b95. PYE PMR mods

XTAL frequency list; see AR november 92, page 6, may translate the info later

Most PMR rigs are good when you know the problems and takes steps
to avoid the bad things with the rigs. Here is described some rigs I have
tested over several years as packet radio nodes and beacons on 2m and 70cm.

PYE modifications

The first PMR rig I had was a PYE reporter, it was back in 1968, but I never got it into use, had
other ideas and built my own solidstate transmitter instead. Also had a PYE Vanguard AM25B, and
made many experiments with it so it was discarded, and I bought an AM25T which was used in my car
until battery was flat because I forgot to switch it off over night. .
Have attended a course for Storno CQF612 and PYE T30FM, and I must admit that I've carried out many
experiments with the PYE equipment at work and really was well reputed for improving these for maritime
mobile VHF operation. PYE has a very bad reputation in Norway, but it is not so much PYE which is bad
as it is caused by some fools who installed germanium diodes in the antenna connection, to drive a relay
used for reporting that the transmitter was on the air. It caused terribly bad intermodulation.

PYE FM10d/AM10d (Cambridge), AM25B, AM25T (Vanguard), F60FM etc

These are old and based on transistors from early 60's with very typical construction
philosophy which is often bad today. They may have some historical collection
value for boatanchor societies.
** Please note that the mains transformer found in F60FM transmitter may be used in a 600-1000W PEP
SSB power amplifier, it is as such a highvalue component overlooked by most of us

** Since the Cambridge has an inverter it could be used as power supply for other boatanchor rig

PYE W15FM Westminster is an old rig and possibly not worth using too much time with,
however, it has some valuable parts. The exciter is good, while the PA is not so good(!).

My last application is the LA3VHF 2m beacon, but used low noise xtal oscillator and Philips
BGY36 PA module. A similar 2m beacon (LA6VHF) was made on PYE T30FM chassis, it uses
the original psu, exciter and power amplifiers.

Have studied the equipment, but have nothing left. The exciter and audio stages are equal to T30FM

F30FM (T30FM and R18FM/R17FM)
Have done some extensive work with these and modified a lot to be improved for maritime VHF, bu I am not sure if it is still worth bringing some info for such equipment. Used one transmitter for a 2m beacon in Kirkenes. It is very much the same as W15FM. Unfortunately much equipment has been modified by unskilled persons and the reputation is worse than it deserves.

Had a lot of these rigs for 2m and 4m since the local police, and electric power board
took at lot of them out of service in late 80's. The local amateurs only wanted new equipment.
PYE has been famous for the relay on 12VDC line, here is the modified
version I use on LA3VHF beacon. The floating ground is very bad for spurious,
an no need if you don't have an English car, but the relay is still a good idea.
It may be an expense at first, but an advantage in the end.


PYE R18FM (F30FM).
19in. rack mounted receiver.
Had a lot of these rigs (with T30FM) to play with since the Norwegian telecomms changed to
Storno CQM612, first the PMR stations in the 70's and later, the maritime mobile stations around 1990.

It is a good receiver. But it is important to cover underside of the RX tuner lid with tape to
avoid it from touching the coils and this upsets the trimming so you need to align it every time
you've had the lid off. Even if the original receiver has good sesitivity at 160MHz, it will not
operate properly on 144MHz (ref.: LA5QEA), but I used a
BF905 MOSFET as RF amplifier and it
was no problem to achieve 20dB quieting for 0.25µV pd signal. BF905's were available at
no cost, but the later BF981 or whatever are supposed to be just as good.
Also tested an S-meter based on the IF signal in R17 and R18.

PYE R17FM is older version of the 19" rack mounted receiver, it is in many respects very much
like W15FM Westminster, and it hasn't the meter on the front panel. It is two versions of PYE Westminster.
1967 version has BJT transistors in the VHF module, while 1968 version has JFETs. Suppose R17FM
has the latter JFETs. We used the IF and AF part of an R17FM for the local repeater
with valve circuits for VHF part of the old Storno (CQM12?) receiver, it was a vaste improvement.

7c PYE T30FM power amplifier mods
The first thing to do is to put solder lugs on as many screws as possible for good ground connections on the
printed circuit boards. Use of the floating ground will only cause bad spurious problems. The power
amplifier needs few modification for proper operation. An unmodified stage
may hardly deliver 12W, but the modified stage easily produces 20-25W RF. And it is just by addition
of some resistors and capacitors for better balance the power to the two power devices. You may well
try some extra 100pF capacitors from base to emitter on either power transistor. It is just what we have
experienced later, but the companies counted a pence when you really don't care for a few extra capacitors
to increase the gain..

Had a lot of these rigs (with T30FM) to play with since the Norwegian telecomms changed to
Storno CQM612, first the PMR stations in the 70's and later, the maritime mobile stations around 1990,
also had some T100MN.

Before you put it into the bin, you should consider that the mains transformer is very useful for a medium power amplifier,
and may have high value on junksale. If you want to build an audio amplifier or PA, you must pay a lot of money to get
a similar transformer today. Two transformers in parallel are good for over a 1kW RF power.

PYE Westminster W15FM

AT10793/5 filter for W15FM (LA5QEA)

AT11437/1 (HC6/U looking can) filter for W15FM (measured by LA5QEA)

see also application of W15FM for LA3VHF 2m beacon on page d31 ,
and application for R17FM as IF amplifier for repeater on page

PYE Europa.
Got over a douzen of these equipment from a friend where they were discarded at the job.
Would never have paid for it, but it is a a few things to salvage. It must be considered how much else it is worth to use time to remove.

Apart from the box, which is suitable for many other projects, I see only four components worth salvaging:
The antenna relay on the left side, two compression trimmers below it, and BLY53 (2N5944) on the rear.

The xtal filter is for 21.4MHz, so it might be needed for your junkbox.

Here it is used to house a INTERLINK 23cm packet transceiver,
PYE Europa is supposed to be rather unstable and the service-man's nightmare.

Since I had some douzens of T30FM and W15FM 2m equipment I see no reason for wasting my time on this type of equipment.

You'll find the data for MD951 type coax-relays in SSB Electronics catalogue 1984. I bought such relays
at a rally in UK, and have used one for my remote 2m BFT66 pre-amp since 1980. According to Ian, G3SEK
the power limit (not switching power) is 450W on 2m, so it is really a useful piece to remove before
you discard the rest! Careful to take care of the old mounting hardware as it is difficult to connect the coax cables without.

se forøvrig følgende artikler om PYE utstyr:
PYE REPORTER (4m) ombygging til 2m            LA1ZH  AR  69-02-033
PYE Vanguard AM25B og AM25T                   LA8AK  AR  92-11-006
PYE Westminster for 50/144/432MHz bånd               AR  94-03-068
PYE Westminster W15FM mottakerforbedring             AR  94-01-007
PYE Westminster for 50/144/432MHz bånd               AR  94-04-100
PYE F30FM 2m 25W sender/mottaker forbedringer  LA8AK AR  90-03-068
PYE utstyr; 12MHz TX xtals                    LA5QEA AR  93-02-036
PYE utstyr brukes til forbedring av rør repeater     AR  92-12-
PYE Westminster deler i 10m mottaker                 AR  93-05-133
PYE Westminster deler i 2m signal generator          AR  88-04-103
PYE R18FM som repeatermottaker (2)                   AR  93-09-248
PYE R18FM som repeatermottaker (1)                   AR  93-06-174
PYE F60FM, FM10d(Cambridge), FM25D(Vanguard)         AR  93-06-174

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