Feature Request: HF AFSK 300 baud

[randal007]

I would love to see a 300 Baud option for AFSK. I'm always useing aprsdroid in remote areas. I still use it but it requires me to connect to a PC with sound modem. If aprsdroud supported it as well as CAT PTT I would no longer need a external TNC.

Perfect use example would be to connect QRPLABs QDX or QMX directly to a phone.

Maybe also add support for USB soundcards.

[abalashov78]

+1 I need a 300 Baud for AFSK as well for using APRSDroid on 7Mhz

[penguin359]

First off, USB sound cards should already work with APRSdroid. That part is handled by the Android operating system when you plug in a USB headset or similar device. PTT support is currently being developed in another pull request and will likely be ready soon.

The AX.25 modem that APRSdroid uses can be found in ge0rg/packetdroid. It is based on the multimon source code, but neither it nor it's successor, multimon-ng, seem to have implemented the HF modems for 300 baud FSK, just the 1200 AFSK and other formats used on VHF/UHF over FM. As it's another variant of FSK which is already supported, it should not be too difficult to try and modify the existing code to support that variant. If you want to tackle that and submit a pull request with the changes to support it, I'll be happy to review it.

[penguin359]

I was doing some reading up on FSK300 and it sounds like it's much more finicky than the more common 1200 baud AFSK. From one article:

"Tuning is more difficult - the incoming audio tones from the receiver have to match the frequencies AGWPE is expecting within 20 or 30 Hz in order to be reliably decoded (that is within 10-15% or so of the 200 Hz shift). Since the receiver tuning directly affects the frequency of the recovered audio, this requires very precise manipulation of the receiver tuning knob. Since most modern HF rigs tune in synthesized steps of 10 Hz, this means that nudging the knob barely one or two clicks from center is enough to completely kill reception. [Many hams still have problems tuning in an SSB signal so that voice sounds reasonably natural, and that requires "only" a tuning accuracy of 50-100 Hz, not 20-30 Hz!]."

Based on that, it sounds like it would be a bit more involved than just tweaking some numbers in the existing 1200 baud modem. Do either of you have any actual experience with getting FSK300 working with an HF right to receive APRS packets?

[abalashov78]

I was doing some reading up on FSK300 and it sounds like it's much more finicky than the more common 1200 baud AFSK. From one article:

"Tuning is more difficult - the incoming audio tones from the receiver have to match the frequencies AGWPE is expecting within 20 or 30 Hz in order to be reliably decoded (that is within 10-15% or so of the 200 Hz shift). Since the receiver tuning directly affects the frequency of the recovered audio, this requires very precise manipulation of the receiver tuning knob. Since most modern HF rigs tune in synthesized steps of 10 Hz, this means that nudging the knob barely one or two clicks from center is enough to completely kill reception. [Many hams still have problems tuning in an SSB signal so that voice sounds reasonably natural, and that requires "only" a tuning accuracy of 50-100 Hz, not 20-30 Hz!]."

Based on that, it sounds like it would be a bit more involved than just tweaking some numbers in the existing 1200 baud modem. Do either of you have any actual experience with getting FSK300 working with an HF right to receive APRS packets?

Hi! Thanks for your attention!

I'm interested in APRS in HF range. As WA I've installed Direwolf as TNC KISS, connected ARPSDroid to DireWolf via blouetooth. And I've used MODEM 300 configuration in DieWolf for HF. Now I'm looking for APRS Digi on 40m & 30m HF.

[randal007]

With modern HF radios I think the dial accuracy is good enough. As I have experimented with 300 baud useing soundmodem with very good success.

But since then I've switched to VARA aprs and it looks like thats how things are shifting towards because that method allows 2 way over packet aprs. so I don't know how much of a need 300baud aprs is anymore but would be nice to have because then you don't need a vara modem.

On Thu, Aug 15, 2024, 2:29 a.m. abalashov78 @.***> wrote:

I was doing some reading up on FSK300 and it sounds like it's much more finicky than the more common 1200 baud AFSK. From one article:

"Tuning is more difficult - the incoming audio tones from the receiver have to match the frequencies AGWPE is expecting within 20 or 30 Hz in order to be reliably decoded (that is within 10-15% or so of the 200 Hz shift). Since the receiver tuning directly affects the frequency of the recovered audio, this requires very precise manipulation of the receiver tuning knob. Since most modern HF rigs tune in synthesized steps of 10 Hz, this means that nudging the knob barely one or two clicks from center is enough to completely kill reception. [Many hams still have problems tuning in an SSB signal so that voice sounds reasonably natural, and that requires "only" a tuning accuracy of 50-100 Hz, not 20-30 Hz!]."

Based on that, it sounds like it would be a bit more involved than just tweaking some numbers in the existing 1200 baud modem. Do either of you have any actual experience with getting FSK300 working with an HF right to receive APRS packets?

Hi! Thanks for your attention!

I'm interested in APRS in HF range. As WA I've installed Direwolf as TNC KISS, connected ARPSDroid to DireWolf via blouetooth. And I've used MODEM 300 configuration in DieWolf for HF. Now I'm looking for APRS Digi on 40m & 30m HF.

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