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Old 28th Sep 2017, 10:08 pm   #21
Biggles
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Default Re: Common Pye PF1 RX deafness problem

I've got a calibrator in the shed but can't remember the make, even though a one sat in the workshop for years. I don't remember it ever going for cal either. It was probably just trimmed using a calibrated signal generator every now and again. The UHF base stations used with the BE470 were usually a dual bay Pye F496. A big grey and black thing with a handle at each end and normally stood on a bench. Anyway, we are hijacking this thread again. Better stop or start a new separate one about UHF handportables!
Alan.

Edit; Just remembered, I think it was made by Racal. And posts crossed with AC/HL
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Old 28th Sep 2017, 10:08 pm   #22
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Default Re: Common Pye PF1 RX deafness problem

We had a small portable device, Racal I think, that did that sort of thing, just generated a signal at 12.5kHz intervals for zero beating. Didn't like being transmitted into though.
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Old 29th Sep 2017, 12:57 am   #23
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Default Re: Common Pye PF1 RX deafness problem

Well, I managed to improve the sensitivity on one of the receiver's to normal levels by replacing the first RF amplifier, TR1. I had no success with the 2nd deaf one replacing this same Transistor and a visual didn't find any problems, but I fitted a BNC socket with 1/4 wave stubby in place of the plate antenna which increased sensitivity a fair bit.

I'm very keen on these PF1s, so now that they're sorted - please feel free to post to your hearts content on this thread. It all makes for interesting and good reading.

A big thank you to all that have offered help by the way.
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Old 29th Sep 2017, 8:21 am   #24
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Default Re: Common Pye PF1 RX deafness problem

Bill,

That would have been a Racal 9055 calibrator which had switched channel spacings. Or the 9053? a simpler version. Very clever bit of kit, it was all we had for maintaining VHF radios when working in remote areas.

Gordon
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Old 1st Oct 2017, 10:13 am   #25
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Default Re: Common Pye PF1 RX deafness problem

Damo, thinking about your other deaf set, and looking at the kind of things handportables are subject to, it may be worth checking the crystal filter as this could have been damaged in a drop. Linking it out may be a quick yes/no check although not ideal. You may have a bad capacitor (tantalum bead? can't remember) somewhere. It may be a bit off frequency too, which wouldn't help, if you have some way of checking this. We used to zero beat the local oscillator by injecting a 10.7MHz low level unmodulated signal into the IF stages and also an on channel carrier from an accurate signal generator (or the transmitter) and tweaking the receiver local oscillator for zero beat i.e. lowest tone heard in speaker. Since the advent of synthesisers this procedure has become obsolete, as you just need to adjust the transmit frequency to the correct value and the receiver is bang on too.
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Old 2nd Oct 2017, 8:06 am   #26
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Default Re: Common Pye PF1 RX deafness problem

Hi Alan,

I have no access to a sig' gen' here - only various multimeters, and a frequency counter.

The set that's not up to par with the others is a fair bit better with an external antenna installed, but I'll try linking out the filter to see if it improves matters.

The frequency is set bang on by the way as the audio reproduction is nice and clear.
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Old 2nd Oct 2017, 9:00 am   #27
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Default Re: Common Pye PF1 RX deafness problem

Our chief tech trusted the main workshop's Schomandel so much he allegedly once rang Droitwich to tell them their 200kc/s transmitter was off frequency...!

I have a pair of PF1s on the shelf here as a reminder of my roots... My son, who is an Airwave user, was fascinated with them. When you think about the technology used to get a voice from A to B now, and then...

As a young WM and WT I remember netting PF1 transmitters against the Racal calibrator. I guess we must have netted the SG1 sig gen too after it's xtal was changed and before it was used on a new freq along with the 10.7MHz marker osc, but I don't remember actually doing that! The SG1 was left on keep it warm and minimise drift. In this area PF1s were used with Pye F450 and F460 base stations and Pye RTC 'Teak Box' and Mascot 50 controllers (with a tulip mic wedged into the operator's console and a footswitch for PTT).
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Old 2nd Oct 2017, 4:31 pm   #28
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Default Re: Common Pye PF1 RX deafness problem

I remember the Pye RTC. Most of the ones we had in control rooms used to make a sort of grumbling rustling sound all the time, mixed in with a bit of mains hum. This was down to noisy carbon resistors in the first stages of the amp. I think there was an OC71 in there? Then came the RTC's big brother, the Mascot 200, full of those little amplifiers with the two pots to adjust for output waveform symmetry. And tulip mikes! Happy days.
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Old 4th Oct 2017, 8:18 pm   #29
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Default Re: Common Pye PF1 RX deafness problem

Quote:
Originally Posted by Damo666 View Post

I have no access to a sig' gen' here - only various multimeters, and a frequency counter.
Do you have a wide coverage scanner receiver? If so try tuning it to exactly 21.4Mhz above and exactly 21.4Mhz below the receive frequency of your PF1.

If you're lucky tuning it to one of those two frequencies will give you a steady, relatively weak carrier signal for the PF1 to receive. If that doesn't work let us know the make / model of your scanner and we may be able to suggest other frequencies to try.
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Old 4th Oct 2017, 8:35 pm   #30
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Default Re: Common Pye PF1 RX deafness problem

This makes me wonder about how a cheap DSP dongle available for digital TV today could be useful for aligning PF1RX.

