QRPGuys DSB Digital Transceiver


Ken wa4mnt <wa4mnt@...>
 

Gang,

We are pleased to offer the QRPGuys DSB Digital Transceiver kit. It includes three easily changed FT8 band modules for 40/30/20m. The kit uses all thru hole components. Price is $40. We are also offering bare band module pcb's for those wanting to experiment with different bands and modes, 4 for $10. Come by and see it at <https://qrpguys.com/digital-transceiver>.

ken - wa4mnt
www.qrpguys.com


JT Croteau <jt.tobit@...>
 

I've really been looking forward to this, I ordered mine earlier
today. I'm going to use it with a Raspberry Pi 4B, USB sound card,
and Gentoo Linux. Antenna will be a QRPGuys UnUnTenna Plus also
ordered today. Good fun ahead.

N1ESE

On Tue, Oct 1, 2019 at 8:59 PM Ken wa4mnt <wa4mnt@gmail.com> wrote:

Gang,

We are pleased to offer the QRPGuys DSB Digital Transceiver kit. It includes three easily changed FT8 band modules for 40/30/20m. The kit uses all thru hole components. Price is $40. We are also offering bare band module pcb's for those wanting to experiment with different bands and modes, 4 for $10. Come by and see it at <https://qrpguys.com/digital-transceiver>.

ken - wa4mnt
www.qrpguys.com



vbifyz <3ym3ym@...>
 

Is DSB transmission of FT8 allowed?

73, Mike AF7KR


Roy Appleton
 

🤦‍♂️

On Thu, Oct 3, 2019, 12:45 PM vbifyz <3ym3ym@gmail.com> wrote:

Is DSB transmission of FT8 allowed?

73, Mike AF7KR




vbifyz <3ym3ym@...>
 

Did some search on this topic, found some heated opinions and discussions.
Looks like It is legal from the FCC standpoint, but questionable from the ham ethics standpoint.
My personal preference would be to use Si5351a for transmit (and for VFO receive), using something like Jason's NT7S Arduino JTencoder library.

Mike AF7KR


JT Croteau <jt.tobit@...>
 

At 1W on 20M, I'm not going to worry about it too much for my very casual use.

N1ESE

On Thu, Oct 3, 2019 at 2:56 PM vbifyz <3ym3ym@gmail.com> wrote:

Did some search on this topic, found some heated opinions and discussions.
Looks like It is legal from the FCC standpoint, but questionable from the ham ethics standpoint.
My personal preference would be to use Si5351a for transmit (and for VFO receive), using something like Jason's NT7S Arduino JTencoder library.

Mike AF7KR



Randy.AB9GO
 

Good morning all,

I was thinking of buying one of these little devices and I had the same
questions in my mind about the DSB mode of operation.

The other thing I was questioning is the design of the final output stage.
I know it's been a tradition in ham radio to either parallel tubes or
transistors to get the wattage rating that you need, but in this case there
should be a single mosfet that can do the job is economically as three? In
addition I like to heatsink the output devices and this really doesn't lend
itself to effective heat sinking. Other than some gimmick add-ons for
TO-92's, were never really designed to be heat sinked. (I know that some
TO-92 devices produced with a small heatsink tab, but that's not what we
have here from the kit pictures.)

Does anyone out there have a suggestion for a sutible single output device
in a TO-220 form factor or similar?

Thank you,
Randy ab9go


This message sent to you from my mobile device via speech-to-text
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Randy.AB9GO
 

I was wondering about the use of an IRF-510 to replace the three BS170's.
Other rigs use this device successfully. What do you think?


I ordered the kit today.

Randy.ab9go@gmail.com


This message sent to you from my mobile device via speech-to-text
technology.

On Fri, Oct 4, 2019, 12:23 PM Randy AB9GO <randy.ab9go@gmail.com> wrote:

Good morning all,

I was thinking of buying one of these little devices and I had the same
questions in my mind about the DSB mode of operation.

The other thing I was questioning is the design of the final output stage.
I know it's been a tradition in ham radio to either parallel tubes or
transistors to get the wattage rating that you need, but in this case there
should be a single mosfet that can do the job is economically as three? In
addition I like to heatsink the output devices and this really doesn't lend
itself to effective heat sinking. Other than some gimmick add-ons for
TO-92's, were never really designed to be heat sinked. (I know that some
TO-92 devices produced with a small heatsink tab, but that's not what we
have here from the kit pictures.)

Does anyone out there have a suggestion for a sutible single output device
in a TO-220 form factor or similar?

Thank you,
Randy ab9go


This message sent to you from my mobile device via speech-to-text
technology.


ajparent1/kb1gmx <kb1gmx@...>
 

Why?

