|[AMRadio] Re: GB> 75A-2 project|
brett.gazdzinski at verizon.net
Sun Jan 27 20:19:07 EST 2008
I would put a kiwa filter in place of the if cans, or
in between them.
Look at the standard filter module, it has no loss through the filter,
works like a mechanical filter, and you can tack the wires onto
the circuit without any drastic drilling or blasting.
I use there filters in the homebrew receivers and they work
better then you would believe.
Plus, they are small.
I dont have a diagram, but the filters work best just
after the mixer and before the 1st IF amp.
In the homebrew receivers, I used a broad band IF trans after the mixer
(from old tube type car radios!) then into the filter.
If you have any radio with a 455KHz IF, these filters are easy to add.
----- Original Message -----
From: <sbjohnston at aol.com>
To: <gzook at yahoo.com>; <amradio at mailman.qth.net>;
<glowbugs at piobaire.mines.uidaho.edu>
Sent: Wednesday, January 23, 2008 12:33 AM
Subject: [AMRadio] Re: GB> 75A-2 project
> Good idea on the swamping resistors... I did confirm that mine did not
> have the values for narrow bandwidth. Another list member pointed out
> early and late-model 75A-2s had different bandwidth performance (early
> favoring AM), so perhaps different values were used.
> Steve WD8DAS
> sbjohnston at aol.com
> Radio is your best entertainment value.
> -----Original Message-----
> From: Glen Zook <gzook at yahoo.com>
> To: sbjohnston at aol.com; amradio at mailman.qth.net;
> glowbugs at piobaire.mines.uidaho.edu
> Sent: Tue, 22 Jan 2008 7:27 pm
> Subject: Re: GB> 75A-2 project
> To widen out the bandwidth you can put additional
> fairly low value resistors across the i.f. cans. If
> you look in the manual you will see a note to remove
> the swamping resistors to narrow the bandwidth.
> Therefore, adding resistors in parallel with the
> existing resistors should broaden the bandwidth.
> Glen, K9STH
> --- sbjohnston at aol.com wrote:
> The widest bandwidth is 4 kHz (crystal filter out,
> just the tuned circuits in the IF stages) and I would
> like to add the capability for a wider choice for
> Hi-Fi AM reception. Anyone know of any articles on
> such a modification? Maybe in the context of
> "updating" the 75A-2 or 3 to mechanical filters? Or
> have any of your own ideas?
> Glen, K9STH
> Website: http://k9sth.com
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