Radio Station Interference

Look at the intermediate frequencies generated within the FM transmitter and the intermediate frequencies used in the receiver's detector circuits. If the two frequencies are close, therein lies the problem; the two pieces of equipment are therefore geographically too close to each other and replacing either the transmitter or the receiver may be a solution to the problem.

Your transmitter may be causing interference at the IF (intermediate frequency) used in her radio. Analog radios work by downconverting the FM signal to IF for amplification. Her car radio, which may be much newer, may use a more modern digital scheme. I would find out how old her inside radios are. If they're fairly old, try a new digital radio in the house. If the new radios work OK, then buy her new ones to replace all her old ones.

Something else to try would be to take the battery powered radio from the house out to the area by the car. If the radio works OK there, then the problem may be RFI coming from the church over the power lines and radiating in the woman's house. If that's the case, an electrician can check the church and the house for proper grounding, or install some filters on the church's power lines to keep it from leaving the building.

Thanks for your feedback. I tried the battery powered radio in her driveway but it still didn't work. Car radios work fine, but not the others.

v

Its very interesting things. We can say its very simple but very complex as well. I suggest your friend would chang her radio position when she listen to it, for example put the radio in another room or from one side to another spot in order that she can get a fit place for listenning.

We can suppose: 1] her room is too close to the station to listen, becasue the signal is strong enough to saturate her radion preamplifier. at the time even if she turn down the knob, its no help.you can prove it by taking far place to see if it could work well. 2]FM station is working at short wave, it can easily be shielded be the wall and easily produced reflect wave. this wave can be added by original signal to produce a empty electromagnetic field ( sometines comb filt effect), so tht you cannt get any signal at present.you cant listen any sound of cause. or by now only but noise. if the reflect signal is closed to original ( but not equal to ) they will produce a beat frequency and will cause the radio either saturation or very noise you cannt cancel it by filtering. The best way is change your place. Of cuase I suppose your radion work at FM band and tune right. if the set not work at the wave band you will not recieve the signal. All the way you carry the set to another spot to see if the set work well. Hope this will be help.

the low cost radio is being desensed by the higher power of the transmitter. The car radio has far better front end selectivity and is thus capable of receiving a frequency with another one close by in frequency but far higher in power.

This cannot be easily fixes as these cheapo consumer radios are not that easy to deal with to add front end selectivity to.

Nothing wrong with the church transmitter

We had in Europe once a time something called "the Luxembourg effect". You can read a little about it in:

http://www.xs4all.nl/~aobauer/luxemburg_effect.htm

I think it can be a type of this because it is just in a local area and near the transmitter and other things in the house can contribute the interference.

This can bee a hard thing to eliminate and the cause can bee the most strange things. Look for things that have 1/4 or 1/2 wavelength of the transmitting frequency.

An other ting can bee a "resonator" in the house that will start to oscillate caused of your transmitter. If the resonator frequency is near and the same as the favorite station, it will disturb the radio. It is the same way as Russian spy's use for bugging secret rooms.

This are only hypothetic ideas but maybee...

I do not think this will be a factor. FM broadcasts are not reflected from the ionized layers of the atmosphere....they go right through.

What is happening if the so called capture effect where FM receivers reject the weaker station and receive the stronger due to the discriminator being 'captured' by the stronger station close by due to lack of high Q tuned circuits in the antenna input and RF stages. This is typical in cheap radios. They do not install them in the first place as price is the object. It is possible to use an RF preselector to help, but you would then have to place the received in a shielded box so it would only get the signal from the preselector. A preselector is a tuneable RF stage you hook up to the antenna and to the radio. Once yu do this the radio must be prevented from receiving a direct signal through the air ( that is why you place it in a shielded box).

The preselector has high Q tuned circuits and it attenuates the interfering station below the point at which it can capture the discriminator.

Yes you are quit right at most ways. if the radio set hasnt got good tune or poor selectivity or bed phase discriminator or out of resonance at some node. She will get interference and noise which cannt be orvercome by any filter.

Lots of good ideas so far. If the antenna is a vertical with ground radials, maybe you can get it higher up to reduce the local signal to the house, or use more ground radials. Get a field strength meter and see if the same signal is in all directions.

Would buying a new, more modern radio for the one person who seems to be affected be a good, cheap and acceptable solution?

Greg

get an old car radio and a 12 volt supply and some speakers. Car radios are very good quality compared the Chinese FM radios

Thank-you for your feedback. That might not be a bad idea to use a car radio, but I would probably have to find an alternative to a battery which would require maintenance and be cumbersome and unsightly. Would an inverter work for the power supply?

Yes, a small power adaptor that gives 12 volts at 1 amp should siffice.

If you get a tape or CD player radio = better.

Speakers, a set of those cheap computer speakers would do.

Best place to get an old radio is from a wrecker sympathetic to the church = donation.

In addition, many people have their old car radio at home from when the upgraded to a full feature radio, so a request from the congregation may get a donated radio and speakers and the power cube.

A car radio out on the table is not very attractive, but it is functional. Since there is not heat in a car radio you can place it in a small box and cut open the side you look at and put the speakers on each side. A handy parishioner would help too.

Thanks again Greg, I have already ordered a reflect antenna for the radio. If that doesn't solve the problem, I will try the car radio idea. Any recommendations on where to get a power adapter? I will keep everyone posted. runder

Thanks for replying Greg. I think that would be a good solution if I could find one. I'm not sure what a good radio is. There are certainly expensive radios, but are they any better? I think I need one with high receptivity, but how can you tell which have it? I've never seen a radio marketed as high receptivity. Any thoughts? Thanks again.

i used to have an old analog FM radio in my car & have observed same situation while passing by a radio station. when i changed the radio to a digital one, this problem did not occur.

Lashkari

Thanks, I'll keep that in mind when I get the car radio.

Dear Sir:

How much power is "Low Power"?

We run into a phenomina, known as desensitizing, when we run multiple radios in the same building. When one radio is transmitting, it blanks out reception on other radios operating on other frequencies. The transmitted signal is so strong that it simply overpowers the front end circuitry of the other radios, which are intended to receive microwatts of power. Two thoughts come to mind. Does your neighbor use an external antenna? If so you could build a very tight notch filter between the antenna and the radio tuned to your frequency. Another thought is to build a phased array antenna (at your end) which would have a cardiode pattern. You could then point the notch in the antenna pattern at the house across the street.

See if there are any ham radio enthusiests in your church. Especially one who is involved in a ham radio club. I should point out that I mean LICENSED amateur radio, and not citizens band. We have the technical expertise to troubleshoot such problems, and hams (in general) are more than willing to help other people.

Best of luck in your problem solving

Bill NW7L <-- my ham call

There is a ham club near our area,Findlay Radio Club, I contacted them and they are willing to advise and possibly put something together for us. Thanks for your help.

I forgot to answer your question about how much power is "low power". In FM radio, low power is 100 watts or less.

I believe the problem is solved. I bought a radio from Radio Shack with an external hook-up for an antenna and a reflect antenna from CCRadio. I took it over to our neighbor who was having interference and they could get their stations just fine. Thanks to everyone who gave me feedback on this question, Runder.

sir-

not to blow off your request, but i read about your church starting a low power and would like to do the same. my email is onerudyburger (at) yahoo.com

would you please reply?