Tai Pan
17th February 2009, 09:48
(K) Inside the CR300 was a circuit, apparently you could make it work as a crystal set. You took off a valve cap and placed it on this apparutus ,twiddled a piece of metal on a crystal, and on total power loss you could still use the CR300. Did anybody ever get it to work, I tried many times without any success.

17th February 2009, 10:01
A rumour put around by shipowners to avoid paying for an emergency RX perhaps (A)

Sounds fascinating - was this xtal set supposed to be fully tuneable?


Tai Pan
17th February 2009, 10:05
Dont think so, only MF, but cant remember

Tai Pan
17th February 2009, 10:28
I think the idea was that having blown all the valves and spares for the CR300, spilled your beer into the emergency rx, shorted out the rx in the AA with the tins of ciggies stashed there and lost the lifeboat rx in the last BOT sports day, and the df having been stolen in Port Said, you could still listen on 500

17th February 2009, 10:41
After all that you'd need to be sending on 500 !


Ron Stringer
17th February 2009, 19:21
Please don't knock the CR300, they didn't build them like that anymore, even when I sailed with them in the early 1960s. I know I cursed their drifting with temperature changes in the tropics whilst I was trying to locate the GTZZ press broadcast intro tapes. But they were really rugged.

On the "City of Lucknow" the radio room was immediately aft of the wheelhouse, on the port side of the bridge deck, and had only one porthole - in the port bulkhead. Because the bridge front was extended slightly outboard of the wheelhouse door, the radio room porthole was screened from any breeze other than almost square on the beam and it was no use putting out a wind scoop. So once we got into any warm weather, the porthole and the radio room door were left wide open all the time, in order to save me from being parboiled by the heat produced by the radio gear.

Not least of which came from the type 975 ''Oceanic'' broadcast receiver and associated distribution amplifer which only worked from 110V d.c. and on our 220V d.c. mains, employed a bloody big dropping resistor housed inside a perforated metal 'cage' bolted to the receiver cabinet. A sort of basic, one-bar, electric fire. Just what you needed in an unventilated radio room when on the Indian Coast or in the Red Sea.

One afternoon at anchor somewhere in the tropics I had been collecting a few ZZZs on my daybed in my cabin on the starboard side of the boat deck. The steward woke me with tea and tabnabs and I sat enjoying them for a minute or two before I noticed that it was absolutely hammering it down outside. Luckily the wind was on the port side, so that none of the rain was coming through the porthole immediately above my bunk, which would have been soaked if the wind had been coming from starboard.

At that point I realised that the rain would be belting down on the port side, where the radio room port was wide open. I shot off along the alleyway and up the stairway to the bridge. As I reached the top I met a stream of water running out of the radio room and heading down the stairs towards me. The radio room was flooded to the depth of a couple of inches - up to the coaming of the door threshold, and spilling over into the stairway.

Fitted directly under the porthole was the CR300 receiver, which was no longer working as the dial was dark. If you are familiar with the CR300 you will recall that the construction was like a deep box with a hinged, lift-up lid secured by a couple of half-turn screws. After shutting the porthole, I released the screws and peered inside the receiver. The water inside was about 4 inches deep. Oh was I in deep sh*t!

Water was leaking out of various openings in the case, around control knobs, fuseholders and the like and after isolating the supplies, I set to to dismantle the set. I removed it from the bench and took it through the wheelhouse to the starboard door and teemed the remaining water onto the deck. I then took it back into the radio room and perched the CR300 on top of the ''Oceanic'' for the night. Then I set about sorting out the flood on the deck.

The following morning before breakfast, I refitted the CR300 on the bench, replaced the fuses in the vibrator power pack and switched on. There were one or two hissing noises but the lights came on behind the dial and she burst into life. Copied the traffic list without any problem.

Sailed with that set for about another year without a single problem. Not sure that an ''Atalanta'' or an ''Apollo'' would have survived an 'early bath' like that.

Tai Pan
18th February 2009, 11:22
Good story Ron. Yes the CR300 was a very good workhorse, had its bad side but very reliable. It would seem I have hit on a subject that is not known to electronic whizz kids, even GTZM types not answering. tapeing GTZZ, thats a bit modern, I always took it by hand and then had to type it onto flimsies. still us oldtimers knew how to operate!.

K urgess
18th February 2009, 11:54
I never sailed with a CR300.
On most of the older ships they had been replaced by Atalantas by the time I got there.
Almost everything built or refitted after 1948 had Mercury/Electra combinations. Except trawlers for some reason that appear to have favoured CR300s (Yeoman) into the 50s.
There's a picture in an early Marconi Mariner showing an Electra fitted in 1949 to the Queen of Bermuda. They were announced by Marconi in the house magazine in May 1948.
So most were gone by the time I joined in '66. Lucky me. [=P]

Ron Stringer
18th February 2009, 14:57

Sorry, I misled you there. I was never lucky enough to be able to tape the GTZZ broadcasts, they were all typed onto those flimsy vellum things that the duplicator required. Had bottles of 'corrector fluid' or something like that to paint over the errors - God help you if any got through.

