Looking for a portable radio that will not overload or de-sense in a strong RF Field. A neighbor at 0.2 miles from a tower with 5.1KW on one freq & 19 watts on another is getting a mix of the two signals across most of his dial--on both of his radios...a Grundig & a Sony. The Grundig reacts so poorly that you can't even tune it to 89.5 (NPR)...the digital readout locks up at 89.6 & finally jumps below 89.1--you literally can't tune the radio to 89.5! I tried the Tecsun PL-310 & it doesn't overload--the stations are not showing up at multiple frequencies, but it de-senses so the neighbor can't reliably hear the weaker NPR station he has listened to before the new RF sources appeared. Everything comes in fine in the guy's driveway on the Pioneer Supertuner IIID...anyone know of a portable radio that will work properly in the face of strong RF?
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Overload Resistant FM Radio
- Thread starter BobOnTheJob
- Start date
A Sony hd tuner or radio is about the best out there for adjacent channel rejection. If it's quite a ways away from the desired station on the dial, you may need a trap http://scott-inc.com/html/fmnotch.htm . If you can, check it with a spectrum or fim-71 to see if it's really a mix leaving their transmitter (no filter on your friend's end will fix it if it's that).
It's clean...the Pioneer car radio only hears the signals on the freqs where they should be. And the radio has to be a portable...the guy likes to sit out on his deck & listen, so a tuner is not an option (unfortunately).OKCRadioGuy said:
K
kenglish
Guest
What is he using for an antenna?
Just for fun, try wrapping the radio in tin foil and see if it helps to shield it at all. Then, try it with a very small external antenna poking out of the foil bag/enclosure. That would tell you if it's getting clobbered at the front-end, or just by conduction through the cabinet. Don't leave it that way too long, due to heat, though.
If it's all due to overload thru the antenna, a cheap fix might be to hook a piece of twin-lead to the antenna and internal ground (on some radios, the external antenna jacks are in parallel with the internal antenna
), and try shorting the twin lead at the quarter-wave length point, until you notch out the higher-powered station. It's the old twin-lead-and-razor-blade trick from early TV days.
You could probably coil up the twin-lead "notch filter" on the back of the radio.
Just for fun, try wrapping the radio in tin foil and see if it helps to shield it at all. Then, try it with a very small external antenna poking out of the foil bag/enclosure. That would tell you if it's getting clobbered at the front-end, or just by conduction through the cabinet. Don't leave it that way too long, due to heat, though.
If it's all due to overload thru the antenna, a cheap fix might be to hook a piece of twin-lead to the antenna and internal ground (on some radios, the external antenna jacks are in parallel with the internal antenna
), and try shorting the twin lead at the quarter-wave length point, until you notch out the higher-powered station. It's the old twin-lead-and-razor-blade trick from early TV days.You could probably coil up the twin-lead "notch filter" on the back of the radio.
The old trusty GE Superradio has always been my favorite. http://www.radiointel.com/review-gesuperradios.htm If you put it on the bench you can fine-peak it for best selectivity. It also allows you to turn off AFC so you have control of the oscillator rather than the radio grabbing the strongest signal.
Although the AM section is superior to the FM section, the FM section works very well by todays standards (especially after they have been tweaked). The radio also sounds very good. I got mine in 79 when I was engineering a directional AM. Best money ever spent on a radio. I use it every day to listen to a Class A that is 50 air miles away in Franklin IN. I use the whip antenna.
Although the AM section is superior to the FM section, the FM section works very well by todays standards (especially after they have been tweaked). The radio also sounds very good. I got mine in 79 when I was engineering a directional AM. Best money ever spent on a radio. I use it every day to listen to a Class A that is 50 air miles away in Franklin IN. I use the whip antenna.
I do have 3 of the Superadios & will be taking them over there to try out. When I was at WENS 97.1, we moved the transmitter to Indy (1985) & there was a neighbor at a similar distance who wanted to keep listening to the Plainfield station on 98.3. We bought him a Superadio & it worked great with 23000 watts a few tenths of a mile away. That may be the answer again.
