Re: [Repeater-Builder] Re: Tuning a MSF5000 UHF repeater

Sun, 13 Nov 2005 05:50:12 -0800

Ok, I do have a SA, so will use that.  Ok, hence then, just like my duplexers on my 2 meter system, I'm thinking the prefilter is for the tx and the post filter is for the receive?  So if I inject a signal into the input of the prefilter of 442.000 and the output to my SA, I should be able to tune these up, same with the post filter for the receive side, if I understand this correctly.
 
Mathew


"Kevin Berlen, K9HX" <[EMAIL PROTECTED]> wrote:
The built in duplex filtering option is simply a very high Q pass filter system. Everything on the TX side should be tuned to your TX frequency. The RX side of the filter is actually the receiver front end. which should be tuned to your RX frequency. Since you have a single frequency application, the tune freq will be the same as your operating frequency. The tune up freq applies only to stations that use multi freq TX/RX.

A RF millivolter is vastly different from your RS VOM. You could possibly sub a spectrum analyzer for the RF millivoltmeter if you have access to one. 73,

Kevin, K9HX

At 08:13 AM 11/13/2005, you 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 Repeater-Builder@yahoogroups.com, 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.


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