Bob,

thanks?for the ti ps!

I will poke some more.

On Wed, Aug 21, 2024 at 3:05?PM Bob Cameron via <bob3bob3=[email protected]> wrote:

Hi Don

I vaguely also remember that squelch action interrupted good decoding, so squelch disabled as one would for Olivia. Most of my tests though were with Thor Micro. FEC can also be enabled/disabled with Domino modes manually so ensure all stations have the same settings. I saw "first block loss" with flamp transfers and Thor 22 as well, which is where my squelch action concerns comes from. For a while there I would manually edit the block list with an additional first. Possibly try a longer idle before sending data for experimenting?

I also have a way out untested theory that sound card resampling/CPU/maths issues may degrade low s/n signals. I'll test that some day!

And on that note I did some VK<>UK tests some years ago using Olivia 16/250 and 32/250 "non standard" modes that yielded a worthwhile improvement over (say) 8/250 for flaky paths. It was "so good" that the UK end requested an RsID be allocated. Very slow of course. Fldigi's s/n and f/o display polling time does mess up and periodically vanish on the super slow Olivia modes though.

Vague thoughts sorry, but thought worth a mention.

Cheers Bob VK2YQA

On 22/8/24 03:58, Don Rolph wrote:

We were exploring Domino EX micro to break through poor propagation?conditions.

Small scale testing?demonstrated?that it functioned, but when we tested at scale with multiple stations we got inconsistent results.

In many cases I could clearly see the signal in the waterfall?but the signal would not decode.? Other times?I could barely see the signal but decoded nicely.

We did address centering issues since this is a very narrow bandwidth signal?but that seemed to provide minimal?impact on the issue.? We also worked to ensure that we did not use software SQL.

It is almost as if when the initial part of the signal was not decoded that the rest of the signal ?could not be decoded either.

Can anyone help provide insight here?? What?are the issues required for successful use of Domino EX micro?

Thanks!

--

73,

AB1PH

Don Rolph

We were exploring Domino EX micro to break through poor propagation?conditions.

Small scale testing?demonstrated?that it functioned, but when we tested at scale with multiple stations we got inconsistent results.

In many cases I could clearly see the signal in the waterfall?but the signal would not decode.? Other times?I could barely see the signal but decoded nicely.

We did address centering issues since this is a very narrow bandwidth signal?but that seemed to provide minimal?impact on the issue.? We also worked to ensure that we did not use software SQL.

It is almost as if when the initial part of the signal was not decoded that the rest of the signal ?could not be decoded either.

Can anyone help provide insight here?? What?are the issues required for successful use of Domino EX micro?

Thanks!

Not going to mention names, so people can avoid this inadequate radio?

Andrew, KA2DDO

________________________________________
From: [email protected] <[email protected]> on behalf of Dave <w1hkj@...>
Sent: Monday, August 5, 2024 9:30 AM
To: [email protected]
Subject: Re: [nbems] FSQ in FLDIGI: center frequency questions

There is one manufacturer of kit radios that is advertized for use with the FT modes.  It is a simple double sideband transceiver.  Even if not overdriven with hot audio it produces both an upper and lower sideband FT signal on the air.  NOT FRIENDLY.  And worse if the audio is overdriven.

David

On 8/4/24 15:01, Bob Cameron wrote:

Great post Dave. I see this QRM on 20m clobbering what is primarily the Olivia operating area quite often.

Maybe even IMD in the TX mixer combined with the obvious other sideband suppression of the more recent "direct conversion" style TX's. TX Sideband suppression in even a "full" rig is somewhere better than 55dB so a strong (main) RX of >S9 will be quite visible AFx2 away on a wfall, especially if a tone pattern. I am also quite embarrassed to say that my Icom TX spec at 1200Hz is only 40dB suppression!

Quite easy to figure out the station ID. Decode the FT8 on 20m using LSB. The double/triple mixing ones will need recording and playing with the sample rate by multiples maybe using Audacity, before playing back through WSJT-x etc. Usually though I just slot in between them..

Cheers Bob VK2YQA

On 4/8/24 18:32, Dave_G0WBX via groups.io wrote:
Hi.

One thing to be aware of, if you run a mode with an audio component less than half the highest audio frequency your radio will pass on transmit, is that any audio distortion products will be radiated at RF too.

Often, it is not a faulty computer/sound-card, but the radio's audio input (mic) stages being over-driven into distortion..

Great post Dave. I see this QRM on 20m clobbering what is primarily the Olivia operating area quite often.

Maybe even IMD in the TX mixer combined with the obvious other sideband suppression of the more recent "direct conversion" style TX's. TX Sideband suppression in even a "full" rig is somewhere better than 55dB so a strong (main) RX of >S9 will be quite visible AFx2 away on a wfall, especially if a tone pattern. I am also quite embarrassed to say that my Icom TX spec at 1200Hz is only 40dB suppression!

Quite easy to figure out the station ID. Decode the FT8 on 20m using LSB. The double/triple mixing ones will need recording and playing with the sample rate by multiples maybe using Audacity, before playing back through WSJT-x etc. Usually though I just slot in between them..

Cheers Bob VK2YQA

On 4/8/24 18:32, Dave_G0WBX via groups.io wrote:

Hi.

