Date   

Re: VARA Path Test Results Revision.

Graham
 

Yes Tony 

One of the  issues was the  peak ratio , its a little vague , but ofdm   coding  seems to  produce  rogue  spikes , 
which may or may not be reduced  and or clipped , as the  vara system is  running  at speed  and is  quite 
'tame'  can only  assume that the  peak  ratio is  actually to  design , rather than  unintended consequence 

Some one  with a  decent spectrum  analyser , with a  'maths' package could  determine , as to  what  the  levels 
are  exactly .. using  conventional  metering , its only  really  possible to  confirm 'similarity'  

Jose is  recommending a level of 25 watts ,  but thats  derived  from the   ft897 ,  that holds with  the  power meter  in  average , minimal
smoothing ,  but  when switched to   peak detect + hold , [ I used  op amp's to provide , precision diode peak detect 
and  sample & hold  , with timed hang ] so  the  meter  is  indicating actual  'peak' values , it shows  x2  at 50 watts 

But this is a  instantaneous 'dc'  reading , analysis of the  spectrum is  needed  to  determine the  power ..


Re: VARA Path Test Results Revision.

Tony
 

On 4/8/2018 12:57 PM, Graham wrote:
the  main OFDM modem maintains transfer to -12 B , so  no data payload
is  transferred below this  level , being arq , unrecoverable data
loss , is  addressed by repeat requests ,  to date  levels  of -12 db
s/n  related  to  psk31 ,
Graham:

Assuming a 3kHz AWGN channel, are you saying the modem is capable of
decoding down to -12db s/n?

Tony -K2MO


Re: VARA Path Test Results Revision.

Tony
 

On 4/8/2018 12:57 PM, Graham wrote:

> Using the standard metering, its  quite difficult to tell, as to the  actual power being  radiated.

Graham:

I'm sure Jose would know the answer to that? What's interesting is that VARA and other multi-carrier modems seem to achieve higher than expected output. In theory, the average power should be reduced to a few watts to prevent clipping, but that doesn't seem to be the case.

I'm told that part of the reason is because the distortion products of a multi-tone modem are nowhere near as bad as a two tone scenario so the transmitter can see moderate levels of ALC with minimal distortion. 

Whatever the case may be, VARA is one fast modem.

Thanks Graham,

Tony -K2MO


Re: VARA Path Test Results Revision.

Graham
 

Hi Tony,

Using the standard metering, its  quite difficult to tell, as to the  actual power being  radiated. 

Testing with the  ic7100 , with  single tone  drive  level and the  vara  b/w representative  test tone .. 

Set to  max carrier , at the point of  ALC , 100 watts  on power meter [ steady  carrier] , ID [ supply] indicates    14 amps  @ 13.~  volts 
Changing over to the  Vara modem , test  signal , the power meter, external ave/pk  ,  set to  'average'   indicates  25 watts , but if  set to  peak detect / hold , then the  meter increases  to   50 watts  indicated  ... that  would suggest the  peak  to average is  3 dB ? but the  metering  still  shows  below the  actual , 

Taking a  close look at the  lcd-ID , that  is  peaking  very close and occasionally to  the  same  point  as the  single carrier .. From that, its reasonable to assume the  Tx is  producing the  same peak power  out  , possibly  at a slight  reduction , depending  on the  available overheads ,  the  mode  was  developed on a ft897d 

Power/B/W  is seemingly  at  odds  with  convention,  eg, Multi-psk , help files , indicate  2 tone  50 baud rtty  to require  -5.5 dB , where  as the  modem is  functioning to  -12 dB s/n with x 4 the  data  rate ,  Yes its true, the  higher the  available power , the  modem will  adapt to make best  use , but in use , its notable that  quite low powers are providing  reliable transfers, -12 dB is in the  psk31 zone ,

 

 looking at the  plot, the level  is  raised  app 15 dB across the   2.4 KHz  b/w , compared to back ground  noise . all  of this  is  harvested by the  DSP ,  one of the  reasons b/w limitation is  undesirable . 

