Date   

Re: OFDM Modes Testing

Gary E. Kohtala
 

Would anyone care to play with OFDM in the afternoon and/or evening hours, say on
80m, 40m, 30m, or ???.

Best regards,

Gary, K7EK


Re: OFDM Modes Testing

K3eui <K3eui@...>
 

I just kept pressing the  LK  button on/off many times

It is going to be "repaired'




On Mar 5, 2021, at 3:16 PM, Frank Olaughlin <wq1o.frank@...> wrote:

Barry,

How did you move the center frequency on OFDM-2000F?  When I change it, it moves in the box, but the actual frequency doesn't change. Same if I adjust it in the WF.

73
Frank
WQ1O


Re: OFDM Modes Testing

Frank Olaughlin
 

Ron,

Good observation!      Thanks.....that works.

Looking forward to the new updates.


73
Frank
WQ1O


Re: interesting test today on 440 FM repeater

KL4YFD ham
 


Hi Barry,

The OFDM 500F, 750F, and 2000F modes should work over repeaters also.
Not certain if they will provide much more robustness, as line-of-sight-FM is already a very clean signal.
OFDM-2000F may work through multiple-linked repeater systems a bit better, but that would need to be tested.

OFDM-2000F and OFDM-2000 were designed to Just-Barely fit into a normal HF-SSB channel.
These modes were at the request of NBEMS-Hawaii mailing-list discussions, wanting a fast-as-you-can mode for HF line-of-sight (island to island)

The only way to get 2000 or 3000 bits/second over HF SSB with OFDM-2000/2000F was to really push the bandwidth-limits to their max.
This required locking the Tx frequency though to prevent signal-cutoff. Rx is still frequency agile to compensate for radio frequency offsets.

So, this is why OFDM-2000F and 2000 are transmit-center-frequency locked to 1325Hz.
 Adjusting even 10Hz either direction would cut-off portions of the signal.
At 2Khz of bandwidth, it is at the very-limit of what stock HF-filters allow (and a bit too wide for 1.8Khz filters).

As far as using OFDM-2000F vs the 8PSK modes... it depends on the repeater system.
When using faster-baud rate single carrier modems, there is a bit more robustness to phase-distortions than slower baudrates.
The faster the baudrate, the wider the signal-bandwidth, spreading-out the phase distortions and allowing decode.
The drawback though is faster baudrates need a higher signal-to-noise ratio to operate (less sensitivity).

Using a slower-baudrate multi-carrier mode like OFDM-2000F will work when there is less signal strength (more sensitive), but at the cost of being far less tolerant of phase-distortions. 
For HF we know the signal is most-likely going to be kinda quiet, and SSB-radios are very phase-stable, so multiple slower carriers win-out as the best solution.

The OFDM modes do spread the bits over multiple carriers, so if 1 carrier is cutoff by filtering or distortions, decode should still be 100%
This also nicely keeps us far-under the FCC baudrate limits for HF, while still allowing good datarates.


Thank you for all the testing,
John Phelps
KL4YFD



On Thu, Mar 4, 2021 at 2:05 PM Barry Feierman <k3euibarry@...> wrote:



John  KL4YFD

Updates....

Is there any reason why the  OFDM500F   and   OFDM750F   should not work on a standard FM analog voice repeater?

Afer all, it is just 'sound'.

We just tried OFDM500F  and it sent a FLAMP flawlessly on a  440 FM voice repeater (linked to two other 440 machines).

So the OFDM500F and 750F  are narrow enough for a typical SSB frequency (and filter) but I think should work fine on FM radios.


What if we were to try the  OFDM2000F   on  80m  SSB?

Obviously we'd need  2 kHz bandwidth  (on 80m in the morning, that's not a problem for a quick test).


I noticed the 2000F  wanted to "center" at   1325 Hz on waterfall.  Why?

We generally center all modes at  1500 Hz  on SSB and on FM.

Any reason why we should not center  2000F  mode at  1500 Hz on a FM voice repeater?


I modified my (old) SignaLink to use the  9600 baud Rx audio, and changed my Icom 706MIIG  to the MENU  9600 baud option,

and then modified the SignaLink to get a bit more Tx audio and everything works FINE on FM setting on the Icom 706.

Just exchanged some FLAMP  using  OFDM2000F  both centered at  1325  and  1500.

We even tried centering OFDM2000F  at   2000 Hz on WF, and it worked as well.

It sounds awful  (like VARA)  but it works!


So  OFDM2000F  is   8  "carriers"  or  sub-carriers, and each has a lower baud than the high values of single carrier  8PSK1000F.

My guess:  OFDM2000F  is going to work better than  8PSK1200F  on our typical radios and FM repeaters  ....

it spreads the information over  8  "carriers"  (lower baud each)  like having 8 wires carrying information  vs.  one wire.

Am I correct?


So far, this has been fascinating.

Oh...  and  NY3J  and  N3FLL  both have the RMA-70  new wide freq modems.  I'm jealous.

I'm still stuck with the old SignaLink, but maybe I'll break down and buy a  RMA modem.

I see the 'new' SignalInks have better wider audio transformers and better chips  (line input vs. mic input).


TU

Barry  k3eui



Re: OFDM Modes Testing

 

Frank,

Try this. After you move center frequency turn on LK then off again and it looks like it frees it up. It looks like Dave is working on a few things and an update is in the works.

