David,
At 12:43 AM 5/25/2016, David Anderson wrote:
When I was active on the linear transponders of AO6 through to AO13
I never used a satellite duplex radio, always separates. We had much
better satellites then, in decent orbits like AO-10. So Yaesu in
particular brought out lovely expensive duplex radios. Great!
However then the linear sats gradually died and were replaced by
digital radio sats. Some FM one channel toy sats, but nothing like
the old wide linear transponders.
The FT-736R and other dual-band multi-mode duplex radios were
produced for the early Heo linear transponder sats - true. And the
market for expensive big box radios faded with only single channel FM
Leo sats. Understandable that mfrs would go where the market is
largest. Kenwood and Icom still market such a radio; Yaesu
stopped. But they didn't drop out of the multi-mode VHF radio
market...just a duplex model.
Only recently with FunCube and the Chinese Sats have we started to
get linear voice transponders back, but again in low fast moving orbits.
Many are now making use of SDR dongles or other SDR receivers as
their receiver for sats, because they have many advantages over the
old way of just being able to listen to your own receive channel.
With an SDR and panoramic can see all of the passband of the
transponder or transponders on multiple satellites at once. You can
point and click on a signal of interest. Record the whole pass and
play it back and see who you missed in the very short pass. You
can run the SDR on a tablet computer in the field, and have more
capability than your old FT-736R of olden days.
And my proposal was not for such? Clearly I stated it should be a
direct frequency SDR, but married with a transmitter which the
funcubes aren't. I mentioned a panadapter and IQ interface to
computer to support modern sw.
In short, until we have high orbit transponders on VHF UHF like
AO-10/13 no manufacturer is going to produce an FT-736R replacement.
I bought an old FT-736R for more reasons than for satellite. But
that should not be confused with my proposal for a KX3-like duplex
radio. Certainly one would not compare the KX3 with a
FT-840. Totally a different product. Totally new tech.
Any plans for a geostationary satellite would not use VHF UHF, but
microwave to get the bandwidth required for a third of the world
trying to access it at one time all the time.
Yes, that is true. That will involve a new mw radio designed for the
digital modes to be used. Amsat is cognizant of the fact that hams
will not be easily do this as was done for AO-40 s-band using surplus
stuff. The VHF radio + transverter will not suffice. The concept
under consideration includes SDR tech.
Things have moved on, a single duplex box isn't what is needed. A
transmitter CAT coupled to an SDR panoramic receiver is much better.
Point on the screen on the signal you see and with Doppler corrected
software set the transmitter you have via CAT to the uplink
frequency. It is also magnitudes cheaper.
Is that not what I talked about? The KX3 is a SDR though limited to
HF/6m + 2m transverter. Perhaps a wide-range SDR would be better but
you still need a comparable transmitter which can operate in
duplex. At present this still is a bunch of boxes wired together
requiring a lot of engineering by the individual vs a complete package.
And such equipment should have more than a single application like
satellite but instead offer a wide range of VHF+ operational activity
- so one could buy just one box for doing all. But you are correct
that the concept should incorporate newest SDR technology with ample
use of computing power. I believe I mentioned all those requirements.
Maybe one can build a wide-range SDR based radio without need for
transverters. A SDR that tunes 50-4000 MHz but with comparable
transmit capability. I'm not sure that one can do direct freq SDR
that far with existing tech. One thing to guard against is thinking
SDR means only a receiver (which current funcube are).
It may be that we are too soon to accomplish that? The first guy to
do it will have the market.
73, Ed - KL7UW
http://www.kl7uw.com
"Kits made by KL7UW"
Dubus Mag business:
[email protected]
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