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How do I use all the OFDM modes?

 

On it lists 8 OFDM modes. Only 3 are actually available in the software. How do I access the remaining 5 modes?
 

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They have been disabled.? Highly experimental.

David

On 4/4/24 16:26, benhut1@... wrote:

On it lists 8 OFDM modes. Only 3 are actually available in the software. How do I access the remaining 5 modes?

 

Experimental? Like not suitable for use over the air yet? Or more like they are broken in the software? I would like a chance to of possible at least experiment with them. I even found where to download the alpha version of the software? but the alpha version still didn't have these experimental features. Is there any way to get a chance to experiment with these new OFDM modes?


On Thu, Apr 4, 2024, 2:50 PM Dave <w1hkj@...> wrote:
They have been disabled.? Highly experimental.

David

On 4/4/24 16:26, benhut1@... wrote:
On it lists 8 OFDM modes. Only 3 are actually available in the software. How do I access the remaining 5 modes?

 

I was getting ready to send the same question - would like to experiment with modes with higher symbol rates.
 

Was testing FLAMP using those modes and found that some of the modem speeds did not decode correctly, Hence their removal.
 

What is flamp?


On Fri, Apr 5, 2024, 10:08 AM Robert, KK5VD via <kk5vd=[email protected]> wrote:
Was testing FLAMP using those modes and found that some of the modem speeds did not decode correctly, Hence their removal.
 

OFDM experimental modes

When the OFDM modes were developed (for testing) a group of us in the Phila area tried these modes on HF (80m NVIS) and on FM simplex 2m and 70cm.

Basically they worked well for traffic modes where you need a high speed but highly robust mode.
In particular, the PaNBEMS experimented with OFDM500F mode.
It was faster than most of the other traffic modes (MFSK32, Thor22) but needed a significant S/N to decode 100%.
On 80m NVIS in morning hours, there are deep fades (2 S units) for a few seconds and that wipes out OFDM (and other modes too).

On FM where we have better S/N and wider bandwidth, the OFDM 2000 MODE worked well.
I wrote to the author of the OFDM modes giving a ton of suggestions.
However, personal issues cropped up and the author was unable to dedicate the time to “do the repairs”.

The mode VARA is amazingly successful. On HF, the VARA HF modem uses a simple sound card and with the proper software competes with Pactor - and will replace expensive dedicated TNC for Pactor.

On FM on 2m/70cm, the VARA FM modem is spectacular.

VARA is “adaptive” in that it can change speeds during the traffic exchance (as can Pactor).
None of the Fldigi modes can do that.
So as the S/N gets better - VARA ramps up to a higher speed (fancy modulation changes).

So for the moment, kiss OFDM modes to the test site.
Explore VARA if you do Winlink or VAR AC or VARA “chat”.
VAR AC is an amazing tool, well supported and growing each week.

de k3eui Barry
PaNBEMS manager
MidAtlantic NBEMS manager
 

Because it requires the one-to-one ACK/NAK throughout the transmission.
Flexnet/Xnet on packet does the same thing. The FLdigi modes are really
set up for one-to-many transmissions and the ACK/NAK would not work.
That is why VARA is a one-to-one transmission mode.

On 4/6/2024 7:46 AM, K3EUI Barry wrote:
None of the Fldigi modes can do that.
--
Charles J. Hargrove - N2NOV
NYC-ARECS/RACES Citywide Radio Officer/Skywarn Coord.

NYC-ARECS/RACES Nets 441.100/136.5 PL
ARnewsline Broadcast Mon. @ 8:00PM
NYC-ARECS Weekly Net Mon. @ 8:30PM


NY-NBEMS Net Saturdays @ 10AM & USeast-NBEMS Net Wednesdays @ 7PM
on 7.036 Mhz USB (alt 3.536)/1500 hz waterfall spot; MFSK-16 or 32

"Information is the oxygen of the modern age. It seeps through the walls topped
by barbed wire, it wafts across the electrified borders." - Ronald Reagan

"The more corrupt the state, the more it legislates." - Tacitus

"Molann an obair an fear" - Irish Saying
(The work praises the man.)

