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tweekend 28th January 2013 04:38 PM

FM antenna help
 
I could use some ideas for solving an antenna issue. This is for a HS radio club the broadcasts 1 hour a day on a local non commercial station. They need to be able to tune in 90.5 FM during their show. I have tried everything from Terk powered antenna to building our own from shielded audio line. No matter what I seem to get bleed over from 91.5, 92.5 and 96.5. Using a Pyle Pt504 digital tuner.

Does anyone have ideas of what to try? Trying to do it as cheap as I can as the radio club kids already chipped in for the tuner and powered antenna. Thanks for brainstorming with me. My head is sore from pounding the wall.

fooeywuffle 28th January 2013 04:42 PM

Yes, get an old receiver that was made using good RF and IF filtering. Ones using ceramic filters just aren't that good.

DF96 28th January 2013 07:06 PM

I'm not clear what you are asking. You want to receive 90.5MHz in the presence of much stronger signals on nearby frequencies? If so, ditch the powered antenna as these can have poor amplifiers themselves and are likely to overload the following tuner too.

An antenna won't be able to separate 90.5 from 91.5 unless they are in very different directions and the antenna is very directional. A big Yagi might do it, but even then unlikely.

A better tuner is your best bet. Alternatively, a narrow-band helical filter.

Johnny2Bad 28th January 2013 07:14 PM

Modern FM tuners are junk. They all use basically the same or similar IC tuner chip, and since no-one has bought any audio gear in the last 20 years for it's radio specs, they buy the cheapest radio chip in the parts bin and throw it in there. Hey, it picks up some radio signals, good enough.

You want an older tuner ... the 80's is when they started to turn to shitte ... that actually works. The only decent radios made today are found in cars as the OEMs actually are driving the research into FM (and other) radio chipsets these days. Even then, not as good as a proper discreet component older tuner or receiver. Not an endorsement of car radios, just letting you know what you're up against.

When looking at a tuner get one that allows you to manually select the sensitivity; ie with a stereo / mono or wide / narrow switch on the front panel. You want an analog tuner ... no digital ones ... so you can dial in somewhat off-band and possibly eliminate some interference from other channels. Automatic anything / digital tuning is your enemy, manual everything / analog tuner is your friend. Your particular application is a demanding one; generic consumer grade gear was never meant to do the job you need done.

Powered antennas are junk; not only can they overload a tuner's inputs they add noise, sometimes a lot of it.

The physical location of your monitor tuner may be too close to your broadcast setup. Need more details about what exactly you use the monitor for and how your station is set up.
But, if you can use some sort of radio link (WiFi, 2-way radio, etc) that would allow you to add distance between the receiver and your your broadcast antenna it might work.

The directional antenna advice is also important but we don't know (no details from you) if it would be helpful or not.

DF96 28th January 2013 08:46 PM

The OP wants to receive while actually at a transmitter site on a nearby frequency? If so, an excellent helical filter is about the only hope. Professionals can do this, but would normally choose not to. The transmitter might need a filter too, to suppress any wideband noise. If this all has to be done cheaply then it all gets harder!

john dozier 28th January 2013 09:09 PM

Post in the swap meet-one of our members might have an old tuner which He/She might donate for a tax deduction. Regards BTW specify HS school donation in the title. Regards

multisync 28th January 2013 09:26 PM

In the late 70's early 80's I used to use a product called "Magnum Sleuth" It was a powered, tunable Fm amplifier. I would use it when I was Dx'ing distant FM stations that were close in frequencies to local strong stations. It had gain and tuning knobs on it. Mine is busted and on the list of those things that I am supposed to get around to fix. I had a 10db FM yagi with rotor and a decent tuner, Yamaha T-7 .

here is what it looks like.

Magnum "Sleuth" FM antenna amplifier Product Reviews

OMG I am going to have to fix my old one as I see they are worth a few bucks now.

Octavia 28th January 2013 10:35 PM

I've had my Magnum Sleuth for years. It works great!

tweekend 28th January 2013 10:54 PM

Thank you all for the help so far. If I am understanding correctly it sounds like I have more of a P.O.S. tuner issue then an antenna issue. I will def trying going that route.

To better explain what we are doing.

90.5 FM WBER in Rochester NY is a non-com educational station that works with a local Radio/TV class to give HS students on air experience. Also, we work with 4 area high schools where each has a 1 hour radio show for their "radio club" during the school year Monday-Friday. These radio clubs have a very basic set up. CD players, mixing boards, mini-stereo input and mics. Basic, to the point, but perfectly simply for HS kids. The signal gets transferred back to WBER over IP encoder/decoders one of our network techs built.

Now for monitoring their on air signal the radio clubs have a simple tuner and speaker set up in the studio. This one club has had nothing but issues getting the signal in. Now while not a super strong signal, I have never before had an issue getting it in. WBER is located in Rochester NY and broadcasts at 2.5K watts. I have received it as far north as Toronto, East as Syracuse and West as Buffalo. The club is in a town called Webster about 10 miles north of the transmitter.

The room the radio club is in has outside windows and believe me I have tried almost everything. Hence after years of reading helpful tips on these boards I finally figured I needed to join and ask for some help of my own. I am trying to do whatever I can to help these kids out as the radio clubs are always looked at by admins as an easy cut to trim budgets, even though they cost next to nothing. So I want to see what I can figure out before I have to ask for money and give people a reason to complain about the club.

Thank you again everyone for your helpful suggestions, it has given me a good direction to start as my forehead was starting to hurt from banging on the table. Any other ideas, feel free to float them my way.

Thanks
Shaun

dmills 28th January 2013 11:32 PM

Ok, firstly ditch the amplified aerial, any gain you actually need (And I suspect that you don't need any) must go after some fairly serious RF selectivity.

Second, find the local ham radio club, and go talk to their aerials guy, I would suggest a simple half wave dipole or such fed down proper RF coax (NOT the same thing as audio screened cable, but not very expensive).
If it is co channel problems then some filtering may be needed, and the hams will be able to help with this.
A tuned stub as a trap is not hard but needs some minor fiddling to get right, much easier with an impedance analyzer (Which they have a good chance of having available).

Third, as has been said, a tuner with some actual selectivity will help, ebay is the usual answer for such things.

Regards, Dan.


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