[NLRS] 857D TESTS

[Dr. Gerald N. Johnson]

My FT-857D bought during the first time I came north to Aurora, probably
four years ago got tested this afternoon. Test set up is a partly
shielded dummy load, 12 feet of Belden 8213, a Tek 6106 probe on a Tek
475 scope. Scope is flat to 200 Mhz, 6 dB down at 400 Mhz. Rise time a
couple nanoseconds.

What I saw. Rf power menu set to 5 watts, on FM 146.25 MHz (didn't
kerchunk the Boone repeater from load leakage), nice gentle envelope
rise, no spike. Envelope rise time something between 10 and 15
milliseconds to 80% voltage. Switched to transverter on. Same pattern.
Tried CW in KOX mode. Same pattern. Same rise for each time the key
closes while in transmit mode. Tried whistling while operating PTT after
whistle start. Same pattern with speech envelope. No spike. RF power
menu entry has no effect and isn't adjustable while in transverter mode.

Now I will try to check out my backup 857D that is older. Has the DSP
factory option but not the 60 meter band channels. Its also had the
computer settings misaligned by being super master reset. DON'T EVER DO
THAT!

The older unaligned 857 has spikes. On CW its putting 6.3 watts to the
load key down (if all is properly calibrated), a spike of 11 watts on
the first key closure (KOX), and a spike of 9.2 watts each following
closure. That spike goes nearly to zero, then there's the proper CW
sloped rise. Not a happy camper. On FM there's a 16.3 watt spike before
the envelope settles at 6.3 watts. On SSB the spike is there when
whistling before closing the PTT, but that spike isn't as big as the CW
spike.

Next I need to go give the unaligned 857 alignment values from my other
857 and a sample printed out from another 857. That might change the
keying, or it might be that there was a circuit change before my latest
857D was made to make it more easy on transverters. I have to fix that
or change my choice of rigs for 10 GHz quickly!

Right now before further settings for the computer, I'd say the 857 with
DSP and without 60meter memories has spikes, the later 857D with 60
meters doesn't have spikes. I've not seen any admission of circuit
changes in the Technical Supplement (Yaesu shop manual) for age so right
now I have no way to know what's been changed. I'll have to cobble a
test circuit for the TX inhibit and check both rigs and right now I
expect different results. Soldering wires to minidin plugs isn't my idea
of fun these days. I hope the Apple serial printer cable doesn't short
any pins together.

Likely in the later radio there's capacitance added to the TX enable
line that makes it rise slowly, either a larger capacitor or an added
capacitor. That's probably the safest place to attack it. In the
Technical Supplement, thats the line that's pulled down by the
transistor driven from the TX inhibit connection.

73, Jerry, K0CQ