[TMC] FSK (not AFSK) with SBT-1K ???

[jvendely at cfl.rr.com]

Hey Nick,

I think your best bet is to treat the XFK as if it were a substitute
VMO (Or CMO, in the case of the SBT-1KE), providing FSK in the usual
2-4 Mc frequency range, and using the VMO or CMO as the external
oscillator input for the XFK. The exciter then converts the XFK 2-4 Mc
FSK modulated signal to the output frequency in the usual fashion (in
the foregoing, I'll assume you'll be using the synthesized SBT-1KE).

1. Disconnect CMO output from CHG 2-4 Mc input, and connect to XFK EXT
osc input, set XFK XTAL switch to EXT.

2. Configure XFK Multiplication Preset jumpers for Mult Ratio of 1 (no
frequency multiplication in RF path)

3. Connect XFK RF output to CHG 2-4 Mc input. You may want to put a 6
or 10 dB pad in line to avoid accidental overdrive. This thing can put
out a few watts.

Note: The XFK FSK output center frequency is offset from the external
CMO input freq by +200 kc, due to its internal mix, so set the CLL and
CMO to generate a signal 200 kc below the normal CMO output freq for
the desired RF output carrier freq (note also that the CMO dial is
offset 250 kc below its output freq). 

4. Adjust CBE for full carrier level, turn off USB and LSB channels.

5. Tune up XFK, set CHG and PAL for desired band, tune and operate as
usual, controlling exciter RF output level with CHG output control. 

For example, if the desired output carrier freq is 7100 kc, the CMO
would normally be set to a dial frequency of 3100 kc, thus producing
the required output of 3350 kc to the CHG. So we want the XFK to
generate this same 3350 kc as its center freq output. Set the CLL/CMO
to produce a CMO output 200 kc below this, or 3150 kc. To do this, set
CMO dial to 3150-250=2900 kc, CLL 1kc and 100 cps controls to 0, tune
CMO for phase lock and peak its output. Then peak up the XFK to
produce the desired output at 3350 kc, and tune the CHG and PAL as
normal for 7100 kc output. Set the XFK to the desired shift (850, of
course!) and start typing... 

It takes a little juggling of RF levels--the CMO output level must be
adjusted to adequately drive the XFK, and the XFK output adjusted to
put the CHG MF meter upscale but below the red. Be really careful not
to overdrive the CHG 2-4 Mc input, as the XFK can produce enough power
to cause damage if over-goosed. You might want to put a 6 or 10 dB pad
in line just to be safe.

It's a lotta knob-twirling all right, but what the hey, that's why we
love these rigs!

73,

John K9WT

	-----------------------------------------From: "Nick England" 
To: "tmc"
Cc: 
Sent: Tuesday July 28 2020 5:39:04PM
Subject: [TMC] FSK (not AFSK) with SBT-1K ???

Don't worry, I'll get around to the point eventually....
 I swapped some email today with K5EF who is restoring an XFK to use
with
 his GPT-750 for RTTY. That prompted me to haul out my XFK which had
been
 sitting on the shelf for years. I couldn't remember if I had ever
even
 checked it out. Removing the covers revealed enough grunge to quickly
 convince me I hadn't.

 OK. look for the XFK manual. Can't remember where I filed it, so
interwebs
 to the rescue and a new download from tmchistory.org. OK, I can feed
the
 XFK with my VOX and drive the PAL-1K portion of the SBT-1K. But
hello, this
 gadget only covers from 1 to 6.9 mc - with no multiplier output - so
how am
 I gonna get on 40m? The manual says to use the multiplier on your
GPT-10K.
 I ain't got no GPT-10K but I do have a manual - I found it right
there next
 to the XFK manual I couldn't find earlier of course.
 And there on page 3-25 is a diagram showing how to hook up your VOX
to
 drive the XFK to drive *ANOTHER* VOX??? No wait, it must be the same
VOX,
 just grabbing the 2-4mc VOX oscillator output and injecting the FSKed
 signal back in before the VOX multiplier.

 Has anyone got a VOX/XFK running? is this what you do?

 Looks like I need to replicate a GPT-10K's MCP to switcheroo between
 running with the VOX/XFK/VOX, VOX/SBE, or SBG as an exciter source.

 Of course I could keep on using AFSK with the SBG or SBE, or I could
use
 the SBE to multiply the VOX/XFK, but hey, this is the TMC hobby -
isn't the
 goal to do everything in the most complicated way possible?
 Ooh, I think I'll need to use my ISK in there too!

 Those people in Mamaroneck were just insane!

 Cheers,
 Nick England K4NYW
 www.navy-radio.com
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