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Radio Receivers That Can Stand Lots of RF

B

bturner

My station has just installed a new 25kw Nautel and we are setting up the EAS system. The radios that worked fine with the Harris Gates 5kw next to them are being blasted by the 25kw transmitter.

Literally the 50 kw Primary is difficult to get clearly in the building and I sure don't want to miss any tests!

Have any of you some suggestions on radio tuners that might withstand being on the rack between the Nautel and phasor. I know I need non-digital radio tuners. I need suggestions on AM, FM and Weather Radio.

Any help on shielding these is appreciated.

I'm wondering if I need special made casing for the receivers and outdoor antenna.

My guys build put stations but are pretty clueless on the little odds and ends once the pattern is in...they're usually gone by then and such stuff is left to a station engineer but these guys are getting to take care of every detail on this build-out.
 
Wow, these look like they could handle things, especially with an outside antenna. I knew the owner wasn't going to get away with a Super Radio and deluxe weather radio.
 
You might be ahead with some of the better portables or an old hi-fi tuner. Moved a translator to our new site--96.9 Class A on the tower, and a 100.1 Class A on another tower about 400 feet away. Translator 93.9 receive, 93.1 transmit.

Couldn't use an Inovonics composite receiver because of a mixing product on 93.7. Same with the Dayton Model 210. Ended up using a Sony HD tuner feeding an 8100 into the Nautel VS300 translator transmitter. Not quite as good as I would like, but entirely adequate.

Soooo.... A couple of suggestions, before you spend a lot of money.

1. If you can get the two primaries (I gather you monitor an AM and an FM) on a car radio at the site, look into a Delco or Ford car radio from the junkyard. You will need a 12 volt supply (Jameco has a bunch) & a UPS to hold up the tuning during power drops.
2. Try out those DX-er favorite portable radios. We use the Grundig G8 traveler for remotes because it fairly sensistive--of course you will need a wall wart supply & a UPS.
3. E-Bay, for the old fashioned Hi-Fi tuners that use a tuning capacitor and fishing line to move the pointer up and down the painted dial...

4. For weather radios, good luck. Oregon Scientific used to make a portable with an external antenna, would come back up on channel after power failure, but that may require keeping batteries in it for this feature. I have had problems with the oscillators in the Armstrong STL receivers bugging these receivers.

Hamtronics make a circuit board kit that can be crystalled for the weather service radio channels. Mounted in a good metal box --with the supply inside, might work pretty good. There's the Gorman-Redlich, but that's pricey. The Dayton receivers may also be a pricey, but safe choice.
 
tpt said:
4. For weather radios, good luck. Oregon Scientific used to make a portable with an external antenna, would come back up on channel after power failure, but that may require keeping batteries in it for this feature. I have had problems with the oscillators in the Armstrong STL receivers bugging these receivers.
Click to expand...

I would think about a commercial two-way radio, like a used Motorola or GE or something like that.

I had to install a 161MHz BAS receiver in the same room as the Nashville NOAA transmitter. My antenna was about 30 feet from the NOAA antenna. Used a Motorola two-way & it worked fine.
 
Might try an old vacuum tube Marantz or Fisher (at least for FM). Tubes are a lot less susceptible to front end overload. And in those days they also used to have RF pre-selector stage in the front end. You will need to keep some tubes handy though. Tube testers are hard to find :)
 
I've found a Sangean CL-100 weather radio works quite well for monitoring NWS. It can be locked "on" so you won't have problems like some of the SAME enabled weather radios do. It's only $60 from Amazon. http://www.amazon.com/Sangean-CL-10...4460438&sr=8-1&keywords=sangean+weather+radio

Come to think of it, a Sangean WR-2 is a realy decent AM-FM radio, at a fair price. http://www.amazon.com/Sangean-WR-2-...8&qid=1384460612&sr=8-1&keywords=sangean+wr-2 You'd need to put it on a UPS to keep it on during a power failure. Otherwise they seem to revert to "off" at the loss of AC power and you'd have to manually reset it. I have one sitting on top of a 150 watt LPFM FM transmitter that shares our STL tower. I use it to monitor our station, not the LPFM. It seems to work OK with just a piece of wire hanging out of the back for an antenna. An added benefit is it has a nice RDS display, which is handy if you want to know if your RDS is actually working.
 
First ... move the receiver. Locating it between the transmitter and the phasor is probably the worse location!
Once you move the receiver away from the very strong RF field, it may work.
 
The McIntosh MR-78 and MR-80 are the best FM tuners, but quite pricey even on the resale market.

Here's a ham site resource that has a lot of info on good FM antennas and tuners. I'd have to go back to the link to see if there are any weather radios, and I'd lose my post.

http://www.ham-radio.com/k6sti/

I know someone else having EAS FM RF issues, and I've been going back and forth with him finding links and possible solutions like this. The EAS receiver was a single chip design, with little IF filtering, and it was causing problems.
 
I've mentioned this on another forum, but if you want to just "get it over with" and don't mind the money, buy a pair of BW Broadcast FM tuners. They are absolutely astounding radios. There are two versions, one for translator use which delivers a corrected composite output (as well as traditional balanced XLR analog). The less expensive version would be very appropriate for EAS. It doesn't have some of the translator specific applications, but otherwise looks very similar to the translator version. http://www.bwbroadcast.com/fm-receivers/rbrx1-fm-receiver/17/product Expensive, but worth it.
 
Notwithstanding what the others have suggested, I agree with Bradgoehl that DaytonInd. would work well. They're very well built and truly perform.

-CO
 
You might be able to get away with a cheaper receiver and one of these (cascaded into a 3 cavity filter).

http://www.microwavefilter.com/tunable_notch_filters.htm

Would still be a lot cheaper than a BW Broadcast tuner. I swear by them for translators, in fact, that's all I install these days. But for an EAS receive it might be expensive overkill that a notch filter would take care of.
 
No matter what receiver you wind up with, try a few toroids (of the proper mix) on all of the cables going in and out of it.
 
If your problem is just the increased RF field in there, you might consider some kind of filter, so the radio front-end isn't getting blasted.

I have a similar situation going on now... pulling in a low-power LP in a building that has a 25kW FM in it. I put one of Chris Scott's notch filters in the antenna line, and that did the trick.

If you're talking AM, you might have a tough one... especially if your new transmitter is running anywhere near the station you have to pick up.

I've used loop antennas and notch filters, with varying degrees of success. In one case, I just had to admit defeat and import the EAS audio from a remote location with Barix boxes.
 
It's been a while since this thread started. I've intended to ask you on another forum if you found a satisfactory solution, and what it was? Just curious...
 
The previously mentioned Sangean works fine at my 50Kw site: JBI
 
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