[TowerTalk] What's heating up ?

[Steve London]

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 at largeriver.net>
> To: n2ic at arrl.net, "Topband" <topband at contesting.com>, towertalk at 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 at contesting.com] On Behalf Of
>> Steve London
>> Sent: Sunday, March 12, 2017 10:42 PM
>> To: Topband; towertalk at 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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