Opinions please - Marconi HR22 SW receiver

[hugozair]

I can only find one reference to the HR22 receiver on the entire site. I have had one in my shed for 30 years and its future is in question ! Is there a market for these things now ? I can't find any info in eBay completed listings except working CR100 going for not much. And living down here in Cornwall, an eBay collect only sale would rule out most of the country. It's very heavy!

The separate power supply is even heavier and has a transformer with 280, 290, 300, 310 V secondary rated at 250 mA - but it's massive! Are these things conservatively rated? I would have guessed at least double that. There are two 10H 200 mA chokes - as big as the transformer.

If I strip the power supply and sell the transformers and chokes separately on eBay to the tube amp builders they would probably fetch a lot more than selling the receiver.

But would this be sacrilege? I got as far as powering the PSU and it blew the mains fuse immediately. The old selenium rectifiers are US so I dropped in a 1000V 15A bridge and all is well .

The receiver must at best be a restoration project. The missing knob/switch on the front panel was for a set of preset xtal channels which, unfortunately I removed years ago.

What's the best thing to do with it ?

[AC/HL]

Judging by the label "Receiver No1", that power supply may have been intended for a Dual Diversity system. 250mA is well beyond conservative!

[HamishBoxer]

Shame to break up and possibly quite rare receiver, certainly has CR100 dial. Too far for me to buy and rescue.

[Sean Williams]

Noooo, please do not break it up!

It is a worthy receiver to use in its own right.

I would hazard a guess that the reason you can't find any reference to the unit is because a lot of them were scrapped!

If it can be couriered, I would like to save it.

[hugozair]

Well it does certainly seem to be rare ! I've now searched the internet and only got one hit. A picture of a radio installation on the Canberra (ship) on a New Zealand ham web site. It's in a rack of other gear and doesn't look quite the same as mine.

Since I posted I decided to take a risk and power it up. No smoke. And with a bit of wire out of the window it worked ! main problem seems to be the rotary switches which are very dirty.

This one came from a ship - I bought it from a retired operator who also gave me the complete workshop manual with circuit diagram on linen backed paper. All still pristine !

[turretslug]

Agree with Hamish and Sean, once the last one is gone, it's too late. With PSU, it'll surely shame even a B40 on the see-saw. Just out of curiosity, what's the toob complement (sorry, valve line-up)?

[hugozair]

The valve list is attached. According to a penciled note nearby the equivalents are :
CV133 - L77, CV140 - EB91, CV2128 - ECH91, CV454 - EF93, and the CV216 in the PSU is a Qs150/40.

[g4aaw pete]

Hello Hugozair

your receiver looks very much like a CR150.
There is a miniature valve version, but I can't remember the model variant.

Regards
Pete

[hugozair]

Yes.. I think I read somewhere it's similar to a CR150. Thanks to online OCR here's a general description.

[Mikebay]

For what it's worth, I have in captivity a successor to the HR22, an HR24, just a bit bigger! Weighs in at approx 200Kg, 7ft high, and in the process of restoration as and when.

[HamishBoxer]

That Mike is serious kit, I just love it.

[Synchrodyne]

Most interesting indeed! As far as I know the HR24 was essentially a point-to-point ISB receiver. A Marconi receiver of this nature, possibly the HR24, was described in “Radio & Television Engineers’ Reference Book”, 3rd Edition (R&TVERB III), p.16-21ff.

From the description, the HR22 looks as if it was a simpler version of the same basic kind of receiver, intended solely for selectable sideband reception of HF double sideband signals using the reconditioned carrier technique. This kind of reception was certainly used by HF broadcasters for program relay purposes. The article on SSB relays in BBC Engineering #84, October 1970 (http://downloads.bbc.co.uk/rd/pubs/a...neering_84.pdf) mentions that relay stations were equipped with SSB receivers for lower interference, lower distortion HF reception long before SSB links were started in 1964, and that the then current fit out used dual-diversity receivers.

I should imagine that reconditioned carrier SSB reception would also have been applicable to passenger ships where the HF broadcast receivers fed large-scale public address systems. The rasping kind of selective fading distortion that happens with conventional AM demodulators would not have been too acceptable when relayed over PA systems.

The point-to-point kind of receiver as described in R&TVERB III was equipped for both suppressed carrier SSB reception, with BFO, and reduced carrier SSB/ISB, with either reconditioned carrier or BFO. It also had two 100 kHz 2nd IF sideband channels, upper and lower, to allow for ISB working. Each had two bandwidth filters, 100 to 3500 Hz for voice, teleprinter, etc., and 100 to 6000 Hz for broadcast reception or a pair of multiplexed voice channels. The carrier channel had a 60 Hz bandwidth filter.

From the description and valve line-up, it looks as if the HR22 lacked a BFO as not being necessary for its intended purpose, and had just one carrier 2nd IF channel, on the basis that just one sideband at a time would be required. To hazard a guess, it would have had the 60 Hz carrier filter and probably both 6 kHz and 3.5 kHz sideband filters, the former covering the full bandwidth of HF broadcast transmissions and the latter for more difficult reception conditions, although of course different values might have been used. From the above-mentioned article, the BBC used 90 to 6000 Hz for its SSB relays, the lower limit determined by the need to keep the sidebands away from the carrier.

The use of reconditioned carrier with a product demodulator amounts to quasi-synchronous (homodyne) demodulation. The problems caused by limiting an incoming carrier with asymmetric sidebands were sidestepped by the very narrow carrier filter.

The valve line-up looks to be fairly normal. The use of the 6BA6/EF93/CV454 in the limiter positions may have been done to minimize the number of valve types required, as typically the 6AU6/EF94 was used for this function. And whilst one might expect to see the 6BE6/EK90/CV453 in 1950s receivers that employ many 6BA6s, it looks as if Marconi cottoned on to the ECH81/CV2128 fairly early on – it was also used in the Atalanta marine main HF receiver.