A lot of  features of the  modem  are not  immediately  obvious ,  take  adaptation to  path  length  and or latency  in the  equipment ,  the  modem is  capable of  establishing  links  with  differing  latency  at  each end of the  path as  well as  adapting  for changes of  path  at the  start  and  during  the  transfer . there being  no  need  for a  hard  switched ,  long/short path. or equipment limitations** 

**NB- Work  continues  on SDR tx/rx  latency   issues , also  testing of the 'FM  VHF'  version  of the  modem now continues 

By maintaining  a fixed  'on air carrier rate'  all  speeds  of the  modem are  provide  with the same  level  of  robustness , where  as deploying , fast  single or  serial carriers  , the 'required' path properties are severely constricted , to  ideal  paths , the  ability to eliminate in band  qrm is  also  maintained by the  retention of the  ofdm modem .

link establishment /  handshaking is  accomplished  using  mmfsk  at  reduced  drive , this  reduces the  power  required in standby 'RX'  to a absolute minimal level   and ensure the  connection  is  maintained in deep qsb,  but as noted , the  main OFDM modem maintains  transfer to -12 B , so  no  data payload is  transferred below this  level , being arq , unrecoverable data loss , is  addressed by repeat requests ,  to date  levels  of -12 db s/n  related  to  psk31 , 


As for implementation ,  that  remains something of  mystery , to  date  it took two  over years  of  development to  reach the this  stage , Initially , it was a  multiple mode  concept , to accommodate the  high speed ofdm  mode,  but , now , all  data  transfer is via the  ofdm  modem ,  real  data  from  deployment  has been quickly  assimilated into new  versions....

On paper the  modem exceeds P4 , however , to date , no tests  have been undertaken , 

VHF  FM is  next .. 

73-Graham
G0NBD



 


Re: VARA Path Test Results Revision.

Tony
 

On 4/4/2018 2:17 PM, Graham wrote:
narrow b/w and robustness  are diametrically opposed

I think there are limitations to this though Graham. Our transmitters
are peak-power limited so we can't simply increase the power to overcome
the relatively poor PAPR (Peak to Average Power Ratio) inherent in
wide-band, multi-carrier modems without causing distortion.

Getting the signal high enough above the noise to realize the
performance of such modems seems challenging and it appears to be the
reason why Pactor engineers chose to included narrow-band protocols with
fewer carriers and improved PAPR.

Jose takes a different approach where the PAPR appears to remain
constant. There must be a benefit to this and it must be in the
technique used to improve PAPR. Not sure if that's easier or harder to
do with ODFM modems?

Tony -K2MO


Re: VARA Path Test Results Revision.

Jouko OH5RM
 

Tony,
Yes I see testing is very time consuming. And looking closer at Jose's message I found he has made the tests I was asking for. 
I hope we here in OH could make some more on band 80m tests in coming weeks. 

Jouko OH5RM


Re: VARA Path Test Results Revision.

Tony
 

On 4/4/2018 12:23 PM, Jouko OH5RM wrote:
Tony, Very interesting comparison. Could you run CCIR 520-2 Moderate and Poor conditions comparison?
Jose has published another comparison but I think it is in ideal conditions and maybe using a different simulation SW
https://www.dropbox.com/s/a2ykmf0to9i52no/VARA_ARDOP.gif?dl=0 73 Jouko OH5RM

Jouko:

It's a time consuming process so it may take a while. In order to get accurate results, the modem needs to make multiple runs through the simulator for 10 minutes or more each run. The process is then repeated for each s/n level. The previous tests took days to complete!

Jose's simulations appear to show higher than expected throughput which normally happens when pumping too much audio from the modem into the simulator. It's matter of calibration.

Tony -K2MO 


Re: New version vara 2-2-0 [activation 5 April ]

Graham
 

Just released ,  comparative  test  of  VARA   2-2-0  and  1-9-1   / ARDOP

vara MAX Speed  increased  to  30,420  Bytes/Min  in good  conditions 

These improvements  will  be  implemented at the  00:00  change over 

[ pc clock time ]

73-G,



Re: VARA Path Test Results Revision.

Graham
 

Tony,

One point ,  or  perhaps  two )

The  path simulators , due to  processing , introduce additional time  overheads ,  Jose's  testing ,  determined ,  ''PathSim add about 1.1 second delay in the communication processing'', not relevant in non-arq  systems  

There exists a  modified version of VARA , with the WAIT timer  extended to 1.5 seconds. to eliminate the  error introduced  by the  test circuit 
which Jose  can send  you .

