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John, A question about AndFlmsg modes... When my FLDIGI friends send PSK250R, the AndFlmsg app switches over correctly to PSK250R, and the copy is good. But when look at the modes list in AndFlmsg settings, I see six types of PSK250R modes; however, basic PSK250R is not one of them. ??? Thanks for all you do. . . . Rob K6RJF

What does THOR 22 digital sound card mode RF SPECTRUM look like when sent over a UHF FM repeater (with permission of the repeater owner) This was sent by the digital net control, N3FLL, on Thursday Sept 19th. Note the presence of four clear sidebands on the RF Spectrum, centered on the VFO carrier frequency of 446.525 MHz THOR22 has 18 closely spaced tones, sent one at a time, at 22 tones/second. It is extremely robust on FM (VHF/UHF) and on HF (SSB) and does well at about 80 word/minute. However, to access the FM repeater, a PL tone of 100 Hz was added (close lines next to carrier at 446.525) The amplitude of the TX audio was adjusted for a DEVIATION of about 2 kHz by the Bessel null method. Note the RX audio level was set to -17 dB (not too loud, not too soft). It is important that the receive audio level not starve nor saturate the sound card. I've found that a level of -10dB to -20 dB works well using a TUNE signal (single pitch sine wave at 1500 Hz). My receiver was a RSP duo and sound card was a Masters Communications DRA-SR - all set for 1200 baud (de-emphasized) audio. The RF spectrum of THOR mode looks very different when sent on HF SSB. de k3eui barry

Recently a question was raised about the optimum TX audio for digital modes on 2m FM. Great question. The old guideline was to listen to your audio with a second FM radio (HT will work fine) "the sound from any of the sound card digi modes should be about the same loudness of a human voice with a microphone" That is a pretty rough guideline, and not a very accurate nor precise guideline. First, some modes sound louder than others: the Olivia, THOR, MFSK modes are simple single-pitch sine waves but always played one tone at a time at a specific duration of each tone (the baud is tone per second). Usually the pitch is 500 Hz to 2500 Hz for the multiple tones. So the tone duration (seconds) is simply 1/baud. Longer duration tones are lower baud values and are easy on the ears; THOR, Olivia, MFSK Thus each THOR 11 tone is twice as long as a THOR22 tone, as well as a smaller bandwidth for the mode. The psk type modes (PSK31, PSK63, 8PSK and VARA) are changes in both phase and amplitude, so the "loudness" of phase-shift modes can be deceiving based on human ears. Humans hearing is more sensitive to sounds from 2000 - 3000 Hz, than sounds at 500 Hz, so higher pitch sounds of any mode will appear louder than lower pitch sounds. The optimum TX audio is based on the deviation on an FM transmitter. Can we measure the deviation (directly, or indirectly) and not the loudness based on human hearing and speaker quality. Yes. If you have access to an SDR that can look at the RF spectrum (I will pick 2m FM) then adjust the amplitude of the TX audio until you get the following picture on your SDR app. I am using an RSP (hardware) and usb cable and RSP Spectrum Analyzer (software) with Windows 10. For this test I set the vfo on the radio (Icom 2820) to 145.690 MHz on an Icom dual-band FM rig. My sound "card" is a Masters Communications DRA SR feeding TX audio into the radio's 6 pin MINI DIN data jack. I set the Fldigi TUNE with the cursor to 1500 Hz in the waterfall. Be sure to turn OFF any TxID signal sounds, and turn off any PL tones - these will mess up the image. Don't try this on a analog voice repeater (that needs PL tones). Look at the RF Spectrum of the 1500 Hz TUNE - note the carrier (@145.690 MHz) and the multiple sidebands. We get this picture (multiple sidebands) on FM, but not on AM or SSB. Louder TX audio results in more sidebands (and a drop in the carrier amplitude). However, on FM, you get the same POWER (watts to antenna) independent of the TX audio level. When the amplitude of the pair of 1st sidebands matches the amplitude (height) of the original carrier --- STOP. Mark the TX audio levels (sound card TX setting, FLDIGI TX attenuator, Windows Speaker output). The deviation is the product of the "modulation index" and the audio pitch in kHz. So at this level of TX audio, the modulation index is about 1.5 and the audio pitch is 1.5 kHz (1500 Hz) so the deviation is about 2.25 kHz. That is about ideal. You won't over modulate and distort the sound card digi modes. Questions? contact me at k3euibarry@...

good copy tonight at 7:30 PM EDT from Philly on 3582.500 kHz (vfo) and @1500 Hz on waterfall with Olivia 8/500 mode Good steady signals tonight received on my 140 ft end-fed NVIS antenna. Was able to check in with 50W tonight. de k3eui barry kennett square PA (SW of Phila PA)

It ooks like FLDIGI will allow one to set an arbirtrary center frequency for FSG, as well as use the traditional 1160 Hz annd 1500 Hz center frequencies. But in testing it looks like FSQ always only transmits on 1500 center frequency. Am I missing something? Thanks! -- 73, AB1PH Don Rolph

Hey folks: I've been stymied by this issue for a while. For "some reason" any text I transmitted in FLDIGI went out in all lower case regardless of whether I entered it with capitals. I finally stumbled across the setting that appears to controls this: 73, N6OPE

It ooks like FLDIGI will allow one to set an arbirtrary center frequency for FSG, as well as use the traditional 1160 Hz annd 1500 Hz center frequencies: But in testing it looks like FSQ always only transmits on 1500 center frequency. Am I missing something? Thanks! -- 73, AB1PH Don Rolph