Plessey PR153A

[Julesomega]

I came across a manual for the PR153A and as there has been no mention of this Maritime receiver here I had to take a look. The handbook is dated 1969.

This seems to be an early British foray into solid state comms receivers, but is functionally not really very appealing to an amateur user. It receives SSB or DSB on 6 fixed frequencies in the range 2 - 30MHz using the conventional configuration with IFs of 1.6MHz and 455kHz. The front-end filters and the crystal osillators are carried in a turret which has to be populated according to the frequencies chosen. It has a fixed bandwidth of 2.8kHz and the turret is motor-driven.

The circuits are entirely conventional, using transistors such as BSY95A, OC170, OC200, AFZ12, 2S721, 2S512, 2N3702, 2G401S. There is only one photo of the unit.

[Synchrodyne]

The Plessey PR153 appears to have been one of several receivers of this type introduced around 1968-69. Others included the Eddystone EC964 and the Redifon R499. But much less information seems to be available on the PR153 than on the other two.

Forthcoming at that time was the introduction of SSB for maritime HF radiotelephone purposes. (Although SSB and ISB had been used for other merchant shipboard communications, such as passenger telephone services, since the late 1940s.) It was thought that for smaller vessels, particularly those without radio operators, simple spot-tuned receivers would be much easier to use.

Here is what Eddystone said in the introduction to its write-up on the EC964:

“IT HAS been internationally agreed that, early in the 1970's, mobile-marine radio transmissions in the m.f and h.f bands will be confined to upper single-sideband operation, except for the 2 182 kHz distress channel. Thus it will become necessary for a large number of ships to be re-equipped with single-sideband equipment. Many of these ships are comparatively small and may not carry experienced radio operators. Difficulties could therefore ensue, owing to the greater skill required to receive s.s.b transmissions satisfactorily with continuously tuned receivers. It can be seen that there is a requirement for an s.s.b receiver which is simple to operate and of low cost. It is the purpose of this article to describe the design of such a receiver to meet the appropriate GPO specifications.”

The EC964 was quite a lot different to the contemporary EC958. The latter was Eddystone’s offering in the general-purpose/SSB category, also being configurable for marine main receiver use, which was done in the EC958/5 variant, rebadged as the Mimco Nebula, positioned as the junior partner to the MWT-origin Mimco Apollo.

The Redifon R499 was aimed more generally at point-to-point operations, not just maritime, and had an ISB option. I understand that it formed the core of the following R550 general purpose and R551 marine receivers.

The category “early British solid-state communications receivers” would probably also include various professional general-purpose types, such as the Redifon R408, Plessey PR155, Racal RA217 & co., GEC RC410/R, Eddystone EC958. MWT did not appear to have had a direct contender in this group, but the Apollo was also offered as a general-purpose receiver, and the Eddystone EC958 was considered to be part of the Marconi range. Whilst GEC had acquired Marconi by virtue of its acquisition of English Electric, that part of the takeover was a case of “..they came back from back from the ride with the lady inside”, as there was no room for the GEC RC410/R” in the already quite expansive Marconi range, and remaining stocks were the subject of a “fire sale” in mid-1971. All in this list had somewhat different topologies and device choices.

The marker for the end of the early solid-state period was probably the arrival of the Racal RA1772. One could say that it made previous forms obsolescent if not obsolete. But the EC958 survived into the early 1980s. I suspect that this was because it was a good fit for situations where lesser performance at lower cost was acceptable. Marconi had stressed the need for a tiered range of communication receiver performance levels and costs, both earlier in the valve era and in the solid-state era.


Cheers,

[Radio Wrangler]

The Plessey general purpose offering of that era was the PR155 and is much better known.

David

[Julesomega]

Interesting that the PR153A offered a choice of SSB or DSB reception: the difference must be that the AGC can be derived from the sum of the sidebands, which is likely to result in far less pumping in pauses of audio. There are separate AGC detectors for the two modes.

