I haven't seen it mention in this thread yet, but the FT-991A isn't VARA Wide capable even with a external sound card.? The radio lacks a data out pin that by-passes the filtering.? Search this group for 991 and you will find plenty of discussion.? I haven't used an IC-7100, but the manual shows an AF OUT and DATA OUT pin.? The DATA OUT pin should provide the bandwidth for VARA Wide.

VARA FM has interesting behavior when set to Wide with a radio that isn't capable.? The initial handshake only transmits in the lower 3000 Hz, so it doesn't test in the 3000-6000 Hz range.? After the handshake, it begins sending the message at a high level if the S/N was good.? The problem is half the bandwidth is missing, so VARA steps down a level and retires sending the message.? It will continue to do this until it hits Level 3, which has a ~3000 Hz bandwidth.? Sometimes it might even drop to Level 1 or 2.

Jeff
WX7OR

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The RMS stations are a lot further away, and would require twice as many transmissions and reliance on infrastructure. I agree with the observation about the sound card on the FT991 which is why I mentioned it as a problem. It's the same on my IC-7100, the data port is required for wide mode operation. I'm surprised that calibration doesn't report the lack of bandwidth- it must catch a lot a people.

We're going to test again tomorrow between north and south. The weather is supposed to be fine. We'll be testing again on Friday. We're also going to try VarAC to go past the file size limit.

This is north to south from Google Earth. The hill looks formidable but as a single sharp peak we seem to be getting knife-edge diffraction.

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1)??? The diffraction "smears" the wave front and creates multipath-type distortion.? This doesn't affect the "calibration" much which uses simple two-tone FSK, but just kills the complex multi-tone QAM audio subcarriers of the fast modes of VARA (or 9600-baud AX.25 packet).

2)??? The diffracted signal on the far side of the hill will be far far weaker than the signal hitting the near side of the hill --- as much as 20-30 dB less.? I.e. far far more path loss than a line-of-sight path of the same distance.? High-speed data modes require fully-hard-quieted "full smash" signals to work reliably.? Even the slightest amount of hiss or "popcorn" noise on the received signal will be fatal. ?

Normally, this means a true line-of-sight path --OR-- a LOT of power (50-100 watts or more) and/or lots of antenna gain. And further, since this is a two-way handshaking operation (unlike one-way APRS beacons), this has to be true in both directions.?? 10-20 watts into a low-gain vertical omni low to the ground? just won't hack it, unless the other end of the path is on a 100-foot-plus tower or hill-top; i.e. typical digipeater location.?? Decades ago, the instruction manual for the Kenwood D700 APRS transceiver warned users to not expect reliable data mode unless the S-meter was reading full scale!??

---

Stephen H. Smith??? wa8lmf (at) aol.com
Skype:??????? WA8LMF
EchoLink:? Node #? 14400? [Think bottom of the 2-meter band]
Home Page:?????????

APRS-over-VARA igates now operating on 30 & 60 meters
??

"Studio B" Ham Shack on Wheels
??

-- APRS over VARA? --
??

?

?

The RMS stations are a lot further away, and would require twice as many transmissions and reliance on infrastructure. I agree with the observation about the sound card on the FT991 which is why I mentioned it as a problem. It's the same on my IC-7100, the data port is required for wide mode operation. I'm surprised that calibration doesn't report the lack of bandwidth- it must catch a lot a people.

We're going to test again tomorrow between north and south. The weather is supposed to be fine. We'll be testing again on Friday. We're also going to try VarAC to go past the file size limit.

This is north to south from Google Earth. The hill looks formidable but as a single sharp peak we seem to be getting knife-edge diffraction.

SET
CONNECTORS
USB Audio SQL - OFF (OPEN)
ACC/USB Output Select - AF
ACC/USB AF Level - 50%
ACC/USB IF Level - 50%
ACC MOD Level - 50%
DATA MOD Level - 50%
USB MOD Level 50%
DATA OFF MOD - MIC,ACC
DATA MOD - USB

VFO Set frequency
Mode FM-D

Here's some docs I put together for our ARES Team:



73 KO4NCC Jeff

I have a good speedy connect, both on FM and HF. But I have no green display on either one and nyinstallation on any system. On VARA HF I likewise have no S/N gauge reading on any system.
Thanks,
Ralph W5RMW

While it is true that P2P winlink is a pain, there are a couple of additional factors involved.?