73, Ron NY3J

On 3/5/21 3:16 PM, Frank Olaughlin wrote:
Barry,

How did you move the center frequency on OFDM-2000F?  When I change it, it moves in the box, but the actual frequency doesn't change. Same if I adjust it in the WF.

73
Frank
WQ1O


fldigi 4.1.18.16 posted

Dave
 

at http://www.w1hkj.com/alpha/fldigi/

Contains fixes to OFDM bugs reported for version 4.1.18.15.  Be sure that both Tx and Rx are using the same version for RsID to work corrrectly.

73, David, W1HKJ

Fri Mar 5 14:20:00 2021 -0600  - alpha  4.1.18.16

  WF-only mode menu
    * add missing modes

  Add OFDM modes for NBEMS - Author: John Phelps <kl4yfd@...>
    * OFDM-500F for HF SSB
      - survives HF NVIS/long path
      - 4-carriers of 62.5-baud 4PSK = 250 bps
      - 1/2 rate K=15 FEC with 4sec interleaver
    * OFDM-750F for HF SSB
      - survives HF NVIS/long path
      - 3-carriers of 125-baud 8PSK = 562 bps
      - 1/2 rate K=13 FEC with 3.2sec interleaver
    * OFDM-2000F for HF-SSB/FM
      - 8 carriers of 125-baud 8PSK = 2000bps
      - 2/3 rate K=13 FEC with 3.2sec interleaver
    * OFDM-2000 for HF-SSB/FM
      - 4 carriers of 250-baud 8PSK = 3000bps
      - NO FEC, meant for line-of-sight
    * OFDM-3500 for FM 9600-port
      - 7 carriers of 250-baud 8PSK = 5250bps
      - NO FEC, meant for line-of-sight
      - Requires Signalink made-after 2018 connected to the 9600-jack

  PSK-modes fix false triggers of DCD-OFF - Author: John Phelps <kl4yfd@...>
    * Certian character combinations were triggering DCD-OFF
    * DCD-OFF code now searches over 6-bit window
    * Prevents rare data-loss bug mid-transmission



Re: OFDM Modes Testing

Frank Olaughlin
 

Barry,

How did you move the center frequency on OFDM-2000F?  When I change it, it moves in the box, but the actual frequency doesn't change. Same if I adjust it in the WF.

73
Frank
WQ1O


Re: [linuxham] fldigi 4.1.18.15 alpha posted

KL4YFD ham
 


Hi Joe,

For the OFDM FEC-enabled modems, the RSID is a part of the modem, and not a separate option that can be turned-off.
This is simply a requirement when using 4PSK or 8PSK modulations due to the frequency-accuracy requirement and FEC design.

The RSID's have been coded into the OFDM "F" modes as the header which both sets frequency (AFC) and flushes-out any previously received noise-bits.
Due to the long multi-second interleaver and the heavy FEC, it is basically required to have this flush pre-data-start.
Without such a flush, noise-bits from 4-6 seconds previously will mix-into the FEC and degrade the decode.

This "use the RSID as modem-header" setup was coded into Fldigi many years ago by John Douyere, VK2ETA and others when multi-carrier capability was first-added.
Was kind of the plan for about 6 years now to use the RSID and an AFC-solution when going multi-carrier.

"RSID as the modem-header" has ended up being a rather slick solution that works even via Web SDR's and old Boat-Anchor HF radios,
both of which are notoriously off-frequency and sometimes a bit drifty. 

73's
John Phelps
KL4YFD



On Fri, Mar 5, 2021 at 9:21 AM Joseph Counsil, KØOG <counsil@...> wrote:
Dave,

The OFDM modem is a nice addition -- Thanks to John for working on development of that!

I find between my two stations (one running on Win10x64, the other on Linux Mint 20.1) that the RSID can not be disabled when an OFDM modem is selected, and sometimes the receiving station grossly misidentifies the OFDM mode, so I miss a transmission.  This is with good signal strengths between the two stations.  I think the RSID needs to be looked at to improve RSID encode/decode performance, and it would be good to be able to control TXID/RXID with the Fldigi buttons (they exert no control on the OFDM modems).  When both stations do get on the same mode, they seem to work fine, but I need to do more testing with weak signals.

73,
-Joe-

w1hkj wrote:
at http://www.w1hkj.com/alpha/fldigi/

Apple dmgs are signed, but not certified by Apple.

  . *bs.dmg   - universal Intel/M1 cpu for Big Sur 11.x
  . *hs.dmg   - Intel x86_64 build on High Sierra 10.13.6
  . *lion.dmg - Intel x86_64 build on Lion 10.7.6

Fri Mar 5 06:30:00 2021 -0600  - alpha  4.1.18.15

  WF-only mode menu
    * add missing modes

  Add OFDM modes for NBEMS - Author: John Phelps <kl4yfd@...>
    * OFDM-500F for HF SSB
      - survives HF NVIS/long path
      - 4-carriers of 62.5-baud 4PSK = 250 bps
      - 1/2 rate K=15 FEC with 4sec interleaver
    * OFDM-750F for HF SSB
      - survives HF NVIS/long path
      - 3-carriers of 125-baud 8PSK = 562 bps
      - 1/2 rate K=13 FEC with 3.2sec interleaver
    * OFDM-2000F for HF-SSB/FM
      - 8 carriers of 125-baud 8PSK = 2000bps
      - 2/3 rate K=13 FEC with 3.2sec interleaver
    * OFDM-2000 for HF-SSB/FM
      - 4 carriers of 250-baud 8PSK = 3000bps
      - NO FEC, meant for line-of-sight
    * OFDM-3500 for FM 9600-port
      - 7 carriers of 250-baud 8PSK = 5250bps
      - NO FEC, meant for line-of-sight
      - Requires Signalink made-after 2018 connected to the 9600-jack

