Joel Maslak jmaslak-aprs at antelope.net
Mon Oct 9 10:43:43 CDT 2006

On Oct 9, 2006, at 9:29 AM, Gregg Wonderly wrote:

> UHF does much better in structure penetration and requires a smaller
> antenna system for the same gain (not power).  9 db of gain can be
> realized with a stacked collinear about the same height as a 5/8s  
> wave mobile VHF antenna (which is 6b of gain).  In the end, if  
> antenna and gain is the problem, the answer is more antenna, or  
> better yet (for density diversification), more digis.  The "better"  
> coverage of VHF is, in fact, the bigger problem the current APRS  
> network has.

I'll add that there will be less chance of corrupted packets from  
noise at 9600, since the packet is on the air a shorter amount of  
time.  Remember, one bit of corruption in a packet results in a lost  

I'm planning a test in a month or so on this.  I'm going to set up a  
UHF station next to my VHF IGate, and compare coverage.  Of course  
it's not possible to have a 100% fair test - audio levels will surely  
be set differently, the VHF J-pole I use at home won't work for the  
UHF station so the antennas will be different, etc.  But it should  
give us a clue on whether or not the difference is significant.  One  
test disproves 1000 theories.

As for large coverage being the bigger problem that VHF has, speak  
for your region.  :)  Wyoming has some very high digis that cover  
tens of thousands of square miles - which are very handy for  
travelers and others.  Yet, there are relatively few collisions and  
such here, due to low density of users (even with the occasional  
Texas station using a WIDE7-7 path, which covers probably 250,000  
square miles around here).  It's not the coverage that's the problem,  
it's the number of users in the collision domain and the size of the  
aloha circle vs. digipeater location and user paths.

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