[Top] [All Lists]

[TenTec] Re: TT vs 756PROII

To: <tentec@contesting.com>
Subject: [TenTec] Re: TT vs 756PROII
From: w5yr@att.net (George, W5YR)
Date: Fri, 01 Feb 2002 21:59:22 -0600
Tom Rauch wrote:
> > I monitor with a little 20 Mhz Gold Star dual-trace scope. I will have
> > to fire up the Tek 465B and fiddle with the synch setup until I can
> > single-sweep those first few dots and see what is happening.
> You probably already do this or something similar, but what I do is
> drive a NPN transistor with a signal generator. I tie the collector to
> the manual key input, and of course the emitter is grounded.
> That allows you to set the generator for a series of "dots", and look
> at the actual keying input. You can set the weight by setting the
> output level on the generator, and if the generator has a DC offset
> you can use it to get a wide range of weight. If not you can add
> your own external dc bias for offset from a small 1.5 volt battery or
> any other supply.
> The second channel goes to the RF output.
> This way you ALWAYS catch the first dot! This also allows you to
> see if the CW is truncated.

Neat setup, Tom - I'll have to try that . . . thanks.
> My IC-706 truncates ALL of the elements by the same amount of
> time when in QSK, and a 775DSP I had (for one day before
> returning it) truncated the leading edges on every element on QSK
> (it did about a dozen other nasty things also, including outputing
> about 300 watts on the leading edge of the first element and
> transmitting on two frequencies at one.
> Please tell me how the PROII behaves!

Well, I have only the PRO to speak about, but it is just about the same as
your 706!

I just got through running some scope checks and monitoring the output
signal on a 765 receiver. Found out a lot I hadn't known!

First, Rob, W8LX, is exactly right about the continuous and constant
element shortening at all speeds with QSK. My little scope is fairly well
calibrated and it shows a consistent 10 msec delay between the sidetone
starting on and the r-f envelope starting up. That is the case at all
speeds up to the spec'ed max of 80 wpm. Without QSK, the sidetone and
output are exactly in synch as you would expect. But with either full QSK
or semi-QSK, the delay is there, making the sidetone sound much different
in terms of keying characteristics from the actual output signal.

I checked the effects of rise and fall times, Tom, and ended up using the
max of 8 msec available for the PRO which is both rise and fall time. I
found that doing that made the dots "sound" heavier in the monitor receiver
and more nearly like the sidetone does with only 2 msec rise/fall times. As
it is now, the transmitted signal on the monitor receiver sounds quite good
to me and I will run with it as it is adjusted and see how it goes.

The really bad news is that the dot/space ratio is really off on my rig,
another thing that I had not noticed because the sidetone keying sounds
different from what is being transmitted. This is the area where the 8 msec
rise/fall time improved this effect, at least to the ear.

At "80 spm" the situation is worst with dots being 15 msec long and spaces
35 msec for a dot+space rate of 20/sec. That ratio is 2.33:1 (or 0.43:1
depending on how you look at it) instead of 1:1!  <:{

At this 80 wpm speed and no QSK, the dots were 2.6 msec long and the spaces
were 2.4 msec for a ratio of 1.08:1. I failed to check that at the lower
speed but I suspect that that ratio is fairly independent of keying speed.

At my usual 20-25 wpm speed, the dots are 45 msec and the spaces are 65
msec for a dot/space rate of 9.1/sec. That ratio is 1.44:1 or 0.69:1
instead of 1:1 . . . <:{

So, Rob, I have to agree that for properly weighted code with the PRO, I
need to drag out the CMOS III or use the memory keyer in the TRX Manager or
the MixW programs. I am pretty sure that they each have true weighting
controls, not just dot/dash ratio like the PRO. 

Tom, the PRO II manual talks only about dot/dash ratio adjustments just
like the PRO manual. What it amounts to is that dash length can be adjusted
from 2.8:1 relative to a dot or space up to 4.5:1. Since dot and space
lengths are different(!) who knows what those ratios mean!   <:}

So, I am somewhat red-faced over these findings, not because that is how
the PRO behaves, but that I had not picked up on it earlier. That is what
comes from NOT getting (ever) a bad keying report and relying upon the
sound of the keyed sidetone as a guide to what is going out over the air.
But, now that I have made the measurements and done the external receiver
monitoring, I am fairly happy with the keying of the rig, especially in my
20-30 wpm range. But, I do intend to look at the software keyers and see
how true weighting affects the sound and to get out the CMOS III and try to
learn all those key combinations again!   <:}

Thanks to you all for your comments, advice and suggestions!

72/73/oo, George W5YR - the Yellow Rose of Texas         
Fairview, TX 30 mi NE of Dallas in Collin county EM13qe   
Amateur Radio W5YR, in the 56th year and it just keeps getting better!
QRP-L 1373 NETXQRP 6 SOC 262 COG 8 FPQRP 404 TEN-X 11771
Icom IC-756PRO #02121  Kachina #91900556  IC-765 #02437

All outgoing email virus-checked by Norton Anti-Virus 2002

<Prev in Thread] Current Thread [Next in Thread>