  PSK-modes fix false triggers of DCD-OFF - Author: John Phelps <kl4yfd@...>
    * Certian character combinations were triggering DCD-OFF
    * DCD-OFF code now searches over 6-bit window
    * Prevents rare data-loss bug mid-transmission

  fmt
    * add callback handlers to
      . btn_unk_enable
      . btn_ref_enable
      . btn_fmt_record
    * reset frequency whenever ref or unk button is pressed

  Win32 Serial Port
    * change
      "if (!hComm)" to
      "if (hComm == INVALID_HANDLE)"

  CW punctuation
    * Allow user to suppress decode/encode of specific
      punctuation characters
    * Allow user to select character to display noise decodes
      . default '*'
      . '_'
      . ' '
      . none

  WX
    * Correct <WX:xxx> weather macro text substitution

  Canada
    * Add missing provinces / regions

  PulseAudio Server String
    * always enable PA server string control to allow user
      to clear or modify entry
    * fix hanging up on server fault message dialog
      . caused by message dialog on being re-entrant

  macOS arm64 builds
    * Change macosx macro to include darwin20 target

  Waterfall buttons
    * Set all buttons to visibile for new installation

  Audio Codec
    * fix for Portaudio h/w codec missing during fldigi startup
      . missing h/w could cause segmentation fault on some systems
      . added try{}catch{} to trx audio path
      . display error message
      . reset audio device to NULL codec

Version 4.1.18


--
Joseph A. Counsil
1310 Woodlawn Drive
Rolla, MO 65401
(573) 341-5186
Amateur Radio: KØOG


Re: fldigi 4.1.18.15 alpha posted

Joseph Counsil
 

Dave,

The OFDM modem is a nice addition -- Thanks to John for working on development of that!

I find between my two stations (one running on Win10x64, the other on Linux Mint 20.1) that the RSID can not be disabled when an OFDM modem is selected, and sometimes the receiving station grossly misidentifies the OFDM mode, so I miss a transmission.  This is with good signal strengths between the two stations.  I think the RSID needs to be looked at to improve RSID encode/decode performance, and it would be good to be able to control TXID/RXID with the Fldigi buttons (they exert no control on the OFDM modems).  When both stations do get on the same mode, they seem to work fine, but I need to do more testing with weak signals.

73,
-Joe-

w1hkj wrote:

at http://www.w1hkj.com/alpha/fldigi/

Apple dmgs are signed, but not certified by Apple.

  . *bs.dmg   - universal Intel/M1 cpu for Big Sur 11.x
  . *hs.dmg   - Intel x86_64 build on High Sierra 10.13.6
  . *lion.dmg - Intel x86_64 build on Lion 10.7.6

Fri Mar 5 06:30:00 2021 -0600  - alpha  4.1.18.15

  WF-only mode menu
    * add missing modes

  Add OFDM modes for NBEMS - Author: John Phelps <kl4yfd@...>
    * OFDM-500F for HF SSB
      - survives HF NVIS/long path
      - 4-carriers of 62.5-baud 4PSK = 250 bps
      - 1/2 rate K=15 FEC with 4sec interleaver
    * OFDM-750F for HF SSB
      - survives HF NVIS/long path
      - 3-carriers of 125-baud 8PSK = 562 bps
      - 1/2 rate K=13 FEC with 3.2sec interleaver
    * OFDM-2000F for HF-SSB/FM
      - 8 carriers of 125-baud 8PSK = 2000bps
      - 2/3 rate K=13 FEC with 3.2sec interleaver
    * OFDM-2000 for HF-SSB/FM
      - 4 carriers of 250-baud 8PSK = 3000bps
      - NO FEC, meant for line-of-sight
    * OFDM-3500 for FM 9600-port
      - 7 carriers of 250-baud 8PSK = 5250bps
      - NO FEC, meant for line-of-sight
      - Requires Signalink made-after 2018 connected to the 9600-jack

  PSK-modes fix false triggers of DCD-OFF - Author: John Phelps <kl4yfd@...>
    * Certian character combinations were triggering DCD-OFF
    * DCD-OFF code now searches over 6-bit window
    * Prevents rare data-loss bug mid-transmission

  fmt
    * add callback handlers to
      . btn_unk_enable
      . btn_ref_enable
      . btn_fmt_record
    * reset frequency whenever ref or unk button is pressed

  Win32 Serial Port
    * change
      "if (!hComm)" to
      "if (hComm == INVALID_HANDLE)"

  CW punctuation
    * Allow user to suppress decode/encode of specific
      punctuation characters
    * Allow user to select character to display noise decodes
      . default '*'
      . '_'
      . ' '
      . none

  WX
    * Correct <WX:xxx> weather macro text substitution

  Canada
    * Add missing provinces / regions

  PulseAudio Server String
    * always enable PA server string control to allow user
      to clear or modify entry
    * fix hanging up on server fault message dialog
      . caused by message dialog on being re-entrant

  macOS arm64 builds
    * Change macosx macro to include darwin20 target

  Waterfall buttons
    * Set all buttons to visibile for new installation

  Audio Codec
    * fix for Portaudio h/w codec missing during fldigi startup
      . missing h/w could cause segmentation fault on some systems
      . added try{}catch{} to trx audio path
      . display error message
      . reset audio device to NULL codec

Version 4.1.18


--
Joseph A. Counsil
1310 Woodlawn Drive
Rolla, MO 65401
(573) 341-5186
Amateur Radio: KØOG


Re: new alpha FLDIGI available for testing new OFDM modes

 

Dave,

I was doing local testing between two machines with 4.1.18.15. It looks like you have to deselect the OFDM modes in the RsID configuration or it will send out the TxID. Also, when you change to OFDM it changes you to 217 Hz on the waterfall.

