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K3 TX delay

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Edward R Cole

K3 TX delay

Sort of following this thread as I use a sequencer+inhibit on VHF+
(with transverters and following amplifiers). With my sequencer
delaying K3 RF for about 300ms there is no issue. QSK not used on CW
(of course). My QRO coax relays would not like

But I am finishing my 300w HF amplifier kit and will be using a dc
open-frame relay for TR switching of RF. I guess I can time it using
my dual trace scope and set K3 TX DLY accordingly (amp will be keyed
with KEYOUT). I do not use CW very much on HF so QSK with 300w is
not necessary (or probably possible). I can always run the K3/10 in
QRP-QSK, of course.

There is one thing I do not see being addressed in this
discussion. Maybe more important than clipping of CW characters is
avoiding QRO "Hot Switching" of RF. Calculate the RF voltage for
several thousand ohms impedance (open circuit) that will result if
the amp is pumping out "globs" of RF before being connected to a good
load. The relay contacts will definitely get burned big time. And
maybe your output devices will have a short live-span.

73, Ed - KL7UW, WD2XSH/45
======================================
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EME: 50-1.1kw?, 144-1.4kw, 432-QRT, 1296-?, 3400-?
DUBUS Magazine USA Rep [hidden email]
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======================================
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Igor Sokolov-2

Re: K3 TX delay

> But I am finishing my 300w HF amplifier kit and will be using a dc
> open-frame relay for TR switching of RF. I guess I can time it using
> my dual trace scope and set K3 TX DLY accordingly (amp will be keyed
> with KEYOUT). I do not use CW very much on HF so QSK with 300w is
> not necessary (or probably possible).

Even if you use PTT CW and set TX delay for 20 ms you will get choppy CW

> There is one thing I do not see being addressed in this
> discussion. Maybe more important than clipping of CW characters is
> avoiding QRO "Hot Switching" of RF. Calculate the RF voltage for
> several thousand ohms impedance (open circuit) that will result if
> the amp is pumping out "globs" of RF before being connected to a good
> load. The relay contacts will definitely get burned big time. And
> maybe your output devices will have a short live-span.
>
>
> 73, Ed - KL7UW, WD2XSH/45

The entire topic stems from the fact that I wanted to avoid hot switching of
the external relays (linear amp, stack switching etc). To acheave that I
have tried to increase TX delay and got choppy CW. So without external
sequencer there is a choise between the two - 'hot switching' or 'choppy
cw'.

73. Igor UA9CDC

> ======================================
> BP40IQ 500 KHz - 10-GHz www.kl7uw.com
> EME: 50-1.1kw?, 144-1.4kw, 432-QRT, 1296-?, 3400-?
> DUBUS Magazine USA Rep [hidden email]
> "Kits made by KL7UW" http://www.kl7uw.com/kits.htm
> ======================================
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Don Wilhelm-4

Re: K3 TX delay

I fail to understand why anyone who is using PTT switching would want to
set the TX DLY parameter to greater than the default of 8 ms. Use PTT
and a footswitch if you are using a slow amp relay.

If your amplifier uses a slow relay, then you really cannot use QSK, so
just use PTT and a footpedal instead - things will work out much
better. There are QSK mods available for amplifiers that use slow
relays. Some mods are relatively inexpensive (the owner does the work),
while other can cost upwards of $400 (purchase a commercial version).

73,
Don W3FPR

On 2/16/2012 11:05 PM, Igor Sokolov wrote:

>> But I am finishing my 300w HF amplifier kit and will be using a dc
>> open-frame relay for TR switching of RF. I guess I can time it using
>> my dual trace scope and set K3 TX DLY accordingly (amp will be keyed
>> with KEYOUT). I do not use CW very much on HF so QSK with 300w is
>> not necessary (or probably possible).
> Even if you use PTT CW and set TX delay for 20 ms you will get choppy CW
>
>> There is one thing I do not see being addressed in this
>> discussion. Maybe more important than clipping of CW characters is
>> avoiding QRO "Hot Switching" of RF. Calculate the RF voltage for
>> several thousand ohms impedance (open circuit) that will result if
>> the amp is pumping out "globs" of RF before being connected to a good
>> load. The relay contacts will definitely get burned big time. And
>> maybe your output devices will have a short live-span.
>>
>>
>> 73, Ed - KL7UW, WD2XSH/45
> The entire topic stems from the fact that I wanted to avoid hot switching of
> the external relays (linear amp, stack switching etc). To acheave that I
> have tried to increase TX delay and got choppy CW. So without external
> sequencer there is a choise between the two - 'hot switching' or 'choppy
> cw'.
>
> 73. Igor UA9CDC
>
>
>> ======================================
>> BP40IQ 500 KHz - 10-GHz www.kl7uw.com
>> EME: 50-1.1kw?, 144-1.4kw, 432-QRT, 1296-?, 3400-?
>> DUBUS Magazine USA Rep [hidden email]
>> "Kits made by KL7UW" http://www.kl7uw.com/kits.htm
>> ======================================
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
> ______________________________________________________________
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Igor Sokolov-2

