[OZAPRS] 6M Radio

[Marcus B]

Glen,

This is a great explanation comparing 6m to 2m, no matter how much I looked
with the help of Google I couldn't find a good comparison of the two (as
well as 10, 70 & 23). And I suppose the affects are amplified in either
direction from those bands.

It makes a lot more sense now why 2m is most often the go to utility band.
I was always confused as to why 6m wasn't used a lot more in Australia.

Marcus.

On Sat., 18 Nov. 2017, 15:18 Glen English VK1XX, <
glenlist at pacificmedia.com.au> wrote:

> 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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>
>
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