It would spot the Local oscillator and could be used for tweaking up the correct harmonic. It could be loosely coupled to the mixer and used to align front end too.

If you did the HF Input modification it could connect to the 10.7MHz IF pre xtal filter and make a band scope/multimode RX (defeat the economiser for that). But then the dongle might make a better UHF RX anyway.

Lastly - try 100kHz IF from PF1 direct into a PC sound card?
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Old 5th Oct 2017, 8:47 am   #31
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Default Re: Common Pye PF1 RX deafness problem

Sirius,

I've got signal sources like handheld rigs that I feed into a dummy load for alignment purposes, just no 10.7 Mhz source to align IF stages, etc'.

I just move the handheld further and further away from the receiver until it's at the best quieting.

I read about the Scanner trick somewhere and set my scanners to 10.7, 21.4 above and below the target frequency but could never get it to work for some reason. So I'm guessing the IF of my Scanner is different.

I have a few scanners, but the one I use most is a Commtel 510.

Last edited by Damo666; 5th Oct 2017 at 9:16 am.
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Old 5th Oct 2017, 4:13 pm   #32
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Default Re: Common Pye PF1 RX deafness problem

It's very easy to make a 10.7Mhz marker oscillator. Someone on here may even have a one they don't need any more. There must be quite a few lying around unused since the advent of synthesisers in PMR sets. They were an essential tool in days gone by. They are a quick and easy yes/no check to see if the IF stages are working. You can also use them on the second harmonic for 21.4MHz IF's too, although the main function is to make sure the local oscillator is aligned for optimum receive sensitivity, by adjusting the radio for zero beat in the speaker.
Alan.
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Old 9th Oct 2017, 2:26 am   #33
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Default Re: Common Pye PF1 RX deafness problem

Biggles,

I've been looking out for one of these Marker Oscillators you refer to, but like the rest of the ubiquitous and common gear from back in the 80s > 90s , the vast majority seems to have vanished or has gone to landfill - the remainder probably stashed and forgotten about in lofts, etc..

The remaining PF1 that's not quite as sensitive as the others is certainly working reasonably now compared to at first test, so there's no rush to source one.

I'll probably get the components together and scour t' tinternet to find a schematic and knock one together some day soon.
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Old 10th Oct 2017, 7:43 pm   #34
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Default Re: Common Pye PF1 RX deafness problem

I had one made by Finglas Dublin. Pye used them for (out) sourcing various signal generators and odd bits of test equipment.

It was the usual palm sized die cast box, painted in light PF1 Blue, with a spring loaded slide switch which made it go. About 3" of wire on a banana plug was the output for "waving around".

Inside was a PCB, with almost the same circuit as a Pye Westminster Single Channel TX Board. Pretty much that is a Colpitts Oscillator for 30pF Parallel Crystals. It had a variable capacitor for calibration.

If you could get one of those and put it with a switch and PP3 in a suitable box, 10.7MHz crystal fitted, it would do.

I seem to recall that the first Pye service depot I worked at gave me a plain aluminium diecast box, some bits, and said you will need one of these. So I built it.
It was in my stuff for a long time but not seen now for many years. Possible re-use of diecast box?

The Pye blue one I still have somewhere. Battery leaked - lots of white furry cack. Board scrapped probably, box and lid I have seen in the last 5years.
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Old 11th Oct 2017, 5:59 pm   #35
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Default Re: Common Pye PF1 RX deafness problem

My 10.7MHz "squawker" was made by using the second-conversion xtal-osc from a water-damaged Pye Westminster [early-1970s cars were notorious for water getting past the door/window seals and someone had installed a Wessie in a Mk.3 Cortina on precisely the place to catch the drips...]

The Wessie 2nd conversion oscillator is on 10.245 or 11.155MHz according to intended frequency-coverage: you wouldn't want a 'birdie' from inside the radio landing on a frequency you were trying to receive].

"Storno" FM two-way gear at the time often used a crystal-discriminator involving a 10.7MHz crystal - so a dead [who killed it by reversing the polarity?] Storno radio yielded up its quartz to be fitted to the Wessie oscillator-board.

My "squawker" was built into one of the 2-outlet bakelite boxes designed for mains sockets. Because I was dealing with quite a few AM radios at the time I included a modulation facility [OC72 transistor and R-C phase-shift oscillator] .
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Old 12th Oct 2017, 4:03 am   #36
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Default Re: Common Pye PF1 RX deafness problem

Modulated - that is Posh!
Yes the 2nd conversion osc is very nearly the same circuit but it lacks the trimmer so pulling to exact frequency needs some attention.

Nice source of 10.7 crystals there - mine were extracted from gash crystal filters quite often.

Have just remembered Finglas also made a switchable marker box. I never had one. It produced 455kHz, 1.4MHz, 6 MHz and 10.7MHz maybe? About 8" x 6" x 2.5". But what was the type number?
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Old 13th Oct 2017, 2:57 pm   #37
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Default Re: Common Pye PF1 RX deafness problem

And then there was the intruder alarm using a PF1 Tx, mounted in a black box with sensor attachment points at the front... Count the bleeps and look up the premises on the list!
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