1) the size limitation of any attached files. IN the SET, which is based on actual fire, one of the stated requirements is ability to send floor plans from the EOC to the incident command. RMS may not be able to handle the size of the attachment.

2) The speed. VARA FM wide may not be available as the local area VHF maybe be in hot zone (plan for the worst, hope for the best)

3) avoiding something just because is a pain in the neck is not a reason to avoiding using something. What works should be the bottom line

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Yes, that looks correct.

> North was using a 8900R with "Rig Blaster Plug and Play" and switched to an FT897D with similar results, using a J-Pole at 10' and later putting it at 25'
> West was using a DRA-100 interface with an Icom 880H. I asked but did not personally verify that he had the radio set to use the 9600 mode. His antenna is a comet GP6 at 50'
> South initially used an FTM400DXR and Digirig with which we were successful, but switched to an FT991 (not "A") later. That, I believe accounts for the South -> North problem as he was using the USB interface in wide mode. It seems reasonable that the acknowledgements, being FSK, would get through OK but the data would not , so north could send but south couldn't. The antenna was repointed when switching the destination between west and north. In retrospect it may have been a little bit off but a 3-el has quite a wide pattern.

We will test again on Wednesday with just the FTM400DXR at south. I have an 880H and a DRA100 (which I've only used so far with an IC-7100) as well and will try to configure it by then to make sure we have the settings correct.

If the issue was with the FT991 then we are still looking for why neither south nor north could receive files from West, but the symptoms seem so similar that it may also be a bandwidth problem at the sending end.

73,
Chris VE3NRT

_._,_._,_

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Be aware that the built-in "soundcard" of the FT-991 does not have enough audio bandwidth to do VARA-FM Fast.? You have to use an external interface like a DRA or recent SignaLink connected to the 6-pin MiniDIN port to do VARA-FM Fast.?

As for the terrain, I think you may not realize how much relief the terrain in your shots has.?? Especially with antennas up only 10-25 feet.

Here are maps and profiles generated by Delorme Topo North America 10.0 .? If you are not familiar with it, it is a DVD-based continuous street level map of all of North America including Canada and Mexico as well as the US.? This is cached entirely on about 5 GB of the local computer's hard disk -- no Internet connection is required, so it works in the boon docks with no cell connectivity. The underlying relief data is the NASA/USGS "Shuttle Radar Topography Mission" data set that relief-mapped the entire land mass of the earth to a common datum in about two weeks about two decades ago. ?

Like Microsoft MapPoint and Street Atlas, Topo N.A. can use a GPS for real-time navigation. You can plot points from entered WGS-84 coordinates derived from other GPS devices.? More usefully for radio purposes, you can draw a line between two push-pinned points and create a cross-section profile of the rise and/or fall of the terrain between the two points.? You can also profile a high-lighted route on roads to determine the most extreme gradient you will encounter, before you try to tow an RV up mountains in the boondocks.? Here are the paths between all three pairs of points you posted.? Note that all 3 paths are non-line-of-site paths that graze mid-points substantially higher than the end points.?? Note that these profiles UNDERPLAY the problem because the graphs DON'T take into account the curvature of the earth's surface.

South-to-North

West-to-North

West-to-South

---

Stephen H. Smith??? wa8lmf (at) aol.com
Skype:??????? WA8LMF
EchoLink:? Node #? 14400? [Think bottom of the 2-meter band]
Home Page:?????????

APRS-over-VARA igates now operating on 30 & 60 meters
??

"Studio B" Ham Shack on Wheels
??

-- APRS over VARA? --
??

?

Interesting information.? This is exactly why we don't recommend using P-P Winlink.? Too much coordination required and too much unpredictability.? The best thing is to find some reasonable RMS stations that you can use.
Jim Price CalOES NCA9TC

The snapshot appears if you view it on the Groups.io VARA-MODEM page.

DoC I think the file is being overwritten because Windows does not detect the sound card and defaults to entries that do exist in Windows 10.

Are you testing the same sound card and USB cable on both PCs? On the Windows 10 PC did you try a different USB port? Are you going directly into a USB port and not a USB hub?

Sorry about posting so many questions but I'm just trying to narrow it down to the cause.

73
John Denison
KD5YOU

Yes, that looks correct.