I would think we can mark the transition to 'mature' solid-state receivers when planar silicon devices had supplanted point contact, probably also accompanied by the use of diode bridge mixers and the introduction of PLL frequency synthesis.

[Dave757]

Hi,

Dont forget the Eddystone 960 (1962)

OK, it was really just a rehashed 940, but I did have
a play with one once, and given the choice I would have
had a 940 any day, but it did work, and it was pretty
early!

Kind regards
Dave

[CarbonMike]

Another bit of history here. In about 1970 Marconi didn't have a small ships' SSB radio in their catalogue to address this new market. Rather than design one they decided to acquire one via the purchase of a small firm in N London- whose name I can't remember. So far so good. Then it was decided to transfer the manufacture of said radio to one of the Marconi factories. I was given the job of organising the transfer. Needless to say there was a lot of resentment at the source company and it turned out to be the worst job I ever had. I should have objected but I was too far down the pecking order.

[Granitehill]

On the subject of Eddystone - I think the 1830 deserves a mention. I have a 1830/5, and it's a bit difficult to understand how it fits into the general scheme of things. It's clearly derived from the magnificent 830, but it's actual role seems to be a bit ill-defined.

The 1830 is described as suitable for "General purpose applications". It's that all right - it can be used for just about anything you can dream up as it can be fixed crystal control, VFO free tune, VFO plus incremental, external synthesizer, or combinations of each. All in all, it's a bit of a Jack of All Trades.

It's a great receiver for amateur radio use, but I guess it was too expensive to sell many in that market. It shows signs of needing further development as the SSB stability is marginal, particularly as it is described as a Marine Reserve Receiver.

I wonder why the 1830 was developed - it isn't quite in the class of the EC958, but it doesn't look a lot cheaper to produce, and the Eddystone 1000 was also a candidate as a reserve marine receiver at a much lower price. Who were the primary customers ?

[John KC0G]

Originally Posted by Synchrodyne

The category “early British solid-state communications receivers” would probably also include various professional general-purpose types, such as the Redifon R408, Plessey PR155, Racal RA217 & co., GEC RC410/R, Eddystone EC958. MWT did not appear to have had a direct contender in this group, but the Apollo was also offered as a general-purpose receiver, and the Eddystone EC958 was considered to be part of the Marconi range. Whilst GEC had acquired Marconi by virtue of its acquisition of English Electric, that part of the takeover was a case of “..they came back from back from the ride with the lady inside”, as there was no room for the GEC RC410/R” in the already quite expansive Marconi range, and remaining stocks were the subject of a “fire sale” in mid-1971. All in this list had somewhat different topologies and device choices.

The marker for the end of the early solid-state period was probably the arrival of the Racal RA1772. One could say that it made previous forms obsolescent if not obsolete. But the EC958 survived into the early 1980s. I suspect that this was because it was a good fit for situations where lesser performance at lower cost was acceptable. Marconi had stressed the need for a tiered range of communication receiver performance levels and costs, both earlier in the valve era and in the solid-state era.

Some of the discussion in the thread on ISB receivers at https://www.vintage-radio.net/forum/....php?t=103464& is also relevant here.

I think that the Collins 651S-1 slightly preceded the RA1772. Any way the RA1772 allowed a great deal to be put into "one box". It did not enable everything, or almost everything to be done in one box as did the Marconi H2900 which was four or more times the price. It is all about performance, price and form factor.

Am I right in thinking that marine radios in the 1970's were supposed to be"set and forget, and hence needed to be accurate to about 1 part in 10^6? Even crystal controlled radios needed to have the crystals in an oven, or be otherwise stabilized.

73 John

[Synchrodyne]

Originally Posted by Granitehill

I wonder why the 1830 was developed - it isn't quite in the class of the EC958, but it doesn't look a lot cheaper to produce, and the Eddystone 1000 was also a candidate as a reserve marine receiver at a much lower price. Who were the primary customers ?

As best I can determine, the Eddystone 1830 served as both a lower cost stablemate for the EC958 and as the direct replacement for the 830 after a production overlap of about two years.

