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Author Topic: Redifon R408 schematic, manual, info  (Read 3783 times)
LU2DFM
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Posts: 91




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« on: May 07, 2011, 05:22:19 AM »

Hi.
I've been offered a R408 receiver with some unknown problem to restore. The receiver is in good general condition, and reportedly complete.

Some early transistorized receivers where not so very good, however I'm told that this Redifone was an standard ship receiver around late '60s and early '70s, almost ubiquitous in the sea with the Marconi ones. Frankly speaking, it's difficult to reconcile that statement with the complete lack of information about them in the Internet.
The receiver may be of interest anyway because of it's non-conventional mechanical design and it's aesthetics.

Well, I'm looking for the service manual (I've suppose that there was some service manual), the schematic diagram, and informed opinions about performance of this receiver.

Many thanks in advance,
73 de Fer
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G3RZP
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Posts: 4619




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« Reply #1 on: May 07, 2011, 05:31:59 AM »

The R408 wasn't too bad, although the specifications for marine receivers were nothing special. The 3rd order IMD requirement was for the product to be 50dB down on a -27dBm input signal, or an input intercept of -2dBm or thereabouts. The big porblem with the R408 was internal spurious whistles, and there are some strangely placed ground leads, which if move about the chassis, reduce them! I was an apprentice in the marine group at Marconi at the time (group headed by G4PC), and an R408 was well gone over by the group producing the Marconi Apollo.

But I don't have  any more info: as you say there is very little info on them. It's surprising where all the marine HF txs and rxs went....not onto the ham surplus market anyway.
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LU2DFM
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Posts: 91




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« Reply #2 on: May 07, 2011, 10:12:22 AM »

The R408 wasn't too bad, although the specifications for marine receivers were nothing special. The 3rd order IMD requirement was for the product to be 50dB down on a -27dBm input signal, or an input intercept of -2dBm or thereabouts.
Then I will assume that the R408 meets them...

The big porblem with the R408 was internal spurious whistles, and there are some strangely placed ground leads, which if move about the chassis, reduce them!
Fabulous, this will guarantee lots of fun!

I was an apprentice in the marine group at Marconi at the time (group headed by G4PC), and an R408 was well gone over by the group producing the Marconi Apollo.
But I don't have  any more info: as you say there is very little info on them. It's surprising where all the marine HF txs and rxs went....not onto the ham surplus market anyway.
Did you remember anything else? Double or triple conversion (lots of birdies, I would think triple), IF bandwidths in CW/SSB, how did they sounded? Did you remember if they had custom made semiconductors or other unobtainum?

Thanks for your comment.
73 de Fer
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G3RZP
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Posts: 4619




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« Reply #3 on: May 07, 2011, 11:14:22 PM »

I can't remember much about the circuit at all. From memory, it tunes in soemthing like 3 MHz segments at HF: it had to have continuous coverage from 15kHz to 28MHz to meet the spec, which became MPT 1204.

>Did you remember if they had custom made semiconductors or other unobtainum?<

Not as far as I recall: in those days,  it was unusual, although they may have rebranded standard devices. Many of the transistors will be obsolete, but it isn't generally hard to figure out what parameters are needed and find a substitute.

I'll enquire of the Vintage and Military Amateur Radio Society if they have any info.
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G3RZP
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« Reply #4 on: May 08, 2011, 12:18:46 AM »

OK, it took 18 minutes to get an answer from the VMARS people.

Ian Smith, G6RHV has a R408 with manual that he is considering selling. The diagrams are large (A3 size) but contact him directly and he may be able to answer enough questions to get you started.

Contact Ian at radioshedtw at yahoo.co.uk

(The radioshedtw at yahoo.co.uk is done like tht to avoid spammers. it is, of course, the normal @ with no spaces)
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LU2DFM
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Posts: 91




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« Reply #5 on: May 08, 2011, 06:03:49 AM »

Well, thank you very much for your time and effort.
I will contact Ian about the manual.  Hope this week I'll take the time to go see the receiver.

73 de Fer


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G3RZP
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« Reply #6 on: May 08, 2011, 06:10:06 AM »

Apparently in the UK, the going rate for a good example is between £180 and £220 - about $290 to $350.

Good Luck

Peter G3RZP
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LU2DFM
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Posts: 91




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« Reply #7 on: May 21, 2011, 05:48:29 AM »

Peter, thanks a lot for your help.
Ian kindly sent me the manuals over the mail, I'm expecting to get them next week.
I will get the receiver next week finally, as I was unable to spare time off work during the past weeks to go for it.

The receiver was traded for a VHF base. It's hard to know what would worth around here, but since it's non-functional the actual value would be somewhat down. A good VHF used radio is about us$300 here, so perhaps I've ended taking it a little high. However the receiver is in good shape, and will provide fun for some time (until it works fine then I'll be bored again).

Anyway, it came with the additional pleasure of contacting very nice fellow amateurs, which prove that there are friendly and kind people ready to help a complete strange, risking be fooled. For this alone it's worth putting it bottom up on the bench.

73 de Fer

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