Contrary expectations ,  narrow b/w  and  robustness  are diametrically opposed , Its noted  , where  as  ARDOP  coding changes the  on-air component to MMFSK at lower  rates  VARA  reamain's  OFDM  at  all  speeds  , as noted by  Jouko,  in poor conditions the  OFDM  coding provides, higher  data  rates and link-survival , at  50 bauds  OFDM modem is  providing  lower  s/n  than  conventions  2 tone  rtty , whilst offering  resistance to selective  path and in band qrm. 

Two  year's  back , this  advantage was not  expected and perhaps  remains  contrary to  expectations , but testing  and  on-air experience is showing this to be the  case ..even with the  increase in the  power density  , provided by the  change  from  ofdm to  mmfsk , the design refinements  in the  vara modem have  eliminated the  advantage .  providing a  constant   rms/duty cycle at all  speeds .

73-Graham
G0NBD


Re: VARA Path Test Results Revision.

Tony
 

Andy:

> I think I recognize that 330 mile path

Thanks for being there!

Tony -K2MO

On 4/4/2018 7:04 AM, Andrew OBrien wrote:
Congratulations for a fine study Tony. I think I recognize that 330 mile path gateway you used on 40M :) .  Dipole antenna with 50 watts.
Andy K3UK

On Wed, Apr 4, 2018 at 2:08 AM, Tony <DXDX@...> wrote:

All:

The plots below show the HF path simulator results for VARA. The ARDOP data shown in each plot was compiled using the same path parameters and added for comparison.

Plot 1 shows the path simulator results for a quiet channel. Throughput is based on file transfer speed only.

                                                                                            Plot 1. 


Plot 2 shows throughput measured over the duration of the entire Winlink session using the same quiet channel path model. The widening in throughput speed between the two modems seems to indicate greater overhead for ARDOP over the course of a Winlink session. The speed gap is less when throughput is based on file-transfer speed only as shown in Plot 1. 

                                                                                Plot 2


Plot 3 shows the on-air (40 meter) throughput data taken from 10 Winlink sessions. Modems were tested twice each session for a total of 20 test runs per modem. Tests were conducted minutes apart with moderate multi-path and strong signals. Throughput is based on file transfer speed - not the total session speed.

The average speed gap between modes was roughly 2:1 which is surprisingly close to the path simulation results shown in plot #1. Variation in throughput speed appeared somewhat greater for VARA which may be due to variations in propagation and the way VARA adapts to those variations.


                                                                                           Plot 3 


Please feel free to send suggestions and comments.

73, Tony -K2MO




Re: VARA Path Test Results Revision.

Jouko OH5RM
 

Tony,
Very interesting comparison. Could you run CCIR 520-2 Moderate and Poor conditions comparison?
Jose has published another comparison but I think it is in ideal conditions and maybe using a different simulation SW
https://www.dropbox.com/s/a2ykmf0to9i52no/VARA_ARDOP.gif?dl=0

73 Jouko OH5RM


Re: VARA Path Test Results Revision.

Andrew OBrien
 

Congratulations for a fine study Tony. I think I recognize that 330 mile path gateway you used on 40M :) .  Dipole antenna with 50 watts.
Andy K3UK

On Wed, Apr 4, 2018 at 2:08 AM, Tony <DXDX@...> wrote:

All:

The plots below show the HF path simulator results for VARA. The ARDOP data shown in each plot was compiled using the same path parameters and added for comparison.

Plot 1 shows the path simulator results for a quiet channel. Throughput is based on file transfer speed only.

                                                                                            Plot 1. 


Plot 2 shows throughput measured over the duration of the entire Winlink session using the same quiet channel path model. The widening in throughput speed between the two modems seems to indicate greater overhead for ARDOP over the course of a Winlink session. The speed gap is less when throughput is based on file-transfer speed only as shown in Plot 1. 

                                                                                Plot 2


Plot 3 shows the on-air (40 meter) throughput data taken from 10 Winlink sessions. Modems were tested twice each session for a total of 20 test runs per modem. Tests were conducted minutes apart with moderate multi-path and strong signals. Throughput is based on file transfer speed - not the total session speed.