> North was using a 8900R with "Rig Blaster Plug and Play" and switched to an FT897D with similar results, using a J-Pole at 10' and later putting it at 25'
> West was using a DRA-100 interface with an Icom 880H. I asked but did not personally verify that he had the radio set to use the 9600 mode. His antenna is a comet GP6 at 50'
> South initially used an FTM400DXR and Digirig with which we were successful, but switched to an FT991 (not "A") later. That, I believe accounts for the South -> North problem as he was using the USB interface in wide mode. It seems reasonable that the acknowledgements, being FSK, would get through OK but the data would not , so north could send but south couldn't. The antenna was repointed when switching the destination between west and north. In retrospect it may have been a little bit off but a 3-el has quite a wide pattern.

We will test again on Wednesday with just the FTM400DXR at south. I have an 880H and a DRA100 (which I've only used so far with an IC-7100) as well and will try to configure it by then to make sure we have the settings correct.

If the issue was with the FT991 then we are still looking for why neither south nor north could receive files from West, but the symptoms seem so similar that it may also be a bandwidth problem at the sending end.

73,
Chris VE3NRT

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Hi Stephen,

Thank you for your offer. Here are the coordinates. While most of our region is flat, there is a big (by Ontario standards) ridge (moraine) down the middle.? I will send the other information later once the team responds, which will also answer Erik's question.

West? 43°56'52.07"N ?79°41'3.95"W (Home QTH, antenna on a tower)
North ?44° 0'22.80"N ?79°40'20.35"W? (Note that the school buses shown in Google Earth had been moved to the west corner)
South ?43°55'29.68"N ?79°32'25.15"W

Interesting comment on the effect of circular polarization. I'll see if I can borrow one for the next test. Our satellite operator is probably taking his down in preparation for field day.

73,
Chris

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A group of us ran a test yesterday with Winlink VARA-FM on 144.950. The path was 14km with a single distinct peak in-between 145m above the northern site and 60m above the southern site. Initially we could send a 90kbyte file P2P between the two locations in about 2 minutes running between level 7 and 9 in FM wide. North was using a commercial J-pole about 8 feet off the ground, while south was using an Arrow 3-el Yagi on a pole (I don't know the height but was it was elevated). We recalibrated before almost every test.
?
A third site (west) was 9km and 13km from north and south respectively. Calibrations yielded SNRs of 23 to 27 dB in all cases.

North and south could initially exchange files at good speed as stated above. We then tried north to west and found that west could not send to north while north could send to west at good speeds. The former would start at level 9 and end up at level 1, with no data transferred at the higher levels.? The latter would send the same file about 3 minutes.

We then elevated north's antenna to 8m, and tested again. It started to rain, which may be significant. We found that south to north did the same thing as the west to north test, starting at level 9 and dropping to level 1, and sometimes disconnecting. North could send to south without issue. We changed back to the original antenna configuration with no improvement. The elevated antenna showed the best signal strength and SNR in calibration.

South tried sending to west and had the same problem.

While with the variable terrain and probably knife-edge diffraction, we're surprised at the extremely variable results without corresponding variation in signal SNR, and also the extreme difference between forward and reverse directions. We're going to review and set up another test, but we would appreciate any suggestions, comments, or similar experiences from others that might account for this?

73,
Chris VE3NRT?

_._,_._,_

---

?Can you tell me where you actually did these tests??? I.e. locations or actual coordinates of the three sites.? I'd like to model it on a? topo map program.? Having spent decades dealing with mobile data on VHF in mountainous terrain (southern California / Los Angeles) for both amateur and public safety radio, I'm curious.? But some questions and random thoughts....

1)?? What kind of radios were you using???????? How much power??? What kind of IF bandwidth??

2)?? What kind of interfaces between the radios and VARA computers? ? Were they connected to the radios via a dedicated flat-response input such as the 6-pin mini-DIN "data" port, or just a mickey-mouse mic & speaker hookup??

3)?? What kind of terrain was this??? Urban areas with multi-story buildings? Suburban low-rise? Open grass lands/farms?? Dense forest? or what?

4)?? You didn't mention what kind of antenna was at the 3rd site.??? The Arrow antenna is of course directional. Was it aimed directly at the 2nd station with the omnidirectional j-pole???? How far off the beam of the Arrow was the 3rd station???