Re: K3 TX delay

Don,
I will try to explain.
Forget about QSK all together.
Apart from linear amp, there are other external relays like stack control
relays, T/R relays when you want to use different antennas for TX/RX etc.
PTT signal can either be controlled by the logger (CW, VOICE Keyer, DIGI
modes) or by PTT footswitch. In both cases PTT signal goes into PTT IN of
K3.
About 6ms later you get sort of PTT OUT on the KEY OUT connector. This KEY
OUT signal controls linear, T/R antenna relays, stack relays etc. Then 8ms
later you get RF out of the K3. These 8ms is not enough for all the external
relays to settle.
PTT delay of 20 ms should be more or less OK (although I would not mind it
to be extended to 30ms) but then CW generated by a logger gets choppy.
I can overcome the problem of non adjustable TX delay of K3 by configuring
my logger to start sending say 30 ms after PTT was asserted. I can even
connect PTT footswitch to the computer, but that will only work for CW
sending from the keyboard, computer voice keyer and digi signals generated
by the computer. If I send from the K3 internal keyer or use k3 mike I am in
danger to hot switch some of the external relays.
Therefore instead of being able to extend TX delay inside K3 I will probably
have to build some sort of circit which will take low level from KEY OUT and
form some sort of positive or negative impulse of a required length (say 30
ms) to apply to INH input of K3. I was hoping to build it inside the DB-15
cabinet since KEY OUT and INH pins are available on the ACC connector. But
there is no any 12 v or 5v pins available on that connector. So it makes
life more complicated.
If you can suggest different approach. which does not involve building
external sequencer, I would really appreciate it.

73, Igor UA9CDC

>I fail to understand why anyone who is using PTT switching would want to
>set the TX DLY parameter to greater than the default of 8 ms. Use PTT and
>a footswitch if you are using a slow amp relay.
>
> If your amplifier uses a slow relay, then you really cannot use QSK, so
> just use PTT and a footpedal instead - things will work out much better.
> There are QSK mods available for amplifiers that use slow relays. Some
> mods are relatively inexpensive (the owner does the work), while other can
> cost upwards of $400 (purchase a commercial version).
>
> 73,
> Don W3FPR
>
> On 2/16/2012 11:05 PM, Igor Sokolov wrote:
>>> But I am finishing my 300w HF amplifier kit and will be using a dc
>>> open-frame relay for TR switching of RF. I guess I can time it using
>>> my dual trace scope and set K3 TX DLY accordingly (amp will be keyed
>>> with KEYOUT). I do not use CW very much on HF so QSK with 300w is
>>> not necessary (or probably possible).
>> Even if you use PTT CW and set TX delay for 20 ms you will get choppy CW
>>
>>> There is one thing I do not see being addressed in this
>>> discussion. Maybe more important than clipping of CW characters is
>>> avoiding QRO "Hot Switching" of RF. Calculate the RF voltage for
>>> several thousand ohms impedance (open circuit) that will result if
>>> the amp is pumping out "globs" of RF before being connected to a good
>>> load. The relay contacts will definitely get burned big time. And
>>> maybe your output devices will have a short live-span.
>>>
>>>
>>> 73, Ed - KL7UW, WD2XSH/45
>> The entire topic stems from the fact that I wanted to avoid hot switching
>> of
>> the external relays (linear amp, stack switching etc). To acheave that I
>> have tried to increase TX delay and got choppy CW. So without external
>> sequencer there is a choise between the two - 'hot switching' or 'choppy
>> cw'.
>>
>> 73. Igor UA9CDC
>>
>>
>>> ======================================
>>> BP40IQ 500 KHz - 10-GHz www.kl7uw.com
>>> EME: 50-1.1kw?, 144-1.4kw, 432-QRT, 1296-?, 3400-?
>>> DUBUS Magazine USA Rep [hidden email]
>>> "Kits made by KL7UW" http://www.kl7uw.com/kits.htm
>>> ======================================
>>> ______________________________________________________________
>>> Elecraft mailing list
>>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>>> Help: http://mailman.qth.net/mmfaq.htm
>>> Post: mailto:[hidden email]
>>>
>>> This list hosted by: http://www.qsl.net
>>> Please help support this email list: http://www.qsl.net/donate.html
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>>

Don Wilhelm-4

Re: K3 TX delay

Igor,

I understand your situation, but the application of PTT does not produce
any RF - nothing will hot switch.
When you "hit the key" (or for SSB begin talking), then RF is produced.
If you arrange your switching to be accomplished by either the PTT or
the K3 KEYOUT, and leave the K3 in non-VOX state, there is no need to
increase TX DLY to any other than the 8 ms default value and therefore
no shortening of CW elements.

73,
Don W3FPR

On 2/17/2012 6:52 AM, Igor Sokolov wrote:

