The radio you have is probably an FSTR250, not 520... the IF is 455 kHz, not 10.7 so the filter crystals made by Comm. Spec will not work. I assume that you have the Sensicon "A" receiver, about 5 inches wide with a rather big IF filter, about 4x4x2. If the last letter on the filter is an "S" it is 5KHz width. if not, it's 15 KHZ.Changing the resistor between the plates of the 6AL5 Discriminator tube to a higher value.. 180K??? if memory serves correct,,will give you more audio recovery. Although the TU540S filter offered is incorrect for the receiver, it can be made to work in the older Sensicon by adjusting the gain of the IF amp. Lance N2HBA ----- Original Message ----- From: Eric Lemmon To: [email protected] Sent: Saturday, February 17, 2007 8:09 PM Subject: RE: [Repeater-Builder] 1953 Motorola BaseRadio for 6meters
Dick, I think you're right about the bandwidth. Communications Specialists, one of the first companies to enter the narrow-banding market, is still in the same business. Com-Spec just might have the filter kit needed. Go here: <www.com-spec.com/narrow.htm> 73, Eric Lemmon WB6FLY -----Original Message----- From: [email protected] [mailto:[EMAIL PROTECTED] On Behalf Of Dick Sent: Saturday, February 17, 2007 2:50 PM To: [email protected] Subject: Re: [Repeater-Builder] 1953 Motorola BaseRadio for 6meters If memory serves, that radio is old enough to be a wideband rig (+/- 15 kHz FM deviation). You can turn down the XMTR FM dev to +/- 5 kHz, but your receiver's bandwidth is more complex to narrow it down to +/- 5 KHz. As it is now, you're nowhere near filling up its RCV bandwidth, so the remaining RCVR bandwidth lets noise through. There used to be some parts around that you could replace in the RCVR to narrowband (+/- 5 KHz), but I suspect they'd be nearly impossible to find now. You might be better off digging up a more modern RCVR and using it. 73, Dick ----- Original Message ----- From: "rod_shaner" <[EMAIL PROTECTED] <mailto:kb8fly%40copper.net> > To: <[email protected] <mailto:Repeater-Builder%40yahoogroups.com> > Sent: 17 February, 2007 11:29 Subject: [Repeater-Builder] 1953 Motorola BaseRadio for 6meters > Hi all, > I'm seeking schematics, manuals, and advice on peaking a working > unit. Its model number is FSTR520BR(FW)1ASP2. Just tearing that model > number apart is a workload! > It was a commercial base radio, and it's crystalled for 52.525 FM. > Right now I'm trying to get as much as possible out of the receiver. > It works, but 25 mile away 40W signal radiated through a vertical > antenna is just out of the noise on this end. My receive antenna's > base is 30 inches off the ground for test purposes. > > Advice is requested. > > Thanks