73, Ron NY3J

On 3/5/21 11:55 AM, Dave wrote:
Early testing of the OFDM modes in 4.1.18.15 has discovered some critical issues.  I will try to have these fixed before your Sunday net.

David

On 3/5/21 8:39 AM, K3EUI Barry wrote:
*****   QST  *****

If you would like to help test the new "alpha"  OFDM  modes  (HF SSB  and  FM)  then please download the latest ALPHA (test) version of FLDIGI  4.1.18.15
and read all about these new changes.

The PaNBEMS net this Sunday (3583.0 kHz  at  0730 hr)  will test the new mode  OFDM500F  with a sample FLMSG and a  FLAMP (open FLAMP on your own after FLDIGI boots)
As you will see, this new mode has a very very long delay (interleaver) of about 8 seconds to deal with the long deep fades common on NVIS  80m paths.

TU  to  KL4YFD  John  for helping create these new  OFDM  modes.
de  k3eui  Barry

=========================================
at http://www.w1hkj.com/alpha/fldigi/
Apple dmgs are signed, but not certified by Apple.

  . *bs.dmg   - universal Intel/M1 cpu for Big Sur 11.x
  . *hs.dmg   - Intel x86_64 build on High Sierra 10.13.6
  . *lion.dmg - Intel x86_64 build on Lion 10.7.6

Fri Mar 5 06:30:00 2021 -0600  - alpha  4.1.18.15

  WF-only mode menu
    * add missing modes

  Add OFDM modes for NBEMS - Author: John Phelps <kl4yfd@...>
    * OFDM-500F for HF SSB
      - survives HF NVIS/long path
      - 4-carriers of 62.5-baud 4PSK = 250 bps
      - 1/2 rate K=15 FEC with 4sec interleaver
    * OFDM-750F for HF SSB
      - survives HF NVIS/long path
      - 3-carriers of 125-baud 8PSK = 562 bps
      - 1/2 rate K=13 FEC with 3.2sec interleaver
    * OFDM-2000F for HF-SSB/FM
      - 8 carriers of 125-baud 8PSK = 2000bps
      - 2/3 rate K=13 FEC with 3.2sec interleaver
    * OFDM-2000 for HF-SSB/FM
      - 4 carriers of 250-baud 8PSK = 3000bps
      - NO FEC, meant for line-of-sight
    * OFDM-3500 for FM 9600-port
      - 7 carriers of 250-baud 8PSK = 5250bps
      - NO FEC, meant for line-of-sight
      - Requires Signalink made-after 2018 connected to the 9600-jack



Re: new alpha FLDIGI available for testing new OFDM modes

Dave
 

Early testing of the OFDM modes in 4.1.18.15 has discovered some critical issues.  I will try to have these fixed before your Sunday net.

David

On 3/5/21 8:39 AM, K3EUI Barry wrote:
*****   QST  *****

If you would like to help test the new "alpha"  OFDM  modes  (HF SSB  and  FM)  then please download the latest ALPHA (test) version of FLDIGI  4.1.18.15
and read all about these new changes.

The PaNBEMS net this Sunday (3583.0 kHz  at  0730 hr)  will test the new mode  OFDM500F  with a sample FLMSG and a  FLAMP (open FLAMP on your own after FLDIGI boots)
As you will see, this new mode has a very very long delay (interleaver) of about 8 seconds to deal with the long deep fades common on NVIS  80m paths.

TU  to  KL4YFD  John  for helping create these new  OFDM  modes.
de  k3eui  Barry

=========================================
at http://www.w1hkj.com/alpha/fldigi/
Apple dmgs are signed, but not certified by Apple.

  . *bs.dmg   - universal Intel/M1 cpu for Big Sur 11.x
  . *hs.dmg   - Intel x86_64 build on High Sierra 10.13.6
  . *lion.dmg - Intel x86_64 build on Lion 10.7.6

Fri Mar 5 06:30:00 2021 -0600  - alpha  4.1.18.15

  WF-only mode menu
    * add missing modes

  Add OFDM modes for NBEMS - Author: John Phelps <kl4yfd@...>
    * OFDM-500F for HF SSB
      - survives HF NVIS/long path
      - 4-carriers of 62.5-baud 4PSK = 250 bps
      - 1/2 rate K=15 FEC with 4sec interleaver
    * OFDM-750F for HF SSB
      - survives HF NVIS/long path
      - 3-carriers of 125-baud 8PSK = 562 bps
      - 1/2 rate K=13 FEC with 3.2sec interleaver
    * OFDM-2000F for HF-SSB/FM
      - 8 carriers of 125-baud 8PSK = 2000bps
      - 2/3 rate K=13 FEC with 3.2sec interleaver
    * OFDM-2000 for HF-SSB/FM
      - 4 carriers of 250-baud 8PSK = 3000bps
      - NO FEC, meant for line-of-sight
    * OFDM-3500 for FM 9600-port
      - 7 carriers of 250-baud 8PSK = 5250bps
      - NO FEC, meant for line-of-sight
      - Requires Signalink made-after 2018 connected to the 9600-jack


new alpha FLDIGI available for testing new OFDM modes

K3EUI Barry
 

*****   QST  *****

If you would like to help test the new "alpha"  OFDM  modes  (HF SSB  and  FM)  then please download the latest ALPHA (test) version of FLDIGI  4.1.18.15
and read all about these new changes.

