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?

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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?

_._,_._,_

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?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? --
??

?

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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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

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

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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? --
??

?

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

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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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.

_._,_._,_

---

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? --
??

?

?

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

Jeff WX7OR wrote:
… the FT-991A isn't VARA Wide capable even with an external sound card.

Not so!…

?

You’re right about the FT-991(A) not outputting “9600bps receive” audio on the corresponding pin of the miniDIN-6 “DATA” connector.

?

However, Yaesu has provided a mechanism for supporting “high speed” VHF/UHF FM data, with an external TNC or rig-interface device, by switching the unfiltered receive discriminator output to the miniDIN-6 “1200bps receive” pin when the radio is set for “9600 bps data” operation.

?

The key to making this work is making sure that the external rig-interface device, and/or radio cable is jumpered (and/or wired) -only- for 1200bps operation, regardless of whether the radio is set in the 1200bps or 9600bps configuration, or whether VARA FM is running in “WIDE” or “NARROW” mode.

Mark - AD7EF

That's the behaviour I saw. The west station (I was at north) sending a file to us said the 6-pin data port was being used with the correct settings, but perhaps it needs to be checked further. I've heard about the 991A problem but as far as I know the 991 is OK, then again I will check with the south operator to make sure he doesn't have the A model, although I've seen reports that it can be made to work in wide mode with some counter-intuitive fiddling.

We've generally been using 50W for testing.? It worked fine with the North antenna at 10'. We started having trouble when we elevated it to 25', although it seems south swapped radios at about the same time. Going back to 10' didn't help.?

I'm glad we've been doing this testing. It's better to discover the issues before we need them.

73,

Chris

Chris,

I apologize. ?Mark is correct. ?You can do Vara Wide with the FT-991A. ?Just use the cabling and jumpers as he describes.

Jeff
WX7OR

On Mon, Jun 10, 2024 at 07:51 PM, CalOES SOCC Officer - Jim Price wrote:

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 -

Our local ARES groups regularly practice Winlink P2P operation over VARA FM links, and have very little trouble coordinating these sessions, using voice, over the same channel that is used for the data session.

Also, don't overlook the benefits of VARA FM digipeater stations for addressing signal path issues for P2P sessions.

The rationale for our practicing P2P data communications over VHF/UHF FM links is that we need to be able to achieve efficient error-free data communications between field operators and our served agencies & EOCs even if internet service is disrupted regionally. There are more than a few examples of how that has actually happened. It's hard to see how email data communications through a VHF/UHF FM RMS gateway station, or for that matter VARA HF links to gateway stations outside the affected area, would be effective in that situation.

Mark - AD7EF

Today we tested again. We moved to a less desirable site at the request of the Fire Chief. Unfortunately a large metal building was in the way which impeded signals sufficiently to make file transfer impossible (between north and south). So we tried using west as a digipeater and it worked quite well, giving us about 20kB/minute transfer rate. I thought that was a slow but the Fire Chief was pleased and that's good enough for me.

We will have a Yagi at north as well as south for the final test on Friday. We are also thinking about using Wi-Fi (or derivative like AREDN) for short range communications at any site where we can't otherwise locate near to the client due to obstructions like the metal building. The idea would be to put a router in between the Winink operator and the operator working with the client. We might get a chance to experiment with that a little on Friday.

Thank you for all the suggestions. They've been very helpful. P2P is the most efficient for us at this location, and provides the ability to exceed the 120kb file limit.?

One anecdote from today was that our south operator created a 100kB text file by repeating the same text over and over. It transmitted in a few seconds. We concluded that the data compression for repeated text is quite good.

73,
Chris

Chris, et.al. Lots of lessons learned in preparation for the actual exercise.? I look forward to the after action report of the event.??

Another option you may wish to test is using a VHF repeater to act as the P2P repeater.? I think you have an FM repeater in that location that may be used.? Talk to the repeater owner, as you may need to turn off a few functions such as the repeater timer length.? The nice thing about using the repeater, is you can carry on both voice and digital communications on the same channel.?

VARA FM when set up as a digipeater can really extend the range. In the Ottawa region, we have set up most of the RMS Gateways to operate both as RMS Gateways AND as VARA FM Digipeaters.? Home stations can also be set up as VARA FM FM Digipeaters.? Licensed VARA FM digipeaters can be linked for up to two digipeaters.?

Please write up your complete report so that other can benefit from your hard work.?

As we collectively move from using Winlink and VARA FM from established home stations and move to being deployed and setting up temporary stations, there is a new set of skills to be developed.?

Thanks for sharing you lessons learned in live time.?

Have fun

Stuart VE3SMF

Hi Stuart and others,

Yes you can use a phone repeater BUT you have to set in VARA-FM program via "Settings" and "VARA setup" at "FM system" in NARROW and not in WIDE.
This is for the all users of VARA-FM via a phone repeater.
Nothing have to change in the repeater itself.

This all means that the the audio-bandwidth is less and thus the level speed is max 11
I did some testing here and NARROW versus NARROW works OK.
NARROW versus WIDE and WIDE versus WIDE is terrible and slow.

Good luck with testing!
' 73
Peter, PE1DCD

Chris,

I just tested the FT-991 today to confirm it is capable of Vara Wide and it is.? It wasn't mentioned before, but make sure the radio is in DATA-FM mode.? It will appear to work in FM mode, but the emphasis/de-emphasis circuitry is not bypassed.? Vara Wide will have variable and less than optimum results in this mode.

Jeff