Unlikely to give more power as its gain is lower than BS170s,
If anything less power as you only can get so much from the
2n3904. It would be easier to heatsink and likely more durable.

The layout and mechanics of that mod might be a pain as well.

Allison
--
Please reply on the group, no private emails we as a group get to share info that way.


Randy.AB9GO
 

Looking for something more durable and easier to heatsink. I never cared
for heatsinking TO-92 devices (not effective in cooling the die) and three
in parallel was never a favorite technique for me. This smells of value
engineering. I'd rather pay another couple of $$ on the kit and do it more
robust fashion than it is now.

Randy.ab9go@gmail.com

This message sent to you from my mobile device via speech-to-text
technology.


ajparent1/kb1gmx <kb1gmx@...>
 

Then the approach I'd take is try it... IT might succeed far more than
expected.

Allison
--
Please reply on the group, no private emails we as a group get to share info that way.


Terry W6LEO
 

Got it built, and it goes thru all the paces of receiving and transmitting on both 30 and 40 mtrs, but wont receive .
I hear noise and a little am harmonics, but no ft8 signalsand no real band noise.

Any ideas?Terry w6leo


Christos SV1EIA
 

Using DSB modulation to Tx a FT8 signal means that you will end up transmitting a second FT8 signal a few KHz away from your intended one.
From what I understand, this will have legal issues also with FCC, it will not be characterized as a 'spurious' but it will certainly be characterized as a 'Out of Band' (OoB) whereas a different method of what is legal or not applies than in the case of spurious, but will definitively be IMHO falling into the non-legal.
Of course based on IARU's determination of what signals should be used in the digital segments, it is obvious that this is not allowed as all digimodes are mainly narrowband.

73,
Christos SV1EIA


Kirk, NT0Z
 

That's an interesting take on the issue, but I'm not sure I agree.
As far as I know there's no FCC (for USA hams, anyway) rule against transmitting digimodes in DSB (or AM, FM, or ISB). It's not common, but I doubt it's "illegal." Short of its collective lobbying and WARC activities, the IARU has only an advisory role in anything it does (when it comes to the regulations of individual countries), so until and unless the IARU encourages individual countries to adopt specific emission rules, it doesn't seem to be an issue.
Until I discovered specific prohibitions, I'd transmit digimodes in DSB without worrying -- as long as I wasn't aiming for intentional interference, and as long as I was using QRPish power levels.
I think unattended digimode (FTx) bots and unattended WSPR operation are much more problematic, as are unattended PACTOR/Winlink stations in general. Just my opinion.
Regards,
--Kirk, NT0Z  Rochester, MN


My book, "Stealth Amateur Radio," is now available from www.stealthamateur.com and on the Amazon Kindle (soon)

On Saturday, October 26, 2019, 7:03:06 PM CDT, Christos SV1EIA via Groups.Io <sv1eia=yahoo.com@groups.io> wrote:

Using DSB modulation to Tx a FT8 signal means that you will end up transmitting a second FT8 signal a few KHz away from your intended one.
From what I understand, this will have legal issues also with FCC, it will not be characterized as a 'spurious' but it will certainly be characterized as a 'Out of Band' (OoB) whereas a different method of what is legal or not applies than in the case of spurious, but will definitively be IMHO falling into the non-legal.
Of course based on IARU's determination of what signals should be used in the digital segments, it is obvious that this is not allowed as all digimodes are mainly narrowband.

73,
Christos SV1EIA


ajparent1/kb1gmx <kb1gmx@...>
 

I largely disagree.

First how your transmit digi and what mode is partially due to band plans.
If your transmitting a DSB signal in the CW segment of 40M thats not cool.
do it higher in the band then its legal for sure. Of course if the CW ops
start complaining that could change. DSB is not a narrow band signal.

Side effect of this is 6 and 2M CW segment that by FCC rule is A1A only
in the USA has people running digimode beacons, in the USA.
Is that ok? No.

Allison
--
Please reply on the group, no private emails, we as a group get to share info that way.


Tom, N8TPN
 

I'm probably showing my naivety and lack of technical knowledge, but I have been wondering why all the discussion has been focused upon the legal aspects of whether this combination of emission (DSB) and mode (FT8) is allowable, rather than any technical discussion about filtering out the unwanted sideband prior to transmission.

I imagine that such a filter by it's very nature would have to be very selective, stripping off the unwanted sideband while leaving the other untouched. The cost of such a filter may be prohibitive.

I would suppose that the best place for such a filter to be inserted would be between the mixer and the final PA stage, so that only lower strength signals need be filtered and removed.