The PaNBEMS net this Sunday (3583.0 kHz  at  0730 hr)  will test the new mode  OFDM500F  with a sample FLMSG and a  FLAMP (open FLAMP on your own after FLDIGI boots)
As you will see, this new mode has a very very long delay (interleaver) of about 8 seconds to deal with the long deep fades common on NVIS  80m paths.

TU  to  KL4YFD  John  for helping create these new  OFDM  modes.
de  k3eui  Barry

=========================================
at http://www.w1hkj.com/alpha/fldigi/
Apple dmgs are signed, but not certified by Apple.

  . *bs.dmg   - universal Intel/M1 cpu for Big Sur 11.x
  . *hs.dmg   - Intel x86_64 build on High Sierra 10.13.6
  . *lion.dmg - Intel x86_64 build on Lion 10.7.6

Fri Mar 5 06:30:00 2021 -0600  - alpha  4.1.18.15

  WF-only mode menu
    * add missing modes

  Add OFDM modes for NBEMS - Author: John Phelps <kl4yfd@...>
    * OFDM-500F for HF SSB
      - survives HF NVIS/long path
      - 4-carriers of 62.5-baud 4PSK = 250 bps
      - 1/2 rate K=15 FEC with 4sec interleaver
    * OFDM-750F for HF SSB
      - survives HF NVIS/long path
      - 3-carriers of 125-baud 8PSK = 562 bps
      - 1/2 rate K=13 FEC with 3.2sec interleaver
    * OFDM-2000F for HF-SSB/FM
      - 8 carriers of 125-baud 8PSK = 2000bps
      - 2/3 rate K=13 FEC with 3.2sec interleaver
    * OFDM-2000 for HF-SSB/FM
      - 4 carriers of 250-baud 8PSK = 3000bps
      - NO FEC, meant for line-of-sight
    * OFDM-3500 for FM 9600-port
      - 7 carriers of 250-baud 8PSK = 5250bps
      - NO FEC, meant for line-of-sight
      - Requires Signalink made-after 2018 connected to the 9600-jack


fldigi 4.1.18.15 alpha posted

Dave
 

at http://www.w1hkj.com/alpha/fldigi/

Apple dmgs are signed, but not certified by Apple.

  . *bs.dmg   - universal Intel/M1 cpu for Big Sur 11.x
  . *hs.dmg   - Intel x86_64 build on High Sierra 10.13.6
  . *lion.dmg - Intel x86_64 build on Lion 10.7.6

Fri Mar 5 06:30:00 2021 -0600  - alpha  4.1.18.15

  WF-only mode menu
    * add missing modes

  Add OFDM modes for NBEMS - Author: John Phelps <kl4yfd@...>
    * OFDM-500F for HF SSB
      - survives HF NVIS/long path
      - 4-carriers of 62.5-baud 4PSK = 250 bps
      - 1/2 rate K=15 FEC with 4sec interleaver
    * OFDM-750F for HF SSB
      - survives HF NVIS/long path
      - 3-carriers of 125-baud 8PSK = 562 bps
      - 1/2 rate K=13 FEC with 3.2sec interleaver
    * OFDM-2000F for HF-SSB/FM
      - 8 carriers of 125-baud 8PSK = 2000bps
      - 2/3 rate K=13 FEC with 3.2sec interleaver
    * OFDM-2000 for HF-SSB/FM
      - 4 carriers of 250-baud 8PSK = 3000bps
      - NO FEC, meant for line-of-sight
    * OFDM-3500 for FM 9600-port
      - 7 carriers of 250-baud 8PSK = 5250bps
      - NO FEC, meant for line-of-sight
      - Requires Signalink made-after 2018 connected to the 9600-jack

  PSK-modes fix false triggers of DCD-OFF - Author: John Phelps <kl4yfd@...>
    * Certian character combinations were triggering DCD-OFF
    * DCD-OFF code now searches over 6-bit window
    * Prevents rare data-loss bug mid-transmission

  fmt
    * add callback handlers to
      . btn_unk_enable
      . btn_ref_enable
      . btn_fmt_record
    * reset frequency whenever ref or unk button is pressed

  Win32 Serial Port
    * change
      "if (!hComm)" to
      "if (hComm == INVALID_HANDLE)"

  CW punctuation
    * Allow user to suppress decode/encode of specific
      punctuation characters
    * Allow user to select character to display noise decodes
      . default '*'
      . '_'
      . ' '
      . none

  WX
    * Correct <WX:xxx> weather macro text substitution

  Canada
    * Add missing provinces / regions

  PulseAudio Server String
    * always enable PA server string control to allow user
      to clear or modify entry
    * fix hanging up on server fault message dialog
      . caused by message dialog on being re-entrant

  macOS arm64 builds
    * Change macosx macro to include darwin20 target

  Waterfall buttons
    * Set all buttons to visibile for new installation

  Audio Codec
    * fix for Portaudio h/w codec missing during fldigi startup
      . missing h/w could cause segmentation fault on some systems
      . added try{}catch{} to trx audio path
      . display error message
      . reset audio device to NULL codec

Version 4.1.18


Re: OFDM Modes Testing

K3EUI Barry
 



Yesterday a few of us tried using OFDM500F  on a  440 FM analog repeater -  it worked well.
I'm sure OFDM750F  would also have worked.

