[AMRadio] Kenwood TS-820 mod for am

John Coleman ARS WA5BXO wa5bxo2005 at pctechref.com
Sun Mar 19 22:26:41 EST 2006

	There is a switch on the panel of the TS820 and for the life of
me I can't think of what it was used for right now and I'm not at the
shack, but its use was never found inviting so BJ, WB5PKD, and I found a
use for it.  You see, the TS-820 uses diode switching to move the XTAL
and SSB filter reference for upper and lower SSB, as well as CW. So we
decided to use the basically unused switch to do the same thing and
removed the filter in one position of the switch as well as activating
the control for the carrier level insertion.  Putting the switch back in
its normal unused position returns the 820 to normal operation as per
its regular function switch.   For example, we set the rigs function
switch in lower SSB for 80 or 40 meters when the "unknown switch" is
place in the proper position the SSB filter is bypassed, as it would be
in CW, but the carrier for XMIT is not exalted, it stays put as it was
for LSB (this make XERO BEATING a snap) and the CW level control becomes
carrier insertion for AM.  It is full AM in XMIT but there is only
product detection for RCVR.  I want to build a PLL detector to make the
product detector lock on RCVD carrier but just haven't done it.  The
TS-820s normal function is to provide about 10 watts carrier to the
SB200 linear (we just turn the audio level down all the way) which then
drive the class C push-pull pair of 250ths which is plate modulated by
four 813s push-pull parallel class AB1.  But the big rig can be bypassed
and the SB200 running about 75 watts AM can be put on the antenna or the
TS820 running a max of 20 watts AM can also be put directly on the
antenna.  Receiving is generally done on the HQ145 or SP600 although
there or other receivers, 4 or 6 about the place that we occasionally
use.  BJ and I are bad about documentation although we are getting
better.  We tend to fly by the seat of our pants when it comes to making
changes or designing something.  But if you're interested I will try to
find the hen scratching we did on some stained coffee napkin and copy it
for you.


-----Original Message-----
From: amradio-bounces at mailman.qth.net
[mailto:amradio-bounces at mailman.qth.net] On Behalf Of Bill Fondren
Sent: Saturday, March 18, 2006 4:42 PM
To: amradio at mailman.qth.net
Subject: [AMRadio] Kenwood TS-820 mod for am

Hello all    First let me say how much I have enjoyed the recent
discussion on linear amplifiers.   I have a Kenwood TS-820 that I would
like to modify for am for a standby transmitter.  A day or two ago I
remember seeing a remark about modifying a TS 820 for double sideband.
I  have a friend who has a 520  and used  screen grid modulation  for am
operation.  The email containing the remark seems to have been deleted.
Any remarks or where to get the information would be appreciated.  Bill
Fondren  K5PML
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