[AMPS] RE: ALC

[rfamps@ic24.net (Steve Thompson)]

-----Original Message-----
From: oz5tg <oz5tg@post2.tele.dk>
To: amps@contesting.com <amps@contesting.com>
To: <amps@contesting.com>
Date: 17 February 2000 00:22
Subject: Re: [AMPS] RE: ALC


>Hi Steve et.al
>
>I find it very interresting that You report problems with the FT990.
>Recently
>we had a serious problem here with an amateur that started using his FT990
>as a backend for a 144MHz transverter.
>
>When the power was turned dovn to 2W for the tranceiver the phasenoise from
>the 990 was big enough to put out a -60dBc. With a 1000W PA  that resulted
>in S9 broadband noisefloor covering several MHz!


We never got as far as finding that problem.

>
>With 100W/2W in/out from an attenuator/dummyload the noisefloor was lowerd
>the equivalent 14dB which made it possible to tolerate with good antennas
>pointing away from him.
>
>Tests with a spectrunanalyzer pointed out the FT990 as the offender. During
>keydown-
>no modulation the 28MHz signal had a 60db S/SN relation and with modulation
>the ratio
>improved with the rising signal. The problem may be related to the internal
>AGC/ALC.
>He sold the FT990 immediately.


Yes, thinking about the total gain after the crystal filter when the ALC
hasn't wound it back, it's obviously going to be a problem.

I guess we should be fair here - the FT990 was not intended for use as a
transvertor driver. The situation would be much improved if the PA was
bypassed for low level output.

Steve



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