"No matter how big and powerful government gets, and the many services it
provides, it can never take the place of volunteers." - Ronald Reagan
 

Have you tried FLMSG ARQ mode to a specific call-sign? It's one-to-one.
Changing the packet size can really improve the throughput.

Craig/KH6CP


On Sat, Apr 6, 2024 at 2:22?AM Charles Hargrove <n2nov@...> wrote:
The FLdigi modes are really
set up for one-to-many transmissions and the ACK/NAK would not work.

Charles J. Hargrove - N2NOV
NYC-ARECS/RACES Citywide Radio Officer/Skywarn Coord.
 

That is true. However, the point he was making was conflating the one-to-one
of VARA, Pactor and yes even FLdigi ARQ vs the one-to-many of the other modes.
The other FLdigi modes improve their throughput by using FEC (forward error
correction), more sensitive modes like Olivia, narrower bandwidth, etc.
We have to use the proper tools and our brains and not assume the software
or hardware are the "best things since sliced bread".

On 4/6/2024 3:11 PM, KH6CP Craig Paul wrote:
Have you tried FLMSG ARQ mode to a specific call-sign? It's one-to-one.
Changing the packet size can really improve the throughput.
Craig/KH6CP
On Sat, Apr 6, 2024 at 2:22?AM Charles Hargrove <n2nov@... <mailto:n2nov@...>> wrote:
The FLdigi modes are really
set up for one-to-many transmissions and the ACK/NAK would not work.
--
Charles J. Hargrove - N2NOV
NYC-ARECS/RACES Citywide Radio Officer/Skywarn Coord.

NYC-ARECS/RACES Nets 441.100/136.5 PL
ARnewsline Broadcast Mon. @ 8:00PM
NYC-ARECS Weekly Net Mon. @ 8:30PM


NY-NBEMS Net Saturdays @ 10AM & USeast-NBEMS Net Wednesdays @ 7PM
on 7.036 Mhz USB (alt 3.536)/1500 hz waterfall spot; MFSK-16 or 32

"Information is the oxygen of the modern age. It seeps through the walls topped
by barbed wire, it wafts across the electrified borders." - Ronald Reagan

"The more corrupt the state, the more it legislates." - Tacitus

"Molann an obair an fear" - Irish Saying
(The work praises the man.)

"No matter how big and powerful government gets, and the many services it
provides, it can never take the place of volunteers." - Ronald Reagan
 

Please compile a copy of FLDIGI for me with all the OFDM modes enabled. I just want to experiment with them myself. I don't have the know-how to compile an advanced program like this.
 

The current 3 modems are sufficient for testing. The other OFDM modems flat out don't work. No point in using them until they get fixed.

Robert
 

Which ones "work" and which ones "don't work"? What kind of problems?

On 6/24/2024 2:56 PM, Robert, KK5VD via groups.io wrote:
The current 3 modems are sufficient for testing. The other OFDM modems flat out don't work. No point in using them until they get fixed.
Robert
--
Charles J. Hargrove - N2NOV
NYC-ARECS/RACES Citywide Radio Officer/Skywarn Coord.

NYC-ARECS/RACES Nets 441.100/136.5 PL
ARnewsline Broadcast Mon. @ 8:00PM
NYC-ARECS Weekly Net Mon. @ 8:30PM


NY-NBEMS Net Saturdays @ 10AM & USeast-NBEMS Net Wednesdays @ 7PM
on 7.036 Mhz USB (alt 3.536)/1500 hz waterfall spot; MFSK-16 or 32

"Information is the oxygen of the modern age. It seeps through the walls topped
by barbed wire, it wafts across the electrified borders." - Ronald Reagan

"The more corrupt the state, the more it legislates." - Tacitus

"Molann an obair an fear" - Irish Saying
(The work praises the man.)

