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Re: K3TZ patch



Hi Steve

A 76cms dish with the K3TZ feed should be excellent. The receive side that
you are proposing sounds right. It is a similar approach to the system I
used in the early 90s with AO-13, using a receiver on 10m for the tunable
IF. I take it that your dish is prime focus ? If it is an offset feed dish,
calculating the true f/D ratio is more involved and I would recommend the
HDL_ANT program from W1GHZ to do the hard work. I use the K3TZ patch feed
here and it works a treat. I have no scaler ring on my feed and it still
performs fine, the scalar ring may reduce noise pick up but its not a big
issue and you'll find the unadorned K3TZ is perfectly OK. With my feed I
used the original LNB mount and as such the positioning of my feed may be
a bit off. Have a play using the AO-40 beacon or a signal source, but you
can mount it with the focus on the active element and I am sure you'll not
be far from optimum.

With the amount of gain ahead of the receiver, your R2000 will be adequate.
I would expect that you'll need to reduce the gain otherwise the noise level
will give you a steady S9 signal. I would suggest that you put an attenuator
between the Drake converter and the 2m-10m converter.

Transmit is equally easy. Instead of spending money on an FT847 (excellent
radio for sure), you could try and find a second hand radio instead. Try
looking for a IC-471A, IC-475A, TS-811A, TR-851A, FT790R + PA, and I am
sure there are others. If you do decide to buy an FT-847 then you could
use that for your receive side on 2m while transmitting on 70cms, this
would save you the 2m-10m converter and having to build an attenuator.

You do not need a huge amount of power on the uplink, especially when the
squint is low.

Please don't wait until April. AO-40 is active now, and at times it is
excellent. With some of the shorter ranges, it is easier now to hear the
satellite and to get a signal into it because of the short ranges involved.
It is an ideal time to experiment with low power or non-optimum receivers
and you can be ready for when AO-40 gets back to 0/0.

Either way, you'll be most welcome when you appear on the satellite.

Good Luck

Jonathan  HB9DRD/G4KLX
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