OFDM2000F  seems to also work well on a standard analog FM voice repeater, and we tried moving the center frequency up to 1500 Hz rather than 1325 Hz and that seemed to help.  We next tried a center frequency of  2000 Hz and that worked, although listening was kind of painful.

So these new OFDMxxxF  modes seem to be way faster and more rugged than other modes for high speed traffic.

We are continuing to test these also on 3583 kHz  (SSB) in the early morning hours via the NH, NY, NJ, and Pa NBEMS nets on the weekends.

So far, very promising results!
TU  KL4YFD

de  k3eui  Barry


Re: OFDM Modes Testing

K3EUI Barry
 

I would like to share an observation that the "available" audio on FM repeaters is 500 Hz to 3000 Hz,
or a  2500 Hz passband.  I would not expect a  OFDM3500  (3.5 kHz) would work, either with new of old SignaLinks.

Go lower than 500 Hz and the audio drops off, and you get close to the PL tones.
Go above 3000 Hz  and I can see and hear the high frequency dropoff.

So if you are testing on FM Simplex, that's one thing, using the wider freq response 9600 baud pins.
But if you are sending audio via typical FM ANALOG repeaters, watch out.

Our experience in Chester County PA is that  8PSK1000F  is just about 100% on FLMSG / FLAMP.
It is much faster than any other FLFIGI mode  (but it sounds awful).
Perhaps the multi-carrier  OFDM  modulation will beat that a bit.
VARA FM  beats every mode we've tried, but VARA is not available in FLDIGI.

And....  be absolutely certain that you have permission to test these digital sound-card based mode on a repeater.
Some repeater owners in my area say "absolutely no digital stuff".

Barry  k3eui


File transfer using FLMsg Form/Transfer

Neil Preston W0NRP
 

We attempted to send some files using the Transfer option under the Form menu. 
We were able to send text files and a .csv file, but could not send any graphics files - jpg, png or gif.

We would use the Transmit file field and select the file to be sent, and use the AutoSend function. This worked for text files but not for the graphics files.  No response.........

The FLMsg Help manual provides very little information about this option.
The illustration shows .jpg files listed in the 'Received files' list. 

Can you provide more details about the functions in this window?

Thanks,
W0NRP


Re: OFDM Modes Testing

Frank Olaughlin
 

John,

We did a two person test on OFDM3500 on Tuesday March 2nd using your latest.

Tester 1: Win 10 Laptop, FT-8900 radio, Newer Signalink, 2m VHF FM
Tester 2: Win 7 laptop, FT-8900 radio, newer signalink, 2m VHF FM

Method was Simplex with 10/9 signals

Observations:

We got about 40-50% text on simplex FM using Fldigi. It was not good enough to use Flamp. We got about 35-40% on flmsg. That was about the best we could do. Best center frequency we found to be 2250 on this version. Nothing else worked.
Version had excellent stability on Win 10, but crashed often on Win 7. The TX on the Signalink had to be at near maximum.

Thanks for all the continued hard work. I know these things are always a work in progress.

73
Frank
WQ1O
Cape Cod and Islands ARES DEC


Re: [linuxham] What is the BW limit for US hams in DIGI bands HF

Bob Cameron
 

For interest

In VK we have "necessary" bandwidth of any mode defined with operating frequency, plus a spectral density figure 80m-10m. ie it boils down to whatever the modulation method needs, rather than specifying a mode, Theoretically a very wide digital mode could be used legally, but agreements/conventions/manners and local bandplans tend to be tighter. Note that this all types of radio emissions, not just digital.

80m-12m "Where the necessary bandwidth exceeds 8 kHz, the maximum power spectral density from the transmitter must not exceed 1 watt per 100 kHz.

10m "Where the necessary bandwidth exceeds 16 kHz, the maximum power spectral density from the transmitter must not exceed 1 watt per 100 kHz.

Generally though it is 2.1kHz below 160m, 8kHz from 160m to 12m, 16kHz on 10m, 100kHz on the bottom half of 6m and no limit from there. Of course one must stay in band!

There is no data rate limitation. It is all bandwidth related.

Cheers Bob VK2YQA

On 3/3/21 7:46 am, KL4YFD ham wrote:

Hi everyone,

Wanted to touch on the bandwidth-rules conversation again since its coming up again,

Due to the outdated FCC rules, there is only an HF bandwidth-limit when using FSK modulation (limit of 1300Hz)
This is the RF bandwidth of 1000Hz spacing FSK @ 300-baud.

47 CFR § 97.307(f)(3)
The symbol rate must not exceed 300 bauds, 
or for frequency-shift keying, the frequency shift between mark and space must not exceed 1 kHz. 

Per the current rules, there is no bandwidth limit for PSK-based modes like OFDM, Pactor, or VARA.
Only the baudrate limitations.

That all said, having a bandplan that separates out wide from narrow digital modes on HF would be a nice addition for US hams.
Hope the ARRL and FCC can work together on some kind of more-coherent set of rules.

73's





Re: [panbems] OFDM Modes FINAL test release

K3EUI Barry
 

WD9EQD  Bill

It looks like this was one of  N3FLL's  transmissions.
He was using less power (40W) and a different antenna (long wire)  but the signal looks good and S/N is adequate.

