[aprssig] aprssig Digest, Vol 53, Issue 25

Patrick winston at winston1.net
Thu Nov 27 23:35:21 EST 2008

Tony are you part of the york region club?  In either case, if you're 
free on Tuesday you should stop by our meeting...  there's actually a 
few people who are of like mind about the poor state of 144.39 within 
the region...  Perhaps if we arranged a sit down we could come up with a 
way to deal with the QRM and make it actually useful to mobile stations..


Tony Komljanec wrote:
> My opinion... Until APRS progresses beyond simple ALOHA, it will not 
> be reliable and without *RELIABILITY* it is a "flash in the pan".  I'm 
> all for slotted, Self Organized (like AIS) or other channel access 
> control methods.   In the mean time.....  
> What is knocking my enthusiasm out of me are the folks who put 6 fixed 
> WX stations in an area each transmitting once per minute on 144.390, 
> combined with long paths with "Ed at home" every few 
> minutes. Overpowered digi's don't help either as when they transmit, 
> every other igate and digi for 50 miles goes deaf.   QRM is very high 
> with FIXED-FIXED traffic while the MOBILE-FIXED gets 
> squashed.  Reliability for mobile message delivery is poor. 
> My area is covered by a couple well placed iGates (and many, many 
> digi's) so even a path of LOCAL or Wide1-1 will get into APRS-IS when 
> the channel is quiet enough.   What can I do within my control (new 
> iGates and digi's) to improve APRS in my area without feeling that all 
> is for naught? 
> Can a bi-directional iGate that is NOT a digi help move traffic to or 
> from the internet if that is what people want for their mobiles, WX 
> stations and telemetry. 
> When is a digi simply adding to the QRM? 
> In my W1 area I hear a lot of traffic that is targeted for APRS-IS 
> being rebroadcasting through high digi's 2 or more hops.  My own 
> underlay (fill-in) iGate contributes message delivery to APRS-IS 
> perhaps 10% of the time (packets which would have otherwise been lost) 
> of what it hears.  The other 90% of the time other wide area (high) 
> iGates successfully hear and move the traffic to APRS-IS before my 
> iGate does (my iGate delivery becomes duplicate an is tossed by IS).  
> If I turn on my iGate's digipeater functions (W1-1), I'm effectively 
> adding redundant packets to the frequency 90% of the time to the 
> detriment of the channel loading.  In the area, W1 is successful when 
> not being killed by fixed station QRM.  For this reason I've tried 
> turning the digi function off. 
> We already have "path correction" to downsize the number of hops.  
> Perhaps an intelligent iGate or digi could ignore packets passing 
> from user selected iGates or wide coverage digi's assuming that the 
> packed is already successfully in APRS_IS?  A fill-in digi with 
> "polite" channel access dumps packets that are repeated by a wide-area 
> digi?  Since position is usually sent by APRS mobiles, the smart digi 
> or iGate could remain fully engaged with close in mobiles (example: # 
> filter m/15)?  This sort of autonomous decision making could reduce 
> the "polution".  Alas, I'm not a programmer, just a very capable RF guy. 
> What can I do within my control to improve APRS in my area without 
> feeling that the effort to improve reliability is futile? 
> Tony K
> ------------------------------
> Date: Wed, 26 Nov 2008 21:38:23 -0500 (EST)
> From: "Bob Bruninga " <bruninga at usna.edu <mailto:bruninga at usna.edu>>
> The dumb-tracker-to-internet .... was just a flash in the pan.
> We have got to overcome this mentality and get back to APRS as a 
> RECEIVE and local RF distribution system where we PUSH information of 
> immediate value to the MOBILE operator.  Then it becomes something 
> that he remains interested in and wants more.
> NOthing wrong with alternate inputs (either 144.99 or UHF) to give 
> locals un-congested INPUT priority, but the output should always be on 
> 144.39 from the high digi (which can hear everything so that it 
> avoides collisios).  In fact such local alternate inputs are 
> receommended, but NOT just to go to an IGate, but to go to RF on 
> 144.39 which is where the intended USER (receiver) is.
> Bob, WB4APR
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