| 
  • If you are citizen of an European Union member nation, you may not use this service unless you are at least 16 years old.

  • You already know Dokkio is an AI-powered assistant to organize & manage your digital files & messages. Very soon, Dokkio will support Outlook as well as One Drive. Check it out today!

View
 

The Products

Page history last edited by David Samways 11 years, 4 months ago

 

 

 

The prime product that made up the backbone of the VHF communications network was the Marconi HM100/150 equipments.  The following documentation can be viewed:

 

  • Specification sheet here
  • Technical specification here



However, the training school in Oshodi also provided training for equipment not always manufactured by Marconi, but was used by the Nigerian Post & Telegraphs Department:

 

  1. ASAC - Automatic Selection of Any Channel, a system used by the more rural communities taking a baseband feed from the VHF system. From memory it was a 6-channel system and I remember tracing the circuit diagrams over many evenings (we only had one copy of the manual) for later dyeline processing so every student could have their own copy. Happy days!
  2. GEC RUCAR (Rural Carrier) – similar to the ASAC above taking its baseband from the HM100 / 150 VHF equipment
  3. Siemens CS12/CR multichannel baseband equipment
  4. Ex-RAF Cossor T-1509 transmitters – further information can be found here - line reference #141
  5. Ex USAF RCA ET-4336 transmitters – further information can be found here  - line reference #3303
  6. Marconi "Atalanta" HF receiver – further information can be found here
  7. GEC 5-channel VHF system.  This was a single RF channel operating up around 170/180 MHz that carried 5 carrier circuits.  One RF channel, 5 speech channels riding on it.  I can’t remember if it used “normal” channel frequencies, i.e. a basic 60 to 108kHz group, but probably not, so more likely used the inverted group below 60 kHz assembled “upside down” if you recall the numbers.  It may even have used a bastard arrangement with one real time speech channel as an EOW and 5 more channels at 4kHz spacing above the 0 to 4kHz EOW.  I can’t even remember whether it used in-band or out-of-band signalling. You will recall (won’t you) that the CS12/CR used a 3825Hz signalling tone that was the equivalent in land line terms of the “P” wire running alongside every copper channel through an automatic telephone exchange. 
  8. Other stuff such as point-to-point communications but I can't recall the detail apart from the fact Marconi provided it. I know I used it in my flat and car so I knew when to collect Doreen from the airport after control had been handed over from Lagos to Kano. Those were the VC10 days!

 

 

Extract from emails received from John Wilson on this subject – what a memory!

 

The baseband equipment allied to the HM100 system was the Siemens CS12/CR, not TMC. I met up with this on my arrival at Enugu and eventually lectured on it at Oshodi. I don't recognise the ASAC reference, but the main line carrier system that we used and was taught by Jim Clarke at Oshodi was made by GEC, as was the RUCAR (Rural Carrier) equipment and the little five channel VHF radio system, all of which systems we had to maintain in the field even though they had no connection with Marconi.

 

My principal task when I first went to Oshodi was to write and teach the first HF radio course held there, largely I guess because of my radio background in HF comms in the RAF and at Pye Telecom. It was quite an experience at Oshodi because I was presented with an equipment room containing a couple of ex-RAF Cossor T-1509 transmitters, an even older ex USAF RCA ET-4336 transmitter and a so-called monitor desk housing a Marconi "Atalanta" HF receiver which was one of the worst designs ever to reach production. In fact, I'm not sure that Marconi actually made the Atalanta, and it may have been produced by Eddystone Radio.

 

How could I forget the Atalanta? It was a pig to use and worse to work on. If you have encountered today’s SDR black boxes driven by computer software you must wonder why all that could be done by a 100 pound suitcase can now be done, and better, with a tiny box with an antenna socket at one end and an Ethernet socket at the other. SDR = Software Defined Radio in case you have not met the term.

 

The job was not without its exciting moments. The T-1509 (AM of course) was constructed using sliding drawers in a five foot rack. Each drawer was seriously heavy, as one might expect remembering typical power supply designs and the sheer bulk of a big modulation transformer, not to mention the RF deck. It was only when one of our "students" pulled out the drawers starting with the top one and working downwards that I realised that the bloody rack had not been bolted to the floor and it was only swift reactions and brute strength that enabled us to get one drawer back into the rack and avoid a student funeral in a very flat coffin.

 

On the ET-4336 (1kW of RF), the access to the guts was by a full length door on the rear of the rack. I was going through the motions of pointing out and identifying the various units through this door, using a pencil in my hand, when some smart-ass student "pressed the tit" and I found myself on the end of a substantial RF arc drawn by the end of my pencil and into my fingers.  The students thought that this was absolutely hilarious as I backed away drawing the arc with me. I was not amused.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Comments (5)

David Samways said

at 8:46 am on Nov 29, 2012

Can anyone add to the equipment list, and maybe more detail? Please add any comments in the box at the bottom of the page.
John Price – you were with GEC in Nigeria, can you help on the GEC stuff?

jdlprice@... said

at 4:09 pm on Nov 29, 2012

Hi David, GEC Telecommunications 5 channel VHF is correct but I cant add any more to your list. Sorry Sah he is not on seat!
How did Nigeria get tangled up in what was at one stage the USAAF system.
Keep up the good work.
Cheers John

David Samways said

at 6:04 pm on Nov 29, 2012

Hi John, the reason is that the Communications side of Marconi is not yet an "established Wiki". At the moment it only includes the two projects - USAF 1960 and Nigeria 1960. It was stated some 15 years ago that Marconi had some 15 contracts woth over over $2 million USD each but as yet nobody has come forward to volunteer anything - they may be "deaf" of course.

johnwilson@freezone.co.uk said

at 6:18 pm on Nov 29, 2012

Sadly, and inevitably, many of the men (and women) who were serving in the far flung corners of the Empire are now dead.I was only in my very early twenties when I was with Marconi in Nigeria and I'm now in my mid seventies. Since the whole Marconi backbone system stopped working when we left and our Oshodi students took it over, and was left to rust away as the jungle enveloped the repeater stations, it's likely that "we few, we happy few, we band of brothers" are the last ones to hold the memories.
John Wilson

David Samways said

at 6:32 pm on Nov 29, 2012

How well put John W. But folks can still come out of the woodwork - Dave Barker for one. John Hardy and JimClarke of similar age are probably still around if only we knew where. Mike Messenger too....

You don't have permission to comment on this page.