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[aprssig] APRS experiment along I-40, mapping vs. voice alert vs. local info

Alex Carver kf4lvz at yahoo.com
Wed Jul 14 18:21:59 UTC 2010

> From: "Robert Bruninga"
> Subject: Re: [aprssig] APRS experiment along
> I-40,    mapping vs. voice
>     alert vs. local info

> Great report!
> > I haven't been a fan of Voice Alert and 
> > never really tried out anything with local info...
> > ... from Columbus, GA to Los Angeles, CA....
> > ... part of APRS (mapping, tracking) worked fine...
> > Local info... I may have seen one or two
> announcements...
> > Voice Alert failed completely...  Over a road 
> > distance of 2,200 miles... not one squawk...
> Welcome to the club! 
> It is so frustrating to be driving past so many other ham
> operators and so many APRS mobiles and not be able to even
> know
> they are there or being able to contact them... 
> Statistically,
> one in every 500 cars is another ham.
> Lets assume that 10% are running APRS.  This means one
> in every
> 5000, which on an interstate is about once every 2 hours or
> so.
> So, of those APRS mobiles that passed by,

Zero APRS mobiles that I saw.  Remember that I had a small D7 and had to keep my eyes on the road ahead most of the time.  The few packets that caused a beep (but not a voice alert squawk) were from weather stations, digipeaters or other fixed stations.  I really didn't see many mobiles at all.  I could pull up the station list in the radio later to see if there were any mobiles.  There might have been one or two but most likely not in simplex range if anything.

> How many were you aware of?

Zero or less

> How many contacted you or struck up a QSO?

Zero because there were none that I saw.

> How many did you try to contact?

Zero because I couldn't pay attention to the screen on the radio.  A portable radio in a rental vehicle limits the possible placement choices and nearly all of them are not optimal for maintaining eyes on the road ahead while manipulating the radio. 

> Did you hear any calls on 52?

No calls on 146.520 though I did have the radio tuned to it most of the time and also scanned the 2-meter band a lot while driving.  I actually heard more traffic over the CB than I did VHF.

> You didn't mention any and it does not surprise me. 
> This
> matches my frustration on my 1800 mile round trips down
> I-81
> from Maryland to Alabama and back through a WELL CONNECTED
> system...
> But if those other APRS mobiles on the open road had been
> running APRS Voice Alert, there would have been a half
> dozen or
> so a day of enjoyable interesting contacts.
> > Honestly, I think that it's just not as interesting to
> > operators as some may have us believe.
> Yes, because so few are transmitting so there are so few
> to
> hear...
> The number one complaint we hear each time we talk about
> Voice
> Alert is from the nay-sayers who don't want to hear all
> that
> Packet Racket.  Which is about as dumb of an excuse as
> there is,
> since you just demonstrated that there are NONE to hear
> over
> 2000 miles across country, because no one is transmitting
> it!
> Its just all the naysayers that have never tried it want
> to
> complain about a problem that does not exist.
> Its like anything in ham radio... If no one call's CQ, then
> the
> band is dead and there is nothing to do.  
> > I was on the air for 14-16 hours a day...
> > beaconing my position once every three minutes...
> Ah, there is a problem.  At a combined speed of over 2
> miles a
> minute, you only have one chance every 6 miles to even be
> heard
> by someone else.  And the simplex range
> mobile-to-mobile is
> usually less than that.  For Voice Alert, you should
> always be
> beaconing at a 1 minute rate.  This gives you a
> possible 3 hits
> per other person you pass.

Perhaps but I wasn't really wanting to blast the airwaves with too many packets.  I figured three was enough but perhaps not.

> But to keep the QRM down (even lower than your 3 minute
> rate),
> that is the power of Proportional Pathing designed into
> the
> D710.  It transmits a local simplex direct packet once
> a minute
> (for nearby mobiles).  But only via a WIDE1-1 once
> every 2
> minutes, and only via the wider area 2 hops once every 4
> minutes.  This is less regional QRM than a fixed 3
> minute rate,
> but gives you a far, far better reliability at voice alert
> and
> close-in nearby tracking.

Remember I had a D7 not a D700 D710.  The thing you have to keep in mind is that a lot of people traveling that far are NOT using their own vehicle.  When I drive that far I always rent a vehicle so I'm limited in what I can install temporarily on the car.

In one shorter trip I took several years ago I did bring my D700 but that's because I rented from the same city where I was living.  

In this case I had to fly cross-country first and then rent the truck to drive back cross-country.  Therefore I was limited in what I could carry on board the airplane which was the D7 and a super small magmount 1/4 wave antenna.

There was no way I could have carried the D700, a big mag mount, cables, etc. just for this trip and I certainly had no way of plugging it in since the accessory outlet in the truck had a small fuse (the rental company disabled the ciagrette lighter and changed the fuse so that it couldn't be operated).  I would have been blowing fuses every time I transmitted with the D700 if I had anything more than low power.


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