[SBE] FW: Question about a Crown exciter and transmitter, over temperature, and spurious signals
crmurray at clearwire.net
Mon Aug 17 23:32:15 EDT 2009
I had a crown that emitted 504.9 MHz fifth harmonic of the carrier
interfering with a TV 19 reception. Not there on the RF output Jack.
It was radiating from the cabinet.
KKNU, Eugene, Ore.
Sent from crmurray at clearwire.net I-phone
On Aug 17, 2009, at 7:49 PM, "Phil Alexander, CSRE, AMD" <dynotherm at earthlink.net
> Having been through an overheat problem at sub-sero outdoor ambient,
> a couple of things come to mind. Installing indoor and outdoor temp
> sensors on the remote control will help understand the scope of the
> problem. Second, consider installing a powered louver ventilator and
> exhaust fan with remote control. That should get you through the
> winter and let you prove at temperature relationship aspect.
> If that is proven, a Baird or similar HVAC unit may be the final
> Phil Alexander, CSRE, AMD
> -----Original Message-----
>> From: Mike Langner <mlangner at swcp.com>
>> Sent: Aug 17, 2009 7:12 PM
>> To: sbe member discussion mail list <sbe at sbe.org>
>> 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
>> interference to some VHF Public Safety equipment at a remote
>> 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
>> Summertime presents no interference.
>> My suspicion is that the FM transmitter building (a typical tiny
>> building) overheats in winter from snow pack into the marginally
>> 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
>> 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
>> 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
>> getting "squirrelly?"
>> Seems to me that I repaired a 100 watt Crown amplifier some years
>> ago which
>> exhibited exactly this problem.
>> Your thoughts?
>> Mike Langner, CPBE
>> 929 Alameda Road NW
>> Albuquerque, NM 87114-1901
>> (505) 898-3212
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