In message <006a01c07673$faf2b2e0$1d0c9bcf@eat>, J. Bradshaw
<ac6tk@cybertime.net> writes
>
>This is normal for many microprocessor controlled radios these days.
>Their output level and swr sensing feeds a closed loop system because
>the PA is made to operate with an unregulated (battery) supply. In the
>IC 706, the uP makes several decisions before operating electronic
>attenuators in the IF (as does the AGC) to set the power out. Note
>that on many of these radios, spurious outputs may not be reduced at
>all for lower power settings. The simple answer for these radios is
>either an attenuator pad and/or lossy Bandpass filters. Another answer
>may be to reduce the gain of the PA stage or at least drop the supply
>voltage to maybe 11-12v, but this leaves the IF wide open. Still another
>answer may be to adjust the negative feed back in the Amplifier so that
>the 706 may be run at rated power without exceeding the tube's ratings.
>
>On the 706 and MKII, It is obvious even on my crude spectrum analyzer
>that for whatever power setting, the radio at 13.8v makes well over
>100 watts at the instant of ptt before dropping to the set value. This is in
>CW or FM mode. I haven't looked for this in ssb mode, nor have I had a
>MKIII on the bench yet. There is no perfect radio. The 706 is a very neat
>portable/mobile rig though.
This is correct whatever the power setting and mode on my 706 version 2
It may also be useful to note however that on some rigs a pulse occurs
for a variety of reasons, such as PTT switch click picked up by mic, ptt
switch pulse induced into mic audio amp. I have seen and cured the
switch pulse on a Heathkit HW5400 and a KW Atlanta using simple
filtering on the mic/PTT socket.
It is not the same problem as the ICOM! Now that we have raised it on
this mailing list I expect ICOM will do something won't they :) ???
Paul
>
>I hadn't looked for that in the TS830 either, but in SSB (on my crude
>instrument) it didn't even make power on PTT until I fed it some audio,
>unless the processor was engaged and picking up background noise.
>
>
>Jim, ac6tk
>
>----- Original Message -----
>From: "Will Angenent" <k6ndv@contesting.com>
>To: "paul" <apollo_six@btinternet.com>; <amps@contesting.com>
>Sent: Wednesday, January 03, 2001 17:59
>Subject: RE: [AMPS] Output Pulse from ICOM 706
>
>
>:
>: According to Icom this is BOGUS! they had my 706 2 times and they can't find
>: the problem, They replaced my 775DSP thou (for the same reason)
>: 73 Will, K6NDV
>:
--
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