"No matter how big and powerful government gets, and the many services it
provides, it can never take the place of volunteers." - Ronald Reagan
 


Charles,

If you download the previous FLdigi ver2.04 revision from the sourceforge site, you will find all 3 implemented OFDM modes, which all 'work', so there's no need to compile an extra version.

Then you can play around and check out, what you wish to test.

But they were intentionally removed from the latest version, because the just didn't work reliably. I tested them thoroughly back then and they would not even decode from a perfect off-file audio reliably. They may function for a number of words but the signal synchronisation is quickly lost. So if you try them, go ahead and investigate bandwidth and speed, but don't trust the decoding performance, because it is simply not functionally implemented, even without the signal degradatiom of anon-air radio link.


Kim KD9XB had planned to try ODFM on his SW Radiogram show, but abandonded the idea because he came to the same conclusion that they were just not mature for a valid test.


If you need high data rates, I recommend the robust MFSK modes, e.g. MFSK64 or MFSK128. If that ain't enoush speed, try higher 8PSK or PSKR modes, they probably offer all you need in terms of speed, but at the expense of robustness. There just is no 'free lunch' in physics. And other than for speed, the OFDM modes would not be helpful anyway, I guess.


Hope this helps explain the situation.


Good luck trying out different digimodes, it's a lot of fun, and most modes do extraordinarily well, the way they are implemented in FLdigi, thanks to Dave Freese's incredible skills, dedication, and kindness to offer all this for free!



Best regards and 73s

Tobias
Am Montag, 24. Juni 2024 um 21:13:09 MESZ hat Charles Hargrove <n2nov@...> Folgendes geschrieben:


Which ones "work" and which ones "don't work"? What kind of problems?


On 6/24/2024 2:56 PM, Robert, KK5VD via groups.io wrote:
> The current 3 modems are sufficient for testing. The other OFDM modems flat out don't work. No point in using them until they get fixed.
>
> Robert

--
Charles J. Hargrove - N2NOV
NYC-ARECS/RACES Citywide Radio Officer/Skywarn Coord.

NYC-ARECS/RACES Nets 441.100/136.5 PL
ARnewsline Broadcast Mon. @ 8:00PM
NYC-ARECS Weekly Net Mon. @ 8:30PM


NY-NBEMS Net Saturdays @ 10AM & USeast-NBEMS Net Wednesdays @ 7PM
on 7.036 Mhz USB (alt 3.536)/1500 hz waterfall spot; MFSK-16 or 32

"Information is the oxygen of the modern age. It seeps through the walls
topped
by barbed wire, it wafts across the electrified borders." - Ronald Reagan

"The more corrupt the state, the more it legislates." - Tacitus

"Molann an obair an fear" - Irish Saying
(The work praises the man.)

"No matter how big and powerful government gets, and the many services it
provides, it can never take the place of volunteers." - Ronald Reagan
 

I would also like to point out another technicality about the OFDM modes in FLDigi in general. They technically are just multi-carrier modes, not OFDM. OFDM means that the spacing of the carriers is such that the center frequency of each carrier is located at the zero points (nulls) of each adjacent carrier. This produces a spectrum with a flat top. However, in FLDigi, the so-called OFDM modes are such that the zero points (nulls) of each carrier are located at the nulls of the adjacent carriers. So this makes them actually not true OFDM modes. Please fix this. You could get higher data throughput (or at least reduce the bandwidth) if you were to cut the carrier spacing in half, so that they were true OFDM modes where each carrier was located at the null of the adjacent carriers.

On Mon, Jun 24, 2024 at 11:56?AM Robert, KK5VD via <kk5vd=[email protected]> wrote:
The current 3 modems are sufficient for testing. The other OFDM modems flat out don't work. No point in using them until they get fixed.

Robert

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