Suppressing Intereference to FM on a mains-powered portale radio.

[Murphyv310]

Hi.
I agree with Terry without being quite as blunt. With all the will in the world you obviously need to discuss with the customer what is causing the problem and if you feel you can cure the problem. I am not sure its a good idea to fit components in a plug top and the mains earth is likely to be dirty too so it won't cure the issue. If you feel that you don't want to proceed, why not suggest rechargeable batteries. I do though think trying the diodes and ensuring the transformer has its faraday screen intact should be done.

[Old Sparky]

Terry, I'm not certain the radio is faulty as such, especially after trying a Sony Radio Cassette in my workshop, and getting simiar interference on that, besides which the Roberts worked perfectly from the mains here at home. I have yet to speak to the owner about this, but did suggest to another member of the family that by running it from batteries there would be, based on my tests, no interference on FM. I will also try the radio, using a mains adaptor incorporating a RFI Filter.

[Murphyv310]

Hi.
I'd most likely have taken a different radio to the customers house to see if the other make of radio performed better, then I would know if I was ******** in the wind or not.

[Old Sparky]

The other afternoon, I took the radio back to 'Oats', a local shop where it is used, usually tuned to Radio2. Running from batteries everything above about 90MHz worked OK in the shop, so Radios 4, 1, Clasic FM and a few others came in at good listenable quality. However below 90MHz there was a problem which meant that good reception of Radio2 on either of the frequencies (88.3MHz & 89.5MHz) we get in this area wasn't possible. I mentioned another radio, but was told they had already tried adifferent one, which was no better. No local retailer stocks mains adaptors incorporating RFI Filters, so I may order one to try. The shop in question (a health food store, btw) is on a busy main through road and directly opposite a popular local pub.

[Mark Hennessy]

So FM reception is not acceptable at this location. That happens... Luckily, there are many alternatives:

1. DAB
2. FreeView
3. FreeSat
4. Internet Radio

At least one of these will work, and depending on what's already at the premises won't necessarily be expensive. Advise your customer to get researching, and in the meantime, I trust they've paid you well for all the time spent on this so far.

[Murphyv310]

Excellent advice from Mark as always
Plus we now know its not likely to be mains bourne interference.

[Terry]

Have you investigated where the interference is coming from? I'm thinking here, as it is battery operated and still giving trouble, checking the performance in various parts of the accommodation available to them.

For example, what happens if you move as far from the road to the rear of the property?

Keep the aerial horizontal as far as possible as it will give a good indication of how well a simple dipole would work - if you can find somewhere where the wanted signal is in a different direction to the interference source, a useful improvement on signal to noise ratio can be achieved.

Have you considered an external aerial? The same check would be a useful pointer where such an aerial might be placed.

I assume that, like many such places, the accommodation is shared so the ideal location might not be accessible but it would be worth a try.

There is no need to add a permanent socket during the testing phase, simply connect the coax between the feed to the telescopic aerial (having first disconnected it from the whip) and the screen to chassis, keeping the connections as short as possible.

[Murphyv310]

Hi.
Terry, I have already explored the possibility of an external aerial and advised the use of a different set to see if it performs better.
I really think this has to put to bed now and I would like to think Sparky follows Marks advice.
I'd initially think a Dab set should be tried then the other suggestions discussed with the customer.
I would also remind anyone still trading that £10 jobs are a no no, this trade has been decimated by those that persist in doing "homers" and those that are scared to charge at a reasonable level. No doubt caused by so many that don't have kids and have little outlay running a home and do it for the love of the job.... aye right!!!! It just spoils it for others. Put me right though if i am wrong. I am always reminded by plasterers, brickies, plumbers and electricians that it us that have killed our trade.
A wake up call to charge properly and not to pander to customers.

[Terry]

I have already explored the possibility of an external aerial and advised the use of a different set to see if it performs better.

Sorry, Trevor. I did scan all the previous posts but missed your earlier suggestion about an external aerial. However, I was primarily trying to address the situation whereby the shop owner may only have limited access to parts of the building.

As for trying another set, Old Sparky says that has already been tried with similar results.

Something else I overlooked is that, after saying that the problem occurs on battery operation as well as mains, Old Sparky is thinking of buying an RFI suppressed PSU to try.

As the battery must be the best RFI suppressed PSU available, it is very obvious that this will be a complete waste of time and money!

[Refugee]

The downstairs in my house is an FM black spot with stereo impossible.
The only solution I have found apart from an out door aerial is to use one of those £8 tesco radios to find a spot with a bit of signal. Once I find a location a shelf has to be built.
Mobile phones are just as bad.