Perhaps a set of filter modules could be designed such that the individual band modules would plug into a filter and then the stacked filter/band module would plug into the PCB headers.

I'm sure there are cost and technical difficulties I am overlooking in my simplistic approach, but again there has been very little discussion in regards to the technical rather than the legal issues here.

73 - Tom

N8TPN


ajparent1/kb1gmx <kb1gmx@...>
 

Tom,

It takes 4 crystal at a counter price of about 50 cents and 4 capacitors at pennies to
make such a filter then you have whats called a SSB radio. It was done by K1SWL
(PSK-80). It was a pretty simple transceiver for the PSK31 watering hole.

Of course you can use one such filter and a second mixer to convert that frequency
to any desired via superhet conversion which has been know for about 80 years maybe.
Then we are talking about standard SSB radio like the PSK31 series for 40/20 and 10M
or a radio just like the BITX40.

Another technique is the nearly as old phasing technique to cancel the opposing sideband
and that is all done mostly at audio so its relatively easy. it can also be done in software.
Pick most of the SDR radios and a few others for that.

The FT8 is legal if generated from a SSB radio. Whats questionable is that DSB
has the other generated sideband so if the actual desired signal falls at 7045(or where ever)
the other is roughly 2khz away at 7043. That means your transmitting on two frequencies at
the very same time. I'd think the CW op at 7043 might not enjoy that. But it may be a case
of a deserted mode and band allows....

Allison
--
Please reply on the group, no private emails we as a group get to share info that way.


Hans Summers
 

Hi all

In my opinion... I don't care about the boring legal aspects... purely
technical:

1) DSB is something of an abomination in that it is difficult or impossible
for two DSB stations to work each other. It's the only mode I can think of,
where you cannot QSO with someone else using the mode. The other side needs
to be using SSB. On FT8, if they were a few Hz apart it would probably not
decode, as far as I can see. You could offset the two stations by more than
the 50Hz FT8 bandwidth, then both sets of transmissions would appear twice,
to the other side. But that would get very confusing, and hardly be
practical... particularly considering the transceiver is not frequency
agile, it is crystal controlled, without an adjustment. Even if an offset
could be arranged between two DSB stations the next DSB station worked
would have to go through the hole rigmarole again.

So DSB relies on the fact that only a small proportion of operators will be
using it. Everyone else will use SSB. In that regard it is like an
anti-vaccinationist. You don't vaccinate your child because you want to
avoid the tiny risk of potentially very serious side effects. But this only
works if most other people DO vaccinate their children, so that yours is
unlikely to come into contact with a disease bearer. But if a significant
proportion of people don't vaccinate their kids then preventable diseases
return and infant mortality starts to go back to pre-vaccination levels. So
NOT vaccinating your kid could be viewed as a rather antisocial action. By
this somewhat tenuous analogy, so could operating DSB...

2) Inefficiency... we consider that the output power, say 2W, is divided
between a wanted Upper Sideband and an unwanted Lower Sideband. So 50% of
the RF output power is wasted. In fact in one view, it is worse than this
because a larger proportion of the available DC *input* power is wasted
too. The fact that it is DSB (two tones), means you must use a Linear. In
this case, Class-A. If FT8 was modulated as SSB then it would be a single
tone and a linear would not be needed; the power amplifier could be Class
C/D/E etc and that would offer higher efficiency. This is the reason that a
triplet of BS170s are here producing around HALF the power of an equivalent
triplet of paralleled BS170s in a CW transceiver, operating at similar
supply voltage and current.

3) Receiver SNR degradation... the fact you are receiving BOTH sidebands
gives a 3dB penalty on the Signal to Noise Ratio, even if there are NO
other interfering stations on the unwanted sideband, only noise.

4) Interference... you are interfering with anyone using the unwanted
sideband. That 3kHz of band below the FT8 is therefore unusable to other
stations. Yes a single DSB is a 50Hz slice in that band. Harmless? Maybe,
if that band segment is also normally used for narrow band modes. But a few
watts of carrier in the middle of an SSB QSO would not be so much fun...
and even a CW QSO will typically be using a wider bandwidth than 50Hz so
the potential for interference is greater. Also bear in mind that the
FS8Call band is 4kHz above FT8. So anyone operating DSB on FS8Call is
likely to be directly stepping on FT8 traffic.

I gave this a lot of thought. Overall I concluded, in my personal opinion,
I just don't think there's much of an excuse for using DSB in 2019. In
1960, maybe. But in 2019... it just isn't that much harder to make a nice
single sideband signal. Just my view.

