Date   

new SW Radiogram program available

 

Hello to all the digital folks out there.
 
A new program for the Shortwave Radiogram broadcasts has now been posted on the SW Radiogram website. Note that a new mode is being tested, and
requires the installation of a new version of FLDigi if you wish to receive the data. See the SW Radiogram website for more information.
 
If you're new to decoding digital, this is a pretty nice way to get your feet wet. You can use your desktop or laptop, or you can use an Android device such as a smartphone or tablet. You can find links to the SW Radiogram website, software for decoding, and wiki articles with extensive details and help at: http://www.udxf.nl/events.html.  
 
If you'd like to see a list of web receivers (which are often reported as being used), receiver, transceiver and SDR applications and more, take a look at the SW Radiogram gateway at https://wiki.radioreference.com/index.php/Shortwave_Radiogram_Gateway
 
Help is also available on Facebook and Twitter. The SW Radiogram website has the links. 
 
Radio Northern Europe International also uses digital modes during its broadcasts. The August schedule hasn't been announced as of this writing.  See https://rnei.org/ for more information.
   
Here's hoping for good propagation 


Re: Understanding APSK and QAM Rohde and Schwartz video #VARA

Graham
 

kristoff

I guess that was the  main idea of the  video. just  demonstrating , the  summation of differing modulations, to  provide the  maximum  loading , of a single  carrier ,  

From there on, things take on there  own  'life' many points ..

The reference's to  Shannon sometimes run wide of the  mark, from what I can gather , the  limit  applies to a  fixed set of  parameters , at a fixed time, where as in a live  path, parameters change , so to  quote a  system reaches  etc, when the  path  changes the  parameters  is  misleading ..

Drm ,  you  can spend hours watching the set of  lights ,  never quire  reach the  top , for  lock ,  used to be  BBC had  test MW station  and  Luxembourg  1440 , which gave a  good  copy,  all  now appear to of stopped , but I note  VK  & USA  ? is  now  running  DRM .. Its not  classic odfm , as the  signal is  structured with  central  core , probably in an  attempt to  make it  more robust .. the idea being, the  core  will  get through ..

with out knowing the  coding , compression and  expansion , its difficult to  actual  measure anything , yes  first use  of  MT63  , the  original  ofdm  data  mode ,  cw could be  seen  inside the  pass  band,  not  affecting the  qso , olivia later gave  much lower s/n ,  probably the  first ham  under the  noise  mode ..

with out knowing , what each frame  conveys , its difficult to  speculate  exactly  , what is being  spread over the  vara ofdm carrier group , or  as to what is relayed  along the  time line  

Take for  example the  Opera data  system . 

this  at first  glance looks like a  simple  ,250 bit  serial  data  stream 
but actually  not, its  burst  packet system,  with very high level of coding  and  efficiency 
Rx decoding ,  requires the  capture  of  a minimum of 40% of the  transmitted  data 
this capture  may be  randomly . in blocks ,  at the  start ,  middle  or at the  end of the  Time line 
sync is  provided by Manchester  coding , so each recovered  bit is  self-sync 
thus it's  very  robust , and being  single tone ,  is  immune to  doppler  spread 
s/n is  dependant on energy  , so simply the  time  line is  extended to  gain  -s/n 
uniquely  it provides a  indication  of the  recovered  data , which  in turn  indicates
the  path  quality , in this case only 1 %  data  was lost, virtually  no  need  for FEC ie simple rtty would be ok 
higher % loss = requirement for  more coding  levels , to combat the  loss / time  line 
[something to  try at the  club  for  uhf etc , the  30 second  mode  is provided for  vhf and up to uWave]

19:40 477 IK1HGI Op8 1487.3 Hz -33 dB |------------------------------ ----------------------------------------------------------------------------------------| Fade: 1%


Of note , now,   the  low [mfsk] range  of  the  VARA mode, is  working at lower  levels than the  olivia mode ,  the mfsk modem proved to be  viable  in the  higher  latitudes , where  various disturbances ,  cause the  signal to be  spread, phase changes , echo . the mfsk modem proved  capable of maintaining  link in these  conditions 

OFDM systems are good at dealing with where where interference at one very precise specific frequency.

Possibly not so, this is a ofdm signal , showing selective fade , a high % of the signal escapes the attenuation , the out come
being, the system continues to function ,

In a simple test , the vara modem continued to function in 50% of the required b/w
equivalent to 50% of the b/w being jammed ...note the waterfall display is for indication only ,
and is not linked to the decode process ..so again, difficult to make direct comparisons ..

73-Graham









Re: Understanding APSK and QAM Rohde and Schwartz video #VARA

Kristoff Bonne
 

Hi Graham,


Thank you for your very long reply.


OK. Let's see if I understand this correctly.

