Receivers that work in FM blanketing contour

[greg.hahn]

I just put on a new FM in a highly populated residential area. I hope I can filter things and not have to buy any new radios. But if it comes to that, does anyone have any recommendations as to what works?

What's a good clock radio?

What's a good boom box?

Any recommendations?

While we're at it, what's your favorite source for RF suppression filters and components?

Thanks!

 

[littlejohn]

Jerrold used to sell a little tuneable filter for $1 which worked well. It was on a 300ohm pigtail. We sent them to folks and told them ' turn the knob till the other station goes away'. For those who couldn't or wouldn't, someone went to their house and did it for them.
Read the Rule (73.333, I think) carefully, and enlist your friendly FCC field officer at the outset. You aren't responsible for overload where high gain antennas or external signal amplifiers are in use. But, anything you do for one in the blanketing area, you must do for all. So, be careful giving out radios. I never had to give anyone a receiver (we were chewing up TVs), but the local Field Office was my salvation in a couple of instances.

 

[radiorob2.0]

IIRC, GE radios as wonderful as they sound great and are sensitive. However they are fall apart in a high RF environment. A few Sony's are able to stand up but many fall apart on the FM band even in normal circumstances. Their AM tuners are a different story. I was able to hear other AM stations on my AMAX walkman standing next to a Power Rock. So your mileage will vary. Rat Shack sells an FM trap that seems to perform its intended purpose.

 

[littlejohn]

Do you have part number for the Radium Chack trap? My parts store tells me the ones I used to buy are no longer available. The Heathen Chinee seem to have moved on to bigger and more profitable things.

 

[greg.hahn]

Do you have part number for the Radium Chack trap? My parts store tells me the ones I used to buy are no longer available. The Heathen Chinee seem to have moved on to bigger and more profitable things.

It's a 15-577. But here is what Thomas Eckels says about that one: "As shown in Figure 2, the Radio Shack FM trap has less than 15 dB of rejection relative to the 3 dB point of the MFC notch filter, while the MFC notch provides more
than 60 dB. The RS FM trap also has a relatively high insertion loss, has nearly 10 dB of amplitude response variation over the band occupied by Channel 6, and tends to degrade the quality of TV signals in low signal
environments.

It can be useful sometimes, but don't get your hopes up.

I haven't really had a TV complaint yet. All of mine are radio, so obviously trapping the entire 88-108 won't make people very happy.

 

[NoTimeForSleep]

Be very careful how far you go to make one person happy. If you replace one radio or telephone you must do it for anyone who complains there. I had a similar problem once but it got into radios, tv, intercoms, phones, computers, etc upon a site move. The tv's were resolved by having sony (worst offender for rf getting into the audio section in my experience here) service come out and install an rf filter inside the units that were affected (the sony repair technician admitted they should have installed these filters at the factory but it was cheaper to do it on a case by case basis at sony's expense!). The clock radio issues I had were resolved by installing small ferrite chokes on the power cords / antenna cables to the units. Doing this with three or four chokes in series dropped the rf field enough on most of them to allow the unit to discern everything.

Read the rules very carefully and do the same for each person, replacing phones or radios will get expensive very quick and is not what you should have to do a lot of times. Installing a few rf clamp on rf chokes is far less expensive then buying radios...

 

[kenglish]

Last time I tested a Radio Shack FM Trap, it was pretty good. But, they don't stock them anymore. Here's a link to something that appears to be the same:
http://www.electronicplus.com/content/ProductPage.asp?maincat=CAB&subcat=CAD

Be aware, though, that the RS attenuates the entire FM Band.

You can have "Bullet Traps" (they are made for Cable TV, shaped like a big bullet) made for your specific frequency, by companies like Microwave Filter Company, and Communications and Energy Company.

http://www.microwavefilter.com/
http://www.cefilter.com/index.asp

Winegard makes a couple of variable traps, for both 75 and 300 ohm.
Amidon Associates is a good place to get ferrites.

 

[BobOnTheJob]

I had to do this 23 years ago this summer...23KW on a 700' tower in a sparsely popluated area of Indianapolis & there was a guy who listened to a class A 1.2mhz above our freq about 15 miles away. The GE Superadio portable pulled the A in fine less than 1000' from our stick. Actually, the whole FM dial was surprsingly normal on that radio. That was 23 years ago, but I'd try a GE Superadio & see if the magic is still there. Never heard another word from the listener.

 

[littlejohn]

the one I used to buy was a plastic molded case which had a small mica cap in series with a piston tuned inductor, the tuner was a screw with a plastic handle which projected out of the housing to tune it. It was on about a tweo inch piece of flatlead with spades on the open end. Parallel it with the VHF antenna inoput - or the 300 ohm input of the radio - and tune the offender away. They had a pretty good Q and a relatively deep notch - 25 - 30 dB - and were cheeeep.

 

[OKCRadioGuy]

I agree be VERY careful giving out radios etc. as you'll have to do if for all that complain. With that being said the best damn radio out there for rejection is the Sony HD tuner model xdr-f1hd. Slam a set of computer speakers on it and not only will the listener be able to get rid of your signal but they also will likely get stuff they've never heard before. The tuner is that good. I retired 1500 dollars worth of filters (bought them used of course at a lower price several years ago) when I bought this tuner. The Sony barefoot does better than anything with the filters... Yeah.. That good. One special note to consider also. If you happen to be co-located with another RF producer, especially broadcast, do a spectrum check to make sure you're not actually generating an intermod mix. I had that happen to me on a translator located at a backup site of another brodcaster. When their backup went on the air (tube type and powerful) it dumped RF into my 250 watt PA and came back out on THE very frequency I need to receive on the translator input. Filters were required on my transmitter output.

 

[greg.hahn]

One that definitely seems to work is the Radiosophy HD100. I have one at the transmitter site and it receives Both class A's 800 KHz away and the C3 400 KHz away with no problems whatsoever.

I have two calls from owners of Bose Wave radios that are wiped out. The Bose uses the power cord as the antenna. If I wrap the power cord with toroids, it will attenuate all stations. But I think I have to do that. Apparently all Bose models have an external antenna jack. After killing the power cord antenna, I'm going to use an external antenna with a MFC trap. Hopefully that will work.

Small clock radios...not sure how successful I'm going to be there. One complainant has a Sony Dream Machine in her bathroom that's wiped out. I hope it's not a power cord antenna again.

 

[techie2]

As far as underwhelming receivers go, the "worktunes" ear protector radio I use while cutting grass is one of the worst I've seen. I'm not in anyone's blanketing contour but it acts like the front end is overloaded. I get the local Class B FM's splattering all over the dial. At least it has a 1/8" input jack for an mp3 player so I can use that instead of trying to find something decent on the few stations it picks up.