Milt, Well, that certainly changes things! I have all three MSR2000 manuals, and the only reference I found to the bandpass filter was in the troubleshooting charts, where it stated that a possible solution to correct low power output was to adjust FL101. Unfortunately, it did not elaborate on the procedure to follow. No doubt, the four coils should be stagger-tuned to achieve a bandpass characteristic.
Have you already tried adjusting the filter for 70cm? Is the filter box sealed, requiring surgery to get into it? Wanna write an article about the tuning process? (;-) 73, Eric Lemmon WB6FLY -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Milt Sent: Tuesday, March 23, 2010 10:01 AM To: [email protected] Subject: Re: [Repeater-Builder] Exciter Filter in a UHF MSR2000 Station Eric, The adjustments for FL101 are very easy to access and are not at all hidden. The problem most likely lies in the physical size of the filter which will limit its low end performance. The exciter tuning chart in the 68P81061E55 service manual shows the low end of the range at 440MHz. The same manual indicates models made to cover the 450-512 MHz range but nothing below these ranges. Interestingly enough the UHF manual is a supplement to the VHF service manual 68P81061E50. I'll defer to Skip or others who have seen the MSR2000 in some of its more unique variants. I'll send you a picture of a board direct when I get the camera hooked up. Milt N3LTQ ----- Original Message ----- From: "Eric Lemmon" <[email protected] <mailto:wb6fly%40verizon.net> > To: <[email protected] <mailto:Repeater-Builder%40yahoogroups.com> > Sent: Monday, March 22, 2010 10:12 PM Subject: [Repeater-Builder] Exciter Filter in a UHF MSR2000 Station >A recent post to this list described the inability of the bandpass filter > FL101 to pass frequencies in the 70cm Amateur band. The schematic diagram > in the UHF MSR2000 service manual shows the four helicals to be > adjustable, > but it seems that the adjustments are concealed. Inasmuch as this filter > prevents many Hams from retuning their stations down to 70cm, I would like > to ask anyone with a spare MSR2000 UHF bandpass filter to allow me to see > if > it can be retuned. My intention is to first sweep the filter on a network > analyzer to see what its "stock" response looks like. Then, if the owner > of > the filter allows it, I would see what is needed to gain access to the > internal adjustments, and if retuning to the 70cm band is possible. I > shall > endeavor to return the filter to its owner after this investigation, > either > tuned as it was originally or tuned to favor 70cm. As you might expect, > this "science project" will form the basis of a how-to article in the > RBTIP. > > I don't have a UHF MSR2000 to experiment on, so I am hopeful that someone > "out there" may have an idle UHF MSR2000 station that can serve as a > source > for the FL101 filter. > > 73, Eric Lemmon WB6FLY > > > > ------------------------------------ > > > > Yahoo! Groups Links > > >
