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[aprssig] Is there a place for APRS on 6 Meters?

Stephen H. Smith wa8lmf2 at aol.com
Tue Jul 28 21:14:35 UTC 2009


--- A Six Meter Revival Is At Hand ----

--- Is There A Place For APRS In It? ---


With the shutdown of analog TV on June 12th, TV channel 2 RF has 
disappeared just about everywhere.   (ALL the TV stations indentifying 
themselves as "Channel 2" on digital in the major cities have "QSY"ed to 
UHF for their digital alter-ego.)  There are only 7 stations left 
physically on channel 2 in the entire country now!  All in smaller 
towns.  Here are the details copied from

     <http://rabbitears.info>


Actual
Digital        
RF        Display
Channel    Channel    Callsign-City-State


2    3    KVBC-DT LAS VEGAS NV

2    2     KNAZ-TV FLAGSTAFF AZ

2    2     WLBZ BANGOR ME

2    5     KREX-TV GRAND JUNCTION CO

2    3     KOTA-TV RAPID CITY SD

2    2     KNOP-TV NORTH PLATTE NE

2    2     KJWY JACKSON WY

What this means is that, for the first time since the early 1950s, 6 
meters is fully usable in nearly all areas of the US.  All the mutual 
interference issues to-and-from channel 2 TV are gone.    Even in these 
seven remaining areas, the steep-skirted emission mask for the digital 
signal should mean far less trash below 54 MHz. Not to mention that any 
"slop" from the digital signal will appear more like random white noise 
rather than discrete birdies, squeals and buzzes in ham receivers.

The S9+ noise level of sync hash and video buzz from the lower sideband 
of half-megawatt ERP signals on channel 2 that rendered 6M unusable here 
in southern California (and many other urban areas) has disappeared.


When KCBS 2 here in L.A. finally turned off their chan 2 analog 
"nightlight" station  on July 12th, the noise floor on 6 meters 
immediately dropped from S-9 plus to S-0 on my TS-690.   [ A 
"nightlight" was an analog station remaining on the air AFTER the JUNE 
12th digital transition, broadcasting exclusively an endless loop of 
information on the digital transition and how to install a digital 
converter box.]


I am predicting a renaissance  of activity on 6M, now that we can 
actually HEAR something.   


Is there a place for APRS here?   Should we (can we) stake out a 
national APRS channel on 6M? 


Obviously, all-in-one compact trackers will be hopelessly impractical on 
this band, due to the size of antennas and effective groundplanes.

On the other hand, I AM interested in the possibilities for APRS from 
mobiles on 6M.  Low VHF has far superior long-haul propagation 
characteristics in open county with far less of the rapid fluttering and 
chopping that mangles data on VHF and UHF at greater distances.  [There 
is a reason that Highway Patrols and State Police still use 39 MHz for 
rural operations...]  With the proliferation of all-mode "DC-to-light" 
100W mobile rigs like Icom 706s and Yaesu FT-857s (both of which have 
rear-panel mini-DIN "data" jacks), the potential for long-haul open-road 
APRS on 6M is there.

Not to mention the occasional DX excitement when the band opens. [If 
this solar ultra-minimum EVER ends....]

Years ago, before APRS, I did some packet data transmission experiments 
on 6 meters from a mobile running a Kenwood TM-742 with 50 watts out, 
here in Los Angeles.  I was absolutely astounded at how the 6M signal 
would propagate over and around hills, and through canyons and passes 
that stopped 2M dead in a mass of multipath phase distortion.   The only 
down side is that there is far more man-made electrical noise on 6M in 
built-up areas than on VHF.   [Low-band Motorola Micors had noise 
blankers, VHF and UHF didn't...]



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

--

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

JavAPRS Filter Port 14580 Guide
  http://wa8lmf.net/aprs/JAVaprsFilters.htm

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

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