored
the SWR on the 40 meter beam while transmitting on 160. No change in 40
meter SWR.
- The M2 balun feeding the KT-36XA on the same tower. I monitored the
SWR on the KT-36XA while transmitting on 160. No change in KT-36XA meter
SWR.
- Gamma match on homebrew 15 meter beam. Gamma match is just a piece of
RG-8 dielectric/center conductor inside aluminum tubing.
Suggestions on how to troubleshoot this ? Start by disconnecting the
feedlines to the baluns ? And once I determine which component is
heating, what then ?
73,
Steve, N2IC
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