[cma-l] New FM transmitter

[Associated Broadcast Consultants]

Hi Neil,

First of all - DO NOT try one of those cheap Chinese transmitters from
Ebay.  It will not meet Ofcom specs and will get you in serious trouble.
I recommend the following approach (apologies if you have already tried 1
and 2).

1/ Firstly try connecting the TX and amplifier to a dummy load.  If you
don't have one, try contacting your local radio amateur radio ham) club.
Then run the transmiiter system into that for a few days.   If it still
trips then it tells you the problem is inside the box (provided you use all
new leads).  If it does not trip it tells you the problem is with the
aerial or leads/connectors.
2/ If it suggests the problem is inside the box, get someone who is handy
with electronics to delve inside.  The most likely source of the problem is
a dodgy connectyor -eg: the bulkhead connector on the case or where the rf
comes out of the circuit board.  Check there are no solder joints.

2/ If all seems OK then why not ask Radica to take a look at it?  It would
surely cost less to repair than to buy a new transmitter.
3/ If those avenues fail, then it looks like new transmitter time.  As you
say you only need a mono transmitter because you have the stereo
generation, audio processing and RDS taken care of with Stereo Tool.
However you will find it difficult to find such a beast with CE mark.
Although you might find some slightly cheaper CE marked transmitters, these
are likely to be unfamiliar to Ofcom and so they might be reluctant to let
you use them.  Therefore it might be easier to buy a Broadcast Warehouse
unit.  They are well known to Ofcom and generally acknowledged to be good.

4/ If you do buy a BW unit you will see that they now include in-build
DSP-X functionality.  This is a cut-down version of their audio processor,
not a simple limiter. When setup correctly they sound really excellent.
Personally I'd rather use the DSPX and internal stereo encoder than Stereo
Tool - likely to sound slightly better, louder and less points of failure.
They do not have in-built RDS though, so you would need to use Airomate
(software) or a cheap RDS encoder (cost for £10s to £100's).

Regards, Glyn

-- 
Glyn Roylance - Principal Consultant
Associated Broadcast Consultants <http://www.a-bc.co.uk/>


On 13 January 2014 18:38, Neil Jordan <admin at radiocracker.org.uk> wrote:

> Hi Folks,
>
> I help with a local charity radio station and we broadcast each year in
> the 4 weeks prior to Christmas under an Ofcom S-RSL.
>
> We currently use a Radica FM5 and FM50 linear amp to boost the output to
> 25W, but during our broadcast last month the FM50 tripped out with high
> VSWR at least once a day. We're confident our aerial and cabling are fine
> so our thinking is that, at over 20 years old, maybe it's time to replace
> the Radica kit.
>
> As a charity station we try to keep operating costs to a minimum so I'm
> asking if anyone can recommend a low-cost FM transmitter of around 30W. We
> have a PC running StereoTool so we don't necessarily need a transmitter
> with in-built compression/limiting or RDS as StereoTool can handle it.
>
> I see cheap transmitters on Ebay from China but I can't see these having
> the CE mark that Ofcom insists on, though I'd welcome any comments on these
> too.
>
> Thanks
> Neil.
> --
> Neil Jordan
> Radio Cracker Ballymena
> admin at radiocracker.org.uk
>
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