Keyboard Shortcuts
Likes
Search
Questions on Running 40m VARA APRS mobile
|
1) May I try out mobile 40m VARA APRS on your West coast network?
2) APRS client is Pinpoint APRS. If you folks do not mind me trying this out on the West coast network, what beaconing interval would you allow or suggest to not perturb the network?
?
Just messing around at home, it has been impressive to say the least. |
|
It's a public network for hams. Use it as needed. That's why it's there.
?
With pinpoint I'd suggest no less than 2 minute intervals, and no less than 30 stationary. Obviously you can't really do this with pinpoint without fiddling with setting when you're not moving. So you may consider an application with smart beaconing to give you better control. |
|
Thanks for the advice. I¡¯m running a pair of shark sticks as a dipole centered inside a pvc drain pipe radome on the lumber rack of the truck. It does well in daytime down to 1 Watt but not out past 500 mi., nothing at night, so the network is isolated for me. I¡¯ll try a vertical off the hitch receiver and compare. A full size inverted vee reliably got out to WA8LMF last night.
?
What would be interesting to me is to run mobile at either 40m or 80m day or night to a full size 40/80 crossed dipole at my home, keep it all local. If I get that far, I¡¯ll find a different frequency from you folks. |
¿ªÔÆÌåÓýOn 1/17/2025 1:07 PM, David Lowry via
groups.io wrote:
This is a quite normal and typical range for 40 meters in the
daytime. The range will lengthen out to continental or DX after
dark.? 80 will have a daytime NVIS range of 200 miles or so in the
daytime,lengthening out to around 1000-1500 after dark; sometimes
greater. The receive capability on 80 meters is severely limited
after dark in the summer due to natural static from thunderstorms
anywhere within about 1000 miles of your receive location. This
severely limits the usability of weak mobile signals after dark. ?
In the depths of winter, though, 80 can be very quiet after dark.
? If your ham stick dipole is only a few feet above the body sheet
metal, most of it's radiation is straight up - ideal for close-in
NVIS (near vertical incidence skywave operation but severely
reducing any long-range transmission.??? A vertical whip will have
FAR more low-angle long-range radiation.
If you do mount any HF antenna on the hitch receiver, be sure to
bond the draw arm to the vehicle body (not just the receiver) with
a heavy broad low-inductance strap like a piece of brass or
aluminum roofing flashing. ? (Not just a piece of 1" braid.)? If
you don't, the draw arm jiggling in the receiver socket will make
only a tentative contact with the receiver and generate horrendous
amounts of noise on receiver and a non-constant SWR on transmit.??
the receive performance will vary wildly, depending on how high
above ground the dipole is.? Low to the ground (10-20 feet will
favor close-in (under 250-300 miles) high-angle NVIS radiation.?
To get low-angle DX radiation, the dipole has to be at least a
quarter-wave above ground; i.e. 30-plus feet on 40m, 60-70-feet
plus on 80m.? The only frequencies being used regularly for APRS-over-VARA are
the single 40 meter channel and the one on 30 meters.? I HAVE been
experimenting with APRS on 60 meters where one tends to get a
fairly reliable 150-250 mile NVIS coverage in daytime and twilight
but not at night. At night on either 40, 60 or 80 meters, you normally have a skip
zone of 150-300 miles. You will hear nothing closer to you than
this.?
|
|
For a mobile you truly want a vertical mounted antenna from the top of the vehicle when possible on 40m. Probably similar on 30m I would guess.
?
If using a hitch mount, you'll want it to be WELL bonded to the vehicle. This will give much different performance over a roof mounted antenna.
?
I'm not sure where you're located, but I would expect you to get in during the night on 40m. But not at all on 30m.
?
Right now on 30m in the dark hours, I can't get out at all. On 40m I have several gates across the country I can get into. This seems to always be the norm for me.? |
¿ªÔÆÌåÓýOn 1/20/2025 2:08 PM, Devan Banman via
groups.io wrote:
? NO!!!?? You can't do that kind of rate on
HF!???? 1)?? The transmission time is much longer on VARA than on the usual 1200-baud 2M VHF.? A simple beacon, especially if it is not in a compressed format like Mic-E,? can take 20-30 seconds.?? At a two-minute repetition rate, you are occupying 1/5 th to 1/4 of the total capacity of the channel.? Note that on a random-access channel with no coordinated timing of the users, that if the channel is occupied more than 18-20% of the time, the probability of data collisions between stations goes up sharply. (The so-called Aloha" limit.)
2)?? On two meters, you are occupying the channel over a city or county-sized area. Many users around even a single state can be using the channel at the same time.?? One HF, you are occupying the channel over ONE-THIRD of North
America or more.
On HF, a reasonable beacon rate is around 15-20
minutes for a mobile, if the channel is being used with
multiple users.
Stephen H. Smith??? wa8lmf (at) aol.com Skype:??????? WA8LMF EchoLink:? Node #? 14400? [Think bottom of the 2-meter band] Home Page:????????? New? 30 Meter?? APRS-over VARA? Frequency As of 1 Jan 2025.?? Details Here: ???? - APRS over VARA? -- ?? "Studio B" Ham Shack on Wheels ?? - ?
|
|
Stephen WA8LMF wrote,
"On HF, a reasonable beacon rate is around 15-20 minutes for a mobile, if the channel is being used with multiple users."