On 10.08.21 12:52, Graham wrote:
On Mon, Aug 9, 2021 at 08:13 PM, Kristoff Bonne wrote:

use a combination of QAM and APSK constelation

Kristoff

Its never immediately  obvious , from the  video,  the  issues round  the  pk-pk  levels of the  vara  modem are  perhaps , a little more  translucent  [as opposed to  transparent ] as are the  various  displays ..
So, if I understand this correctly, the goal of the videos is just to show the principle that multi-order PSK and PSK+AM based modulation-schemes (APSK or QAM) can cram more bits into one symbol.

Correct?


The hybrid ...
What exactly do you mean by hybrid?
A hybrid AM/PSK scheme (like APSK and QAM), or a hybrid of APSK and QAM constellations (like the one used by MIL-STD-188-110D, as shown in the end of the video)?


serves to  maximise the  pay load of a  single  carrier ,  perhaps more  fragile, but ,  that's  linked to  the rate ,  the  faster , with the  same energy , then the  higher  becomes the  errors , either  reduce the  rate ,  more  energy/time ..or  increase the  energy , again more  energy , just the  rate of supply  increases ..
OK, this is understand.

I guess is the Shannon-Hartley theorem on the capacity of a radio-channel which links the maximum bitrate to the S/N ratio.



So, is the  issue with  single  high  speed  carriers ,  quite  incompatible with turbulent  conditions  encountered  on HF
one  single  jamming  signal in the  pass band
and everything stops
OK, but this is common to any radio-channel. If the interference fills up a complete channel, there is not much you can do about it.

The only way around that is by using some kind of 'spread-spectrum' technique to distribute your bits over a wide piece of spectrum, or that distributes it in a very specific order (chirp, PRN-based CDMA) to avoid having a correlation between the interference and the wanted signal.

Lora is a very nice example of that. We have been playing around with aprs-over-lora (on 433.775 MHz) in our local radioclub here, and I must say that we really have been  very impressed how well it works in a pretty congested piece of spectrum like the 433 MHz ISM band.


,higher rates fall  over due to  delays and  multi path  etc ..
I do understand that multipath limit the baudrate of a carrier (as delayed copies of an earlier symbols might interfere with the current symbol) but I never understood why delay should be a limiting factor of a simplex radio-channel.



then comes the maximum  rate  compatible with HF ,
Its reasonable , to  take a  guide from the  vara  modem , the maximum rate for  HF is nearly  x10 slower than the  300 baud limit , quoted as  a limiting  factor  , 300 providing a b/w limitation  , for  single  carrier  systems ,  under ideal conditions ,  anything and  everything  works , \

DRM broadcast requires , direct or  single  hop  , anything  after ,  then  it fails to  'lock'
[ as the  sun spot cycle  progresses , the  opportunity for multiple hop connections will  increase]
Well, there aren't that much DRM broadcasts on HF anymore, but I did once manage to receive DRM broadcasts from AIR directly from India to Europe. I am not sure if this was single-hop.



B/W utilisation , Much the  same as  say a   Tank with  tracks , and multiple wheeled  vehicle ,/one track  off ,  stops/, one  tyre  off  , keeps  going ..

Taking the vara   modem has the  optimum   single  carrier  rate for  HF ,

Then ,  as can be seen,  in the  OFDM  levels,  multiple  low rate  carriers   , are  combined , to  provide ,  maximum  rate, maximum  ''in channel ''  jamming /  qrm rejection , where as the on-air  carrier spectrum's  are   provided with  16 ? fixed patterns ,
not  seen, in the coding  of the  modem is the  mathematical  'engine' that seeks to  distribute the  payload  , making  best  use the  the available  channel b/w  and recover it post demodulation .
OK, I am not an expert in VARA (is the source-code available somewhere?) but most data-comm systems I know use a interleaving to distribute the bits (and therefor the biterrors) around in the bitstream so that the Error-correction mechanism can better deal with it.
(Error-mechanisms have difficulties to deal with errors that are close together)

I remember, years ago, having a QSO in olivia when somebody started doing PSK31 smack in the middle of our channel. The interesting thing was, the system had absolutely no issue with that as it only affected one single carrier of the OLIVIA comb and our QSO was still completely 100 % error-free.
That is the power of spread-spectrum techniques, interleaving and FEC, I guess!



.selective  qsb can  remove  sections the  b/w, but  as long as the  minimum criteria is met , for the  recovered  data , the  pay-load can be extracted   if not ,  a more  robust  level  can be  selected , or vice versa
The way I see it is like this.

Take this scenario:
- you receive a the signal that is 3 db over the minimal S/N ratio required to demodulate the signal.
- Two systems:
a/ a single-carrier system taking up the complete bandwidth of a channel
b/ a OFDM system where the bits are distributed over a comb of 8 carriers. (each taking up 1/8 of the bandwidth of a channel).

1/ Image selective qsb that reduces the signal-level of 1/8th of the bandwidth of the channel by 10 db.

