To: | <amps@contesting.com> |
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Subject: | [AMPS] RE: ALC |
From: | rfamps@ic24.net (Steve Thompson) |
Date: | Thu, 17 Feb 2000 10:50:41 -0800 |
-----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 -- FAQ on WWW: http://www.contesting.com/ampsfaq.html Submissions: amps@contesting.com Administrative requests: amps-REQUEST@contesting.com Problems: owner-amps@contesting.com Search: http://www.contesting.com/km9p/search.htm |
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