OFDM is a multi-carrier  PSK modulation.  The signal in the WF looks very clean.

Do you know how to turn on the FLDIGI  Spectrum View  (whole monitor screen)?

For yesterday's tests, I was running about 200W to 300W.

Barry  k3eui


Re: What is the BW limit for US hams in DIGI bands HF

Gordon Gibby
 

Gently, I think your assertions are incorrect on both levels. This is a very complicated issue, and one of the chief goals of the amateur service is not the pleasure of the participants, but instead the advantages to the nation and its citizens that are listed in 97.1.     I have grappled with a lot of these concerns and I think intense regulations are not in the best interest of the amateur radio service.  people generally manage to get along and progress continues to be made in astonishing ways on many fronts.

My two cents worth

Gordon L Gibby KX4Z 


On Mar 2, 2021, at 15:47, KL4YFD ham <kl4yfd@...> wrote:



Hi everyone,

Wanted to touch on the bandwidth-rules conversation again since its coming up again,

Due to the outdated FCC rules, there is only an HF bandwidth-limit when using FSK modulation (limit of 1300Hz)
This is the RF bandwidth of 1000Hz spacing FSK @ 300-baud.

47 CFR § 97.307(f)(3)
The symbol rate must not exceed 300 bauds, 
or for frequency-shift keying, the frequency shift between mark and space must not exceed 1 kHz. 

Per the current rules, there is no bandwidth limit for PSK-based modes like OFDM, Pactor, or VARA.
Only the baudrate limitations.

That all said, having a bandplan that separates out wide from narrow digital modes on HF would be a nice addition for US hams.
Hope the ARRL and FCC can work together on some kind of more-coherent set of rules.

73's



On Tue, Mar 2, 2021 at 12:25 PM Barry Feierman <k3euibarry@...> wrote:
Duane  N6RVA

I will read all of this again, carefully.

But I do not agree with your conclusion (at this time).
Maybe I am missing something.


At present, MANY digital stations are operating HF with a bandwidth greater than 2 kHz.  Even the famous SATERN net on 20m operates with a wider BW than  2 kHz, and on 20 meters!  Unattended  ACDS  Winlink stations are limited to 500 Hz outside the  3585-3600 kHz but we are not talking about Winlink ops.

Some history
Going way back (before sound card modes) the old  RTTY  shift was 850 Hz, due to the lousy selectivity of receiver.  So I think that MAY be where the  1 kHz  "shift" maximum came from in these ancient FCC rules.  The ARRL proposal of a BW limit in place of a baud limit made sense, of course, even if it was not adopted by FCC.


I even asked the guys at ARRL what the max BW of digital signals could we use for NBEMS  EMCOMM nets and they said  "same as SSB phone".  NO one said  500 Hz  or   1000 Hz.

So who is missing what?
The modes we are using (sound card generated) are NOT a RTTY shift. We have no "shift" on OFDM modes of frequency.

Do you think we (NBEMS) are doing something illegal now if we use a BW of more than 1 kHz on an 80m SSB net on 3583 kHz?

I agree that the optimum BW is well under 2 kHz on a busy 80m band, But we at least know that THOR 100  and  MFSK128  do work and are reliable on 80m NVIS paths.

What is your recommendation for what the NBEMS nets should do about modes?  The new  OFDM F  modes are going to be well below 1 kHz and I like the  500F  mode  (make good neighbors).
There is no reason to go wider than 1 kHz on 80m, unless there was a real emergency and we absolutely needed MFSK128.

So what is the bottom line?


Barry


Begin forwarded message:

From: Duane Patocka <N6RVA@...>
Date: March 2, 2021 at 2:10:23 PM EST
To: Barry Feierman <k3euibarry@...>, "KD2DO (NY NBEMS) Paul Conaway" <conawayny@...>, KC2VUT Bill Kelleher NJ NBEMS <banker1@...>, N1GB George Blakeslee NH Dig Net <george.blakeslee@...>
Cc: frankrocap <n3fll@...>, NY3J Wenig Ron <rwenig@...>, "K3UG (Barry4)" <bthaysen@...>
Subject: Re: What is the BW limit for US hams

Barry et al.,

In November of 2013 the ARRL requested that the FCC remove the 300 baud symbol rate and replace it with a 2.8 kHz bandwidth limitation, the FCC agreed to removing the baud symbol rate but did not grant the 2.8 kHz bandwidth request.
------------------------------------------------------

ARRL Renews Request for FCC to Replace Symbol Rate with Bandwidth Limit

09/18/2019

In ex parte comments filed on September 17 in WT Docket 16-239, ARRL renewed its request that the FCC delete symbol-rate limits for data transmissions in the Amateur Service rules. As it did in its initial filing, ARRL asked the FCC to couple the removal of the symbol rate limits with the adoption of a 2.8 kHz bandwidth limit. In response to a 2013 ARRL Petition for Rulemaking (RM-11708), the FCC proposed deleting the symbol-rate limits but declined to replace them with the 2.8 kHz bandwidth that ARRL wanted.

-----------------------------------------------------
Currently, this means the maximum bandwidth for digital data can be no greater than 1 kHz per 47 CFR § 97.307(f)(3) - Emission standards.

In January of 2020 the ARRL proposed a new Band Plan with the following recommended changes to the 80 meter band:
RTTY and NB data 3.500 to 3.600 MHz
RTTY, NB data and WB data 3.600 to 3.650 MHz

Narrow Data < 500 Hz
Wide Data < 2800 Hz

I have included the proposed ARRL Band Plan as attachments to this email.

