[Hammarlund] (Fwd) Re: GB> Sweep method for alignment.

[Kenneth G. Gordon]

Another one from the Glowbugs List.

Ken W7EKB

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On Apr 10, 2006, at 11:40 PM, Brad Thompson wrote:

> Hello, Ken and the group--
> Did anyone mention disabling (or switching off) the AVC if it's 
> present in the receiver?

Yes, we did.

> IIRC, doing so can make a difference in the
> swept  characteristics because the IF's response can get distorted
> by the AVC's action.
>
> 73--
>
> Brad AA1IP

   Hi Brad and the group,

   My take on this is that 'it depends'. With some of the better tube   
era receivers you need to thread carefully, as they may have the 
unbypassed cathode resistor in the IF stages, which will largely 
mitigate the detuning effect. Also high quality domestic VHF FM 
receivers may have one or more limiter stages, where you may have to 
choose the best compromise in signal strength for best overall 
passband shape.

   I sweep the 10.7MHz IF strips in my domestic tube receivers by 
snatching the sweep out signal from my scope and feeding it as 
modulation waveform to my signal generator, set to FM mode. Works 
remarably well, even though I will probably try to find a 'proper' 
sweep generator' some day.

   Vy 73 de

     Frank, OZ1IOC.

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