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AndFlmsg modes question
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? |
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Re: No receive on FLDIGI
Normally this is caused by the audio device setup in Flrig/Fldigi and maybe windows. Windows has a habit of messing with the audio. And also make sure the Signalink is on. This is what usually happens on our nets. On Sat, Sep 28, 2024 at 4:06?PM Al via <k2hro=[email protected]> wrote:
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John W. Totzke W?JWT |
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what does RF spectrum of THOR 22 look like when sent by FM on UHF repeater
开云体育
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
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flrig 2.0.05.75 alpha release
开云体育Index of /alpha/flrigCorrected read errors on Windows OS.? See readme.txt for full list of changes. The MacOS dmg is a universal build for Sonoma, Intel and Apple silicon.? I am currently not able to build a dmg for earlier OS versions. 73, David |
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Re: how to set the FM TX deviation with an SDR
What I've never understood is why the SDR receivers that I've used do not offer a window that looks like an oscilloscope display of what would be the equivalent of discriminator audio, like the scope on an old Cushman service monitor.? Then you could read the deviation right off the scope graticule, and observe any clipping, distortion, hum, etc.? SDR's have all this super-duper processing going on, so why use some of that computational oomph to show an oscilloscope view of the discriminator audio?
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Paul, ad7i
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how to set the FM TX deviation with an SDR
开云体育
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
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Re: Michigan Digital Traffic Net (MIDTN)
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OLIVIA VS. THOR?
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I find it interesting that the daytime 80m NBEMS nets (Pa/NY/NJ/NH) tend to use THOR22 (78 wpm and 500 Hz) for checkins and THOR32 and MFSK32 for traffic (FLMSG). Prop paths around 7-9 AM are near vertical for a range of a few hundred miles. I love THOR - it is easy to tune in and it sounds pleasant to listen to.
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?
But in the evening NBEMS nets after sunset on 80m, it seems that Olivia rules. Why is that?
Does Olivia do better with the evening skip of a thousand miles?
Olivia 8/500 prints with longer delays, and Olivia 8/500 is the dominant mode I hear on the?
Michigan and Minn NBEMS nets in the evenings around 3582-3583 kHz.
?
thoughts?
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?
de barry k3eui
Philly
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Michigan Digital Traffic Net (MIDTN)
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
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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)
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Audio Level Meter
开云体育? ? ? ? Setting Optimum RX audio levelsIt helps to set the amount of RX audio your sound card sees (hears) carefully. Whatever digi audio meter you decide to use for RX levels, I found that decoding works best when the SENDING station’s tune level (@1500 Hz audio pitch) is set to about -10 to -20dB on your rx audio level meter Louder sounds 0 dB to -10 dB ?can distort the peaks Very softer sounds like -30 to -50 dB starves the sound card Remember the “Goldilocks Rule”. ? ? do not SATURATE and do not STARVE the sound card RX audio level Transmitting with optimum audio is a different ball game ? ? On SSB set the TX audio level for barely any ALC at whatever power you want ? ? ?I usually aim for 25-40 watts out on a TUNE signal on a 100W rig, zero ALC ? ? On FM, set the level to get the desired ‘deviation’ (about 2-3 kHz) which you can set if you have access to an SDR with an RF spectrum display. |
Dave
John W Totzke - W0JWT - MO
K3EUI Barry
ad7i RADIO
