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[TenTec] Pegasus/Jupiter keying - In search of Perfect CW :-)

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Subject: [TenTec] Pegasus/Jupiter keying - In search of Perfect CW :-)
From: WA3FIY@radioadv.com (WA3FIY)
Date: Sat, 2 Feb 2002 21:39:39 -0500
There are [or have been] several interesting threads running which 
seem to be slowly converging into a good discussion of keying 
characteristics of Pegasus/Jupiter [PJ's for short], Omni VI+, Icom 
756Pro and also some general comments regarding key clicks, etc.

The thing I find interesting about the latest round of discussions is 
that we are beginning to take the subjectivity out of the discussion 
and are looking at some numbers that describe what we are hearing.

So in that spirit, I decided to run some tests on my PJ's much like 
George, W5YR has been running on his Pro.  In short, the PJ's look 
pretty good.  Perfect?   No, but pretty good when held up in 
comparison to the rest of the pack.

The test set-up consisted of my Jupiter running in both native 
Jupiter mode and in Pegasus emulation mode.  The Jupiter was 
connected to a dummy load with a -20 db coupler to my triggered 
oscilloscope.  I operated the Jupiter with the internal keyer enabled 
and had a Radio Adventures Co. CodeBoy keyer connected to the PTT 
line on the accessory connector.  The 'scope was being triggered by 
the keyer output when I used the external keyer and by the RF 
envelope when operating the internal keyer.

I am not done with the tests but here is what I have found so far.

Sidetone - Sidetone output timing from the PJ's EXACTLY tracks the 
RF envelope, even to the point of having a smooth rise and fall time at 
make and break.   So, you don't really need to connect into the rf 
output to know what your keying waveshape looks like.  Just connect 
into the line out and monitor the sidetone to see what the keying 
timing is like.  AND, you do not need any off air monitor to hear what 
your signal is doing.  Just listen to the sidetone.

Rise and Fall times - The rise and fall times are 3mS on all but the 
first element in a transmission.  The first element has a 2 mS rise 
time on the first element and a 3 ms fall time.  This finding exactly 
duplicates the photos in the QST reviews as best I can tell from the 
pictures.  I was a little confused by this.  This is QSK.......why would 
the first element be different from any other?   And, what is 
considered a "first element"?  I think I have the answer which I will 
get into a little later.

Keying spike - Although difficult to see in the QST photos, the PJ's 
do have a VERY SMALL keying spike on the first element.  The first 
element has about a 2% voltage overshoot which is a 4% power 
overshoot!  The percentage of overshoot remains constant over the 
full power output range.  So at 10 watts out, the overshoot reaches 
10.4 watts and at 100 watts output, the overshoot hits 104 watts.   I 
cannot imagine this small amount causing any amplifier to trip or do 
anything else nasty.  Subsequent elements have a barely detectable 
overshoot which is so small I can't measure it with any accuracy.  I 
believe the overshoot and the faster rise time of the first element 
are related and I will get to that matter later as mentioned above.

Weighting - Here is where it gets a little complicated because of the 
flexibility of the Ten Tec and N4PY control software user 
programming and my ignorance.   I am not exactly clear how to set 
the user selectable weighting to "nominal" values, meaning values that 
would yield the 1:1 and 3:1 dit and dah to space ratios.  In fact, I got 
bogged down on these tests and moved on to testing with an external 
keyer.  Basically though, the Jupiter was shortening the dits a 
noticeable amount at very high speeds, speeds in the 60+ WPM range. 
 It also shortened the dits at slower speeds but, although 
measurable, I could not detect it by casual listening at speeds below 
30 WPM.   I need to learn more about the setup though before I can 
draw any meaningful conclusion other than, at the speed you usually 
operate, set the weighting to a value that sounds good in the sidetone 
and your signal will sound the same on the air.

External keyer - I confirmed something which may already be 
broadly known here, that is, you can key the PJ's nicely by keying 
the PTT line.  I connected my CodeBoy both the official Ten Tec way 
thru the key jack and the unofficial way thru the PTT line on the 
accessory connector, and all measurements were IDENTICAL!  That 
is a nice undocumented feature.   The CodeBoy has exactly 1:1 and 
3:1 dit and dah to space ratios in it's default mode and that is what I 
started testing with.  When keying the PJ's, I noted a couple things.  

