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Clamsman Transmit Problem


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I've now sorted the "imagineered" Clansman installation for my Stolly, which has a PRC352 with TUAAM, Initiate Box, IBHA, IB3 and a pair of CB2s. If I plug a handset into the spare connector (SK1) on the 352, it will transmit and an SWR meter shows 20W forward power and 0W reverse, so the TUAAM is obviously doing its thing. However, if I try transmitting using a handset or pressel connected to the CB2s, the 352 doesn't transmit. It receives OK and the intercom function of the harness is working. Have I missed something obvious?

 

Andy

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I've now sorted the "imagineered" Clansman installation for my Stolly, which has a PRC352 with TUAAM, Initiate Box, IBHA, IB3 and a pair of CB2s. If I plug a handset into the spare connector (SK1) on the 352, it will transmit and an SWR meter shows 20W forward power and 0W reverse, so the TUAAM is obviously doing its thing. However, if I try transmitting using a handset or pressel connected to the CB2s, the 352 doesn't transmit. It receives OK and the intercom function of the harness is working. Have I missed something obvious?

 

Andy

 

Hi Andy,

 

See this, it may help

 

http://www.ferret-afv.org/manuals/clansman_wiring_harness_and_control_boxes_description.pdf

 

Regards

 

Bob

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Unfortunately not, I've already got the intercom side of things working.

 

I'm wondering if I need to connect the 352's "Remote" terminals to the "Radio" terminals on the IBHA?

 

Andy

Edited by andym
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Andy

 

Figure 1 of http://www.fv432.co.uk/manuals/fv432ClansmanManuals/clansmanfv432installationpart007.PDF shows both audio socket 1 and the remote terminals of the 351/352 connected to the IBHA so I think you are correct.

 

Regards

 

Iain

73 de G0OZS

 

That's what I thought, but it seems a bit odd to have to cobble something on top of the existing 7-pin connection. Why doesn't the IBHA handle this internally by putting the required impedance across the microphone lines? Strange.

 

Andy

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I can only suspect that it was to make the IBHA simpler. The IBHA is needed because the PRC sets lack a separate harness connector found on UK/VRC-321 and UK/VRC-322. The Harness microphone/PTT circuitry works more like the remote than a headset using lower audio levels and changes in the DC resistance across the audio lines for keying (and indeed the RT321 harness audio input and remote terminals are internally connected according to EMER H592 Fig 26). In the case of the RT351/2 using the radio's own remote input saved building the equivalent of a CRL/R box into the IBHA. The CRL/R is needed together with the IBHA when connecting the RT320 which has no remote terminals to a harness.

 

Documentation of the way the harness evolved is most likely lost in the mists of time but I suspect that the origins of Clansman in simultaneous semi-independent projects by BCC (later part of RACAL), Plessey, MEL and Marconi led to a need for the various interface boxes that could have been avoided had the sets all been specified and designed consistently with harness operation as a requirement - the ARFAT box needed to use the UK/VRC-353 with the RACAL(BCC) TUUAM ATU is another case of this. RACAL used pre-existing BCC technology to a considerable extent which led to the need for adapters to "Clansman standard" solutions by Marconi and MEL.

 

Clansman is in any case a considerable advance on Larkspur with the intercom in the harness boxes rather than a radio and an inherent rebroadcast capability independent of harness using the remote terminals of the radios

 

Regards

 

Iain

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I still think it's a bit odd. Unfortunately that particular copy of the FV432 manual is missing the page with the figure showing the Larkspur wiring diagram, but I note that the IBRA (as opposed to IBHA) doesn't have any remote terminals. Neither does the SANIE, which replaces the IBHA when it's used for BATES. I need to have a play with mine at the weekend and see what happens.

 

Andy

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  • 9 months later...

To answer my own question for completeness and future reference, when using an IBHA (the standard arrangement in a Clansman harness) a PRC351/2 needs the remote cables connected to the IBHA and then to be switched to "Remote" or it won't transmit. However, if you're using a SANIE instead of the IBHA, typically in a BATES installation, you don't need the remote cables and it can stay switched to "Local". There must be some logic there somewhere ... icon_e_smile.gif

 

Andy

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