> Don,
> I will try to explain.
> Forget about QSK all together.
> Apart from linear amp, there are other external relays like stack control
> relays, T/R relays when you want to use different antennas for TX/RX etc.
> PTT signal can either be controlled by the logger (CW, VOICE Keyer, DIGI
> modes) or by PTT footswitch. In both cases PTT signal goes into PTT IN of
> K3.
> About 6ms later you get sort of PTT OUT on the KEY OUT connector. This KEY
> OUT signal controls linear, T/R antenna relays, stack relays etc. Then 8ms
> later you get RF out of the K3. These 8ms is not enough for all the external
> relays to settle.
> PTT delay of 20 ms should be more or less OK (although I would not mind it
> to be extended to 30ms) but then CW generated by a logger gets choppy.
> I can overcome the problem of non adjustable TX delay of K3 by configuring
> my logger to start sending say 30 ms after PTT was asserted. I can even
> connect PTT footswitch to the computer, but that will only work for CW
> sending from the keyboard, computer voice keyer and digi signals generated
> by the computer. If I send from the K3 internal keyer or use k3 mike I am in
> danger to hot switch some of the external relays.
> Therefore instead of being able to extend TX delay inside K3 I will probably
> have to build some sort of circit which will take low level from KEY OUT and
> form some sort of positive or negative impulse of a required length (say 30
> ms) to apply to INH input of K3. I was hoping to build it inside the DB-15
> cabinet since KEY OUT and INH pins are available on the ACC connector. But
> there is no any 12 v or 5v pins available on that connector. So it makes
> life more complicated.
> If you can suggest different approach. which does not involve building
> external sequencer, I would really appreciate it.
>
> 73, Igor UA9CDC
>
>
>> I fail to understand why anyone who is using PTT switching would want to
>> set the TX DLY parameter to greater than the default of 8 ms. Use PTT and
>> a footswitch if you are using a slow amp relay.
>>
>> If your amplifier uses a slow relay, then you really cannot use QSK, so
>> just use PTT and a footpedal instead - things will work out much better.
>> There are QSK mods available for amplifiers that use slow relays. Some
>> mods are relatively inexpensive (the owner does the work), while other can
>> cost upwards of $400 (purchase a commercial version).
>>
>> 73,
>> Don W3FPR
>>
>> On 2/16/2012 11:05 PM, Igor Sokolov wrote:
>>>> But I am finishing my 300w HF amplifier kit and will be using a dc
>>>> open-frame relay for TR switching of RF. I guess I can time it using
>>>> my dual trace scope and set K3 TX DLY accordingly (amp will be keyed
>>>> with KEYOUT). I do not use CW very much on HF so QSK with 300w is
>>>> not necessary (or probably possible).
>>> Even if you use PTT CW and set TX delay for 20 ms you will get choppy CW
>>>
>>>> There is one thing I do not see being addressed in this
>>>> discussion. Maybe more important than clipping of CW characters is
>>>> avoiding QRO "Hot Switching" of RF. Calculate the RF voltage for
>>>> several thousand ohms impedance (open circuit) that will result if
>>>> the amp is pumping out "globs" of RF before being connected to a good
>>>> load. The relay contacts will definitely get burned big time. And
>>>> maybe your output devices will have a short live-span.
>>>>
>>>>
>>>> 73, Ed - KL7UW, WD2XSH/45
>>> The entire topic stems from the fact that I wanted to avoid hot switching
>>> of
>>> the external relays (linear amp, stack switching etc). To acheave that I
>>> have tried to increase TX delay and got choppy CW. So without external
>>> sequencer there is a choise between the two - 'hot switching' or 'choppy
>>> cw'.
>>>
>>> 73. Igor UA9CDC
>>>
>>>
>>>> ======================================
>>>> BP40IQ 500 KHz - 10-GHz www.kl7uw.com
>>>> EME: 50-1.1kw?, 144-1.4kw, 432-QRT, 1296-?, 3400-?
>>>> DUBUS Magazine USA Rep [hidden email]
>>>> "Kits made by KL7UW" http://www.kl7uw.com/kits.htm
>>>> ======================================
>>>> ______________________________________________________________
>>>> Elecraft mailing list
>>>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>>>> Help: http://mailman.qth.net/mmfaq.htm
>>>> Post: mailto:[hidden email]
>>>>
>>>> This list hosted by: http://www.qsl.net
>>>> Please help support this email list: http://www.qsl.net/donate.html
>>> ______________________________________________________________
>>> Elecraft mailing list
>>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>>> Help: http://mailman.qth.net/mmfaq.htm
>>> Post: mailto:[hidden email]
>>>
>>> This list hosted by: http://www.qsl.net
>>> Please help support this email list: http://www.qsl.net/donate.html
>>>
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Nick Kennedy

Re: K3 TX delay

In reply to this post by Igor Sokolov-2

I use semi-break-in with my AL-811 amplifier.

TX delay set to 8 ms. Key Out line to amplifier. No separate PTT switch
- T/R control by paddle only. Semi-break-in delay set to 0.5.

I do not get choppy CW.

73-

Nick, WA5BDU

On 2/16/2012 10:05 PM, Igor Sokolov wrote:
>> But I am finishing my 300w HF amplifier kit and will be using a dc
>> open-frame relay for TR switching of RF. I guess I can time it using
>> my dual trace scope and set K3 TX DLY accordingly (amp will be keyed
>> with KEYOUT). I do not use CW very much on HF so QSK with 300w is
>> not necessary (or probably possible).
> Even if you use PTT CW and set TX delay for 20 ms you will get choppy CW
>
>

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W2RU - Bud Hippisley

Re: K3 TX delay

In reply to this post by Don Wilhelm-4

One thing I haven't seen mentioned in this discussion is the sending speed at which the benefits of QSK "disappear" in the K3.

Speed in words per minute (wpm) is very roughly equal to the number of dashes in a 5-second interval. Thus, at 25 wpm, there are 25 dashes in 5 seconds, or 5 dashes per second. But a dash consists of 4 "periods": three consecutive "mark" periods, followed by a single "space" period. So...in one second there are 5 x 4, or 20 such periods in 25 wpm CW, and therefore a single period is theoretically 50 milliseconds (ms) long. Of course, if keying "weight" is set above 50% (or 1.0-to-1.0 mark / space ratio for dots), the key-up period is LESS than 50 ms. A similar calculation at, say, 35 wpm, gives us a key-up (or "space") period of about 35 ms.

