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

To: <tentec@contesting.com>
Subject: [TenTec] Pegasus/Jupiter keying - In search of Perfect CW :-)
From: RMcGraw@Blomand.Net (Robert & Linda McGraw K4TAX)
Date: Sun, 03 Feb 2002 12:52:05 -0600

Very good presentation!  I'd like to see more high level, concise
presentations like this.  Even I could understand what was measured and what
was observed.


----- Original Message -----
From: "WA3FIY" <wa3fiy@radioadv.com>
To: <tentec@contesting.com>
Sent: Saturday, February 02, 2002 8:39 PM
Subject: [TenTec] Pegasus/Jupiter keying - In search of Perfect CW :-)

> 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
> 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
> neighbor.
> 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, so
> 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
> facts.
> 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 now.
> maybe another time.
> -73-
> -Lee-
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