[RTTY] FSK interface circuit troubles

[Alfred Frugoli]

The one thing I didn't mention is that I'm running a KW TS-940, this seems
to be a detail of interest in all the replies I've gotten.


73 de Al, KE1FO

-----
Visit my amateur radio contesting blog at ke1fo.wordpress.com.


On Tue, Dec 9, 2008 at 10:16 PM, Alfred Frugoli <ke1fo at arrl.net> wrote:

> Hello folks,
>
> I'm trying to build up the interface listed at the bottom of
> http://www.aa5au.com/rttyinterface.html#PNP_Transistor_FSK_Circuit using a
> PNP transistor.  I'm using generic PNP transistors from Radio Shack (the
> package says they're 2n3906 but there are a mix of various numbers in the
> package) and a 1k resistor.
>
> I'm building up the circuit for use with Software FSK in Writelog (using
> RTTYwrite not MMTTY).  I originally built the NPN circuit at the top of the
> page and got inverted keying.  Then I built up the PNP circuit and all was
> well.  I then went to build up a 2nd identical interface, and it did not
> work.  I took apart the case of the first interface to make sure they were
> wired identically.  I put it in line without the case to make sure it
> worked, and it did not.  Since that point I have not been able to build a
> working interface, and the original that did work, no longer does.
>
> I have tested the RTTY port on the rig, and all is well there - when I
> ground the center pin it shifts tones.  I've tested the Serial port, and I
> get either +9v or -9vdc between pin 3 and signal ground depening on the
> state of the serial port.  I've tried a different USB/Serial converter, and
> no joy there, so I'm assuming I've done something wrong in the circuit.
> I've tested my transistors prior to inserting them in the circuit and they
> seem to be good both before being in the circuit and after not working (i.e.
> nothing is zapping them when they get connected to the rig and serial
> port).  I've "reversed" the transistor (i.e. swapping emitter and collector
> leads just in case the transistor is miswired/mislabeled).  I've tried
> connecting the base back to the "ground" connection of the RTTY port on the
> rig rather than to pin 5 of the serial port (signal ground).
>
> Everything I've tried has resulted in the rig not shifting tones.  The
> USB/Serial converter has an LED to show activity, and when I send I can see
> activity on the prort, but the rig just stays on a single tone and does not
> shift at all.
>
> I don't know what else to try, except maybe a lower value resistor, but
> that doesn't seem to make sense since the circuit worked once.
>
> Thoughts?
>
> 73 de Al, KE1FO
>
> -----
> Visit my amateur radio contesting blog at ke1fo.wordpress.com.
>