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[aprssig] Mobile Digipeating

Dr. John w3ate at earthlink.net
Sat Sep 17 12:32:12 UTC 2011


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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