First, the delay between key closure and RF [and sidetone] output is 
20mS at all speeds.  That can be seen in the QST photos.  [I just 
realized that I did not test for delay when operating split.....I'll do 
that and report later].  BTW, this has nothing to do with keyer 
weighting.  This 20mS is the time required to shift internal circuitry, 
most especially the PLL, from receive to transmit condition and is not 
user adjustable.

Secondly, the dit to space ratio drops below 1:1 by a greater degree 
as the speed increases, indicating that there are some uncompensated 
timing issues in the firmware of the PJ's.  However, the CodeBoy has 
a "space" trimmer pot which when properly adjusted yielded a 1:1 
ratio over the full speed range of the CodeBoy which is 10 to 40 
WPM.  In uncompensated form, the dah's became a little light at high 
speeds but after the space adjustment, the dah's were again at 3:1.  
At this point, using the CodeBoy, I have the recommended 1:1 and 3:1 
ratios over the full speed range of the CodeBoy [which BTW exceeds 
my speed range  :-)  ] and I have sidetone reflecting the transmitted 
code elements exactly and I have Ten Tec QSK about which I need 
say no more because it is hard to improve upon and I used too many 
ands in this sentence.    Sorry!       :-)

Now.............about the rise time and "spike" such as it is, on the first 
element.   First of all, what is a "first" element?   Since this is a full 
QSK rig are not all elements a "first" element?  NO, they are not!  
The first element is the element sent after the rig has been at rest 
for some period of time, maybe in the neighborhood of a second or 
two.  Ten Tec would know better than I what that time is.  It is the 
time in which the ALC circuit timing resets after sending elements.  I 
believe this explains the different rise time and the spike.   

IMHO, one of the outstanding features in several generations of Ten 
Tec rigs is the ALC stabilized output at ALL power levels.  This 
feature is present in the PJ's and I hope TT includes it in the new 
rigs coming.  BUT, there is one VERY MINOR drawback.......and that is 
the effect on the first element.  Let me repeat, the effect on the 
first element is measurable but NEGLIGIBLE!   It is a fly speck!  

Here is what I think is happening.  After resting, the ALC circuit is 
reset.  When the first key closure comes along, the transmitter is 
running "open loop" with respect to ALC stabilized power output.  TT 
has very nicely built in a controlled rise time in the open loop mode so 
key clicks are minimized.  As the power is rising, it eventually hits 
ALC threshold at which point the loop closes and stabilizes output 
power at the set level.  That transition from detection of ALC 
threshold to stabilized output takes a finite amount of time and it is 
during that time that the overshoot, the very small overshoot, occurs.  
Once the ALC loop is closed, the transmitter system gain is reduced 
by some apparently small amount and subsequent rise times are a 
little longer as a result of the reduced system gain.  This attention to 
small detail is not found on may rigs I have owned and that have been 
discussed here.   A tip of the hat to Ten Tec as a friend of mine 
would say.  Can this be improved on?   Sure.......at a cost.   Does it 
need to be improved on?   In my opinion, not at all!

The rise and fall times of 3mS seem to be a good compromise too.   
Short enough to create distinct elements to cut through QRN and 
QRM but long enough to minimize key clicks, hence being a good 

The PJ's are nice CW radios!

********REQUIRED DISCLOSURE************

I do not have a financial interest in Ten Tec except by virtue of 
being a customer of both ham radio gear and OEM enclosures for the 
CodeBoy and DigitalDial which my company Radio Adventures Co. 
manufactures.   Obviously I do have a financial interest in the 
CodeBoy, a nice little keyer.    :-)

**********PERSONAL NOTE*************

I commented early in this post about taking subjectivity out of our 
discussions of some of these matters.  I would like to qualify that 
statement somewhat.  Subjectivity is certainly important because it 
pretty much tells us what we like and don't like about our gear.  It 
really doesn't matter much what the numbers say if I don't like this 
thing!   If I don't like it......I don't like it.   Or.........If it like it, 
what about the numbers.   It is just that sometimes I think we go 
rambling on talking about our subjective likes and dislikes almost as 
though they were statistical, mathematical facts, when in fact, they 
are simply likes and dislikes.   So please understand that I know the 
importance of subjective opinion but also I know the importance of 
statistical fact.   Both have their place in our discussions and I hope 
more of us will take the time to dig through the rhetoric and find the 

This is a great group.   Keep up the lively discussions on all the 
important matters like the dots, etc.    :-)    Oh, my Pegasus is black 
and my Jupiter is red  and my .................................... oh well, not 
maybe another time.



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