[SBE] FW: Question about a Crown exciter and transmitter, over temperature, and spurious signals

[Eargle, Raymond L]

Yes to your questions, Mike, I worked for KFBK,KGBY,KSTE,KHYL as an engineer. we had the older units and the newer. I can say with out A/C we would play other adjacent channels on our air until we got our A/C back. Really can rune a day with out a good balance cool air good A/C is a must have. The Circuit in your equipment are being damage with such a varable of temp your down time would be less if you keep a good balance of air. Well best of luck; If A/C not possiable Fan vents, like turbans roof vens may help.

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From: sbe-bounces at sbe.org [mailto:sbe-bounces at sbe.org] On Behalf Of Mike Langner
Sent: Monday, August 17, 2009 4:12 PM
To: sbe member discussion mail list
Subject: [SBE] FW: Question about a Crown exciter and transmitter, over temperature, and spurious signals

Hello everyone !


I'm about to try to "fix" a problem on a site where an FM transmitter operating at about 1 kW power output and about 1 kW erp may be causing interference to some VHF Public Safety equipment at a remote mountaintop site.

Access to the site in wintertime is an arduous snowshoe/snowcat trip, so nobody involved in the problem has been there in wintertime when the problem occurs.

Summertime presents no interference.

My suspicion is that the FM transmitter building (a typical tiny mountaintop building) overheats in winter from snow pack into the marginally designed airflow/vending, and the equipment overheats.

The equipment in question is a Crown FM 100 exciter operating at about 60 watts, and a Crown FM2000A transmitter operating at 1050 watts.

The system employs a Shively 2604-3A bandpass cavity filter in the output.  The radio station owner voluntarily purchased and installed the filter as a goodwill gesture and to attempt to stop any spurious signals from getting to the antenna.

My sense without going up the mountain (I was there once a number of years ago) that the Crown equipment is overheating, generating spurious signals that may be emitted through the cabinet or by inter-chassis wiring.

I have gotten reports that the building is "hot" in wintertime.

Does anyone have any experience with "hot" Crown exciters or transmitters getting "squirrelly?"

Seems to me that I repaired a 100 watt Crown amplifier some years ago which exhibited exactly this problem.

Your thoughts?


Thanks!

Mike/

Mike Langner, CPBE
929 Alameda Road NW
Albuquerque, NM 87114-1901

(505) 898-3212

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