- In the OFDM system, this will kill of one of the eight carriers.
But as the underlying interleaving distributes those (one-out-of-eight) error-bits over the complete stream, and that the FEC system is very well capable of correcting one biterror out of 8, the end-result is the the stream is still received error-free
- in the single-carrier  PSK signal, that 10 db "selective qsb" will be spread out over the complete bandwidth, resulting in an overall 1.25 db drop in the S/N ratio, .. so no errors here neither.

2/ image that the selective qsb is not -10 db, but -30.
- In the OFDM system, this actually has the same result.
It is still one carrier out of 8 that is drowned, so -for the overall- is it still 1/8 of the bits lost, something that can be handled by the underlying FEC
- in the single-carrier PSK , the overall interference over the complete is now 3.75 db (30 db/8), which is more then the 3 db margin so the signal is lost.


But, I do know that this is a very theoretical approach with some well-known variables.

Also, a single-carrier PSK system has a better spectral density then OFDM (look at the gap of spectrum in between the carriers that isn't used, and there it the guard-interval in the time-domain), so the actual usable raw bitrate of a OFDM will always be lower then a pure single-PSK carrier.



My impression is that OFDM systems are good at dealing with where where interference at one very precise specific frequency.


NB: Reaching the limitation of psk,  the  lower  levels  revert to   mfsk , simply as during  trials ,  high  latitude users
encountered link  survival issues  coupled to  psk modulation , mfsk provides ''the'' most   robust and  energy efficient
modem ,
Interesting.
What is the reason for this and why at higher latitude? More multipath? More selective qsb?



Hope that  fills in some of the  gaps ,
Well, I haven't really looked at HF datacommunication up to now.

It's interesting to learn how the radio-channel on HF compares / differs from on VHF/UHF, and what techniques are used to deal with them.


73-Graham
g0nbd
73

kristoff - on1arf


Re: Understanding APSK and QAM Rohde and Schwartz video #VARA

Graham
 

On Mon, Aug 9, 2021 at 08:13 PM, Kristoff Bonne wrote:
use a combination of QAM and APSK constelation
Kristoff

Its never immediately  obvious , from the  video,  the  issues round  the  pk-pk  levels of the  vara  modem are  perhaps , a little more  translucent  [as opposed to  transparent ] as are the  various  displays .. 

The hybrid serves to  maximise the  pay load of a  single  carrier ,  perhaps more  fragile, but ,  that's  linked to  the rate ,  the  faster , with the  same  energy , then the  higher  becomes the  errors , either  reduce the  rate ,  more  energy/time ..or  increase the  energy , again  more  energy , just the  rate of supply  increases ..

So, is the  issue with  single  high  speed  carriers ,  quite  incompatible with  turbulent  conditions  encountered  on HF
one  single  jamming  signal in the  pass band and everything  stop's  ,higher rates fall  over due to  delays and  multi path  etc ..

then comes the  maximum  rate  compatible with HF ,

Its reasonable , to  take a  guide from the  vara  modem , the maximum rate for  HF is nearly  x10 slower than the  300 baud  limit , quoted as  a limiting  factor  , 300 providing a b/w limitation  , for  single  carrier  systems ,  under ideal  conditions ,  anything and  everything  works ,  DRM broadcast requires , direct or  single  hop  , anything  after ,  then  it fails to  'lock'  
[ as the  sun spot cycle  progresses , the  opportunity for  multiple hop connections will  increase]

B/W utilisation , Much the  same as  say a   Tank with  tracks , and multiple wheeled  vehicle , one track  off ,  stops,  one  tyre  off  , keeps  going ..

Taking the vara   modem has the  optimum   single  carrier  rate  for  HF ,

Then ,  as can be seen,  in the  OFDM  levels,  multiple  low rate  carriers   , are  combined , to  provide ,  maximum  rate,  maximum  ''in channel ''  jamming /  qrm rejection , where as the  on-air  carrier spectrum's  are   provided with  16 ? fixed  patterns ,   not  seen, in the  coding  of the  modem is the  mathematical  'engine' that seeks to  distribute the  payload  , making  best  use the  the  available  channel b/w  and recover it post demodulation . 

.selective  qsb  can  remove  sections the  b/w, but  as long as the  minimum  criteria is met , for the  recovered  data , the  pay-load can be  extracted   if not ,  a more  robust  level  can be  selected , or vice versa 

NB: Reaching the  limitation of psk,  the  lower  levels  revert to   mfsk , simply  as during  trials ,  high  latitude users
encountered link  survival issues  coupled to  psk modulation ,  mfsk provides ''the'' most   robust and  energy efficient 
modem , 

Hope that  fills  in some of the  gaps , 

73-Graham
g0nbd 

.










 


Re: Understanding APSK and QAM Rohde and Schwartz video #VARA

Kristoff Bonne
 

Hi Steve,


First of all, I am still pretty new to learning digital communication.
(currently playing around in GNU Radio trying to learn PSK demodulation ...).


Thank you for your reply.
First of all, no problem to get into the details. That's usually the best way to learn things.


