FAA 4cx-250B Transmitter

David L. Foreman davelf11 at COX.NET
Fri Feb 1 21:22:56 EST 2008

----- Original Message ----- 
Sent: Friday, February 01, 2008 15:15
Subject: [BOATANCHORS-TEMPE] FAA 4cx-250B Transmitter

> Several years ago I came up with a Collins Transmitter that is 
> probably A.M. as is all prime FAA com gear. The following is on an 
> attached metal label on the hinged front cover which is about 3"X2":
> Transmitter, VHF 50- WAtt, Federal Aviation Agency, Type TV-36, 
> Contract FA 64WA-5251, Ser 222, Collins Radio, Cedar Rapids, Iowa. 
> It's built like the proverbial S.H.  About 20" cube. Looks like it 
> could fit into a standard relay rack. It includes the power supply.It 
> is in a completely enclosed cabinet. The final tank consists of a 
> piece of metal tubing about 2" in diameter and a foot long for the 
> inductance. All kinds of gearing to tune, etc.  Has transistors except 
> for the 4CX-250B final which is housed in a solid metal cage. I 
> haven't determined how high the final will tune but I think way above 
> 118-136 MC. The 50 watt rating is way below the capability of the 
> final tube and the size of the power supply.  I have several jpeg 
> photos. I'd like any info someone may have on this radio. Thanks. Fred 
> w7prv at teleport.com
> Why Wait? Move to EarthLink.

That may be one of the UHF transmitters.

For example, the aviation vhf emergency frequency is 121.5 and the uhf 
freq. is 243.
The civil aircraft uses vhf and the Air Force etc. uses uhf. So towers 
will have transmitters and receivers on both vhf and uhf and transmit on 
both so both civil and military can hear that the tower etc. is talking 
to some one that the other can't hear. Below is and example  of both 

 Hilo TOWER                                       118.10        263.10
 Hilo APPROACH/DEPARTURE         119.70        269.20
 Honolulu CERAP APP/DEP                 120.25       323.00

Dave Foreman 

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