?
Hay Stephen on your road trip in October your beacon rate for Vara was about three minutes.
?
I do understand that was a test comparing Vara to AX-25. I am seeing 8 to 15 stations on the 30M Vara channel every day with varying beacon intervals. In addition, the length of the beacon also varies from 10 to over 20 seconds.?
?
I think there needs to be some consensus on beacon intervals. I would propose a base station I-Gate beacon on RF at no more than 20 munities intervals. Mobile stations on short trips no more than 4 minutes and long road trips no more than 8 minutes.
?
As far as the beacon length, I started out with PinPoint with a length of about 20 seconds. I understand PinPoint is not compressed. This may change with a new release. Today I changed to APRSIS32 and the beacon length, which is compressed, is about 10 seconds. I will give this some time to see how this works out.
73
Wayne
WA5LUY
?
? |
|
Here's my 2 cents...
NO!!! ? You can't do that kind of rate on HF! ? ?
1) ? The transmission time is much longer on VARA than on the usual 1200-baud 2M VHF. ?A simple beacon, especially if it is not in a compressed format like Mic-E, ?can take 20-30 seconds. ? At a two-minute repetition rate, you are occupying 1/5 th to 1/4 of the total capacity of the channel.?
Note that on a random-access channel with no coordinated timing of the users, that if the channel is occupied more than 18-20% of the time, the probability of data collisions between stations goes up sharply. (The so-called Aloha" limit.)
Let's start with this. Not all beacons are alike. Data saving measures are hidden within VARA modems code. Uncompressed beacons are actually compressed within VARA, which is why the math doesn't add up when you look at the data sizes. VARA uses tricks to reduce the tocall, digi paths, acks, and other things. It balances the slowest speed possible with data length, and the compressed tricks it has hidden within. This is why an uncompressed beacon is more data, but uses a slower speed. It was designed this way to allow the most robust signal and lowest speed with a simple beacon.
Every user is different, so how they operate their beacons will greatly vary. So the above should help determine what's best for you speed and time wise, and the air time consideration. Whether you utilize the 1/4 or 1/5 of the air time definitely matters.... but only if the airwaves are actually being used.?
I've been using 30m for 3 weeks 5 days a week or more in the mornings and evenings. I've been the only one mobile during that entire time that I've seen or heard. So what's best practice for my usage and consideration of the network? Easily 2 minute +/- intervals using smart beaconing. There's no problem doing such either. Even if we had a couple other stations, it still wouldn't be a problem. We've tested multiple stations in our 1 year of operations on 40m. It's rare you'll see more than 1 mobile station at any given time. With that, you are now pointing out a crucial flaw of 30m. The band skips across too much of an area, meaning it could see congestion much quicker. Though unlikely, as basically no one seems to go mobile on the band. As you said, "On HF, a reasonable beacon rate is around 15-20 minutes for a mobile, if the channel is being used with multiple users." I find that just ridiculous unless the band is congested or heavily used. Which is never. So 2-4 minute smart beaconing intervals are perfectly sufficient. Whether on 30m or 40m. I'm more concerned with the base stations spewing out all the crap "DX" beacons every 30 seconds. Or those who push out the "grid position". Or stations who's messaging is off, but they beacon every 2 minutes with their base station.? "I think there needs to be some consensus on beacon intervals. I would propose a base station I-Gate beacon on RF at no more than 20 munities intervals. Mobile stations on short trips no more than 4 minutes and long road trips no more than 8 minutes. ? "As far as the beacon length, I started out with PinPoint with a length of about 20 seconds. I understand PinPoint is not compressed. This may change with a new release. Today I changed to APRSIS32 and the beacon length, which is compressed, is about 10 seconds. I will give this some time to see how this works out." One problem you're missing here is how VARA works. Compressed or not, it's about the speed when using uncompressed, not the time or length like other packet types. This is why VARA uses speed 1 with uncompressed, because it's specifically designed to use the lowest speed for uncompressed packets. If it didn't, it would use speed 2 exactly like compressed or Mic-E due to the length of data.
So with that, 2-3 minutes and smart beaconing is an acceptable interval WHEN the band isn't being heavily used. Which seems to be never. We adjust as we go, not based on something that isn't happening or never happens. When stationary (as a mobile), 15-30 minutes is acceptable and best practice. When a base only, 30 is best. Pinpoint doesn't support smart beaconing, so this requires being a little more diligent with operations and changing it based on how you are travelling. ? |
|
If you want the most availability of the band. Stop sending DX status beacons. Stop double beaconing. Meaning don't send statuses, grid position, or other beacons types. Avoid excessively long comments even. There are lots of things that can be done at the base stations to allow more air time, which can help provide more time for mobile users, or messaging users, of which I think should have priority.
?
There are a lot of things to consider. But most importantly, use the freaking network! Don't let it sit there going to waste. This isn't some nonsense ARES RACES net that's completely worthless. I'm sure someone will love that comment. Also have contact info on QRZ. In case there is an issue, or some reason someone might want to contact you. Community efforts are the key here. Get out there, have fun, enjoy the bands, and use APRS!? |
wa5luy