I am however a bit surprised. The video-article you mentioned was about the modulation-scheme of a single-carrier (QAM vs APSK).
How is the issue of single-tone vs. parallel tone (i guess this is 'single-carrier' vs OFDM) you mention in your message below related to this?



On to the discussion of QAM vs APSK.
As you say, the main goal is to get as much bps over a radio-channel.
As is mentioned in the video, the more you cram bits closer together, the less robust the signal is to noise. (isn't it that you need 3db S/N per extra bit you want to cram into one symbol?)

If we are talking about data-communication, you have no knowledge about the data being carried, which means that all bits are considered to be equally important.  In that scenario, the most logical form is create a constellation in which all bits are equality spaced, i.e. a square.
If I look at the constellation of AFSK, the bits are much closer together then in QAM, so this is a clear advantage of QAM over AFSK.

Now, according the video, the advantage of AFSK over QAM is that you can use non-linear amplifiers; as any non-linearity will just result in the 'circles' of the APSK constellation being more spread out which is something that can easily be detected


As said, I am far from an expert on digital communication but I did read about 'data-aided' techniques where the sender emits certain known data-pattern which allow the receive to determine the characteristics of the radio/receiver channel and 'retune' itself if needed. (think of the 'pilot-tones' in OFMD that act as PSK references)
I do not understand why this principle can not be used here (QAM) too. If the transmitter sends out certain predetermined QAM-patterns beforehand, it should allow the receiver to determine if the is an issue with non-linearity of the transmitter and adapt itself.
So I am not sure what is really the advantage of APSK over QAM.


Concerning the discussion below, if I correct, the discussion is about single-carrier vs OFDM.
As far as I understand it, the big advantage of ODFM over single-carrier is related to multipath, especially in mobile-communication in VHF and above. (which is why T-DAB and DVB-T use OFDM).
I cannot really comment on the logic of OFDM on HF, but I am still amazed how multipath can really 'suck out' part of a radio-channel on HF. Just look at what it does to the signal of a DRM transmission!

I guess the main difference between OFDM and single-carrier on HF, is that n OFDM selective multipath will take out one or a few carriers completely, not affecting the other carriers; while on a wideband PSK signal, the interference is "spread-out" over the complete carrier so that all bits are impacted, but less so.
It probably depends on how the underlying error-correction mechanisms deal with this if this has an impact on the actual BER or not.



If I am correct, ISB, 2-ISB, 4-ISB (at least in this context) is dynamically allocating multiple adjacent channels and use it as one single channel. Is this correct?

In that context, it looks to me like the 40, 80 or 160 MHz 'wide' channels in 802.11n and 802.11ac WiFi on 5 GHz.
(I've always been amazed on how they can actually build wifi-chips which can process 160 MHz of bandwidth at once!) Just image the ADC and the processing-power to process that much bandwidth at once!


What are 'burst waveform techniques'?
I do not know that term.



Kristoff - ON1ARF

On 09.08.21 22:34, ALE wrote:

Hi Kristoff ,

Without getting into the complex details as to why,  In the Military as well as a number of Commercial and even some Amateur Radio waveforms these days, as you strive to increase the Over the Air data rate throughput you need to work with more complex forms of modulation to either increase the number of data bits per symbol or more densely pack it, especially with Serial (Single) Tone modems which are now predominate I Military communications as they are superior to Parallel tone modems. With Parallel tone modems you can increase the throughput by just adding more carriers or increasing the symbol rate for a given form of modulation, But many designers have been maintaining the number of carriers and symbol rate and implementing more complex modulation.

There are many challenges and tradeoffs involved. The Military basically hit the wall with Serial tone modems as they did with Parallel tone waveforms. At 256-QAM they did something new and old again, they sort of dusted off the Parallel waveform approach without actually going there and add a few new twists. They took the serial tone modem and started running it on ISB, then 2-ISB and then 4-ISB. Then they went to what is called Wideband, they allocate 24kHz and now 48kHz channels where the actual in use channel starts where not occupied, say the first or 2nd 3kHz portion and extends continuously where not occupied until the full bandwidth id reached iif possible. The PSK carrier is placed where appropriate for the resulting bandwidth occupied. This is the approach taken with MIL-STD-188-110D Appendix D and 4G ALE to MIL-STD-188-141D Appendix G.

Bach to a less than 3kHz channel in the Commercial modem world, some dozen years ago now SCS seen the futility iwth Parallel modems and went to serial tone for PACTOR IV, implementntig aspects found in a number of Military waveforms as they had done with PACTOR III prior. They get into QAM for the highest throuhput as does STANAG 4539 and use Burst waveform techniques as does 3G ALE in STANAG 4538. They lowered the symbol and center of the PSK carrier from that of the Military to fit Commercial and Amateur SSB filter bandwidth. This was all achieved under the guidance of the most reknowned German STANAG modem engineer. That coupled withe SCS Memory AQR provided SCS with the then best and still best in a 3kHz only channel HF modem available, better than the STANAG and MIL-STD modems in a 3kHz channel in my opinion.