The average speed gap between modes was roughly 2:1 which is surprisingly close to the path simulation results shown in plot #1. Variation in throughput speed appeared somewhat greater for VARA which may be due to variations in propagation and the way VARA adapts to those variations.


                                                                                           Plot 3 


Please feel free to send suggestions and comments.

73, Tony -K2MO



VARA Path Test Results Revision.

Tony
 

All:

The plots below show the HF path simulator results for VARA. The ARDOP data shown in each plot was compiled using the same path parameters and added for comparison.

Plot 1 shows the path simulator results for a quiet channel. Throughput is based on file transfer speed only.

                                                                                            Plot 1. 


Plot 2 shows throughput measured over the duration of the entire Winlink session using the same quiet channel path model. The widening in throughput speed between the two modems seems to indicate greater overhead for ARDOP over the course of a Winlink session. The speed gap is less when throughput is based on file-transfer speed only as shown in Plot 1. 

                                                                                Plot 2


Plot 3 shows the on-air (40 meter) throughput data taken from 10 Winlink sessions. Modems were tested twice each session for a total of 20 test runs per modem. Tests were conducted minutes apart with moderate multi-path and strong signals. Throughput is based on file transfer speed - not the total session speed.

The average speed gap between modes was roughly 2:1 which is surprisingly close to the path simulation results shown in plot #1. Variation in throughput speed appeared somewhat greater for VARA which may be due to variations in propagation and the way VARA adapts to those variations.


                                                                                           Plot 3 


Please feel free to send suggestions and comments.

73, Tony -K2MO


5350 BPM on 40M with VARA

Andrew OBrien
 

The Icom is working much better than the Flex with VARA.  50 watts on 40M to Arkansas.

Andy K3UK

RMS Trimode 1.3.18.8
K3UK has 228 minutes remaining with KB5LZK
[WL2K-5.0-B2FWIHJM$]
;PQ: 32466896
CMS via KB5LZK >
   ;FW: K3UK
   [RMS Express-1.5.11.4-B2FHM$]
   ;PR: 74532206
   ; KB5LZK DE K3UK (FN02HK)
   FC EM 7AZ8W8DY99IY 46156 21829 0
   F> B2
FS Y
*** Sending 7AZ8W8DY99IY.
FF
*** Completed send of message 7AZ8W8DY99IY
*** Sent 1 message.  Bytes: 22051,  Time: 03:20,  bytes/minute: 6606
   FQ
*** --- End of session at 2018/04/01 03:56:50 ---
*** Messages sent: 1.  Total bytes sent: 22051,  Time: 04:05,  bytes/minute: 5384
*** Messages Received: 0.  Total bytes received: 0,  Total session time: 04:05,  bytes/minute: 0
*** Disconnecting
*** Disconnected from Winlink RMS: KB5LZK @ 2018/04/01 03:56:53
*** Session: 4.2 min;  Avg Thruput: 5350 Bytes/min;   1 Min Peak Thruput: 5350 Bytes/min


ARIM Messaging Program v1.7

Bob NW8L
 

Hello,
 
ARIM v1.7 is available for download:
 
https://www.whitemesa.net/arim/arim.html#inst
 
Bug fixes, point to RPM build instructions.
 
Details in change log excerpt below.
 
Files are also available at the ardop applications Files area at
groups.io:
 
https://ardop.groups.io/g/applications/files
 
and in the Files area at the arim-ham Yahoo group:
 
https://groups.yahoo.com/neo/groups/arim-ham/files
 
Station NW8L will be on dial 14.066 in daytime, 7.101 at night and
sometimes 10.131 for a while in-between, for testing.
 
73, Bob NW8L
 
v1.7  31Mar2018
---------------
1. Fix latent bug which can cause a segfault when processing
   ill-formed commands in certain circumstances.
2. Add missing header file #include to fix broken build on Red Hat
   derived Linux systems.
3. Update INSTALL and Help docs with link to instructions for building
   an RPM package from the ARIM source distribution on Red Hat derived
   Linux systems, and using it to install ARIM. Instructions and .spec
   file are maintained by David Ranch, KI6ZHD, thanks!
4. Update PDF Help file and arim.5 man file to correct spelling of
   configuration file parameter 'name'.


