[aprssig] Clarification on Wide 1 digi characteristic please

[Stephen H. Smith]

On 3/1/2010 10:05 AM, Michael Singewald wrote:
> My APRS call is N1PLH-7 and I am in the zipcode of 06855.  I believe 
> that I may be able to receive a Wide 2 digi if I were using a mobile 
> or base, however, I am only using a portable VX-8DR at the moment and 
> I hear the local Wide 1 digi (WX1CT) just fine.
>
> I am still just learning how to interpret paths as shown on APRS.fi 
> and on my radio.  I am not even sure how determine which digis are 
> Wide 1 or 2.

You have to be able to see the symbols for the various digipeaters 
either on a map, or on your display screen.  Lookup their own calls on 
APRS.FI or findu.com   The six-pointed green star "digipeater" symbol 
will be overlaid with different letters or numbers depending on whether 
it is a low-level home WIDE1-1 or a high-elevation wide-area WIDEn-N.   
The digi's own periodic beacon may also make it clear what kind it is.


> I can check for paths that they might be included in and see if there 
> call is in the first or second slot, but is that the best way?

1)     WIDE1-1 should ONLY be in the first hop of your outgoing transmit 
path setting.

2)     Low-level home fill-in WIDE1-1 digipeaters ONLY respond to WIDE1-1.

3)     True high-level WIDEn-Ns respond to all values of n and N 
including WIDE1-1.   It doesn't matter if your first hop hits a home 
digi or a wide digi -- any system within direct range of your 
transmitter will repeat the FIRST hop of your packet.

4)    The following HOP(s)  [i.e. any entry(s) in your path setting 
after the first one] will (or should) ONLY be processed by high-level 
WIDEn-N digis.  The assumption is that once your packet has been 
assisted by a nearby home station in reaching a high-level more distant 
WIDEn-N, that other WIDEn-Ns will be able to hear the first WIDEn-N.

5)     Since ANY digipeater can respond to the first hop, there is no 
obvious way, looking at the transmitted path on APRS.FI (or your own 
receiver), to tell what kind of digi processed the first hop.   The 
following hops (if any) will normally only be true wide-area WIDEn-N digis.

Note that the path list, as you transmitted it, will be re-transmitted 
at each hop.  The key is to note whether a given hop is marked as "USED" 
with an asterisk (*) next to it.  Depending on the sophistication and 
settings of each digipeater, you may also see "real" callsigns replacing 
(or in addition to) the generic WIDEn-N "callsigns".

For a full discussion of digipeater principles and path settings,see my 
web page at:

<http://wa8lmf.net/DigiPaths>



>
> So, I need to know how I can tell which type of digi is which (Wide 1 
> or 2), and then how I can see if I can hear that particular station 
> directly.  Or, am I going about this all wrong to try and understand 
> the network in my area?

Each digi beacons periodically.    By monitoring for a while, you should 
be able to tell which digis if any, you can hear.  The path of these 
incoming beacon packets should tell you whether you heard them directly, 
or via another digi. Of course, you must BE ABLE TO RECEIVE to determine 
this; i.e. dumb transmit-only trackers can't give you this information.


Each time your radio transmits, if you then see one incoming report with 
your own packet when your radio unkeys, you can tell that at least one 
digi re-transmitted your signal.   If a few moments later, you see a 
second retransmission of your own packet, you can tell that a second 
digi heard the first one and re-transmitted again on another hop.  Of 
course, if the second digi is too far away for you (on the ground) to 
hear directly, it may re-transmitting the first one (that you did hear), 
but you WON'T hear the second one yourself.


>
> Another thing, I Gates are nice, but I am a bit of an RF snob and it 
> is too bad a couple of the local stations are only I Gates that 
> receive.  As I drive through these areas, my radio hears nothing, but 
> my packets are making it to the internet only.

There is nothing you can do about this.    Other than crusade for more 
local APRS activity at your local radio club.......


------------------------------------------------------------------------

--

Stephen H. Smith    wa8lmf (at) aol.com
EchoLink Node:      WA8LMF  or 14400    [Think bottom of the 2M band]
Skype:        WA8LMF
Home Page:          http://wa8lmf.net

NEW!    Universal HF/VHF/UHF Antenna Mounting System
   http://wa8lmf.net/mobile/UniversalAntMountSystem.htm

"APRS 101"  Explanation of APRS Path Selection & Digipeating
   http://wa8lmf.net/DigiPaths

Updated "Rev H" APRS            http://wa8lmf.net/aprs
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