One thing to be aware of, if you run a mode with an audio component less than half the highest audio frequency your radio will pass on transmit, is that any audio distortion products will be radiated at RF too.

Often, it is not a faulty computer/sound-card, but the radio's audio input (mic) stages being over-driven into distortion..

On Sun, Aug 4, 2024 at 3:03 PM, Jim Falls

<radio-tuber@...> wrote:

Now, THAT is impressive. Yet another way to plug up the digital bands. The perpetrators are probably totally unaware if these products are not visible on their waterfall.?

Dust off the Rettysnitch……

Jim Falls K6FWT?

On Aug 4, 2024, at 01:32, Dave_G0WBX via groups.io <g8kbvdave@...> wrote:

?

Hi.

One thing to be aware of, if you run a mode with an audio component less than half the highest audio frequency your radio will pass on transmit, is that any audio distortion products will be radiated at RF too.

Often, it is not a faulty computer/sound-card, but the radio's audio input (mic) stages being over-driven into distortion..

As an extreme example, this is seen quite a lot these days on 20m caused I suspect by over zealous FT8 operators who want to screw the last ounce of wattage from a simple QRP rig.?? See below for a graphic example.

<FT8 distortion QRM.png>

My RX (a TS870s) was only showing some S2 on the meter so is not my RX overloading.? Inserting 20dB attenuation in the antenna feed didn't help either.? (On a totally different RX and separate antenna, the same could be seen also.)

If someone recognises it as NOT FT8, then what could it be?? (I never seem to have the wide band SDR running at the times I see this, to try and correlate it to a fundamental signal.)

It is obvious to my eyes though, that it is audio distortion products, as the QRM "structure" is the same but at different widths, indicating it is harmonic distortion from the same baseband signal, and escaping on the Lower Sideband, so what the level is at the fundamental on USB is anyone's guess!

This was captured yesterday at about 15:46z, and persisted like this on and off for about 15 minutes.

I know others have seen similar QRM from the FTx crowd on other bands too.? It would be nice if WSJTx had a harmonic RX mode that could be used to identify the culprit so they could be informed that they have an issue!? (But I'm not holding my breath on that.)

The problem is NOT FTx itself, it's the user(s) who do not appreciate what happens when (at a guess) a high level audio signal is fed into a low level Microphone input.? Plus, the use of simple TX's that have poor unwanted sideband suppression.

But similar can happen with any signal fed into an analogue type SSB radio, if it's early transmit audio stages are over-driven.

Take care, and 73.

Dave G0WBX.

-- 
Created on and sent from a Unix like PC running and using free and open source software:

Hi.

One thing to be aware of, if you run a mode with an audio component less than half the highest audio frequency your radio will pass on transmit, is that any audio distortion products will be radiated at RF too.

Often, it is not a faulty computer/sound-card, but the radio's audio input (mic) stages being over-driven into distortion..

On Aug 4, 2024, at 01:32, Dave_G0WBX via groups.io <g8kbvdave@...> wrote:

? Hi.

One thing to be aware of, if you run a mode with an audio component less than half the highest audio frequency your radio will pass on transmit, is that any audio distortion products will be radiated at RF too.

Often, it is not a faulty computer/sound-card, but the radio's audio input (mic) stages being over-driven into distortion..

As an extreme example, this is seen quite a lot these days on 20m caused I suspect by over zealous FT8 operators who want to screw the last ounce of wattage from a simple QRP rig.?? See below for a graphic example.

<FT8 distortion QRM.png>

My RX (a TS870s) was only showing some S2 on the meter so is not my RX overloading.? Inserting 20dB attenuation in the antenna feed didn't help either.? (On a totally different RX and separate antenna, the same could be seen also.)

If someone recognises it as NOT FT8, then what could it be?? (I never seem to have the wide band SDR running at the times I see this, to try and correlate it to a fundamental signal.)

It is obvious to my eyes though, that it is audio distortion products, as the QRM "structure" is the same but at different widths, indicating it is harmonic distortion from the same baseband signal, and escaping on the Lower Sideband, so what the level is at the fundamental on USB is anyone's guess!

This was captured yesterday at about 15:46z, and persisted like this on and off for about 15 minutes.

I know others have seen similar QRM from the FTx crowd on other bands too.? It would be nice if WSJTx had a harmonic RX mode that could be used to identify the culprit so they could be informed that they have an issue!? (But I'm not holding my breath on that.)

The problem is NOT FTx itself, it's the user(s) who do not appreciate what happens when (at a guess) a high level audio signal is fed into a low level Microphone input.? Plus, the use of simple TX's that have poor unwanted sideband suppression.

But similar can happen with any signal fed into an analogue type SSB radio, if it's early transmit audio stages are over-driven.

Take care, and 73.

Dave G0WBX.

-- 
Created on and sent from a Unix like PC running and using free and open source software:

Running FLRIG version 2.0.05.? I had s-meter, power meter, SWR etc working.? Somewhere along the line they stopped working.? I must have done something to make them stop working but I don't know what it was.? I have checked here and in the help, I don't see how to turn them back on.? Any hints?

--

richard
kd8noa

_._,_._,_

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