In Amateur Radio, at least here in the U.S. we are ham strung by the 300 baud symbol rate limitation imposed by the FCC. Thus serial tone modems cannot be exploited, Parallel tone modems are the only only approach to achieve high throughput.

/s/ Steve, N2CKH

At 03:13 PM 8/9/2021, you wrote:
Hi,


I'm a bit puzzled about this.

After watching the video, I I understand that QAM and APSK are two different systems, each with their advantages and disadvantages, and either with the specific usecase.

So I do not understand why combining QAM and APSK is then a good idea. You mix systems, therefor creating something that has the disadvantages of both.



What is the technical argument for these mil-comm systems to use a combination of QAM and APSK constelation?



Kristoff (on1arf)


On 06.08.21 19:01, ALE wrote:

Hi Graham,

QAM is fun, working to develop Military data modem and ALE serial tone modem QAM waveforms.

In my attached photo the QAM waveform in the constellation display is an MS110B offering, going into MS110C/D Appendix D and 4G ALE get even more complicated, I have not made it to 256-QAM yet, the Appendix waveforms and 3G ALE are in my near future however.

The SCS P4 serial tone modem stops at 32-QAM in less than a 3kHz channel, but the Military waveforms hit a the much higher QAM  count and throughput in a 3kHz channel and then can increase the bandwidth and shift the PSK carrier up to incrementally increase the throughput.

My friend Dario maintains an excellent easy to understand technical blog on pretty much all the waveforms to be found on HF if one is interested in those subject matters at:

http://i56578-swl.blogspot.com/

<http://i56578-swl.blogspot.com/>/s/ Steve, N2CKH

At 02:21 PM 7/3/2021, you wrote:
R&S  , Useful series of  videos covering  aspects of radio
This video  is applicable to the  VARA modem  coding ,
makes  sense of the  displays  -

73-Graham
g0nbd


This video provides an introduction to the basic concepts of amplitude and phase shift keying (APSK) and quadrature amplitude modulation (QAM).
You-tube link :-

Understanding APSK and QAM <https://www.youtube.com/watch?v=1xGncBvWv6U>






Re: Understanding APSK and QAM Rohde and Schwartz video #VARA

ALE
 

Hi Kristoff ,

Without getting into the complex details as to why, In the Military as well as a number of Commercial and even some Amateur Radio waveforms these days, as you strive to increase the Over the Air data rate throughput you need to work with more complex forms of modulation to either increase the number of data bits per symbol or more densely pack it, especially with Serial (Single) Tone modems which are now predominate I Military communications as they are superior to Parallel tone modems. With Parallel tone modems you can increase the throughput by just adding more carriers or increasing the symbol rate for a given form of modulation, But many designers have been maintaining the number of carriers and symbol rate and implementing more complex modulation.

There are many challenges and tradeoffs involved. The Military basically hit the wall with Serial tone modems as they did with Parallel tone waveforms. At 256-QAM they did something new and old again, they sort of dusted off the Parallel waveform approach without actually going there and add a few new twists. They took the serial tone modem and started running it on ISB, then 2-ISB and then 4-ISB. Then they went to what is called Wideband, they allocate 24kHz and now 48kHz channels where the actual in use channel starts where not occupied, say the first or 2nd 3kHz portion and extends continuously where not occupied until the full bandwidth id reached iif possible. The PSK carrier is placed where appropriate for the resulting bandwidth occupied. This is the approach taken with MIL-STD-188-110D Appendix D and 4G ALE to MIL-STD-188-141D Appendix G.

Bach to a less than 3kHz channel in the Commercial modem world, some dozen years ago now SCS seen the futility iwth Parallel modems and went to serial tone for PACTOR IV, implementntig aspects found in a number of Military waveforms as they had done with PACTOR III prior. They get into QAM for the highest throuhput as does STANAG 4539 and use Burst waveform techniques as does 3G ALE in STANAG 4538. They lowered the symbol and center of the PSK carrier from that of the Military to fit Commercial and Amateur SSB filter bandwidth. This was all achieved under the guidance of the most reknowned German STANAG modem engineer. That coupled withe SCS Memory AQR provided SCS with the then best and still best in a 3kHz only channel HF modem available, better than the STANAG and MIL-STD modems in a 3kHz channel in my opinion.

In Amateur Radio, at least here in the U.S. we are ham strung by the 300 baud symbol rate limitation imposed by the FCC. Thus serial tone modems cannot be exploited, Parallel tone modems are the only only approach to achieve high throughput.

/s/ Steve, N2CKH

At 03:13 PM 8/9/2021, you wrote:
Hi,


I'm a bit puzzled about this.

After watching the video, I I understand that QAM and APSK are two different systems, each with their advantages and disadvantages, and either with the specific usecase.

So I do not understand why combining QAM and APSK is then a good idea. You mix systems, therefor creating something that has the disadvantages of both.



What is the technical argument for these mil-comm systems to use a combination of QAM and APSK constelation?



