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. http://www.kiwa.com/index.html Brett N2DTS ----- Original Message ----- From: <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]>; <[email protected]>; <[EMAIL PROTECTED]> 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 > > [EMAIL PROTECTED] > http://www.wd8das.net/ > ------------------------------------------------ > Radio is your best entertainment value. > ------------------------------------------------ > > > -----Original Message----- > From: Glen Zook <[EMAIL PROTECTED]> > To: [EMAIL PROTECTED]; [email protected]; > [EMAIL PROTECTED] > 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 > > > --- [EMAIL PROTECTED] 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 > > > > _________________________________________________________________________ > ___________ > Never miss a thing. Make Yahoo your home page. > http://www.yahoo.com/r/hs > > > > > > > ________________________________________________________________________ > More new features than ever. Check out the new AOL Mail ! - > http://webmail.aol.com > ______________________________________________________________ > Our Main Website: http://www.amfone.net > AMRadio mailing list > List Rules (must read!): http://w5ami.net/amradiofaq.html > List Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:[email protected] > To unsubscribe, send an email to [EMAIL PROTECTED] with > the word unsubscribe in the message body. ______________________________________________________________ Our Main Website: http://www.amfone.net AMRadio mailing list List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:[email protected] To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
