[Kenwood] SM-220 Final Chapter

[Bryan WA7PRC]

John Parker wrote:
> Well guys,
> I feel really stupid and foolish.
> I did not check my TS-450S at all prior to the
> purchase of my SM-220.  
> The 450S doesn't have any connection that you can
> connect the SM-220 to!
> A little homework would have saved me a big
> headache.
> I just thought that since the i.f. is 8.83mhz, it
> would be a shoe in.  Not so much!!!
> Is all lost?  Or should I save it for a Kenwood
> TS-940S that I hope to
> obtain one day.
> 
> 73,
> 
> John KD7KFT

Hi John,

I did this very thing when I wanted to connect a
panadapter to my TS-120S/-130S rigs (also 8.83MHz IF).
 To minimize loading of the mixer, I fabricated a
buffer amplifier using "dead-bug" construction
technique and tapped into the IF ahead of the rig's IF
filter at the input to the IF board.  This point is
Lo-Z, and my buffer has a 2K ohm input impedance and
about 18dB of gain.  The output is coupled into a
length of RG-174/U 50-ohm coax (about 0.1" OD), and
terminates at ground and an unused pin on the
Accessory connector on the rear of the rig.  The
amplifier is simply a common emitter amplifier
(2N3904, etc) with a parallel-tuned collector.

Of course, your rig will be different (triple
conversion vs double conversion).  You'll want to tap
into the output of the 2nd mixer.  It looks like the
secondary of L73 after Q28 on the RF board
(X44-3130-01) is your target.  See
http://tinyurl.com/b85qlt for the tap point I would
select. 

vy 73,
Bryan WA7PRC