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.
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
:
:
: -----Original Message-----
: From: owner-amps@contesting.com [mailto:owner-amps@contesting.com]On
: Behalf Of paul
: Sent: Wednesday, January 03, 2001 2:49 PM
: To: amps@contesting.com
: Subject: [AMPS] Output Pulse from ICOM 706
:
:
:
: Has anyone come up with a solution to the problem of the large pulse
: produced from an ICOM 706 when initially keyed and even with the power
: output turned down?
:
: I'd like to use mine with a grid driven linear but apart attenuating the
: output of the 706 on full 100 watts output unless there's a fix then it
: doesn't seem possible.
:
: Paul
: --
:
:
:
: --
: FAQ on WWW: http://www.contesting.com/FAQ/amps
: Submissions: amps@contesting.com
: Administrative requests: amps-REQUEST@contesting.com
: Problems: owner-amps@contesting.com
:
:
:
: --
: FAQ on WWW: http://www.contesting.com/FAQ/amps
: Submissions: amps@contesting.com
: Administrative requests: amps-REQUEST@contesting.com
: Problems: owner-amps@contesting.com
:
:
--
FAQ on WWW: http://www.contesting.com/FAQ/amps
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
|