[aprssig] Coverage holes in OK?

[Lynn W. Deffenbaugh (Mr)]

On 1/6/2012 2:34 PM, Alex Carver wrote:
> I just drove cross country from FL to CA using the Florida Turnpike, 
> I-75 to Georgia, I-22/US-280/US-78 to Tennessee, then I-40 to 
> California (check my route on aprs.fi).

It helps to tell us what station to look at on aprs.fi and what date 
range, but I believe it was KF4LVZ (thanks to your e-mail address, not 
any signature here) and from Jan 01 through Jan 04 (thanks to my 7 day 
APRS database).

> I had my D700 with me at 25 watts with a 3 minute beacon going out as 
> WIDE1-1,WIDE-2-2 (covered all areas so that I didn't have to fiddle 
> with the radio en-route).

Hopefully that was WIDE2-2 and the WIDE-2-2 was a typo?

> Looking at the map, there were some huge holes in Oklahoma.  I didn't 
> exactly expect that given the flatness of OK.  I was picked up very 
> well in Oklahoma City but didn't get digipeated or gated until I 
> reached Amarillo, TX.  East of Oklahoma City there was another large 
> hole between Oklahoma City and Ft. Smith, AR.

If you want an idea of coverage before doing such an extensive drive 
(handy for telling the family where NOT to be concerned if they don't 
see you moving), see http://tinyurl.com/APRSAct24 and 
http://tinyurl.com/APRSAct00 for APRS coverage maps.  You have to look 
closely at the file dates to find the most recent and now that I look at 
them, I need to restart the batch job for the new year.  But there's 
enough there to get the idea.

>
> Note, I'm considering a hole as an area where I traveled 50 miles or 
> more without a single gate or digipeat (digipeat being the D700 saying 
> MY POS if it managed to hear its own packet).  All these areas were 
> quiet both in the car and on APRS-IS given the track data.  Other than 
> these hols coverage was pretty good even in remote places and small 
> towns (like Alexander City, AL).  Coverage in NM, AZ, and CA most 
> likely benefited from mountain top sites that could cover huge areas 
> easily.

Well, not hearing a MY POS doesn't necessarily mean that you're in a 
hole, but you're in an area where one of the following is true.

a) No digipeater was within range or
b) Digis in range didn't decode your transmissions or
c) Your D700 didn't hear the digipeat or
d) Your D700 didn't decode the digipeat.

In a perfect world, all APRS hardware would decode all other APRS 
hardware, but since the Kenwood APRS radios transmit non-emphasized 
audio (I'm told), any XR-2211-based digi that's being fed de-emphasized 
audio may have trouble decoding Kenwoods.  De-emphasis (audio out) 
lowers the high tone to be quieter than the low tone causing issues with 
XR-2211 demodulator chips - see 
http://www.febo.com/packet/layer-one/transmit.html.

Your mention of "quiet in the car" provides a better correlation that 
you were indeed in a hole and not suffering from one of the above 
issues, IMHO.

>
> The coverage holes or areas where I failed to be gated were the following:
> Gainesville, FL to Valdosta, GA (fairly large)
> Albany, GA to Columbus, GA
> Birmingham, AL to Tupelo, MS
> Memphis, TN to Little Rock, AR
> Fort Smith, AR to Oklahoma City, OK (mentioned above)
> Oklahoma City, OK to Amarillo, TX (mentioned above)
> Amarillo, TX to Tucumcari, NM

See http://tinyurl.com/78bhsrm for renderings of your APRS utilization 
for your trip.  Note that the Jan 01-Jan 06 total trip comes between the 
day detail for Jan 01 and Jan 02.  The 24 hour SE and SW coverage maps 
for December (http://tinyurl.com/869twr9) pretty much bear out your 
definition of where the holes are.

Lynn (D) - KJ4ERJ - APRS Infrastructure Visualization

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