But to avoid generating excessive clicks, the leading and trailing edges of RF output during each mark element ramp up or down gradually, with the total interval at either end of the element having been measured at 4 ms (onset of RF output to 100%) in one specific "clickless" K3. If we assume we have adjusted the weight using the 50% RF output level as the reference (an assumption that is, itself, worthy of a completely separate posting), there's another 4 ms (1/2 x 2 x 4) that we have to subtract from each space period.

Of course, for QSK to truly be QSK, we have to be able to hear receiver audio output for at least part of the "space" period between two consecutive "mark" elements (either dot or dash). The minimum K3 TX Delay that can be set via the CONFIG menu is 8 ms. It's my understanding that at least part of that delay is for "covering" the time it takes all the various synthesizer and DSP circuits in the K3 to switch from RX to TX, especially since the RX and TX frequencies can be different when in QSK mode. It's also my understanding that there's a similar delay at the END of a transmitted element, when all the circuits have to return to their RX states. Because frequencies and other circuit parameters are actively changing during those two periods, it's unlikely that useful RX audio is available at any time during either 8 ms interval.

Clearly, then, there is a MINIMUM total interval of (2 x 8) + 4, or 20, ms when no received signals can be heard by the K3 user between mark elements. In fact, even at the 8-ms setting, it's very possible that MORE than 16 ms of each space period is "blanked". I say that because a number of us have found that to get proper weight from the K3 in QSK mode, we have to artificially adjust the length of its "mark" periods (with, for instance, the "Compensation" parameter of a WinKey or other suitable outboard keyer) by adding 6 or 7 ms to each key-down interval. (Note that this a fixed interval for a given K3 regardless of sending speed, and is not "weight" in the conventional sense. Good keyers, like the WinKey, allow weight, ratio, compensation, and other parameters to be independently adjusted.

So now, with the K3 CONFIG menu set to 8 ms (its minimum value), we have 20 + 7, or 27, ms of each "space" when the receiver is blanked. Interestingly, that's just about the length of an entire space at 35 wpm! So, for all practical purposes, QSK is simply not possible with a K3 at CW speeds above 35 wpm. Below that speed, the ability of QSK to help you detect the presence of the other station is statistical, depending on whether enough of the character elements sent by the other operator happen to coincide with some part of the narrow usable window within your own transmitted "space" intervals to cause you to conclude he's really sending again.

But it gets even worse: That same K3 above was measured as having 15 ms total delay from initial closure of its KEY OUT line to the start of RF output when using the "new" QSK mode with TX Delay set to 8 ms, the minimum possible. Further, there was an additional 15 ms delay between the cessation of RF output and the lifting (opening) of the KEY OUT line. Since RX audio is muted the entire time the KEY OUT line is closed, then we have to add another 14 ms [2 x (15-8)] to the 27 ms; that gets us to 41 ms, the entire "space" interval between consecutive "mark" elements at 24 wpm or higher!

Conclusion: Modern transceivers filled with synthesizers and DSP circuitry are no match for properly designed analog receivers such as the old Hallicrafters and Collins units when it comes to QSK performance. For the K3 and most other modern transceivers, at common CW contest speeds "QSK" doesn't mean what it used to ("able to hear the other station between our own transmitted DOTS"); the best we can do above 25 wpm or so is to hear the other station between CHARACTERS.

The K3's QRQ mode may be better in this respect than the figures discussed above but, since QRQ mode currently does not allow the use of RIT, XIT, or Splits of ANY delta-f, no matter how small, it's of limited interest to me since my primary interest in QSK is knowing when a DX station has come back to someone while I'm still sending.

Finally, with respect to amplifier QSK: I am aware of five ways of enjoying QSK capability when using a separate amplifier:
1. PIN diode circuits (Alpha 87A, some Ameritron models, some outboard PIN-diode "boxes) triggered by the KEY OUT line from the K3
2. High-speed reed and vacuum relay combinations (current Alpha models, AG6K circuitry, etc.) triggered by the KEY OUT line from the K3
3. Electronic bias switching (EBS) in conjunction with a shunt-type vacuum tube TR Switch (E. F. Johnson, e.g.) and requiring NO trigger signal
4. EBS in conjunction with a separate RX antenna (always with suitable RX front-end protection, of course) and requiring NO trigger signal
5. Diplexing schemes which don't care if / when the transmitter is keyed

Most important, the clunky, noisy, typically open-frame relays used for manual, PTT T/R switching in many amplifiers should NEVER be considered capable of being used in QSK mode! In fact, many of these relays are sufficiently slow that they shouldn't even be used in VOX mode because they'll be "hot-switching" RF, even with the delays in the K3.

PIN diodes and EBS can be VERY fast — with total switching times under 1 or 2 ms. Inexpensive reed and vacuum relay circuits typically perform in 2 or 3 ms, thanks to the use of speed-up circuit techniques. With respect to #3 above, the maximum voltage out of the RX ANT terminal of a Johnson TR Switch during transmitter key-down periods is high enough to trigger the internal RX front-end protection circuitry in the K3, so it is not a viable approach, even though I have successfully used Johnson TR Switches with Kenwood solid-state transceivers for over a quarter century.

And FAR more than a "quarter century" ago I began my own ham "career" with a form of #4. I used a separate receiving antenna and the EBS was very simple: all my CW rigs and amplifiers back then were operated in Class C mode, and fully cut off during key-up intervals!

