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Re: Anyone FT-847 ....

on 2/21/00 3:26 PM, Christopher Cox at cobox@urec.net wrote:

> Sorry to interrupt, but it would appear you guys somehow are holding the
> prints to this radio.

This info is in the schematics and block diagram that come with the radio.
If you read them you'll see.

> Are you saying the only difference between the 1200baud and 9600baud packet
> connections is the audio I/O level?
> Are these connections FM only?
> What does the audio I/O from the 'DATA IN/OUT' 1/8" jack tie to?

OK, The Data IN/OUT jack on the rear is a AFSK connection for HF packet and
RTTY.  This is explained in the manual.

On the FM side of things, you have the 6 pin mini DIN connector that is used
for BOTH 9600 and 1200 baud packet.  Here is the explanation of the pins:

Pin 1: Data In - This is for BOTH 1200 baud and 9600 baud data.
Pin 2: Ground
Pin 3: PTT
Pin 4: RX Data - 9600 baud
Pin 5: RX Data - 1200 baud
Pin 6: Squlech

OK, when you select the 9600 or 1200 baud rate from menu 23, what happens is
that the TX data side (pin 1) is switched.  The 9600 baud data goes through
Q1041 which is a switch and Q1040 which is an amplifier.  Then it goes to
Q1081 which is another switch.  From there it goes to the mic amp and then
directly to the modulator input of the VCO (the varactor diode).

The 1200 baud data goes directly to Q1081.

This is seen on the block diagram at the bottom and it is just right about
where the vertical fold is.

The only difference between the 1200 baud and 9600 baud selections on TXD is
really Q1040, the amplifier.  And you can successfully run 9600 baud data
through at the 1200 baud switch setting.  I've done it.

On the RX side, the incoming data is split at Q1083-1

The 9600 baud data goes directly to Q1083-2 (another buffer amp) and then
out the back of the radio.

The 1200 baud data goes through all the De-emphasis and audio high pass
filtering, etc.  It finally ends up going out the radio at Q1102-2.

You can find Q1083-1 along the crease in the center of the page just up a
few inches from the input circuitry mentioned above.

So regardless of your switch settings on menu 23, data is sent to BOTH pins
4 and 5 regardless of whether it is 1200 baud data or 9600 baud data.  This
is why you can set the radio at 1200 baud on menu 23 and successfully send
and receive 9600 baud.

The audio levels in the input certainly are different.  Page 17 of the
manual gives the specs:

For 9600 baud the level is 2.0 V p-p and at 1200 it is 40 mV p-p.
On the output 9600 baud is 500 mV p-p and 1200 is 300 mV p-p.

Now, given that 9600 is a much greater signal level than 1200 I have no idea
of why you need the extra buffer amp in place at the 9600 baud input side.
You'd think that would make the signal going to the mic amp even stronger.
I have no idea.  Perhaps the amplifier's purpose is more for impedance
matching than signal gain.  I've not really traced the schematic fully in
order to understand it.
> I have been trying to figure out how to connect my DSP-2232, SSTV, and
> PSK31 to and am a little confused as to what port offers what.

SSTV and PSK31 would go to the AFSK port in the back.  The DSP-2232 would go
to the AFSK port for HF stuff and the mini-Din for VHF stuff.



Jon Ogden



"A life lived in fear is a life half lived."

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