[Amps] RF Choke At Amp Output ??

[Jim W7RY]

The only problem installing anything shorted  (stub, antenna choke etc) on 
the output connector is that you arc the T/R relay when it goes into 
transmit mode!

Why not just put a choke or 100K resistor on the output of the tank? Then 
it's protected when not transmitting too.

73
Jim W7RY

----- Original Message ----- 
From: "Ian White GM3SEK" <gm3sek at ifwtech.co.uk>
To: <amps at contesting.com>
Sent: Wednesday, August 19, 2009 11:27 PM
Subject: Re: [Amps] RF Choke At Amp Output ??


> Bill, W6WRT wrote:
>>ORIGINAL MESSAGE:
>>
>>On Thu, 20 Aug 2009 01:37:32 +0000, RICHARD SOLOMON <w1ksz at q.com> wrote:
>>
>>>Several HB Amp circuits I see have an RF Choke across the Output. Other 
>>>than
>>>the obvious (protection against Plate Coupling Cap short), what are the 
>>>other
>>>Pro's and Con's ?
>>>
>>>I was thinking I should use an Ohmite Z-50 on the output of my 6 Meter 
>>>Amp.
>>>Comments ??
>>
>>REPLY:
>>
>>If your antenna is an open circuit for DC as many are, there would be a
>>HV pulse
>>applied to the coax through the plate blocking cap. If the DC leakage on 
>>your
>>coax and antenna is very low, this pulse could take a long time to decay. 
>>This
>>pulse is equal to your HVDC and might be enough to arc the coax, the 
>>antenna
>>itself or any switches, etc, in the feedline.
>>
>>It's been about 50 years since I used a Z-50, but from what I remember
>>it should
>>be ok.  :-)
>
> A shorted quarter-wave coaxial stub would make a more robust safety
> 'crowbar' than a choke wound with fine wire, and it also attenuates the
> 2nd harmonic in the FM band.
>
>
> -- 
>
> 73 from Ian GM3SEK
> http://www.ifwtech.co.uk/g3sek
> _______________________________________________
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> Amps at contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>


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