[1000mp] Mk. V "User mode" for PSK31

[Kok Chen]

On Nov 2, 2010, at 2:34 PM, John Becker wrote:

> What I'm having trouble with is the fact that when the FT-1000 is switched to "Pkt", it is LSB but the convention for PSK31 seems to be USB. I'm not sure how to configure the "User" mode.

Your software should allow you to change the sideband of the audio PSK signal.  I use PKT mode for PSK31 myself (and also use LSB with MFSK16 and DominoEX, which are "sideband dependent").  I use homebrew software, so I can control the sideband of the audio signal, but I can't imagine any other software that won't allow you to invert it, since it is a no-brainer and simple enough to implement.

That being said, BPSK31 uses *differential* PSK demodulation.  I.e., it looks for 180 degree phase shifts between bit times.  It does not matter if it is -180 degrees or +180 degrees, since both are the same.

As a result, an audio BPSK31 signal can be sent and received with either USB or LSB, even if the software cannot "invert" the spectrum.

QPSK31 is a different story -- it uses 0, 90, 180, 270 degree shifts, and it does matter if you sent 90 or 270 degrees.  If your software cannot invert the spectrum, you will need to use USB to transmit QPSK31.  MFSK16 and DominoEX are also sideband dependent.

> I'm decoding PSK31 transmissions, and I'm transmitting, but so far I haven't made any contacts, so I probably have something set wrong.

If you see RF power out, and the ALC meter is not showing any bars, people should be able to copy you.  

Make very sure there is no bars in the ALC meter.  ALC will raise the IMD and if transmitted IMD is poor enough, people will not be able to copy you -- or, they also might want to avoid working a dirty splattering station, HI.

What I typically do on my FT-1000MP (PKT Mode) is to turn RF Power all the way up (fully clockwise) and then use the Mic Gain knob to control the audio drive, which in turn controls how much RF power is transmitted.  At the same time, I monitor the ALC indicator to make sure that no bars appear on it.

Another thing to do to keep IMD low is to not max out the output power.  PSK31 is not a full duty cycle mode.  The signal is envelope modulated with 3 dB crest factor.  So, 50 watts average power out will hit 100 watt peaks on the transmitter.  If the PA clips at 100 watts, you will need to use less than 50 watts average RF output when idling.  In fact, if you have a fast reacting RF Power meter and have set the average output to 50 watts with an idling PSK31 signal, you will see the meter flicker upward as you type.  The idle Varicode puts out the lowest RF power in PSK31 (50 watts in this example).

Be sure the RX and TX clarifiers are zeroed out, too.

73
Chen, W7AY