No I was meaning the punched tape loops (or wheels, if that is what they employed) used by the coast station to give a station ident before sending the Press. We used to have a bit of paper where we wrote down the various HF station callsigns and the current cursor log number, to help tune the station in. Unfortunately on ships without aircon, the radio room temperature would vary with not only the external temperature, but dependent on the amount of use of the radio equipment.

So you might have logged the 8MHz frequency for the Press as '163' one night, but going there the following night there would be no sign of the station, even as transmission time approached. Then began a frantic search for the signal so that the main items were not missed. With even an Electra, there was some chance that you would be near to the intended tuning, but the CR300 could have drifted miles away.

In the Caribbean, at night-time in winter we could often hear Portishead on 4, 8 and 12 MHz, but all at QSA2 or 3, and sometimes one or more frequency would be subject to heavy fading. Trying to pick the best one, that you hoped would last for the full 30-45 minute broadcast, was somewhat fraught at times, made worse because the bloody station was never where you had left it on the dial of the CR300!

On a good day, the station ident would run for about 15 minutes before transmission time. Other days in would only start a minute or so before the gun went. You would be searching frantically, as the panic grew, from band to band. Then of course, there were the days when they started late (and one when they sent the Press with the paper tape the wrong way round in the machine). No wonder my hair started to recede after a few months aboard.

18th February 2009, 15:54
Talking of the CR300 drifting reminded me of a very embarrising moment. I used to keep a little notebook of tuning dial numbers for every radio station I came across and on one ship we were going south towards Magellan Straits and I noticed that the tunings had changed to a uniform amount all round. So - clever clogs retuned the tuning condensors to bring settings back to original list. Worked fine at first but naturally it didn't work throughout the tuning and so it wasn't long before I couldn't pick up anything and it took me a long time to get it back to where it should have been.
I learnt to think twice before trying to be clever.

Tai Pan
19th February 2009, 09:08
OK Ron, miread you about tapes. I think all CR300 had a book with vernier numbers settings built up over years., but as you say, could drift like mad, however in ten years using them I never had a fault or replaced a valve, built like a brick ****house.

21st February 2009, 03:00
I never sailed with a CR300.
On most of the older ships they had been replaced by Atalantas by the time I got there.
Almost everything built or refitted after 1948 had Mercury/Electra combinations. Except trawlers for some reason that appear to have favoured CR300s (Yeoman) into the 50s.
There's a picture in an early Marconi Mariner showing an Electra fitted in 1949 to the Queen of Bermuda. They were announced by Marconi in the house magazine in May 1948.
So most were gone by the time I joined in '66. Lucky me. [=P]
My first trip on my own was on the Hull trawler Newby Wyke, main rxr Atalanta, with a CR300 alongside it. That was in 1966. (Main txr was an Oceanspan V.) The Atalanta's drive cord - for the main tuning dial, not the bandspread - broke and I could find nothing to replace it but a thread from an unravelled green nylon fishing net repair line, which was slippery and stretched if under too much tension. I came home with the Atlanta left on 2182 kHz and used the CR300 for everything else - including phone calls. Don't remember having any problems.

K urgess
21st February 2009, 11:38
Wow. (EEK)
I suppose I should change that to
"Except trawlers for some reason that appear to have favoured CR300s (Yeoman) into the 60s." [=P]

13th May 2009, 23:44
I Have A Cr300 And It Still Works.

Ian M

16th May 2009, 16:03
All credit to the designers of the CR300. Mechanically it was very robust and apart from the drift in the tropics it was a pleasure to use. I used to leave the top lid open so that the heat generated internally could escape.

On one of the CR300 I worked with, the ball bearings used on the main tuning condenser dropped out. I can only assume that the constant vibration from the engine over the years loosened the lock nuts holding the main tuning condenser. I removed the condenser and gave it to the Chief Engineer. He subsequently had one of his lads turn down a very high tolerance shim which were fitted instead of the ball race and it worked just as well. I tried for hours to locate two ball bearings but could which fell out but never did find them despite the assistance of a magnifying glass.

I sailed with that receiver for ten or more months before eventually getting it replaced by the Marconi Depot in Durban RSA.

I never replaced a Valve or had to effect any repair to the receiver apart for the one mechanical problem, which was caused by horrendous vibration

Great Receiver and fond memories of many long hours chasing stations around the dial!