Bud, W2RU

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Igor Sokolov-2

Re: K3 TX delay

In reply to this post by Don Wilhelm-4

Don,
What you are saying translates into " Do not talk into the mike or touch
keyer for 30 ms or more after you press PTT footswitch". I know that. But
this method can hardly be called fool proof for contesting. In fact, even 8
ms delay woul not be needed.

73, Igor UA9CDC

> Igor,
>
> I understand your situation, but the application of PTT does not produce
> any RF - nothing will hot switch.
> When you "hit the key" (or for SSB begin talking), then RF is produced.
> If you arrange your switching to be accomplished by either the PTT or the
> K3 KEYOUT, and leave the K3 in non-VOX state, there is no need to increase
> TX DLY to any other than the 8 ms default value and therefore no
> shortening of CW elements.
>
> 73,
> Don W3FPR
>
> On 2/17/2012 6:52 AM, Igor Sokolov wrote:
>> Don,
>> I will try to explain.
>> Forget about QSK all together.
>> Apart from linear amp, there are other external relays like stack control
>> relays, T/R relays when you want to use different antennas for TX/RX etc.
>> PTT signal can either be controlled by the logger (CW, VOICE Keyer, DIGI
>> modes) or by PTT footswitch. In both cases PTT signal goes into PTT IN of
>> K3.
>> About 6ms later you get sort of PTT OUT on the KEY OUT connector. This
>> KEY
>> OUT signal controls linear, T/R antenna relays, stack relays etc. Then
>> 8ms
>> later you get RF out of the K3. These 8ms is not enough for all the
>> external
>> relays to settle.
>> PTT delay of 20 ms should be more or less OK (although I would not mind
>> it
>> to be extended to 30ms) but then CW generated by a logger gets choppy.
>> I can overcome the problem of non adjustable TX delay of K3 by
>> configuring
>> my logger to start sending say 30 ms after PTT was asserted. I can even
>> connect PTT footswitch to the computer, but that will only work for CW
>> sending from the keyboard, computer voice keyer and digi signals
>> generated
>> by the computer. If I send from the K3 internal keyer or use k3 mike I am
>> in
>> danger to hot switch some of the external relays.
>> Therefore instead of being able to extend TX delay inside K3 I will
>> probably
>> have to build some sort of circit which will take low level from KEY OUT
>> and
>> form some sort of positive or negative impulse of a required length (say
>> 30
>> ms) to apply to INH input of K3. I was hoping to build it inside the
>> DB-15
>> cabinet since KEY OUT and INH pins are available on the ACC connector.
>> But
>> there is no any 12 v or 5v pins available on that connector. So it makes
>> life more complicated.
>> If you can suggest different approach. which does not involve building
>> external sequencer, I would really appreciate it.
>>
>> 73, Igor UA9CDC
>>
>>
>>> I fail to understand why anyone who is using PTT switching would want to
>>> set the TX DLY parameter to greater than the default of 8 ms. Use PTT
>>> and
>>> a footswitch if you are using a slow amp relay.
>>>
>>> If your amplifier uses a slow relay, then you really cannot use QSK, so
>>> just use PTT and a footpedal instead - things will work out much better.
>>> There are QSK mods available for amplifiers that use slow relays. Some
>>> mods are relatively inexpensive (the owner does the work), while other
>>> can
>>> cost upwards of $400 (purchase a commercial version).
>>>
>>> 73,
>>> Don W3FPR
>>>
>>> On 2/16/2012 11:05 PM, Igor Sokolov wrote:
>>>>> But I am finishing my 300w HF amplifier kit and will be using a dc
>>>>> open-frame relay for TR switching of RF. I guess I can time it using
>>>>> my dual trace scope and set K3 TX DLY accordingly (amp will be keyed
>>>>> with KEYOUT). I do not use CW very much on HF so QSK with 300w is
>>>>> not necessary (or probably possible).
>>>> Even if you use PTT CW and set TX delay for 20 ms you will get choppy
>>>> CW
>>>>
>>>>> There is one thing I do not see being addressed in this
>>>>> discussion. Maybe more important than clipping of CW characters is
>>>>> avoiding QRO "Hot Switching" of RF. Calculate the RF voltage for
>>>>> several thousand ohms impedance (open circuit) that will result if
>>>>> the amp is pumping out "globs" of RF before being connected to a good
>>>>> load. The relay contacts will definitely get burned big time. And
>>>>> maybe your output devices will have a short live-span.
>>>>>
>>>>>
>>>>> 73, Ed - KL7UW, WD2XSH/45
>>>> The entire topic stems from the fact that I wanted to avoid hot
>>>> switching
>>>> of
>>>> the external relays (linear amp, stack switching etc). To acheave that
>>>> I
>>>> have tried to increase TX delay and got choppy CW. So without external
>>>> sequencer there is a choise between the two - 'hot switching' or
>>>> 'choppy
>>>> cw'.
>>>>
>>>> 73. Igor UA9CDC
>>>>
>>>>
>>>>> ======================================
>>>>> BP40IQ 500 KHz - 10-GHz www.kl7uw.com
>>>>> EME: 50-1.1kw?, 144-1.4kw, 432-QRT, 1296-?, 3400-?
>>>>> DUBUS Magazine USA Rep [hidden email]
>>>>> "Kits made by KL7UW" http://www.kl7uw.com/kits.htm
>>>>> ======================================
>>>>> ______________________________________________________________
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>>>>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>>>>> Help: http://mailman.qth.net/mmfaq.htm
>>>>> Post: mailto:[hidden email]
>>>>>
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Igor Sokolov-2

Re: K3 TX delay

In reply to this post by Nick Kennedy

That is right Nick. That is because your TX delay is set at 8 ms. But if
Rx/Tx transition time of your AL-811 is greater then 8 ms you get "hot
switching" every time your start to transmit.