5)??? High-speed data is incredibly intolerant of multi-path reflections.? When signals arrive both directly from the sending station,? and over longer paths after being reflected by tall buildings, water towers,? bare (un-vegetated) hill sides, etc off to the side of the direct path,? they arrive at the receiver at slightly (nano-seconds or micro-seconds) different times.? [Hills with grass and trees tend to absorb VHF/UHF signals while bare rocky hill sides tend to reflect and scatter them.] ?? What should be successive data symbols in the transmission wind up overlapping each other due to the time delays on the longer indirect paths, smearing and mangling the data.? [This is exactly the same phenomenon as "ghosting" in classic analog NTSC broadcast TV. You don't see it in digital TV because the screen just goes black when the multi-path-induced errors overwhelm the built-in forward error correction of the digital signal.]

When the error rate starts overwhelming the built-in forward error correction of the transmission, the VARA program responds by slowing down the transmission rate so that the overlap becomes a smaller percentage of each packet. Which of course reduces the net data throughput.

6)??? Under normal conditions, the direct-path signal should be overwhelmingly stronger and should "cover up" any indirect-path signals. But you seem to say even the direct path was grazing a hill-top, which can radically reduce the signal strength (like 20-30 dB less!) compared to a true literal optical line-of-sight path.? The result is that the direct path signal might not be any stronger than indirect-path signals reflected from objects off to the side.? So NO decisive capture by one version of the signal.?
?? The only real solution to this problem is to use high-gain HIGHLY-DIRECTIONAL antennas at both ends of the path. Note that? more power or omni-directional gain antennas WILL NOT fix this problem - the RATIO of desired to undesired signals doesn't change.?

6) ?? I don't know for sure, but I suspect that VARA's reported initial data throughput starts out as a "wishful thinking" value, that is then corrected downward to more realistic (lower) values as experience with NAKs/ACKs accumulates during a transmission.

7)? ? Further, after being diffracted by grazing a hill top, signals tend to become stratified - formed into thin layers vertically with alternate strong and weak layers.? Sometime moving the receive antenna only a few feet/meters vertically will change the receive signal level 10 or 15 dB. Counter-intuitively, sometimes moving the antenna LOWER will improve the signal! ? ?
? ? Not to mention that shallowly grazing a non-line-of-sight edge can actually change the polarization of the signal. I.e. a signal arriving at the edge vertically can leave the edge as a horizontally-polarized signal.? (A lot of the "mobile flutter" on distant (non line-of-sight) mobile signals at VHF/UHF is actually constantly-changing polarization.) ?

In the late 1970s, I worked at Collins Radio in Cedar Rapids, Iowa. At the time, repeaters were not ubiquitous as they are today.? People routinely used 100-150-watt-plus amplifiers on 2M mobiles to work simplex 50-100 miles (80-160 Km)? across the gently-rolling terrain of Iowa to fixed stations with 8-element or more beam antennas. ? One normally expected mobile flutter and rapid fade-outs/fade-ins as mobiles moved down Interstate-80 at 70 MPH / 110 KMh.? I used two 8-element KLM? beams vertically side-by-side fed in phase with a divider harness to produce vertical polarization.?
??? I then tried mounting the two antennas one leaning 45 degrees to the left and the other 45 degs to the right (i.e. 90 degs apart) and fed them with a phasing harness with an extra 1/4-wave of coax on one leg. ? This creates circular polarization instead of planar vertical-only.? The effects were spectacular - the mobile flutter and fading on long simplex paths totally disappeared!?? Note that you DON'T need to have CP antennas at both ends of the path - the normal vertical-only mobile whip at one end of the path will work as long as the other end of the path has a CP antenna.??

I had the same experience with a two-meter repeater covering a narrow canyon road in Los Angeles. The narrow winding rocky-walled canyon road was a nightmare of multi-path phase distortion and rapid-fire fluttering when the repeater at the summit used the usual vertical gain antenna.? I switched the repeater to a circular-polarized? crossed-yagis? antenna intended for satellite tracking pointed down into the canyon.?? Again, the results were night-and-day - the flutter and spattery audio phase distortion on mobiles in the canyon completely went away.? ? ? ?? ?? ??

---

Stephen H. Smith??? wa8lmf (at) aol.com
Skype:??????? WA8LMF
EchoLink:? Node #? 14400? [Think bottom of the 2-meter band]
Home Page:?????????

APRS-over-VARA igates now operating on 30 & 60 meters
??

"Studio B" Ham Shack on Wheels
??

-- APRS over VARA? --
??

?