I will admit that the tune-up procedure is rather unclear and probably is missing some important information.
You need something capable of detecting the 447 MHz signal. An RF voltmeter is a high-impedance meter that's sensitive at those frequencies. An ordinary VOM would have problems at a couple hundred kHz. You can use a spectrum analyzer as a detector, except that they usually have 50 ohm input impedance and won't be as sensitive as the RF voltmeter. What you need to do is connect an RF source to one end of the filter and terminate the other end. This can be either the PA or a 50 ohm dummy load. You connect the tuning probe (short cable with a BNC connector at one end and an exposed coax at the other) to your RF voltmeter's input, and shove the probe into the tuning hole adjacent to the tuning slug. This is the same cable you use to tune the receiver's front end, but instead of injecting a signal into the probe, you use it to sense RF in the filter/duplexer. The rest of the procedure is probably OK. You tune the first slug nearest the signal source for a peak on its tuning hole, then tune the next slug for a dip, which is a much sharper indication than the peak. Then you move the tuning probe to the next hole and tune the next slug for a dip, etc. You can't repeat the process without presetting all the coils like the manual says. If you do try to go back, you'll find that the peaking and dipping goes on forever and you will never end up with the proper tuning. All the coils interact and the optimum position changes as you tune other coils. The 3-section filter between the exciter and PA input is often called the pre-filter. The 4-section filter between the PA and the antenna TEE cable is called the post-filter. Both of these are bandpass filters which serve to minimize the amount of energy on the receive frequency. Each of these tuned coils provides about 15dB of rejection of the signal 5 MHz away. By the time you get through the receiver, there's basically nothing left of the transmitter's signal to interfere. Bob M. ====== --- Mathew Quaife <[EMAIL PROTECTED]> wrote: > Sitting here looking at the tune up procedure for > the filter, it tells me to insert a rf > millivoltmeter probe into J18 and insert a 225 mV > signal into the the output of the post filter. I > did this, and get nothing on the meter at all. Now > I'm not sure if there is a difference between my RS > Volt-Ohm meter and an RF millivoltmeter. I do have > the test meter for the MSF5000. If you could help > me to understand, is the post filter tuning the pass > frequency of 447.000 which is the receive of the > system, and the prefilter for the 442.000 transmit. > Or is the unit simply filtering all of 447.000 to > handle the isolation of the transmit frequency. It > also says to refer to the Station Parameter Booklet > to for the appropriate tuneup frequency, I'm > assuming that would be the input of the repeater at > 447.000? > > "Kevin Berlen, K9HX" <[EMAIL PROTECTED]> wrote:Here is > something else to try. This assumes that the PA > pre-filter has been tuned to your frequency. With > the TX filter bypassed, but everything else hooked > up, try turning the power set control down a little. > It may be that you are simply driving the PA too > hard and it is shutting down. There are two > different versions of the high power PA, One with a > single circulator, and one with a triple circulator. > I don't recall the exact figures, but the ouput of > the PA has to be "de-rated" depending on which > circulator arrangement you have. With the triple > circulator, the power out of the PA into the TX > filter should be in the vicinity of 70-80 watts or > so. The manual will have this info in it. > > As stated by others the TX filter is a real pain to > tune, but once set up they work well. The pre-filter > is a little easier. Hope this helps, and good luck! > 73, > > Kevin, K9HX > > > At 05:50 PM 11/12/2005, you wrote: > > > "Bob M." <[EMAIL PROTECTED]> wrote: > > > I get the impression that if you HAD a manual, > you > > wouldn't be asking all these questions. > > > > > > Yes I have the manual, however some of it appears > to greek to me, but as I ask questions, it makes > more sense. > > > Anyway, tuning the internal filter/duplexer is a > royal > > P.I.T.A. The first thing I do is remove the outer > skin > > from the cabinet. This gets you easy access to > the > > connectors on the F/D. The procedure requires a > sig > > gen, an RF voltmeter, and the tuning cable you > used > > with the receiver, however it can be done with a > > spectrum analyzer that has a tracking generator. > > You'll also need an accurate, low power, 50 ohm > dummy > > load. > > > I do have a service monitor here to help in the > aide of this project. > > > > > > > > > Rather than go through the entire procedure and > bore > > everyone, I'll send you, or post, the couple of > pages > > from my manual. The procedure must be followed > > exactly. You can't go back and re-adjust the > coils. > > They get done in a particular sequence and if you > fool > > with them again, you won't get the performance > that's > > needed. > > > The VCO drives the intermediate power amp (IPA). > This > > sends 3-9 watts out to the three-coil section of > the > > F/D, and this feeds the input of the power amp > (PA). > > The output of the PA goes into the four-coil > section > > of the F/D, and this feeds the TEE cable that > joins > > the receiver to the antenna connector. These > cables > > are cut for a specific Tx/Rx relationship, and > your > > new freqs must match that. For example, the > normal > > commercial repeater transmits on, say, 460 MHz, > and > > receives on 465 MHz. The fact that it receives > higher > > than it transmits can't be changed when you use > the > > station in the amateur band. Your receiver must > still > > be 5 MHz higher than the transmitter's output. > They do > > make cables for the other direction, but they're > > extremely rare. There are color bands on the TEE > cable > > that identify the freq range and direction. > Hopefully > > you have the proper cable. If not, either you'll > have > > to try to make one, buy one (they're probably NLA > from > > Motorola), choose another repeater frequency > where the > > offset direction is appropriate, or not use the > > station at all. > > > > > > I am receiving higher at 447.000 and transmitting > at 442.000 > > > The controller samples the IPA and PA output > levels > > and if they aren't within the range they think is > > normal, you'll get a PA failure error. If the F/D > > isn't tuned correctly, you'll get too much loss > in the > > system and the sensing circuits will tell you > > something's wrong. The digital stations will > > extinguish an LED. > > > > > > If I disconnect the pa, and the F/D, would this > not eliminate the problem between the IPA and the > F/D? > > > Bob M. > > ====== > > --- Mathew Quaife wrote: > > > > Thanks Bob, I did finally get that one, got > them > > > locked, and the receiver is nearly tuned, > however no > > > repeat as of yet. I went from a 3 beep now to a > 2 > > > beep. Looking for that. > > > > > > Mathew > > > > > > > > > "Bob M." wrote: > > > The VCO coils are only present on the UHF > stations, > > > and as I recall, that's what you have. > > > > > > Pull the RF tray out and swing the control tray > up, > > > then turn the VCO Lock knobs to the TRANSIT > > > positions. > > > This will push them down into their cavities in > the > > > RF > > > tray casting. On each side, lower rear, you > will see > > > two or three holes in a triangular pattern. The > > > upper > > > two are often used to hold cable ties, but the > lower > > > one lines up with the VCO coil's slug. Insert > your > > > 5mm > > > Allen wrench in there - the slugs are exactly > the > > > same > > > as the ones in the front of the RF tray and > adjust > > > the > > > same. With the meter plugged in, adjust for a > value > > > of > > > 38 +/- 2 uA on the appropriate metering pin (I > think > > > it's pin 5 but don't hold me to that). > > > > > > Perform the adjustment on the highest frequency > on > > > both Transmit and Receive. This is the first > step in > > > any UHF MSF5000 alignment. > > > > > > Bob M. > > > ====== > > > --- Mathew Quaife wrote: > > > > > > > Ok, I think I have missed it, or misplaced > it. > > > > Which ones are the VCO adjustment pots. All > the > > > > manual tells me is to adjust the VCO pots, > but I > > > > have no diagram showing which ones they are. > > > > > > > > Mathew > > > > > > > > > > > > "Bob M." wrote: > > > > Cute method. I believe even the digital > station > > > can > > > > output some tones, although I've never heard > them. > > > > > > > > Mathew also asked (originally) what else > needed to > > > > be > > > > adjusted when moving the frequency. The > > > transmitter > > > > is > > > > already wide-band and other than the VCO, it > > > doesn't > > > > have any adjustments at all. > > > > > > > > The two VCOs, the five receiver > mixer/injection > > > > coils, > > > > the six receiver front end coils, and the > seven > > > > duplexer/filter coils are it (that's > enough!). Of > > > > course you also have squelch, output power, > > > > deviation, > > > > etc, to contend with, but these shouldn't > vary > > > much > > > > with frequency, certainly it's a lot more > stable > > > and > > > > consistent than some of the radios like > MaxTracs > > > > where > > > > there are 16 frequencies to adjust deviation > and > > > > power. > > > > > > > > Bob M. > > > > ====== > > > > --- nj902 wrote: > > > > > > > > > --- In [email protected], > Mathew > > > > > Quaife wrote: > > > > > "...I put in the new eprom, and all it does > is > > > > beeps > > > > > at me. .." > > > > > > > > > > > > > > > ______________________________________________________________________ > > > > > > > > > > The alarm tone beeps are generated once > every 10 > > > > > seconds, and if more > > > > > than one alarm condition occurs > simultaneously, > > > > the > > > > > various alarm > > > > > tone beep messages will be sent one after > > > another > > > > > (separated by about > > > > > one second) starting with the highest > numbered > > > > alarm > > > > > to the lowest. > > > > > > > > > > Each alarm tone beep message consists of a > > > series > > > > of > > > > > tones. The > > > > > number of tones in the series is equal to > the > > > > number > > > > > of the alarm > > > > > signal. Station alarms numbered 1 through 7 > are > > > > > internal station > > > > > alarms and indicate faults that have been > > > > diagnosed > > > > > within the > > > > > station. > > > > > > > > > > These alarms correspond to the four data > bits at > > > > > Address 12 of the > > > > > MUXbus, and three (BD0-BD2) of the four > data > > > bits > > > > at > > > > > address 13. > > > > > > > > > > 3 = Synthesizer unlock > > > > > > > > > > See service manual 68P81062E75, Maintenance > and > > > > > Alignment page 9, > > > > > Section 6.3, VCO Adjustment Procedure. > > > > > __________________________________ > > Yahoo! FareChase: Search multiple travel sites in > one click. > > http://farechase.yahoo.com > > > > > > > Yahoo! Groups Links > > > http://groups.yahoo.com/group/Repeater-Builder/ > > > [EMAIL PROTECTED] > > > http://docs.yahoo.com/info/terms/ > > > > > Yahoo! FareChase - Search multiple travel sites in > one click. > > > > > > > > --------------------------------- > YAHOO! GROUPS LINKS > > > Visit your group " Repeater-Builder" on the web. > > > To unsubscribe from this group, send an email > to: > [EMAIL PROTECTED] > > Your use of Yahoo! Groups is subject to the > Yahoo! Terms of Service. > > > --------------------------------- > > > > > > > > > --------------------------------- > YAHOO! GROUPS LINKS > > > Visit your group "Repeater-Builder" on the web. > > To unsubscribe from this group, send an email > to: > [EMAIL PROTECTED] > > Your use of Yahoo! Groups is subject to the > Yahoo! Terms of Service. > > > --------------------------------- > > > > > > > --------------------------------- > Yahoo! FareChase - Search multiple travel sites in > one click. __________________________________ Yahoo! FareChase: Search multiple travel sites in one click. http://farechase.yahoo.com Yahoo! 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