Kristoff (on1arf)


On 06.08.21 19:01, ALE wrote:

Hi Graham,

QAM is fun, working to develop Military data modem and ALE serial tone modem QAM waveforms.

In my attached photo the QAM waveform in the constellation display is an MS110B offering, going into MS110C/D Appendix D and 4G ALE get even more complicated, I have not made it to 256-QAM yet, the Appendix waveforms and 3G ALE are in my near future however.

The SCS P4 serial tone modem stops at 32-QAM in less than a 3kHz channel, but the Military waveforms hit a the much higher QAM count and throughput in a 3kHz channel and then can increase the bandwidth and shift the PSK carrier up to incrementally increase the throughput.

My friend Dario maintains an excellent easy to understand technical blog on pretty much all the waveforms to be found on HF if one is interested in those subject matters at:

http://i56578-swl.blogspot.com/

<http://i56578-swl.blogspot.com/>/s/ Steve, N2CKH

At 02:21 PM 7/3/2021, you wrote:
R&S , Useful series of videos covering aspects of radio
This video is applicable to the VARA modem coding ,
makes sense of the displays -

73-Graham
g0nbd


This video provides an introduction to the basic concepts of amplitude and phase shift keying (APSK) and quadrature amplitude modulation (QAM).
You-tube link :-

Understanding APSK and QAM <https://www.youtube.com/watch?v=1xGncBvWv6U>



Re: Understanding APSK and QAM Rohde and Schwartz video #VARA

Kristoff Bonne
 

Hi,


I'm a bit puzzled about this.

After watching the video, I I understand that QAM and APSK are two different systems, each with their advantages and disadvantages, and either with the specific usecase.

So I do not understand why combining QAM and APSK is then a good idea. You mix systems, therefor creating something that has the disadvantages of both.



What is the technical argument for these mil-comm systems to use a combination of QAM and APSK constelation?



Kristoff (on1arf)

On 06.08.21 19:01, ALE wrote:

Hi Graham,

QAM is fun, working to develop Military data modem and ALE serial tone modem QAM waveforms.

In my attached photo the QAM waveform in the constellation display is an MS110B offering, going into MS110C/D Appendix D and 4G ALE get even more complicated, I have not made it to 256-QAM yet, the Appendix waveforms and 3G ALE are in my near future however.

The SCS P4 serial tone modem stops at 32-QAM in less than a 3kHz channel, but the Military waveforms hit a the much  higher QAM  count and throughput in a 3kHz channel and then can increase the bandwidth and shift the PSK carrier up to incrementally increase the throughput.

My friend Dario maintains an excellent easy to understand technical blog on pretty much all the waveforms to be found on HF if one is interested in those subject matters at:

http://i56578-swl.blogspot.com/

<http://i56578-swl.blogspot.com/>/s/ Steve, N2CKH

At 02:21 PM 7/3/2021, you wrote:
R&S  , Useful series of  videos covering  aspects of radio
This video  is applicable to the  VARA modem  coding ,
makes  sense of the  displays  -

73-Graham
g0nbd


This video provides an introduction to the basic concepts of amplitude and phase shift keying (APSK) and quadrature amplitude modulation (QAM).
You-tube link :-

Understanding APSK and QAM <https://www.youtube.com/watch?v=1xGncBvWv6U>


Re: Understanding APSK and QAM Rohde and Schwartz video #VARA

Graham
 

Fun -)

Yes, Ros allays  maintained  designing  digital  modes, was his  Hobby  

I thought  that series  of  videos  posed by R&S , gave a good  over view,  as many  asked
as to  what  exactly the , varying  patterns related to on the  Vara display, 

73-Graham 

 


Monitor function locks up VARA . #VARA

Graham
 
Edited

Monitor function locks up VARA . 
 
Point being  made , ''It appears to only show up in certain pc configurations''
 
Some background, 
 
The  monitor was coded  to  provide  off  air  monitoring ,  but , where as the  modem , each  tx/rx/tx exchange , deal's  only with the  level  in play at the  time  ..  thus , CPU loading  is held at  minimum ....as can be  observed from the  platforms  already running the  modem , in traffic  mode  .. 
 
However, the  monitor  function is  dealing  , in real time , with  scanning  all  16  level variations ,  taking  considerable processing power , far in excess of the  modems  requirement to  pass  traffic ..
 
This  now apperres  to manifest, as  PC build  configurations **,  its not really  something that  requires a  coding fix, but  perhaps  some ''user group''   user  input to  establish the  base line ,  in terms of  processing  power needed  to run the  monitor

..**  As it's a  'large  numeric'  function ,  its possible windows  is  looking to  load the  video  processor , something to investigate , gpu loading ?
 
The inference being ,  a newer pc is required, perhaps ,  more elegant to establish a  base line as to  what works  ?
 