73, Igor UA9CDC

>I use semi-break-in with my AL-811 amplifier.
>
> TX delay set to 8 ms. Key Out line to amplifier. No separate PTT switch
> - T/R control by paddle only. Semi-break-in delay set to 0.5.
>
> I do not get choppy CW.
>
> 73-
>
> Nick, WA5BDU
>

Vic Rosenthal

Re: K3 TX delay

In reply to this post by W2RU - Bud Hippisley

A very interesting discussion of the question "how fast is your QSK?".
Another question is "how smooth is it?" -- by which I mean, do you hear
any clicks or other audio artifacts when sending?

The K3 is better than many modern radios in these respects, but is far
from perfect. The problems in both areas stem mostly from the use of
common circuitry for transmit and receive and the need to 'turn them
around' rapidly when sending CW.

Short of a full-duplex setup with the transmitter and receiver in
different locations, the best way to achieve superior QSK is with a
separate receiver and transmitter. Then the problem is greatly
simplified into finding a way to switch the antenna quickly --
electronic t/r switches using vacuum tubes come to mind -- and a way to
protect and mute the receiver without introducing artifacts.

I wonder if, for a CW operator, the benefit of a transceiver is
overrated? Imagine a setup with a simple CW transmitter separate from a
K3, which could be used as a receiver only. All that you would need to
regain the convenience of a transceiver would be a button to match the
transmitter to the receiver frequency, something which would be easy to
do with a CAT program.

I may well try this with my K2 as transmitter.

The absolute best QSK I've ever had in my station was in the late
1960's, a Hallicrafters HA-5 hetrodyne VFO followed by a Heath DX-60 and
a single 813 amplifier. The receiver was a Drake R4B which needed one
bypass capacitor added to the input of the first audio stage to mute in
complete silence. T/R switching was handled by a simple tube switch in
the plate circuit of the 813, which, like Bud's rigs, was class C.

On 2/17/12 7:15 AM, W2RU - Bud Hippisley wrote:

