My son-in-law listens to FM radio at work inside a steel building and the reception is poor. He uses a pocket radio with earbuds. If I put a cheap plastic T shaped FM antenna outside and run the wires inside what can I use to boost the signal from there so his radio can pick it up? His music is important to him, also it helps mask the noise of the machinery. Thanks ahead of time.
It is a bad idea to use low isolation earbuds and turn up the music to mask noise
get decent sound isolation 1st with IEM or closed back full sized headphones
http://headwize.com/articles/hearing_art.htm
if the noise level exceeds OSHA specs the employer MUST provide ear protection or reduce the exposure
finding a FM radio with antenna connection screws on the back could be a challenge today but they do exist but won't be portable
leaky feeder systems exist for difficult RF transmission environments
today it would be much easier to use a mp3 player or a FM microphone style transmitter fed by a PC audio out streaming a internet radio station
get decent sound isolation 1st with IEM or closed back full sized headphones
http://headwize.com/articles/hearing_art.htm
if the noise level exceeds OSHA specs the employer MUST provide ear protection or reduce the exposure
finding a FM radio with antenna connection screws on the back could be a challenge today but they do exist but won't be portable
leaky feeder systems exist for difficult RF transmission environments
today it would be much easier to use a mp3 player or a FM microphone style transmitter fed by a PC audio out streaming a internet radio station
jcx said:
He's not turning up the music to mask the noise, I'm just saying having the earbuds in there helps. Like earplugs?
There are no computers in the work environment, certainly none with an internet connection. Only those that run the CNC equipment and they are not PCs.
He has an mp3 player but he tires of listening to the same thing and wants radio, too.
gareth said:
Thanks for that, gareth, but I don't have the slightest idea what I would be doing inside an FM radio. My knowledge of electronics is not that good yet. Would such an adjustment help bring in some of the strongest stations? That's all he wants, I think. Just the closest stations.
What I'm wondering is if I connected an FM radio to the outside antenna and put some kind of transmitter -- like the ones used to transmit from player to car radio, only stronger -- on there would that work?
Hi,
Well if you were going to use an FM transmitter of the type you suggest then it would need to be pretty good.
By the sounds of things you work in a machine shop built in a steel frame building. Steel frame buildings like to 'bounce' the signal around and thus dissipating quality signal, basically.
An external aerial/antennae feeding your sons radio would be the ideal solution but is probably impractical due to the obvious hazards in your workplace. Theres no point in wrapping your nearest and dearest around the lathe is there?? ;-)
So, you could try what you yourself have suggested but I would try to get a good quality transmitter (to send onto your sons radio), I say this because I use an iPod in the car. The radio transmitter that I use(d) was probably about the best that was reasonably priced (£30) but I found that it wasn't very high output and was prone very prone to external interference, e.g. the beloved speed camera (not) and traffic lights etc. When the transmitter encountered these then I basically had no reception and this always seemed to coincide with your favourite record which was completely annoying.
Meanwhile back at the ranch, the machine shop you work in is probably prone to emmitting RF noise an d by using the transmitter you mention I feel that you may be disappointed but maybe you will be able to get a better design than I had and everything will be fine.
Well if you were going to use an FM transmitter of the type you suggest then it would need to be pretty good.
By the sounds of things you work in a machine shop built in a steel frame building. Steel frame buildings like to 'bounce' the signal around and thus dissipating quality signal, basically.
An external aerial/antennae feeding your sons radio would be the ideal solution but is probably impractical due to the obvious hazards in your workplace. Theres no point in wrapping your nearest and dearest around the lathe is there?? ;-)
So, you could try what you yourself have suggested but I would try to get a good quality transmitter (to send onto your sons radio), I say this because I use an iPod in the car. The radio transmitter that I use(d) was probably about the best that was reasonably priced (£30) but I found that it wasn't very high output and was prone very prone to external interference, e.g. the beloved speed camera (not) and traffic lights etc. When the transmitter encountered these then I basically had no reception and this always seemed to coincide with your favourite record which was completely annoying.
Meanwhile back at the ranch, the machine shop you work in is probably prone to emmitting RF noise an d by using the transmitter you mention I feel that you may be disappointed but maybe you will be able to get a better design than I had and everything will be fine.
My nephew had the same problem as you with the FM transmitter in his truck, I sent him a headphone amplifier to use between the player and the FM transmitter and it works beautifully now. You have to adjust the volume back and forth between the radio and the player to eliminate distortion but once that's done it's much better.
