[Amps] More parasitic choke questions

[Roger]

On 7/29/2010 6:31 PM, Bill, W6WRT wrote:
> ORIGINAL MESSAGE:
>
> On Thu, 29 Jul 2010 16:27:58 -0400, "Carl"<km1h at jeremy.mv.com>  wrote:
>
>    
>> I dont understand how moving the resonant frequency of the coil up and using
>> the same resistor raises the Q?
>>      
> REPLY:
>
> If you are talking about the suppressor coil, it is not resonant and
> has little effect on the VHF parasitic frequency because it is
> bypassed by a low value resistor. Its purpose is to provide a
> low-impedance path for the HF current around the resistor.
>    

Radio Handbook, 20th edition (17.22), " In the process of adjusting the 
resistor coil combination, it may be found that the resistor runs too 
hot. The heat is usually caused by the dissipation of the fundamental 
power int he resistor, which is an indication of too many turns in the 
suppressor coil. Just enough turns should be used to suppress the 
parasitic oscillation, and no more. Once the circuit is properly loaded 
and the parasitic suppressed, no parasitic power will be present and no 
power other than primary power will be lost in the resistor of the 
suppressor."

73

Roger (K8RI)
> If one did not care about bypassing the HF around the resistor, one
> could have only the resistor without a coil at all and the parasitic
> suppression would be equally effective. Power loss would be high of
> course, but it would work. I have never seen it done that way and I
> mention it only to help folks understand what the purpose of the coil
> is. I am not recommending it.
>
> 73, Bill W6WRT
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