New version vara 2-2-0 [activation 5 April ]

Graham
 

New version  VARA 2-2-0

NB Now incorporates ,  planned  system  changeover  date ,
New  version will  activate  5 April  at  23:59:59   local  time 

New  version remains  compatible , with  previous  issue , prior

to changeover date .
 

Posted to  vara group :- 

Jose EA5HVK 
13:16 (5 hours ago)
 
I have done some settings in speed performance in the new VARA v2.2.0.
 
Some improvements are already available, but others only start working since next thursday 5 april at 23:59:59 (PC time).
 
So, this version is compatible with old versions until thursday 5 april, where changes will be done automatically.
 
please, update this new version before 5 april.
 


Re: 2 meter Aircraft Scatter experiment using OPERA #opera

Graham
 
Edited

Short Aircraft Scatter  test   G0NBD <> G6AVK
Range  ~ 200 miles  , 2  meters 
using  Opera op05  [30 second]

Tx.Rx actually  stable,  Opera is  showing the  average frequency over the  TX period 

AFC action can be  seen working as  data lost  [ % Fade] is  showing 
from 0 to 6% 

73-Graham
G0NBD

 

20:43 144180 G0NBD de G6AVK Op05 199 mi -19 dB F:3% in Essex, JO01ho 1500.0 Hz
20:40 144180 G0NBD de G6AVK Op05 199 mi -18 dB F:2% in Essex, JO01ho 1503.9 Hz
20:30 144180 G0NBD de G6AVK Op05 199 mi -15 dB F:3%_Ini in Essex, JO01ho 1500.0 Hz

20:14 144180 G0NBD de G6AVK Op05 199 mi -18 dB F:3% in Essex, JO01ho 1492.2 Hz

20:13 144180 G0NBD de G6AVK Op05 199 mi -16 dB F:3% in Essex, JO01ho 1527.3 Hz

20:11 144180 G0NBD de G6AVK Op05 199 mi -19 dB F:3% in Essex, JO01ho 1511.7 Hz

20:05 144180 G0NBD de G6AVK Op05 199 mi -21 dB F:2% in Essex, JO01ho 1511.7 Hz

20:04 144180 G0NBD de G6AVK Op05 199 mi -16 dB F:7% in Essex, JO01ho 1511.7 Hz
20:03 144180 G0NBD de G6AVK Op05 199 mi -19 dB F:0% in Essex, JO01ho 1515.6 Hz
2
20:02 144180 G0NBD de G6AVK Op05 199 mi -19 dB F:2% in Essex, JO01ho 1515.6 Hz

20:01 144180 G0NBD de G6AVK Op05 199 mi -15 dB F:6% in Essex, JO01ho 1507.8 Hz

19:54 144180 G0NBD de G6AVK Op05 199 mi -16 dB F:3% in Essex, JO01ho 1507.8 Hz



Spec-lab  plots , showing  multiple reflections  and  doppler  shift 
taken by  G6AVK 




Re: K3UK Winlink Station

Tony
 

Andy:

The ARQ timing is clearly off so I think it's safe to assume it's a latency issue. it's not just Vara, it's ARDOP as well. As per Rick's post, there are things you can try. In the meantime, do you have another rig?

Tony -K2MO


Re: K3UK Winlink Station

Andrew OBrien
 

Do my tones sound OK?  Or does it still seem like a timing issue ?  At my end I see you disconnect and then the welcome  message appears on my screen ready to send  and then you disconnect .  One more VRA if you can
Andy 

On Thu, Mar 29, 2018 at 7:42 PM, Tony <DXDX@...> wrote:
On 3/29/2018 7:39 PM, Andrew OBrien wrote:
Couple more tries if you can Tony... I'm trying to capture video of what is going on...

Will do Andy.







Re: K3UK Winlink Station

Tony
 

On 3/29/2018 7:39 PM, Andrew OBrien wrote:
Couple more tries if you can Tony... I'm trying to capture video of what is going on...
Will do Andy.

1061 - 1080 of 51575