I'm  running,  quite old  now ,  intel  i7  2.6 GHz, 16 g ram  + GT610  video, [legacy driver !] , win10 64 ,  no issue's   

quick check ,   modem  shows 2.5 %  cpu  ,  monitor 'on'  5%  cpu  
 
73-Graham


Re: VARA FM stations and repeaters are not compatible with new VARA FM versions #VARA

Oliver K6OLI
 

There seem to be quite a few on the Canadian side:

Callsign: VA3ETN-10
Frequency: 144.930 MHz

Callsign: VE3ZPW-10
Frequency: 145.090 MHz
Frequency: 446.950 MHz

They look to be about 50-65km from your qth as per QRZ, mostly over water.
Kudos to our Canadian friends!

We recently did an exercise where we connected from mobile field stations (10W, N9TAX antennas) to the Tijuana gateways (25W, omni) from the L.A. area. That was around 220km (135miles).
Audio levels need to be set right with a good antenna 20+ ft in the air and good propagation helps. But it can be done.

73 de Oliver K6OLI


Re: VARA FM stations and repeaters are not compatible with new VARA FM versions #VARA

Andrew O'Brien
 

Olivia , very interesting info. I will have to look in to whether there is anything like that in western New York . Last I checked , there were no FM VARA stations within 150 miles of my QTH. 

Andy


On Aug 7, 2021, at 12:41 PM, Oliver K6OLI <km6dmf@...> wrote:

Hi Andy,

Here in SoCal we have a collaboration project we call the "VARA FM Autobahn". It connects Ventura, Los Angeles and San Diego County ARES groups and CREBC in Tijuana. The goals are to provide area coverage, leverage mutual aid and provide access to HF gateways for potential forwarding of out-of-area messages. Regional communications are important in SoCal, so we do try to provide multiple paths for traffic through VARA FM, Packet, AREDN Mesh and HF.

The Autobahn comprises of 10 gateways, which we leverage by having every user station enabled as a digipeater with SSID -4. Not sure if that counts as a "reasonable" number :-)

Jer K4WOF and his group in Florida have similar VARA FM network supporting their mission.

73 de Oliver K6OLI


Re: VARA FM stations and repeaters are not compatible with new VARA FM versions #VARA

Oliver K6OLI
 

Hi Andy,

Here in SoCal we have a collaboration project we call the "VARA FM Autobahn". It connects Ventura, Los Angeles and San Diego County ARES groups and CREBC in Tijuana. The goals are to provide area coverage, leverage mutual aid and provide access to HF gateways for potential forwarding of out-of-area messages. Regional communications are important in SoCal, so we do try to provide multiple paths for traffic through VARA FM, Packet, AREDN Mesh and HF.

The Autobahn comprises of 10 gateways, which we leverage by having every user station enabled as a digipeater with SSID -4. Not sure if that counts as a "reasonable" number :-)

Jer K4WOF and his group in Florida have similar VARA FM network supporting their mission.

73 de Oliver K6OLI


Re: VARA FM stations and repeaters are not compatible with new VARA FM versions #VARA

Andrew O'Brien
 

Reasonable , not “resonance “ 

Andy


On Aug 6, 2021, at 11:58 AM, Andrew O'Brien via groups.io <andrewobrie@...> wrote:

How is the use of VARA on FM going ? Is there a country where a resonance network of FM stations have developed ? 


Andy


On Aug 6, 2021, at 10:23 AM, Graham <g0nbd@...> wrote:


From  VARA  google  group 

73-G


These VARA FM stations and repeaters are not compatible with new VARA FM versions.
 
I would recommend update to a new VARA FM version as soon as be possible to accept new connections


Outdated VARA FM stations.jpg


Re: Understanding APSK and QAM Rohde and Schwartz video #VARA

ALE
 


Hi Graham,

QAM is fun, working to develop Military data modem and ALE serial tone modem QAM waveforms.

In my attached photo the QAM waveform in the constellation display is an MS110B offering, going into MS110C/D Appendix D and 4G ALE get even more complicated, I have not made it to 256-QAM yet, the Appendix waveforms and 3G ALE are in my near future however.

The SCS P4 serial tone modem stops at 32-QAM in less than a 3kHz channel, but the Military waveforms hit a the much  higher QAM  count and throughput in a 3kHz channel and then can increase the bandwidth and shift the PSK carrier up to incrementally increase the throughput.

My friend Dario maintains an excellent easy to understand technical blog on pretty much all the waveforms to be found on HF if one is interested in those subject matters at:

http://i56578-swl.blogspot.com/

/s/ Steve, N2CKH


At 02:21 PM 7/3/2021, you wrote:
R&S  , Useful  series of  videos covering  aspects of radio
This video  is applicable to the  VARA modem  coding ,
makes  sense of the  displays  -

73-Graham
g0nbd


This video provides an introduction to the basic concepts of amplitude and phase shift keying (APSK) and quadrature amplitude modulation (QAM).
You-tube link :-

Understanding APSK and QAM


Re: VARA FM stations and repeaters are not compatible with new VARA FM versions #VARA

Andrew O'Brien
 

How is the use of VARA on FM going ? Is there a country where a resonance network of FM stations have developed ? 


