[aprssig] How About 40M APRS ?

Stephen H. Smith wa8lmf2 at aol.com
Wed May 28 12:37:04 CDT 2008

Dave Baxter wrote:
> Hi..
> FYI..   We have some limitations this side of the pond in regards to
> 30m.....
> ----------------------------------
> 10 MHz (30m) Neccesary UK Usage Bandwidth
> 10,100-10,140 kHz 200 Hz Telegraphy (CW)
> 10,116 kHz - QRP (low power) Centre of Activity
> 10.140-10.150 500 Hz Narrow band modes

Interesting.   Here in the U.S. any non-voice mode (CW or data) ONLY can 
be  used anywhere in the entire 10.100 to 10.150 band.  No SSB at all.  
By contrast with 60 meters where 5 spot channels are for USB voice only, 
with NO non-voice modes allowed at all.    [Frustrating because I would 
LOVE to use my "mobile SSTV LiveCAM" on 60M.]
I just discovered that our regs have been liberalized to allow SSTV 
(normally only allowed in the voice bands due to it's occupied bandwidth 
and the customary use of voice comments between pics) to now be used on 
the non-voice 30M as long as it's occupied bandwidth is 500 Hz or less.  
It turns out there is an ultra-narrowband version of analog SSTV 
(MP73-N) provided in the current verison of mmSSTV that is now legal to 
use on 30M , leading to mixed PSK31/SSTV QSOs.  The main calling freq 
for this is a suppressed carrier freq of 10.132  USB.  

I'm thinking of kludging up my Kenwood TS-50 which normally monitors the 
10.149.200/10.149.400 pair for HF APRS in North America 24/7 to scan 
10.132 SSTV as well.   [You can see the 30M HF APRS RX on my UIview 
webserver at:


Note that due to both my horribley noisy RX location in southern 
Californa and the currently horribly low state of the sunspot cycle, you 
may see nothing on the map for hours at a time.   Best times are during 
just before sunset and sunrise local (US Pacific Time).

> In regards to 40m, the recomendation is not to use "Digi Modes" above
> 7.100.   Have to say I didn't know that!...   Probably as we only have
> the top 100k as secondary users, subject to non-interferenct to other
> users, inside or outside the UK.

This agrees pretty well with 40M usage in North America. Upper half is 
voice, lower half is non-voice CW and data.  (The upper 150 KHz of 40 is 
almost totally unusable after dark in North America due to MASSIVE 
interference from mega-power shortwave broadcast signals that share the 
upper part of 40.)    PSK31 is very active at 7070 USB where it avoids 
the broadcast interference.


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

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