[Amps] Shunt Feed Tower Issues

[Barry Kirkwood]

Would help if you told us abit more about the tower set up.
How much capacity are you using to tune out the reactance?
It may be possible (even easy) to rejig the feedpoint so that you are 
feeding at a lower impedance point, hence lower voltages.
Think vacuum variable a bit overkill, myself, unless you are amongst the 
idle rich.
FWIW; I am using 50ft (15m) tower with 20ft (6m) spike to loading wire to 
make inverted L.
Gamma match at 40ft (12m) with heavy wire, spaced about 1.2m avearage from 
lattice tower.
Works against 2 elevated 1/4 wave radials.
At 1830 is about 300 ohms, comes to 50 ohms 1:1 with about 300pf series.
Tuning cap English Cyldon 500pf , gap between moving plates approx 5mm (air 
space is less)
No sign of arc from 2 x 3-500z.
73
Barry

end
Barry Kirkwood PhD ZL1DD
Signal Hill Homestay
66 Cory Road
Palm Beach
Waiheke Island 1240
NEW ZEALAND
ph/fax 64-9-372-5161
www.waiheke.co.nz/signal.htm
----- Original Message ----- 
From: "Harold B. Mandel" <ka1xo at juno.com>
To: <yv5mbx at arrl.net>
Cc: <amps at contesting.com>
Sent: Monday, November 01, 2004 11:13 PM
Subject: Re: [Amps] Shunt Feed Tower Issues


> Dear Javier,
>
> Your absolute best solution is to use a vacuum variable to tune the
> tower.
>
> Choose one with enough KVaR and HV rating to be well beyond 2X your
> maximum
> transmitted power so that voltage potentials arising from
> frequency-originated
> mistunings are within its working range.
>
> Hal Mandel
> W4HBM
> On Mon, 1 Nov 2004 13:46:24 -0400 "Javier" <yv5mbx at arrl.net> writes:
>> I was using an air variable capacitor (bought from Henry Radio) to
>> adjust my tower on 160 mts, the swr were about 1.2.
>>
>> Last friday I installed a more powerfull amp (1300 watts) and after
>> few hours of operation the capacitor arced so  along the weekend in
>> installed a cpacitor bought as Kit from Ten-Tec but the swr it abt
>> 2.
>>
>> I have stored an old Dentron GLT-1000 Tuner. Is my understanding
>> that the power rating of this device is abt 1000 watts, but I would
>> like to know if using this device could be suitable to be used in
>> 1.8 Mhz at 1300 watts.
>>
>> Ideas welcome.
>
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