Duane
N6RVA

On 3/1/21 6:44 PM, Barry Feierman wrote:

Hi guys

For the 80m NBEMS weekend nets, what is the "WIDEST" bandpass we should be using to pass traffic  (drill or in a real emergency)?


If there is a BW "limit" for US hams when operating a station on the HF bands, it is not clear  (to me)  what that limit is, in Hz. 
And the opinion of some of the best digi guys at ARRL.  I asked them.

Forget the baud limit (300). We are not talking baud.
  What is the BW limit for HF digi modes below 29 MHz?

My belief is that it is essentially the same as what KL4YDF responded:

"No wider than a phone signal" ...  or  2.8 kHz for an SSB digi mode.

I am not speaking about an auto Winlink unattended station......  that is 500 Hz.

Here is the response I got from one of the guys who writes the software for FLDIGI digital modes, John  KL4YFD.
I think we should all stay to a reasonable BW unless we are in a real crisis. For me, that is about 1 kHz.  And  500 Hz  seems prudent.

So when we use MFSK32  we are being prudent.
When we jump to  MFSK64  or  THOR50x1  (under 1 kHz) it is only for brief testing purposes, to see if it works faster.  It does.
But I would not want to run  MFSK128  on an 80m band in the morning hours....  that is asking for trouble.  MFSK128 works great on an FM 2m repeater.

Barry

On Mar 1, 2021, at 4:37 PM, John Phelps <kl4yfd@...> wrote:


I did read an email by someone saying 500Hz is the limit, but that is not the case for FCC rules the USA. Possibly for European or Canadian hams though.
People use Pactor3 at 2.4Khz width routinely for WinLink, without issue.

In addition to the 300-baud rule, we only have this in the USA:
(2) No non-phone emission shall exceed the bandwidth of a communications quality phone emission of the same modulation type
So, basically, no wider than SSB voice at about 2.7Khz. 

The other rule only pertains to fully-automated stations (unattended, on a timer).
NBEMS is control-operator-present though manually clicking send, so does not apply.
(2) No transmission from the automatically controlled station occupies a bandwidth of more than 500 Hz. 

So there are 500Hz bandwidth rules, but only if unattended and fully automated.
If operator is present, and controlling, then 2.7Khz to "not be wider than phone"

John
KL4YFD

On Mon, Mar 1, 2021 at 9:34 AM Barry Feierman <k3euibarry@...> wrote:

yes  ..   I did try some quick  OFDK750F  for a minute.

No results yet.  We concentrated on the  500F  gear.

We could live with a  750 Hz BW  data signal on busy  80m  NBEMS net,  but that's about the BW limit we are comfortable using.


I have had TWO requests:   where in the FCC  rules does it state a  BW limit on HF ?

I can't find any  BW  limit, only a   300 baud limit (useless).

But a  K2  station claims there is a  1 kHz limit for the SHIFT  of a  RTTY  signal.

That must be going back 30+ years when I heard shifts of  850 Hz  (selectivity must have been crude back then)


Barry


On 3/1/2021 12:28 PM, John Phelps wrote:

Hi Barry,

OFDM-500F was great decode most of the time for me on SDR.

Thought I saw a 750F transmission for a second, but missed pressing record in-time.
Did anyone else get a decode of the OFDM-750F? I've only tested it here in simulations so far.

Todays testing means I need to make the interleaver longer in the OFDM code longer to handle the fades.
Its about 0.5 to 1 second too short at the moment. NVIS is a noisy-beast of a channel.

Good to hear you have about 200W going out on 80m. 
Was looking into some used RM-Italy HF amps if they were needed for testing, but you already have more power than that (and better quality).

Thanks again for all the help and tests,
John 
KL4YFD




On Mon, Mar 1, 2021 at 9:11 AM Barry Feierman <k3euibarry@...> wrote:

Hi John  KL4YFD


I just responded earlier.


We are in GREAT shape so far with  OFDK500F.


Yes,  my  Icom 7610  and Heathkit SB220  was about  200W.

I can run up to  700 W  with that amp on  80m.

No ALC, and clean on a Tek oscilloscope monitoring my Tx output.

The other ops were all running about 30-50 W  on TUNE, less on  OFDM of course.


I think there is a SDR web in Milford Pa.

Ron NY3J  has some experience with the SDR  sites since his local QTH is very noisy.


Barry

cc  NY3J


On 3/1/2021 11:46 AM, John Phelps wrote:

Hi Barry,

Thank you for the testing!

I was able to receive the OFDM test transmissions on 3580Khz using this web-sdr:
I think at 145 miles away this puts me out of groundwave but in NVIS-range.

I received the FLAMP 80m_propagation.213 message successfully.
Recordings of the session are here:
The OFDM results were mixed for me. Sometimes great, sometimes 50%
The NVIS channel was fading about 8-10 db periodically, for a minute or two, then recovering.
Do you have an HF amplifier?  Boosting Tx power by 8dB would overcome most fades and only be 150watts (assuming 25watts without amp).

The THOR and MFSK modes were nearly-perfect copy, maybe 1-2 errors total.

For the future OFDM tests, could you enable Tx-RSID?
I haven't figured-out how to auto-enable it in code... but the OFDM modes use RSID as the header and AFC mechanism both. There isn't actually a modem-header/preamble without it. 

73's and thank you again, 
John Phelps
KL4YFD

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