The 1830 used some of the EC958 signal modules, and in RF performance, stability aside, it was probably close to that model. But it lacked the high-stability feature of the EC958, which applied over the range 1.6 to 30 MHz, and which involved a rather complex circuit (with appropriate screening and compartmentalization) including a narrow-band Wadley loop that locked in 100 kHz increments, an AFC system and premixer system for interpolation. It’s worth studying, but for laypersons like me quite a bit of time was needed to work right through it. (Even more complex is the Marconi Hydrus, which had two Wadley loops (locking at 1 MHz and 100 kHz) and a premixer system.) High stability on the 1830 was provided at spot frequencies in the traditional manner, through the use of crystals.

These advertisements from the 1970s give some sense of Eddystone’s target markets for the 1830 series:





The Eddystone 1000 series was a much simpler single-conversion receiver that I think could be said to have been the bottom tier model in Eddystone’s professional range. (The EB35, EC10, etc., were more consumer market products.) It appears to have been proximate to the valve-era Eddystone 940 in terms of basic performance, but more verstaile in that it had more options available.




The 1830 was superseded by the 1837/8, broadly similar from the signal circuit viewpoint, but using a then-new digital counting drift correction method to obtain high stability throughout the HF range. This was probably one reason why it qualified as a marine main receiver whereas the 1830 did not.





Cheers,

[Radio Wrangler]

Wadley converters, where the received signal is mixed twice, once with a VFO and once with the filtered difference between the same VFO and a comb spectrum can be concatenated to do 1MHz steps, then 100kHz steps and so on, but the limitation is when the Wadley converter's filter between its two signal path mixers has to be too narrow for the signal being received.

A get-around is to not put the sihnal through progressive Wadley converters, but instead put a fixed oscillator through a reversed chain of Wadley converters. This creates a frequency synthesiser whose output can be osed as the LO in a conventional superhet signal path. Such a machine needed only a set of VFOs to be each set approximately for each digit.

The other way was to build a "Direct Synthesiser" where one from a bunch of component frequencies was divided down and mixed with another selection from the same bunch, divided down and mixed with another.... and so on. This recursive structure gave any amount of resolution funds could afford, but the frequency dividers were troublesome before fast digital counters came along. Until that point, Wadley was the best game in town.

Early synthesis techniques are fascinating. I once suggested the Wadley approach get revisited with tunable lasers and comb generators as a terahertz range spectrum analyser. New devices can resurrect old ideas.

David

[Radio1950]

I would like to try out that Plessey PR153A.

The Eddystone 1830 was a good reserve receiver, and would have performed OK with crystal control in fixed coms service on SSB.
Built to a company spec, and to a budget, but it is well made.

It was the best of times, and the worst of times; the 1830 analogue receiver was one of the last of the better ones.

But ... the world was changing with a digital revolution, which enabled the use of high stability PLL oscillators and digital frequency readout.
No comparison, but we tend to look back and compare apples and oranges.

I have an 1830/1 in my workshop, built in the mid 1970s, and I have been using it over the past three months.

It is a lovely thing to use for general listening, and has very good short term frequency stability, when used with variable tuning. A bit noisy though.

My organisation bought a batch of about twenty of these 1830 receivers in about 1976 for tertiary (ie to backup primary and secondary) point to point coms on AM HF, and for technician monitoring of HF AM and SSB, and MF beacons.

[Synchrodyne]

Originally Posted by Radio1950

My organisation bought a batch of about twenty of these 1830 receivers in about 1976 for tertiary (ie to backup primary and secondary) point to point coms on AM HF, and for technician monitoring of HF AM and SSB, and MF beacons.

That appears to be a good illustration of the type of application for which the 1830 was developed. What were the primary and secondary receivers that it backed up?

Originally Posted by John KC0G

Some of the discussion in the thread on ISB receivers at https://www.vintage-radio.net/forum/....php?t=103464& is also relevant here.

Thanks. That reminded me that I had found some additional material for that thread, but after it had closed. Rather than take this one too far off-topic, I’ll post it in a new thread.

