PSK31 Power Output vs. Bandpass Response

On PSK31, when I am transmitting a signal at 14.073 and above, my output drops to zero.  The rig is set at 14.070.  What is causing this power level drop, and how I can fix this? 

The drop-off in power level is due to the audio bandpass of your transmitter.  This will vary from rig to rig, but is normal.  A Typical SSB transmitter has its audio bandpass "shaped" to pass audio from around 300 Hz to around 3000 Hz  (the normal frequency response of the high-intelligibility spectrum of spoken words). The exact response will vary somewhat from rig to rig, but those numbers are typical.  As you approach those limits, the audio response "falls off" ... starts dropping in level.  If you go even close to the upper or lower limit of your rigs audio response curve, the power begins falling off, and gets lower and lower, until, past a point in either direction, the output falls to essentially zero. 

The solution is to simply move up or down in frequency a bit with your transceivers main tuning control. For instance, lets say you want to work a station that is at 14.074, and your rig is tuned to 14070.  Your transmitter would need to transmit audio tones (the PSK "warbles") at about 4000 Hz ... but your rigs audio response is already "rolled off" at 4000 Hz, so if you just click on the signal at the 14074 spot, the output power will drop way off, maybe even to zero.  If you move your RIGS frequency up a bit, perhaps to 14072, that will move the desired stations signal 2000 Hz down the waterfall, right into the middle of your SSB transmitters audio bandpass!  Now, you only need to click on the signal at it's new spot on the waterfall, and all will be fine. 

There is nothing "sacred" about the 14070 spot on your rigs dial, you can tune around as needed to move any desired signals into the bandpass.  With a little experimenting, you can easily learn what the lower and upper limits of your particular rigs "full output power bandpass" is, and just adjust your rigs frequency dial a bit whenever you need to bring desired signals into the bandpass.

PSK31 operators have made a habit of typically leaving their transceiver's main tuning dial set for the common PSK spots of 7070, 10140, 14070, etc. to allow for the convenience of doing MOST of the tuning by just clicking on signals on the waterfall.  Because other operators often have their rig set to that frequency, signals will mostly appear within the acceptable bandpass of the transceiver ... but you can always tune up or down the band a bit to move the desired signals into the bandpass of your rig.  You probably have noticed that the receiver also has a bandpass (usually a bit wider than the transmitters, depending on filter selection) and that's why you can see the background (waterfall) noise level fall off (fade out) above and below the receivers bandpass.