> One thing I haven't seen mentioned in this discussion is the sending
> speed at which the benefits of QSK "disappear" in the K3.
>
> Speed in words per minute (wpm) is very roughly equal to the number
> of dashes in a 5-second interval. Thus, at 25 wpm, there are 25
> dashes in 5 seconds, or 5 dashes per second. But a dash consists of
> 4 "periods": three consecutive "mark" periods, followed by a single
> "space" period. So...in one second there are 5 x 4, or 20 such
> periods in 25 wpm CW, and therefore a single period is theoretically
> 50 milliseconds (ms) long. Of course, if keying "weight" is set
> above 50% (or 1.0-to-1.0 mark / space ratio for dots), the key-up
> period is LESS than 50 ms. A similar calculation at, say, 35 wpm,
> gives us a key-up (or "space") period of about 35 ms.
>
> But to avoid generating excessive clicks, the leading and trailing
> edges of RF output during each mark element ramp up or down
> gradually, with the total interval at either end of the element
> having been measured at 4 ms (onset of RF output to 100%) in one
> specific "clickless" K3. If we assume we have adjusted the weight
> using the 50% RF output level as the reference (an assumption that
> is, itself, worthy of a completely separate posting), there's another
> 4 ms (1/2 x 2 x 4) that we have to subtract from each space period.
>
> Of course, for QSK to truly be QSK, we have to be able to hear
> receiver audio output for at least part of the "space" period between
> two consecutive "mark" elements (either dot or dash). The minimum K3
> TX Delay that can be set via the CONFIG menu is 8 ms. It's my
> understanding that at least part of that delay is for "covering" the
> time it takes all the various synthesizer and DSP circuits in the K3
> to switch from RX to TX, especially since the RX and TX frequencies
> can be different when in QSK mode. It's also my understanding that
> there's a similar delay at the END of a transmitted element, when all
> the circuits have to return to their RX states. Because frequencies
> and other circuit parameters are actively changing during those two
> periods, it's unlikely that useful RX audio is available at any time
> during either 8 ms interval.
>
> Clearly, then, there is a MINIMUM total interval of (2 x 8) + 4, or
> 20, ms when no received signals can be heard by the K3 user between
> mark elements. In fact, even at the 8-ms setting, it's very possible
> that MORE than 16 ms of each space period is "blanked". I say that
> because a number of us have found that to get proper weight from the
> K3 in QSK mode, we have to artificially adjust the length of its
> "mark" periods (with, for instance, the "Compensation" parameter of a
> WinKey or other suitable outboard keyer) by adding 6 or 7 ms to each
> key-down interval. (Note that this a fixed interval for a given K3
> regardless of sending speed, and is not "weight" in the conventional
> sense. Good keyers, like the WinKey, allow weight, ratio,
> compensation, and other parameters to be independently adjusted.
>
> So now, with the K3 CONFIG menu set to 8 ms (its minimum value), we
> have 20 + 7, or 27, ms of each "space" when the receiver is blanked.
> Interestingly, that's just about the length of an entire space at 35
> wpm! So, for all practical purposes, QSK is simply not possible with
> a K3 at CW speeds above 35 wpm. Below that speed, the ability of QSK
> to help you detect the presence of the other station is statistical,
> depending on whether enough of the character elements sent by the
> other operator happen to coincide with some part of the narrow usable
> window within your own transmitted "space" intervals to cause you to
> conclude he's really sending again.
>
> But it gets even worse: That same K3 above was measured as having 15
> ms total delay from initial closure of its KEY OUT line to the start
> of RF output when using the "new" QSK mode with TX Delay set to 8 ms,
> the minimum possible. Further, there was an additional 15 ms delay
> between the cessation of RF output and the lifting (opening) of the
> KEY OUT line. Since RX audio is muted the entire time the KEY OUT
> line is closed, then we have to add another 14 ms [2 x (15-8)] to the
> 27 ms; that gets us to 41 ms, the entire "space" interval between
> consecutive "mark" elements at 24 wpm or higher!
>
> Conclusion: Modern transceivers filled with synthesizers and DSP
> circuitry are no match for properly designed analog receivers such as
> the old Hallicrafters and Collins units when it comes to QSK
> performance. For the K3 and most other modern transceivers, at
> common CW contest speeds "QSK" doesn't mean what it used to ("able to
> hear the other station between our own transmitted DOTS"); the best
> we can do above 25 wpm or so is to hear the other station between
> CHARACTERS.
>
> The K3's QRQ mode may be better in this respect than the figures
> discussed above but, since QRQ mode currently does not allow the use
> of RIT, XIT, or Splits of ANY delta-f, no matter how small, it's of
> limited interest to me since my primary interest in QSK is knowing
> when a DX station has come back to someone while I'm still sending.
>
> Finally, with respect to amplifier QSK: I am aware of five ways of
> enjoying QSK capability when using a separate amplifier: 1. PIN
> diode circuits (Alpha 87A, some Ameritron models, some outboard
> PIN-diode "boxes) triggered by the KEY OUT line from the K3 2.
> High-speed reed and vacuum relay combinations (current Alpha models,
> AG6K circuitry, etc.) triggered by the KEY OUT line from the K3 3.
> Electronic bias switching (EBS) in conjunction with a shunt-type
> vacuum tube TR Switch (E. F. Johnson, e.g.) and requiring NO trigger
> signal 4. EBS in conjunction with a separate RX antenna (always with
> suitable RX front-end protection, of course) and requiring NO trigger
> signal 5. Diplexing schemes which don't care if / when the
> transmitter is keyed
>
> Most important, the clunky, noisy, typically open-frame relays used
> for manual, PTT T/R switching in many amplifiers should NEVER be
> considered capable of being used in QSK mode! In fact, many of these
> relays are sufficiently slow that they shouldn't even be used in VOX
> mode because they'll be "hot-switching" RF, even with the delays in
> the K3.
>
> PIN diodes and EBS can be VERY fast — with total switching times
> under 1 or 2 ms. Inexpensive reed and vacuum relay circuits
> typically perform in 2 or 3 ms, thanks to the use of speed-up circuit
> techniques. With respect to #3 above, the maximum voltage out of the
> RX ANT terminal of a Johnson TR Switch during transmitter key-down
> periods is high enough to trigger the internal RX front-end
> protection circuitry in the K3, so it is not a viable approach, even
> though I have successfully used Johnson TR Switches with Kenwood
> solid-state transceivers for over a quarter century.
>
> And FAR more than a "quarter century" ago I began my own ham "career"
> with a form of #4. I used a separate receiving antenna and the EBS
> was very simple: all my CW rigs and amplifiers back then were
> operated in Class C mode, and fully cut off during key-up intervals!
>
> Bud, W2RU
>
>
> ______________________________________________________________
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--
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/
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Don Wilhelm-4

Re: K3 TX delay

In reply to this post by Igor Sokolov-2

Igor,

Please explain how the 8 ms is relevant when using PTT instead of VOX.

In PTT state, Keyout follows PTT (not the keyclosure) - so the amplifier
relay circuit should be closed
as long as the operator closes the footswitch or whatever is used for
PTT first. Keying will most likely begin long after the footswitch is
activated. In other words, the 8 ms is not relevant, and no hot
switching should occur.

73,
Don W3FPR

On 2/17/2012 10:51 AM, Igor Sokolov wrote:
> That is right Nick. That is because your TX delay is set at 8 ms. But if
> Rx/Tx transition time of your AL-811 is greater then 8 ms you get "hot
> switching" every time your start to transmit.
>
>
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Nick Kennedy

Re: K3 TX delay

In reply to this post by Nick Kennedy

I'd like to see a feature to allow different TX-DLY settings for QSK and
semi-breakin. If I seldom use my amplifier and it requires > 8ms, I
have to change TX-DLY before using it. But since I prefer fast QSK in
general, I have to set it back again when I go barefoot.

73-

Nick, WA5BDU

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alsopb

Re: K3 TX delay

In reply to this post by Don Wilhelm-4

Don,

It isn't the 8ms that is relevant, it is how the K3's coding behaves in
subsequent CW characters when the TXDLY is varied from 8 -20 ms. PTT
is irrelevant.

Higher values produce QSD regardless of how the amp is keyed. It occurs
regardless if one is using the K3's internal keyer or an external keyer.

