Radio Interferance

[Service Engineer]

I was gonna suggest some RF chokes be fitted to his CPU in the first instance. Then if that didn't work a possible re-wire using screened cable.

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MESSAGE

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Can you please help?! I have a hard wired alarm system (control panel Melcom ST6000). A radio ham has recently moved into a property across the road and his equipment is setting off my alarm. If there is a solution, I would be very grateful for your advice. Many thanks.

Any other suggestions to the above query before I send a reply.?

[Guest]

A decent panel?

[amateurandy]

I was gonna suggest some RF chokes be fitted to his CPU in the first instance. Then if that didn't work a possible re-wire using screened cable.

Any other suggestions to the above query before I send a reply.?

If he's also getting interference elsewhere, e.g. radio or TV he can ask Ofcom to investigate (used to be the Radio Communications Agency I think). They may do this for free, or charge

[Guest rjbsec]

Send him a link to the ACT Meters webste.

We have one site next to a radio ham, had a DA Abacus with all screened cable - in for about 12 years - never a problem.

[sparky83]

I would say a decent panel aswell!

[hullofaplace]

Ahh that thread brings back memories of an age old argument that came about on the estate i used to live on many moons ago a bloke decided to set up a huge rig for his cb and cause allsorts of interference on tv's (it was a while ago) and a neighbour of my parents snook into his garden one evening and pushed a pin into the coax which fed his aerial and then cut the pin flush so it couldnt be seen, not sure if it damaged this blokes cb kit but it certainly put him out of action for a week or so untill he replaced his coax.

I wouldnt suggest that's your solution as tresspassing is illegal just thought i'd share that story !!!!

[mjw]

I was gonna suggest some RF chokes be fitted to his CPU in the first instance. Then if that didn't work a possible re-wire using screened cable.

Any other suggestions to the above query before I send a reply.?

If he is going to re run cable and used screened cable....tell him to earth it at one end only!!!!!!!!!!

[breff]

I bet it has crappy detectors with little or no immunity to rf as well.

[arfur mo]

I was gonna suggest some RF chokes be fitted to his CPU in the first instance. Then if that didn't work a possible re-wire using screened cable.

Any other suggestions to the above query before I send a reply.?

hi dave,

most licenced 'hams' will do all they can to stop interferrence with neighbours equipment from happening - if told it's a problem. being licenced means most have the technical skills to do so, as its part of the examinations to demonstrate this ability. the cause could be simply a 'leaky' coax connection and simply sorted.

1st stop is talk nicely to the ham before getting heavy, as usually he won't want any problems with the authoritie's poking there nose in, they are usually very proud of their kit and its pefomance with no signal 'loss' if my pal is anything to go by, any leakage equals less Tx range if not using a local repeater.

i don't know of the alarm panel, but if its fairly old upgrading may be needed to get better rfi rejection. you can put a coil in each wire at the panel by winding 5 turns around a terminal screwdriver but tedious and not guarentee.

if this is exsplained to the ham it may persuade him to be very helpful as he will know your poster is not going to want to spend a wad of money on a new system so he can chat arround the world and is liely to kick-up.

regs

alan

[luggsey]

I was gonna suggest some RF chokes be fitted to his CPU in the first instance. Then if that didn't work a possible re-wire using screened cable.

Any other suggestions to the above query before I send a reply.?

First action is to record the times of your suspect RFI problems, after a week or so have a friendly chat with the radio amateur and ask him if he would compare the times you have had RFI to the times he has been transmitting in his log book. You can then be sure if the problem is with the radio amateurs transmitting or something else. If the times match then the amateur will be able to make "station checks" on the frequency band concerned. If no 2nd, 3rd, 4th harmonics are present then he should tell you. At this stage the amateur "may" reduce power if that is causing problems with field strength or if already using low power he may suggest that your equipment has low immunity to RF and there is nothing he can do. Most modern amateur equipment when properly used does not cause any problem, if this "radio amateur" is in fact a CB operator then thats a different ball game!

As for screened cable, there is a right and wrong way to use screened cable to stop RF problems, I can tell you more if you decide to go that way.