Andy


On Aug 6, 2021, at 10:23 AM, Graham <g0nbd@...> wrote:


From  VARA  google  group 

73-G


These VARA FM stations and repeaters are not compatible with new VARA FM versions.
 
I would recommend update to a new VARA FM version as soon as be possible to accept new connections


Outdated VARA FM stations.jpg


VARA FM stations and repeaters are not compatible with new VARA FM versions #VARA

Graham
 


From  VARA  google  group 

73-G


These VARA FM stations and repeaters are not compatible with new VARA FM versions.
 
I would recommend update to a new VARA FM version as soon as be possible to accept new connections


Outdated VARA FM stations.jpg


new SW Radiogram program available

 

Hello to all the digital folks out there.
 
A new program for the Shortwave Radiogram broadcasts has now been posted on the SW Radiogram website.
 
If you're new to decoding digital, this is a pretty nice way to get your feet wet. You can use your desktop or laptop, or you can use an Android device such as a smartphone or tablet. You can find links to the SW Radiogram website, software for decoding, and wiki articles with extensive details and help at: http://www.udxf.nl/events.html.  
 
If you'd like to see a list of web receivers (which are often reported as being used), receiver, transceiver and SDR applications and more, take a look at the SW Radiogram gateway at https://wiki.radioreference.com/index.php/Shortwave_Radiogram_Gateway
 
Help is also available on Facebook and Twitter. The SW Radiogram website has the links. 
 
Radio Northern Europe International also uses digital modes during its broadcasts. The August schedule hasn't been announced as of this writing.  
See https://rnei.org/ for more information.
   
Here's hoping for good propagation&nbs


new SW Radiogram program available

 

Hello to all the digital folks out there.
 
A new program for the Shortwave Radiogram broadcasts has now been posted on the SW Radiogram website.
 
If you're new to decoding digital, this is a pretty nice way to get your feet wet. You can use your desktop or laptop, or you can use an Android device such as a smartphone or tablet. You can find links to the SW Radiogram website, software for decoding, and wiki articles with extensive details and help at: http://www.udxf.nl/events.html.  
 
If you'd like to see a list of web receivers (which are often reported as being used), receiver, transceiver and SDR applications and more, take a look at the SW Radiogram gateway at https://wiki.radioreference.com/index.php/Shortwave_Radiogram_Gateway
 
Help is also available on Facebook and Twitter. The SW Radiogram website has the links. 
 
Radio Northern Europe International also uses digital modes during its broadcasts. The August schedule hasn't been announced as of this writing.  See https://rnei.org/ for more information.
   
Here's hoping for good propagation 


new SW Radiogram program available

 

Hello to all the digital folks out there.
 
A new program for the Shortwave Radiogram broadcasts has now been posted on the SW Radiogram website. 
 
If you're new to decoding digital, this is a pretty nice way to get your feet wet. You can use your desktop or laptop, or you can use an Android device such as a smartphone or tablet. You can find links to the SW Radiogram website, software for decoding, and wiki articles with extensive details and help at: http://www.udxf.nl/events.html.  
 
If you'd like to see a list of web receivers (which are often reported as being used), receiver, transceiver and SDR applications and more, take a look at the SW Radiogram gateway at https://wiki.radioreference.com/index.php/Shortwave_Radiogram_Gateway
 
Help is also available on Facebook and Twitter. The SW Radiogram website has the links. 
 
Radio Northern Europe International has announced its new schedule for program 19.  
See https://rnei.org/2021/06/30/radio-northern-europe-international-show-19-announcement-post/
 
Here's hoping for good propagation 


Re: Opera QSO party running on 7038

Graham
 



Reliable dx spots , [ actual power = 50% carrier , dur to  duty cycle ]

18:02   7038 SV1XV de SV8RV Op2 155 mi -5 dB F:0% in Zakynthos(Zante) isl.GREECE 1523,4 Hz with 25w + Vertical
18:02   7038 SV1XV de RX3DHR Op2 1357 mi -10 dB F:10% in  1498,0 Hz with 25w + Vertical
18:02   7038 SV1XV de G0NBD Op2 1655 mi -22 dB F:5% in Liverpool - 1502.9 Hz with 25w + Vertical
18:02   7038 SV1XV de VK3KCX Op2 -27 dB F:3% in Melbourne 1499.0 Hz

18:04   7038 RX3DHR de SV8RV Op2 1445 mi -17 dB F:19% in Zakynthos(Zante) isl.GREECE 1524,4 Hz with 10w + AVT4
18:04   7038 RX3DHR de SV1XV Op2 1357 mi -12 dB F:20% in Athens 1501.0 Hz with 10w + AVT4
18:04   7038 RX3DHR de G0NBD Op2 1674 mi -21 dB F:13% in Liverpool - 1503.9 Hz with 10w + AVT4

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