Returning to the Plessey PR153, there is nary a mention of it on the internet, nor does it come up in a search of Wireless World (at https://www.americanradiohistory.com...d_Magazine.htm), so it was a very obscure model. Possibly it used similar circuits and devices to those of the PR152.

I imagine that small vessel marine receivers were sold directly to vessel operators, or at least via chandlers/agents. That was in contrast to the “full works” receivers, which were provided – usually with operators - as part of the contract between the radio equipment/service suppliers, such as Mimco, and the shipping lines. Thus the opportunity was there for makers, such as Plessey, who were not in the “full service” marine business to nevertheless participate in the small vessel market. The move to SSB may have enhanced that opportunity in that simple but specialized equipment was required, and not just a derivatives of regular lower end HF receivers. Eddystone already had a well-marine sales network through which for example its 670 series cabin receivers were sold, so developing the EC964 may have been a “no brainer”. The EC964 was the forerunner of quite a few spot and fixed frequency receivers. On the other hand, the marine version of its EC958, as a “full works” unit was applied mostly or perhaps entirely as the Mimco Nebula.


Cheers,

[Synchrodyne]

Originally Posted by Synchrodyne

Thanks. That reminded me that I had found some additional material for that thread, but after it had closed. Rather than take this one too far off-topic, I’ll post it in a new thread.

The new thread is now started at: https://www.vintage-radio.net/forum/...74#post1135074


Cheers,

Mod edit: Threads merged.

[Radio1950]

"That appears to be a good illustration of the type of application for which the 1830 was developed. What were the primary and secondary receivers that it backed up?"

Nothing glamorous I am afraid, but it was all about reliability and stability.

Civil Aviation Australia used-
AWA C55184, AM, single frequency, crystal, valve, early to 1981.
Philips TCA 1596, AM SSB, four frequency, crystal, solid state, 1965 until 1980s.
Codan 7004, single frequency RF heads, PLL Osc set, in mother frame, 1980s until 2000s.

[Julesomega]

I have just seen a picture of another Plessey solid-state receiver from this period, this time a general purpose receiver for land-based use
Plessey PRD250

[G6Tanuki]

The presence of a fist-mic would suggest that it is a transceiver.

There were various similar radios around in the 60s and 70s: the KW 2000CAT, Pye SSB125T/SSB130/SSB200 for example.

Fixed-frequency (crystal control), they were generally intended for things like foresters, oil-exploration teams, United Nations operations/disaster-relief - basically anywhere where there were no phones and VHF line-of-sight comms wasn't going to work.

This was the era too when semiconductors would work tolerably in all stages of a transceiver except the PA: so it was normal for such radios to be 'hybrid', gaining the low-power-consumption benefits of semiconductors in the receiver but still using a couple of valves (with HT from a solid-state inverter) for the transmitter 'final'.

[Julesomega]

Originally Posted by G6Tanuki

The presence of a fist-mic would suggest that it is a transceiver.

Um, that's what I meant

[Julesomega]

Originally Posted by Radio1950

Civil Aviation Australia used-
AWA C55184, AM, single frequency, crystal, valve, early to 1981.
Philips TCA 1596, AM SSB, four frequency, crystal, solid state, 1965 until 1980s.
Codan 7004, single frequency RF heads, PLL Osc set, in mother frame, 1980s until 2000s.

I don't know what that Philips TCA 1596 would be like, but I have just seen another single-channel HF receiver by Philips, in this case Philips RO 960. This could be supplied for one of four bands, 1.6-3.2MHz, 3.2-6.4MHz, 6.4-12.8MHzx or 12.8-25MHz.
CW, MCW, DSB or SSB is selected by wire internal links. IF is 1.4MHz, the channel oscillator can be a TCXO or OCXO. It has a small front panel and a long body. Operator controls are RF and AF Gain. The manual does not trouble users with any photos.

[Synchrodyne]

Evidently Plessey had a history of manufacturing single-channel HF receivers. The attached WW 1959 July-August item mentioned the PR51 series.

Cheers,