From: Garey Barrell 
Subject: Re: [drakelist] TR7 X-talfilter bandpass


Garey Barrell  made an utterence to the drakelist gang
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Dick -

If you are saying what I think you're saying, the ultimate rejection of 
all the filters is specified as greater than 100 dB.  IF the passband 
tuning is set correctly, either variable or the five pots up on the 
power supply board, you should NOT hear the "other side" of zero beat!

I would suspect the -5V supply (actually ~-3.5V) or the MPN3404 PIN 
diodes that switch the filters in and out.

73, Garey - K4OAH
Atlanta

Drake C-Line Service Manual
http://hr99.home.mindspring.com/R-4C_Servicez/>



Dick Harms PA2DW wrote:

> Hi all,
>  
> Yesterday I worked on the TR7 of Evert/PA2KW who had a loss of 20 dB 
> of receiver gain. It appeared that the J310 on the second filter PWB 
> did not get its supply, because the 47 Ohm resistor in the drain was 
> "cracked". Hard to see, but easy to measure...
>  
> After we but back the TR7 in service, we listened the band on CW with 
> both the 250 and 500 Hz filter. Evert has had a TR7 before and he 
> recalled that the bandpass in CW on his previous TR7 was better. What 
> we noticed is that the CW signal was audible at both sides of the 
> zero-beat point. The difference between the signal that was within the 
> filtercurve and the one that should be out of that, was only 20 dB. We 
> adjusted the PBT carefully but that gave no improvement. At home I 
> checked my own TR7 and it appeared almost the same! On my R4C it was 
> however much much better, certainly when I switched on the Sherwood 
> 600 Hz roofing filter of course.
> Now the question is, is this indeed normal on the TR7? Or do Evert and 
> I have some problem in the x-tal filter?..
> Any info is most wellcome.
>  
> Best 73, Dick/PA2DW

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