73 Hans G0UPL
http://qrp-labs.com
http://hanssummers.com


Todd Carney
 

Hans,

Your anti-vax anti-social analogy is quite apt. I don't understand the
allure of DSB (or the superstition against vaccines, for that matter). If
one is going to suppress the carrier, why not suppress the superfluous
sideband as well? As you point out, it's not that hard, but I suppose it's
the crystal filters that seem daunting to some, and the phasing method of
generating SSB is near rocket science to the uninitiated.

OTOH, your anti-social critique of DSB-SC also applies to the traditional
AM mode. It's not used much anymore--only a small number of boat-anchor
fans, and even they probably use SSB a lot more than AM. So when they're
hogging 6+ kHz of bandwidth it's not a big deal (except, perhaps, during a
contest) because most everyone else is on SSB.

Of course, your wasted-power argument applies even more to AM than
suppressed-carrier DSB. But unless you're battery dependent, that doesn't
matter that much. A nice old boat anchor pumping wasted watts into the
atmosphere at least helps keep the shack warm on a cold winter night.

73,

Todd K7TFC

On Wed, Oct 30, 2019, 12:17 AM Hans Summers <hans.summers@gmail.com> wrote:

Hi all

In my opinion... I don't care about the boring legal aspects... purely
technical:

1) DSB is something of an abomination in that it is difficult or impossible
for two DSB stations to work each other. It's the only mode I can think of,
where you cannot QSO with someone else using the mode. The other side needs
to be using SSB. On FT8, if they were a few Hz apart it would probably not
decode, as far as I can see. You could offset the two stations by more than
the 50Hz FT8 bandwidth, then both sets of transmissions would appear twice,
to the other side. But that would get very confusing, and hardly be
practical... particularly considering the transceiver is not frequency
agile, it is crystal controlled, without an adjustment. Even if an offset
could be arranged between two DSB stations the next DSB station worked
would have to go through the hole rigmarole again.

So DSB relies on the fact that only a small proportion of operators will be
using it. Everyone else will use SSB. In that regard it is like an
anti-vaccinationist. You don't vaccinate your child because you want to
avoid the tiny risk of potentially very serious side effects. But this only
works if most other people DO vaccinate their children, so that yours is
unlikely to come into contact with a disease bearer. But if a significant
proportion of people don't vaccinate their kids then preventable diseases
return and infant mortality starts to go back to pre-vaccination levels. So
NOT vaccinating your kid could be viewed as a rather antisocial action. By
this somewhat tenuous analogy, so could operating DSB...

2) Inefficiency... we consider that the output power, say 2W, is divided
between a wanted Upper Sideband and an unwanted Lower Sideband. So 50% of
the RF output power is wasted. In fact in one view, it is worse than this
because a larger proportion of the available DC *input* power is wasted
too. The fact that it is DSB (two tones), means you must use a Linear. In
this case, Class-A. If FT8 was modulated as SSB then it would be a single
tone and a linear would not be needed; the power amplifier could be Class
C/D/E etc and that would offer higher efficiency. This is the reason that a
triplet of BS170s are here producing around HALF the power of an equivalent
triplet of paralleled BS170s in a CW transceiver, operating at similar
supply voltage and current.

3) Receiver SNR degradation... the fact you are receiving BOTH sidebands
gives a 3dB penalty on the Signal to Noise Ratio, even if there are NO
other interfering stations on the unwanted sideband, only noise.

4) Interference... you are interfering with anyone using the unwanted
sideband. That 3kHz of band below the FT8 is therefore unusable to other
stations. Yes a single DSB is a 50Hz slice in that band. Harmless? Maybe,
if that band segment is also normally used for narrow band modes. But a few
watts of carrier in the middle of an SSB QSO would not be so much fun...
and even a CW QSO will typically be using a wider bandwidth than 50Hz so
the potential for interference is greater. Also bear in mind that the
FS8Call band is 4kHz above FT8. So anyone operating DSB on FS8Call is
likely to be directly stepping on FT8 traffic.

I gave this a lot of thought. Overall I concluded, in my personal opinion,
I just don't think there's much of an excuse for using DSB in 2019. In
1960, maybe. But in 2019... it just isn't that much harder to make a nice
single sideband signal. Just my view.

73 Hans G0UPL
http://qrp-labs.com
http://hanssummers.com




Mike Carden - VK1MC
 

Thank you Hans and Todd for so clearly expressing the concerns I have about
using DSB. I'll confess to having built a DSB transmitter that I have
stared at, and never quite been reckless enough to power on.

Also Todd, I'm Australian and your User Name gives me trouble.

https://en.wikipedia.org/wiki/Todd_Carney

--
MC