RF Interference from low-voltage lamps. - UK Vintage Radio Repair and Restoration Discussion Forum

rico2_uk · 5th Jan 2007, 4:24 pm

I wonder if anyone has a bright solution. I have restored a lovely old Roberts R200 which after solving the old AF117 problem and a couple of caps now is just like new. -- well until I switch on my Low voltage down lighters- that is

I have this issue with several radio sets, so my question is is their some form of filter you can put in that solves this? Help gratefully received

regards and thanks

ppppenguin · 5th Jan 2007, 4:31 pm

The problem is caused by the electronic "transformers" that supply 12V to the downlighters. These are cheaper, smaller and lighter than the traditional wound transformers but can generate RFI because they are switchmode power supplies operating around 30-50kHz. Some ideas:

Make sure the low voltage leads from the transformers to the lamps are as short as possible. Ideally no longer than a foot.
Find which transformer(s) are offending and change them. Either to a new electronic one or even a real wirewound one.
Get rid of the LV downlighters
Listen in the dark

If one electronic tranny is used to power multiple lights this usually means long-ish low voltage leads which is bad news.

Darren-UK · 6th Jan 2007, 4:52 pm

Indeed yes. We've had similar discussions before and you'll find downlighters ( or rather the switchmode supplies they use ) are not the only modern items which can - and do - cause RFI

.

rico2_uk · 7th Jan 2007, 3:44 pm

So Sadly does this mean there is nothing I can do about it

Darren-UK · 7th Jan 2007, 3:48 pm

All you can really do with no expenditure to speak of is to limit the number of RFI-causing gadgets in your house and/or try to use your radio/s as far away from any such gadgets as possible. It's made worse if your ferrite-fitted radio needs to operate with the ferrite rod pointing towards any source of RFI ( which may come from a neighbouring building as well as from inside your own house.

Other members may suggest a few high-tech solutions. As Jeffrey said above, you could try replacing the electronic transformers with wirewound examples.

This is a widespread problem nowadays which will effect most AM radios; it's the fault of certain types of modern electronic equipment, not the radios - regardless of their age.

Geoff G4ICD · 7th Jan 2007, 4:19 pm

Quote:

Originally Posted by rico2_uk

So Sadly does this mean there is nothing I can do about it

As has been suggested, simply change the transformer for a "wound" version (about £4 from your electrical wholesaler), did the same here.......problem solved..........Geoff

5th Jan 2007, 4:24 pm	#1
rico2_uk Retired Dormant Member Join Date: Sep 2003 Location: Welwyn Posts: 3	RF Interference from low-voltage lamps. I wonder if anyone has a bright solution. I have restored a lovely old Roberts R200 which after solving the old AF117 problem and a couple of caps now is just like new. -- well until I switch on my Low voltage down lighters- that is I have this issue with several radio sets, so my question is is their some form of filter you can put in that solves this? Help gratefully received regards and thanks

5th Jan 2007, 4:31 pm	#2
ppppenguin Retired Dormant Member Join Date: Dec 2003 Location: North London, UK. Posts: 6,168	Re: Roberts Radio Interferance The problem is caused by the electronic "transformers" that supply 12V to the downlighters. These are cheaper, smaller and lighter than the traditional wound transformers but can generate RFI because they are switchmode power supplies operating around 30-50kHz. Some ideas: Make sure the low voltage leads from the transformers to the lamps are as short as possible. Ideally no longer than a foot. Find which transformer(s) are offending and change them. Either to a new electronic one or even a real wirewound one. Get rid of the LV downlighters Listen in the dark If one electronic tranny is used to power multiple lights this usually means long-ish low voltage leads which is bad news.

6th Jan 2007, 4:52 pm	#3
Darren-UK Retired Dormant Member Join Date: Apr 2003 Location: Blackpool, Lancashire, UK. Posts: 4,061	Re: Roberts Radio Interferance Indeed yes. We've had similar discussions before and you'll find downlighters ( or rather the switchmode supplies they use ) are not the only modern items which can - and do - cause RFI .

7th Jan 2007, 3:44 pm	#4
rico2_uk Retired Dormant Member Join Date: Sep 2003 Location: Welwyn Posts: 3	Re: Roberts Radio Interferance So Sadly does this mean there is nothing I can do about it

7th Jan 2007, 3:48 pm	#5
Darren-UK Retired Dormant Member Join Date: Apr 2003 Location: Blackpool, Lancashire, UK. Posts: 4,061	Re: Roberts Radio Interferance All you can really do with no expenditure to speak of is to limit the number of RFI-causing gadgets in your house and/or try to use your radio/s as far away from any such gadgets as possible. It's made worse if your ferrite-fitted radio needs to operate with the ferrite rod pointing towards any source of RFI ( which may come from a neighbouring building as well as from inside your own house. Other members may suggest a few high-tech solutions. As Jeffrey said above, you could try replacing the electronic transformers with wirewound examples. This is a widespread problem nowadays which will effect most AM radios; it's the fault of certain types of modern electronic equipment, not the radios - regardless of their age. Last edited by Darren-UK; 7th Aug 2007 at 6:01 pm. Reason: Removed unnecessary quote.