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[aprssig] Mobile Digipeating

Eric Hansen skyssx at gmail.com
Sat Sep 17 12:41:18 UTC 2011


No, you can make one anywhere, but you're not going to get a protected repeater pair.

Sent from my iPhone

On Sep 17, 2011, at 8:32, "Dr. John" <w3ate at earthlink.net> wrote:

> Mobile repeaters in the amateur environment is not authorized. As repeaters need to be registered at a fixed position
> 
> Dr. John Gregory /W3ATE-8
> 
> --------------------------------------------------
> From: "Tom Russo" <russo at bogodyn.org>
> Sent: Saturday, September 17, 2011 1:02 AM
> To: "TAPR APRS Mailing List" <aprssig at tapr.org>
> Subject: Re: [aprssig] Mobile Digipeating
> 
>> On Fri, Sep 16, 2011 at 10:34:30PM -0600, we recorded a bogon-computron collision of the <dnchls at gmail.com> flavor, containing:
>>> I am in search and rescue and use APRS so others can keep track of me.
>> 
>> You're in good company.
>> 
>>> I
>>> live in New Mexico where we have many digipeaters on mountain tops, but we
>>> still have many dead zones.
>> 
>> I've been watching your tracks.  I'm not sure the dead zones are as dead as
>> all that.  Still, there are some notable places where there are searches and
>> that have spots where you can't be heard.
>> 
>>> I have a YAESU VX-8DR ht that I carry with me
>>> both when practicing and on actual searches. I am considering buying a
>>> Kenwood TM-D710A. I would like to use the 710 in my mobile as a digipeater
>>> to either get back to search base on a search or to a mountain digi when I'm
>>> practicing so my family can know where I'm at on APRS.fi. I would typically
>>> be within a couple of miles from my truck when I transmitted an APRS signal
>>> from my ht. How much power does the 710 transmit when in digipeater mode?
>> 
>> It transmits with the same power that you have set for its own APRS
>> transmissions.
>> 
>>> Would this be a situation where using a mobile would be useful? Presently,
>>> it just doesn't seem I have the punch I need when using the ht.
>> 
>> It would help if your truck is generally within range of your handheld, the
>> truck is in a good place where it is getting digipeated, and you don't have
>> terrain in between you and the truck that prevents the truck from hearing you.
>> 
>> In this case you could use your truck's callsign as the first hop in your
>> digi path, and WIDE2-2 next in the path.  That'd let your truck beacon you
>> with more ooomph.
>> 
>> The downside of this is that if you wind up in a spot where your truck's
>> radio can't hear you, you won't get anywhere even if a WIDE can hear you,
>> because they won't premptively digipeat before your truck.
>> 
>> It's unfortunate that Yaesu chose not to implement "Proportional Pathing" in the
>> VX-8*R series radios.  The VX-8R lets you set 8 paths, but rather than
>> cycling through them, it simply concatenates them for every transmission. I'm
>> unfamiliar with the VX-8DR, maybe it does have proportional pathing.  With
>> proportional pathing, you can set multiple digi paths, but rather than using
>> them all at once, it cycles through them for each transmission.  Then you
>> could have "TRUCK,WIDE2-2" for every third transmission,
>> "WIDE1-1,WIDE2-2" for every third transmission, and "WIDE2-2" for every third.
>> That would take care of making sure that at least SOME of your packets get
>> to a wide digi --- either directly, or through your truck, or through a fill-in.
>> 
>>> Unfortunately, the people I know both in SAR and amateur radio have never
>>> played with mobile digipeaters and are pretty clueless on the matter.
>> 
>> Clueless?  I don't think that's a fair statement.
>> 
>> To date, most SAR activities in the state have managed without pressing need
>> for mobile digis.  NM SAR Support's comms trailer does have a TNC programmed
>> to digi WIDE1-1, so if your path is WIDE1-1, WIDE2-2 (which is OK in NM for
>> low-powered stations and ONLY low-powered stations... there was a big
>> discussion on that subject recently, and you should check the archives
>> about it, I won't open that can of worms again), then the comms trailer in
>> base will serve as a fill-in digi if needed.  We also have a portable digi we
>> can place in the search area when necessary.  It is rarely necessary, but it
>> does get deployed now and then.
>> 
>> You should also set your D710 to do TEMPn-N digipeating, but I'm sure
>> Bob B. will pipe in here quickly about that one.  Right now, very few people
>> in the SAR community have their radios set up for it, so counting on the
>> availability of TEMPn-N on searches is not a safe bet just yet.  But if you
>> set your own truck to do TEMPn-N, then when you know you aren't reaching
>> a wide with your handheld on a search, and you know you can hear your truck,
>> you can tinker with your path to use TEMPn-N for a while to be sure of getting
>> out.  You'd use "TEMP1-1,WIDE2-2" in that case, and as long as your truck
>> can hear you you're good.
>> 
>> One thing you should NOT do is set your truck to digipeat WIDEn-N as if it
>> were permanent infrastructure.  Some folks in NMSAR did do that for a while
>> and it was a terrible mistake --- it meant that ALL traffic heard by the
>> incident comms trailer was getting digipeated if it had any wide hops left.
>> That meant the APRS radio in the trailer was transmitting all the time, and
>> desensing lots of nearby voice radios every few seconds.
>> 
>> -- 
>> Tom Russo    KM5VY   SAR502   DM64ux          http://www.swcp.com/~russo/
>> Tijeras, NM  QRPL#1592 K2#398  SOC#236 http://kevan.org/brain.cgi?DDTNM
>> "One man alone can be pretty dumb sometimes, but for real bona fide
>> stupidity, there ain't nothin' can beat teamwork." - Edward Abbey
>> 
>> 
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