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RE: AO-40 status report by DJ4ZC



> >Well, if there was a transmitter that I would prefer to fail 
> it would be the
> >70cm transmitter!  Mode U/V has long been considered the 
> "primary" mode of
> 
> Tell that to the Japanese, for whom severe terrestrial interference
> makes the 2m band nearly useless as a satellite downlink.  Or to those
> of us unfortunate enough to live near large power lines emitting
> significant noise power on the 2m band.

I think we're all in different situations.  Here in Australia, there's
considerable variation in preferences (I'm running a survey of the local
SO-35 users for this reason).  Some of the issues include:

Pager crud on 2 metres (making it unsuitable as a downlink in some areas)
Cable rubbish on some 70 cm freqs (same issue, but for 70)
Typical station configurations (especially on FM), which favours 2m as a
downlink.
Power line noise and other crud on 2m
Pirate stations on 2m uplinks

and the list goes on.

The main point is you're not going to satisfy everyone with one mode, so a
choice of modes is needed. 

> Naturally I would prefer that *everything* on P3D work, but given a
> choice between 2m and 70cm, 70cm is clearly far more important.

Not when you bring the HF bands into it, they're more likely to be paired
with 2m, which will open the bird up to some areas, such as the SW Pacific
islands, where 70cm in any form is rare to nonexistent, but a number of ops
have 2 metres. (the rest of us who have 70, many of us can make the jump to
microwave).  Again, horses for courses.  But not having 2m would certainly
curtail some serious DX opportunities.

I found that one out when canvassing for SO-35 contacts on HF.

> If you assume the use of simple, semi-omnidirectional ground antennas
> (e.g., patches) and take into account path loss and background noise
> levels, 70cm is clearly the optimum downlink frequency for an amateur

I'm yet to see that, I didn't get good results out of 70 until I went for a
beam.

> satellite. 2m is just too noisy and crowded. 13cm is far better, but
> it requires a ground antenna with at least some directionality.

Directionality isn't a problem with P3D, can use manually rotated antennas
(I'll be doing that with a portable stand on 13cm).  Just need to make
occasional adjustments as the bird moves slowly around the sky.

For me, I have to point on 70 anyway, so might as well go up the bands. :-)
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