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Re: FT-847 CAT

At 06:33 AM 11/3/00 -0500, you wrote:
>Which FT-847 computer tuning program will work Split Frequency, Same Band
>with Doppler Correction that will be needed to work the ISS Alpha? 

Hi Guys,
I worked on this last weekend. Some bad news here.
The answer is that the FT-847 will NOT support this so NO 
programs can work this way. Here is the scoop:

We know that it will not work in satellite mode. While you
can set the vfo's the radio will not transmit, it will give
you an "Error" when you PTT.

So, how about FM repeater mode? The problem with this approach
is that the radio's smallest Tx tuning step in this mode is 10KHz.
This leads to a tuning error so large as to make it useless.

Let me show why this doesn't work. Let us say (for illustration)
that the downlink is 146.000 MHz and the uplink is 147.000 MHz.
Let us also say that the ISS is approaching with velocity such
that the Doppler shift on the downlink is +3KHz. Since the up and
downlinks are on the same band, the Doppler shift on the uplink
will also be about 3KHz.

So, we set the Rx vfo to 146.003 MHz. We want the transmitter to
be 147.000 MHz - 3KHz or 146.997 MHz. What do we set the repeater
offset to? If we use 1.00 MHz, the tx will be on 147.003 MHz which
is 6 KHz too high. If we use 0.99 MHz, the tx will be on 146.993 which
is 4 KHz too low. If we didn't do any Doppler correction at all,
the error would only be 3KHz!

The error of course depends on how close the Doppler shift happens to 
be to a multiple of 5 KHz with 2.5 KHz and 7.5 KHz being worse case.
All in all, this does not seem to be a useful tuning method.

So, how about split mode? No luck here either. When you set the
main VFO and the PTT is on, the radio does NOT update the transmit
frequency. There are no CAT commands to control VFO A vs. B either
so there is just no way to set the transmit frequency.

BOTTOM LINE: There is no way to control an FT-847 via
the CAT interface for ISS operation. If anyone thinks I got
something wrong here, please let me know. This is one of those
cases where I hope I missed something!

Now an editorial comment: Yaesu are you listening? The FT-100
handles this just fine (using InstantTune V1.07) why can't you
get the CAT interface right on the FT-847??????

Kenwood, read the above before you finish the TS-2000!


Tony AA2TX@amsat.org
North Andover, MA

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