I'm about 12 miles south of 95.9 in Franklin. Can you hear WYGB 100.3 on the Superadio? If so, what city are you in?
I'm about 12 miles south of 95.9 in Franklin. Can you hear WYGB 100.3 on the Superadio? If so, what city are you in?
Bob, when I built WQNU 2 years ago, 23 KW and surrounded by homes and apartments, I knew I'd have trouble. What I didn't realize is how few radios are being made today, and how poorly it's being done.
I literally went to Best Buy and bought one of every radio they had. And I took every one of them back to the store after testing, because there wasn't a keeper in the bunch.
The two best radios that I found at the time was the Boston Acoustics Solo and, believe it or not, the Radiosophy HD100
The Boston Acoustics was sold at the Target close to my transmitter site for $99.
Both are portable, but neither runs on batteries, if that's a deal breaker.
Both radios have an external antenna that attaches with an F connector, so it's easy to put on a trap if necessary, but at most of the places I needed them, they worked without the trap.
NEITHER of them work worth a hoot at one of my transmitter sites- a single bay on top of a building. But I've been able to make them work darn near everyplace else.
I had a guy with a GE SuperRadio that was eaten up with RF. He never let me come over and fix it, so I don't know how mine would have worked. But the SuperRadio wasn't the answer for him.
I literally went to Best Buy and bought one of every radio they had. And I took every one of them back to the store after testing, because there wasn't a keeper in the bunch.
The two best radios that I found at the time was the Boston Acoustics Solo and, believe it or not, the Radiosophy HD100
The Boston Acoustics was sold at the Target close to my transmitter site for $99.
Both are portable, but neither runs on batteries, if that's a deal breaker.
Both radios have an external antenna that attaches with an F connector, so it's easy to put on a trap if necessary, but at most of the places I needed them, they worked without the trap.
NEITHER of them work worth a hoot at one of my transmitter sites- a single bay on top of a building. But I've been able to make them work darn near everyplace else.
I had a guy with a GE SuperRadio that was eaten up with RF. He never let me come over and fix it, so I don't know how mine would have worked. But the SuperRadio wasn't the answer for him.
I have a Sony Walkman NWZ-E436 (about the size of a stack of 15 playing cards) which seems to work pretty well in high RF environments. Just uses the earphones as the antenna. I can literally sit at the base of a 6kW station's tower and pull in a 2nd adjacent translator which is not co-located. Not really listenable, but enough to tell that its there.
http://www.crutchfield.com/S-wHQJMopbYJe/p_158S436FBK/Sony-NWZ-E436-Black.html
If you're looking for something to listen to stations outside the 54 dBu contour, forget it. I like this one more for RF immunity than DX ability.
http://www.crutchfield.com/S-wHQJMopbYJe/p_158S436FBK/Sony-NWZ-E436-Black.html
If you're looking for something to listen to stations outside the 54 dBu contour, forget it. I like this one more for RF immunity than DX ability.
BobOnTheJob said:
speakerman said:
My long time friend from pre teen days (Walt the repeater coordinator) told me about your modified Dorrough processor. The 525 had awesome audio and great range. It was too bad some Bozos did not respect what you created. I don't operate 2 much any more...spend most ham radio time on 40 in the summer and 75 in the winter. I still do some 6 when the band is open.
B
BabyDJ
Guest
http://www.amazon.com/Grundig-Traveler-Digital-G8-Shortwave/dp/B001QTXKF6
Best FM section on a portable ever.
Best FM section on a portable ever.
It is a shame...when I became a ham in 1966, the whole band was filled with a few ladies & many, many gentlemen. The final days of the Mighty 5.25 were a far cry from what I cut my teeth on.speakerman said:
The DAP-310 processor was tweaked so that the low end was below 300, the mid was 300-2000 or so & the highs were 2000-5000hz. The goal was to do something unheard of on a repeater...make the output sound better than the input. It was a success in that repect. Thanks for noticing all those years ago.
Just an update...I took a GE Superadio II that I had handy to the neighbor's house & while it wasn't perfect, it did pick up the stations he's interested in cleanly. 5100 watts at 0.2 miles comes close to trashing an SRII, but fortunately, not quite.
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