Back to the shop-transmitter thing, what do you think about this:
http://sound.westhost.com/project54.htm
Back to the shop-transmitter thing, what do you think about this:
http://sound.westhost.com/project54.htm
It certainly seems OK and with transmission up to several hundred metres, excellent. If you are confident then go for it, Rod has some good designs and can wholeheartedly be recommended.
Note what he says about the circuit self-oscillating though, you want to get it right. He even offers design for an RF probe that can detect the oscillations in conjunction with a scope, sounds good. Also, as Rod states, you need to get the inductors right aswell, crucial (in combination with the capacitors) for good operation.
Again, if you feel confident you have nothing to lose, and besides radio is an excellent 'introduction' into electronics.
Thanks
Gareth
Note what he says about the circuit self-oscillating though, you want to get it right. He even offers design for an RF probe that can detect the oscillations in conjunction with a scope, sounds good. Also, as Rod states, you need to get the inductors right aswell, crucial (in combination with the capacitors) for good operation.
Again, if you feel confident you have nothing to lose, and besides radio is an excellent 'introduction' into electronics.
Thanks
Gareth
Will I need to build two of these for stereo? Also the article says I will need a pre-emphasis circuit, I'm assuming for my purposes the line circuit. Do I need to build one of each for each audio signal, left and right?
Would I be able to run a coax from the outside antenna to a radio set close to where he works and use one of those small transmitters from there? Would this require an antenna booster?
Would I be able to run a coax from the outside antenna to a radio set close to where he works and use one of those small transmitters from there? Would this require an antenna booster?
unclejed613 said:
You know, I thought about that but it seemed too simple to work, I thought it would require some elaborate power setup. Okay, point me to a tutorial on dipoles or high gain antenna construction. I'd Google it, but I'm sure somebody on this forum knows right where to find a good design.
SharpyWarpy said:
Hi sharpy,
You would need to build two of these for stereo.
A pre-emphasis circuit helps improve the signal to noise ratio by amplifying lower-level high frequency sounds more than the low frequency sounds before transmission. You would then need suitable de-emphasis in your sons reciever to have an opposig effect and thus a flat frequency response. I think in America you use a time-constant of 75uS (micro seconds) with a break frequency of 2100Hz.
SharpyWarpy said:
If you want a really good book covering everything you need to know about this subject then I would highly recommend Basic Radio by Ian Poole published by Newnes, ISBN 0-7506-2632.
Thanks
Gareth
a good high gain antenna would be a 5/8 wave vertical. these have about 6db gain over a dipole. google "J-POLE" antennas. these are the simplest, and can also be constructed with 300 ohm twinlead. most of the ones you see on the web are for 2 meters(146Mhz center freq) and would need to be recalculated for FM broadcast (about 100Mhz center freq). it's just shy of 1.5 times the length. try multiplying the lengths given for 2M (146Mhz) by the ratio of the two frequencies (146/100) and it's 1.46. so your dimensions for the antenna would be 1.46 times longer.
j-poles usually need to be adjusted for SWR, but since you're using them for receive-only and a passive radiator, just make sure you make both exactly identical, and you should get good results. if you have a way of testing the SWR of both antennas at 100Mhz, that would be even better. if you end up a MHZ or two, it's ok, as long as both antennas are identical.
j-poles usually need to be adjusted for SWR, but since you're using them for receive-only and a passive radiator, just make sure you make both exactly identical, and you should get good results. if you have a way of testing the SWR of both antennas at 100Mhz, that would be even better. if you end up a MHZ or two, it's ok, as long as both antennas are identical.
I was going to suggest the two antenna (passive repeater) idea.
What about putting one of those little TV/FM signal booster amplifiers between the antennas?
I'm assuming the shielding of the metal building would help prevent feedback (oscillation) from the indoor antenna to the outdoor antenna.
What about putting one of those little TV/FM signal booster amplifiers between the antennas?
I'm assuming the shielding of the metal building would help prevent feedback (oscillation) from the indoor antenna to the outdoor antenna.
it would oscillate. those antenna amplifiers have a lot of gain, and to pad one down to the point where it doesn't oscillate would defeat the purpose of having it. a passive system would probably be best. any active system would have to be direct connect to the receiver, or a frequency translator (shift everything up or down 1Mhz) to keep it from oscillating. even if you could get the antennas positioned properly so that an antenna amplifier wouldn't oscillate, all it would take is somebody walking around within a couple of wavelengths of either antenna for it to begin oscillating.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.