Hi Guys, Well, I don't have many answers for you. I am new in this field and trying to learn and am sharing what I have heard from others who claim to have had this problem with a Mastr II. The gentleman at Pacific Research who manufactures the controller has write up on this in their manual but since I'm not the expert here I'm unable to tell if it's not applicable to the Mastr II without asking the question.
I'll put it on the analyzer again and look but I'm pretty sure there's a pronounced spike in the discriminator output up around 450khz. There is, without a doubt, some unexpected high frequency noise on the discriminator audio there that's throwing off the offboard squelch. In the mean time I've wired up the Mastr II's RUS output with a 10k resistor and a 2N2222 transistor to provide a open collector output to drive the controller with external squelch and this is working quite nicely. Sorry for any confusion, I'm just going to give up on the digital squelch. Thanks, Mark Hagler W7WMH Seattle --- In [email protected], Wayne <[EMAIL PROTECTED]> wrote: > > > Wjhat nobody seems to be pointing out is the simple fact that the Mastr > II series does not normally use a 455 KHz IF frequency. It would have to > be a special IFAS board with a second converter to get from the normal > 11.2 MHz, or 9.4 MHz in low band and 800 MHz units, plus a very few that > have a 10.7 MHz IF frequency. I have one of the latter boards, quite a bit > different that the normal IFAS boards. > So tell me just how you arrived at 455 KHz? > A single conversion receiver using 455 KHz would be super prone to severe > image problems. > Please cite the exact location showing any Mastr II using a 455 KHz IF > frequency? > BTW, what schematics have you looked at for the Mastr II RX units? > > Wayne WA2YNE > Mastr II repeater on 441.950TX > > > On Sat, 31 May 2008 15:55:28 -0500, Willis M. Hagler <[EMAIL PROTECTED]> > wrote: > > > Hello Ron, > > > > The audio emphasis for FM is a different issue. When I put the > > discriminator output from the Mastr II receiver on a analyzer you can > > clearly see a spike way out at 455khz which I believe is the IF > > frequency in the receiver. > > > > This controller has a auto-squelch feature (it does not use a COS/RUS > > line at all) and it listens for the presence of high-frequency noise > > coming off of the receiver to control the squelch. When a nice, full > > quieting FM signal shows up the high frequency noise goes away and the > > controller will detect this and kick on the transmitter. > > > > This detection circuit is behaving poorly on the Mastr II because this > > strong 455khz component is throwing it off and making it shut down the > > squelch because it thinks there's a lot of high-frequency noise even > > when the signal is actually full quieting. > > > > Running the audio through a 10 mH inductor tied to a 1000pf cap to > > ground should cause it to roll off the very high audio frequency and > > solve the problem.... but here's what I run into trouble, there's > > thousands of parts out there that say "10 mH inductor" so I'm over my > > electronics head now! > > > > Thanks, > > > > Mark Hagler > > W7WMH Seattle > > > > > > > -- > Using Opera's revolutionary e-mail client: http://www.opera.com/mail/ >
