[Drake] TR7 PA problem: part 3

[ltaft at charter.net]

Guido,

I think the predriver board has a increasing gain with frequency response.  Also the 15 and 10 meter bands switch in gain increase networks in the feedback ALC loop.  This means that Drake designed in compensation for the amp decreaseing gain versus frequency.  

Your statement that drive input level signals are constant over the bands means something is wrong in the early part of the xmtr.

I will try to make some measurements to confirm.

73, Larry  K2LT
drakerepair.com 
> 
> From: "ik2bcp - Guido Tedeschi" <guido.ted at tin.it>
> Date: 2005/02/05 Sat PM 10:54:26 GMT
> To: <drake at mailman.qth.net>
> CC: ltaft at charter.net,  ltaft at 2fords.net
> Subject: Re: [Drake] TR7 PA problem: part 3
> 
> Hello Larry,
>     many thanks for the answer.
> Do you say that about 12dB of gain difference between 1.8 and 18MHz is 
> normal?
> If my PA is fine, what do you think about my problem?
> Please, look at my previous two message on the list ("TR7 PA problem" and 
> "News about TR7 PA problem")
> 73 and thanks
> Ciao
> Guido, ik2bcp
> 
> 
> ----- Original Message ----- 
> From: <ltaft at charter.net>
> To: <drake at mailman.qth.net>
> Cc: <ltaft at 2fords.net>
> Sent: Saturday, February 05, 2005 5:29 PM
> Subject: Re: [Drake] TR7 PA problem: part 3
> 
> 
> > You should have an increase in drive signal as the frequency increases. 
> > The gain of the amp decreases with increasing frequency.
> >
> > Using an oscilloscope on the input to the amp board I measured the 
> > following:
> >
> > At 3.5 MHz
> > Input to amp board 1.6 volt peak to peak.
> > Output 120 watt output.
> >
> > At 28 MHz
> > Input to amp board 6.2 volt peak to peak.
> > Output 85 watt output.
> >
> > 73, Larry  K2LT
> > drakerepair.com
> > 800-687-9161
> 
> 
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