[OZAPRS] 6M Radio

[Glen English VK1XX]

Hi Robert

my 2$ worth : a primer on 6m performance and what to expect. it is
certainly a curiosity and there is much to be learned from playing about
with it.

1) mobile performance on 6m is in the toilet, unless you work very hard
on your vehicle antenna. This is due to low height above ground
producing near antenna fresnel blockage, higher radiation angles and
higher ground losses. 
so you need power to overcome antenna efficiency -  100W.
But most HF/6m radios do 100W .

2) if comparing to 2m, 6m has only advantage in very hilly, and multiple
hilly terrain, many hills in the way. 

2.5) 6m also has a advantage with regard to heavy foliage forest
attenuation. (Less)

3) 6m has less picket fencing, and the short delay multipath (due to
nearby scatterers) is not as deep as the reflections are not as strong
or coherent.- advantage.

4) galactic noise (alone) is about 10dB more than at 2m. The only
'advantage' of this that sloppier systems will work 'cause they are not
as affected by coax losses and high recv noise figures.

5) 6m base station antennas need to be ~ 1.7x the height  of a 2m
antenna to get the same takeoff.  People make the mistake of NOT putting
the lowest frequency antenna at the top of the mast.

So, if the base stations are ideal, and there are multiple obstructions
in a path, 6m signals will be stronger than 2m on long , difficult paths
that are diffraction paths (not troposcatter) paths.  The signals are
stronger but the noise floor of 6m masks the signals, so you got to be
prepared to work at narrower bandwidths to take advantage of it. Once
the path becomes a troposcatter path, you might well be better off on 2m.

So, apart from the curiosity which is 6m FM, I think that 300 baud 6m
SSB HF packet would be a better utility, because it has a roughly 10dB
advantage on 1200 bps AFSK FM . maybe 13 dB depending on the demod...

Mobile footprints of 6m repeaters are generally much smaller than 2m
repeaters at same sites. This is due to alot of things but many of the
above.

Troposcatter is in the toilet, but ionscatter is of interest (900-1500km).

-glen



Having said all that,
On 18/11/2017 2:48 PM, Robert wrote:
> Hi All.
>
> Just thinking about playing around with 6M APRS.
>
> So my questions are.
>
> What is the freq that is used in Aust.
> What would be a good radio to use, or modify to use on 6m
> What TNC details/config is needed.
>
> Thanks in Advance.
>
> Robert
> VK2KGV
>
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