From: Garey Barrell 
Subject: Re: [drakelist] AM Filter Advice for TR-7


Garey Barrell  made an utterence to the drakelist gang
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Jim -

Something else is going on if you are hearing a signal that is 45 kHz away!

There is a 4-pole crystal "roofing" filter in the first IF (48 MHz) that 
is 8 kHz wide, which sets the maximum bandwidth of the receiver.  This 
is what sets the receiver b/w when the R-C network filter is installed.  
While this is not a 1.8:1 shape factor, 100 dB ultimate rejection 
filter, it certainly is going to be a long way down at 45 kHz from it's 
center frequency if everything is working normally.

Unless you are living next to CHU and listening to a QRP signal from 
Tibet, something else is wrong!  You don't have the calibrator switched 
on do you?  Or the RV-7/75 external PTO?  Is the card cage shield in 
place with ALL screws?   DO you live under the CHU tower?  :-)

73, Garey - K4OAH
Atlanta


Jim DiMauro wrote:

>"Jim DiMauro"  made an utterence to
the drakelist gang
>----------------------------------------------------------------------
>Hi All:
>
>I have a TR-7 that I'd like to use on AM every so often.  The trouble is
>that the radio doesn't have an AM filter.  A previous owner had installed
>the resistor mod that's supposed to act like an AM filter, but the result is
>far too wide to be useful.  For example, if I'm listening to a QSO on 7290,
>I can hear CHU on 7335.  Now that's wide!
>
>I'm looking for recommendations on AM filters, specifically which ones
>perform well.  Should I look for an original Network Sciences SL-6000 that
>Drake supplied, or are the better options out there like Sherwood and Kiwa?
>All input will be appreciated.
>
>Thanx & 73,
>Jim
>WA2MER
>  
>
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