David Hopper wrote:

On Mon, 20 Mar 2006 13:09:32 -0800, Tim Wescott
wrote:



That was useful, but I forgot to ask:

Is the space (no pulse) frequency the nominal frequency, or is it (more
sensibly IMHO) 1/2 the shift below -- or at least _some_ amount below
the nominal?

If I were designing such a rig I would have the space frequency (off, no
pulse, whatever) be 1/2 of the shift _below_ the nominal frequency, and
the mark frequency be 1/2 of the shift _above_. I may shade the space
frequency to be a bit closer to the nominal frequency to balance out the
spectrum, but I doubt that I'd stick it right onto the nominal frequency.



You got my curiosity up so I dragged in the ol' service monitor to see
what my 9C was doing. All of the pix were with the freq error meter on
the 1.5KHz range and the scope scale was on the +/-1.5KHz range.

The first was using a FP-TP-FM module on 08 (50.960MHz):

http://www.mindspring.com/~sbhopper/FP-TP-FM_08.jpg

Modulation is +/-1500Hz. The freq error meter is showing about 1KHz
low, but I am assuming it is the service monitor adjusting to the
non-symetrical deviation.


The second pic is with a FT-TP-FM module on 60 (72.990MHz):

http://www.mindspring.com/~sbhopper/FP-TP-FM_60.jpg

Inverted from the 6 meter.


The third pic is with the TP-FSM syntesized module set to channel 60:

http://www.mindspring.com/~sbhopper/TP-FSM_60.jpg

Same as the crystal module except the modulation is just a tad lower.

FWIW,
David - WD4JKH



That pretty much says it all. I guessed that +/-1500 was the number to
shoot for -- apparently your TX (Futaba?) agrees with me.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

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