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Old 21st December 2012, 10:08 PM   #1
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Default FM signal boost

I have several employees who wear soundproof earmuffs with a built in AM/FM radio. They work inside of a slump block/steel building. These radios were able to get great reception until maintenance installed a different type of light bulbs in the work area. Now they only get a Spanish channel. Maybe there was some sort of antennae that was coincidentally removed at the same time. Is there an easy way to boost the FM reception inside the room that will allow them to listen to whatever station each individual prefers? As none of them are Hispanic, they are not happy campers right now.
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Old 22nd December 2012, 01:55 AM   #2
DUG is online now DUG  Canada
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Easiest way

Install a car antenna on the outside of the building and another on the inside...hook them together using 50 ohm (or 75 ohm) coax that is multiples of 2 meters (about 79") long. The shorter the better actually.

Old standard Ford antennae will work. These are 1/4 wavelength at 100MHz.

A good cheap source is auto wrecking yard...Sorry, auto recycling establishment.

The next step up is to install an FM amplifier in the coax line, but you have to make sure the input (outside) antenna is away from the output (inside) antenna.

Post the results.
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Old 22nd December 2012, 10:59 AM   #3
DF96 is offline DF96  England
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Change the lightbulbs. I assume they are low energy? Many of these emit large amounts of RFI from the cheap Chinese electronics inside. Some are better, and include proper suppression components. Experiment: higher cost bulbs may sometimes be better for RFI but no guarantee of this.
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Old 22nd December 2012, 11:42 AM   #4
FoMoCo is offline FoMoCo  United States
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Quote:
Originally Posted by DUG View Post
Easiest way

Install a car antenna on the outside of the building and another on the inside...hook them together using 50 ohm (or 75 ohm) coax that is multiples of 2 meters (about 79") long. The shorter the better actually.

Old standard Ford antennae will work. These are 1/4 wavelength at 100MHz.

A good cheap source is auto wrecking yard...Sorry, auto recycling establishment.

The next step up is to install an FM amplifier in the coax line, but you have to make sure the input (outside) antenna is away from the output (inside) antenna.

Post the results.
Cool idea. I never thought of a passive system with two antenna. I think it would work quite well if it was the building being a shield.


Quote:
Originally Posted by DF96 View Post
Change the lightbulbs. I assume they are low energy? Many of these emit large amounts of RFI from the cheap Chinese electronics inside. Some are better, and include proper suppression components. Experiment: higher cost bulbs may sometimes be better for RFI but no guarantee of this.
This is a better idea. Treat the cause and not the symptom. Probably not the easiest to implement though.
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Old 22nd December 2012, 10:41 PM   #5
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Or get one of those car units that converts audio to FM for use with older car radios. Then set up an antenna outside the room with the tuner audio output connected to this device. But some of the new lamps are very good a generating interference.

Or get one of these:
FM10C - FM Stereo Transmitter Kit - Ramsey Electronics
http://www.ramseyelectronics.com/hk/....asp?page=amfm
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Old 22nd December 2012, 11:11 PM   #6
DUG is online now DUG  Canada
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Originally Posted by Speedskater View Post
Or get one of those car units that converts audio to FM for use with older car radios. Then set up an antenna outside the room with the tuner audio output connected to this device. But some of the new lamps are very good a generating interference.

Or get one of these:
FM10C - FM Stereo Transmitter Kit - Ramsey Electronics
Ramsey Electronics
Retransmitting only one station will not make everyone happy.
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Old 23rd December 2012, 03:04 PM   #7
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Thanks to all who have responded. The company that I work for, will not be paying for any type of fix for the problem so I will be doing it all myself. I will probably try the 2 antennae/amplifier idea once we get back to work. If that doesn't work, I will have to try and submit a PO for more expensive light bulbs and a lot of them. That idea will most likely get rejected so I hope the first idea works.
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Old 23rd December 2012, 06:16 PM   #8
tvrgeek is offline tvrgeek  United States
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Even cheaper, Just get a length of coax and strip 31 inches of shield off each end.

If the light bulbs are the problem though, you are probably screwed.
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Old 24th December 2012, 09:17 PM   #9
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I fear that some of these new high efficiency lights are also high efficiency RFI noise makers. I got some 4 foot fluorescent shop lights for my garage, they made a lot of noise on my Sony FDR-X1 HD tuner and my old Nakamichi clock radio. Took them back and got a cheaper brand of shop lights that I know were quite.
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