Overall, I’d say that the HR22 is representative of what was probably quite a rare type of receiver, one with a fairly narrow purpose, and one that may have had a relatively limited customer base. There might not have been too many others of this type offered by other makers. And using its line output to feed a good amplifier and speaker system would probably deliver HF reception quality that would be difficult to match except with more modern receivers fitted with the very best PLL synchronous demodulation systems.

Cheers,

[hugozair]

Many thanks to Synchodyne. I think you have nailed it exactly. One bit of info I'd forgotten was that the chap who sold it to me (£55) years ago said it was for relaying broadcast programs around the ship. I bought it in Southampton so it's very likely the ship was a passenger liner.
As you pointed out, it has no BFO, and it also has no loudspeaker output stage - just 600 ohm line feed. The audio performance was also important as it's listed in the manual as being "within 2db from 250 > 6Khz. very AM.
It has an amazing 100Khz filter built in a sealed box 8 x 4 x 3.75 inches with a very sharp response. I will scan some more info and upload it.
Anyway it's clear I must do something good with it so in the first instance I will contact the Fort Perch Marine Radio museum (http://www.fortperchrockmarineradiomuseum.co.uk) as I'm quite prepared to give at least the receiver away. Still not sure about the power supply though as I do need to raise some cash LOL. I will upload the receiver block diagram soon.

[hugozair]

Message sent to Fort Perch. I await a reply.
Scan of receiver block diagram and response plot of the carrier filter.

[Synchrodyne]

So it is a fairly straightforward design, somewhat less complex than the Marconi ISB receiver described in R&TVERB III, block schematic attached. I should imagine that the very narrow carrier IF filter would have been a relatively costly item. Partial AGC volts on the final signal IF stage is interesting and looks to be consistent with the HR22’s mission. As far as I know that is a feature associated with high quality AM receivers, in order to minimize modulation rise distortion, whereas with communications receivers, achieving a wide AGC range was typically a higher priority.

Cheers,

[PaulM]

FYI, here's the 1961 Marconi catalogue page for the HR22. Pretty much as discussed, but is confirmation.

Cheers,

Paul M

[Synchrodyne]

Good to have the confirmation as to its nature!

I have the impression from that catalogue page that the HR22 could be fitted with either the 3.5 kHz or the 6 kHz sideband filter, the former for voice and the latter for broadcast or a pair of multiplexed voice channels. In that aspect, it would appear to have been similar to the HR21, described at: http://www.radiomuseum.org/r/marconi..._receiver.html, whereas the more elaborate models had switched 3.5 and 6 kHz filters.

Cheers,

[hugozair]

I've now heard from the Fort Perch Marine museum who unfortunately can't take it. They haven't enough space to exhibit the stuff they have already. That's a great pity because I can't find any other place that looks a likely home for it.

However, thanks to all the information provided here I will see that it goes somewhere. It seems possible that it's the last one left. So here's an initial offer.

I will give the receiver free to anyone who can collect it. I will also include the power supply minus the mains transformer and the two chokes. Although it is located near Penzance I can drive it to an address in Winchester at Christmas time from where they could be collected. Preferable during the first two weeks of January.

The receiver needs an ht supply of 100mA at 230V plus an additional 25mA via the 150V gas stabilizer valve circuit. The front panel fuses and switch will be left in place as well as the stabiliser. A relatively easy build. The PSU includes the 3U steel case shown in the pdf.

The receiver will need a lot of work. The plating on the chassis is very dirty. The right hand meter didn't show any reading when I tried it. The rotary switches will at least need plenty of switch cleaner but at least I did receive signals with it. It appears to be the 6Khz bandwidth version.

If no one is interested I'll try it on eBay with a start price set at what I think I can get for the txfmr and chokes....Roger

PS..There is a spare valve base in the Rx which was for the spot frequency Xtals. Would it be possible to use this to build a BFO and allow it to receive normal sideband signals ?

[PaulM]

If it really is the 'last of its kind', then it would seem very sad to break up its power unit. It really does 'belong' to the receiver and should, ideally, be kept with it in original condition.

I think that it should be perfectly possible to find a home for the receiver and the intact power supply for a sum well exceeding the value of the transformer and choke.

Sadly, being based in Lincoln and not planning any trips to the far south any time soon, I can't really make an immediate offer, much as I would like to. However, I'm sure that the VMARS community would wish that this receiver and its PSU could somehow be maintained as a pair with somebody able to offer a reasonable sum and meeting your time frame.

Have you thought about the Chelmsford based Sandford Mill museum which has (of course) a large collection of Marconi kit? They may not be able to offer money, but it would be a great home for it. See: http://www.chelmsford.gov.uk/sandfordmill

Save the HR22!

Best regards,

Paul M

[hugozair]

I'll keep trying to see that it gets to a collector, group or museum.
I have messaged the Chelmsford council (what a business - had to register with enough info to get a passport !) and the Radio Officers Association.

I've found a box of NOS Marconi valves (7 x 6ba6/CV454, 2 x D77, 2 x L77/CV133 and a QS150/40/CV216 ) which will come with it. The documentation includes three pages dated 2/10/61 from Marconi test division of volts/current/etc measurements taken throughout the circuit, presumably on commissioning it.

I acknowledge one PM sent on behalf of a friend who would be interested but will take no action on that at the moment.

As far as collection from Winchester is concerned, that can be arranged at about 2 monthly intervals when my partner visits her home. So Christmas trip is not a deadline.

At least if you Google HR22 now this thread pops up No1 !
Roger