Speculation:
It appears the delay affects other timings within the K3. It appears
that at high values of TXDLY and CW speed the keying character timings
get messed up. In otherwords, TDXLY isn't like a simple delay line. It
is most likely an attempt to approximate the input TDXLY value by
changing the timings in many routines.

Only Elecraft knows for sure how TXDLY is implemented in code.

73 de Brian/K3KO

On 2/17/2012 18:58, Don Wilhelm wrote:

> Igor,
>
> Please explain how the 8 ms is relevant when using PTT instead of VOX.
>
> In PTT state, Keyout follows PTT (not the keyclosure) - so the amplifier
> relay circuit should be closed
> as long as the operator closes the footswitch or whatever is used for
> PTT first. Keying will most likely begin long after the footswitch is
> activated. In other words, the 8 ms is not relevant, and no hot
> switching should occur.
>
> 73,
> Don W3FPR
>
> On 2/17/2012 10:51 AM, Igor Sokolov wrote:
>> That is right Nick. That is because your TX delay is set at 8 ms. But if
>> Rx/Tx transition time of your AL-811 is greater then 8 ms you get "hot
>> switching" every time your start to transmit.
>>
>>
> ______________________________________________________________
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Igor Sokolov-2

Re: K3 TX delay

In reply to this post by Don Wilhelm-4

> 73,
> Don W3FPR

Don,

Think of SSB contest. You run high power and quite a bit of signal
processing to have punchy signal. You press that foot switch and 8 ms later
you already have some RF from ambient noise on the external relays that are
not settled yet. Besides when in the contest quite often one starts speaking
into the mike even before PTT foot switch is engaged. I for one cannot think
of the sequence (press PTT, wait 30 ms, start speaking) when I am trying to
work pile up at 6 QSO per minute.

73, Igor UA9CDC

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Igor Sokolov-2

Re: K3 TX delay

In reply to this post by alsopb

Actually both are relevant and related.
Adjustable TX delay is nice, useful and required feature. Current
implementation of it is not usable 100%. One either should stick to 8 ms
fixed or use no CW. The availability of INH signal in the radio allows
building external delay with wide range of adjustment. Yet it would be much
more elegant to have such a delay implemented internally.

73, Igor UA9CDC

> Don,
>
> It isn't the 8ms that is relevant, it is how the K3's coding behaves in
> subsequent CW characters when the TXDLY is varied from 8 -20 ms. PTT
> is irrelevant.
>
> Higher values produce QSD regardless of how the amp is keyed. It occurs
> regardless if one is using the K3's internal keyer or an external keyer.
>
>
> Speculation:
> It appears the delay affects other timings within the K3. It appears
> that at high values of TXDLY and CW speed the keying character timings
> get messed up. In otherwords, TDXLY isn't like a simple delay line. It
> is most likely an attempt to approximate the input TDXLY value by
> changing the timings in many routines.
>
> Only Elecraft knows for sure how TXDLY is implemented in code.
>
> 73 de Brian/K3KO
>
> On 2/17/2012 18:58, Don Wilhelm wrote:
>> Igor,
>>
>> Please explain how the 8 ms is relevant when using PTT instead of VOX.
>>
>> In PTT state, Keyout follows PTT (not the keyclosure) - so the amplifier
>> relay circuit should be closed
>> as long as the operator closes the footswitch or whatever is used for
>> PTT first. Keying will most likely begin long after the footswitch is
>> activated. In other words, the 8 ms is not relevant, and no hot
>> switching should occur.
>>
>> 73,
>> Don W3FPR
>>
>> On 2/17/2012 10:51 AM, Igor Sokolov wrote:
>>> That is right Nick. That is because your TX delay is set at 8 ms. But if
>>> Rx/Tx transition time of your AL-811 is greater then 8 ms you get "hot
>>> switching" every time your start to transmit.
>>>
>>>
>> ______________________________________________________________
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>>
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>> Checked by AVG - www.avg.com
>> Version: 10.0.1424 / Virus Database: 2112/4815 - Release Date: 02/17/12
>>
>>
>
>
>
> -----
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Edward R Cole

Re: K3 TX delay

In reply to this post by Edward R Cole

Don and Igor,

I didn't think it out completely when I first posted. This is
because this is the first time I will use a HF amp. VHF amps nearly
all have RF sensed TR (Plus the means for PTT control). I do not
like RF sensing as I can not see how one avoids hot switching.

MY system for running the HF amp will be using a good old toggle
switch (same function as a foot switch). That will the K3 PTT
(KEYIN) and the control the amp PTT (KEYOUT) before I ever touch the
CW key. For SSB there is no issue since PTT switching will be
accomplished before I speak (thus producing RF). I cannot use that
for AM or FM but I have not used FM on 10m so not an issue (at this
point). The only thing I will have to check is if paralleling my
sequencer input with the amplifier PTT will cause any control issues
(both using pull-up +13.7v and grounding the PTT line). Possible
using some steering diodes will isolate them. I don't want to have
to remember to switch over anything. On HF only the amp will use TR
switching so pretty simple. I will not have to lengthen the TX-DLY.

I haven't decided if I want to use inhibit for HF. It is implemented
for VHF at present using the BAND0 control line to activate it. I
will add BAND1 (for 222) and DOGOUT1 (for 6m) to add inhibit on those
two bands. Probably do not need inhibit on HF (unless I am forgetful
throwing the "toggle switch"). I have to do that for CW on VHF so
probably become habit.

This should take the old-timers back to the days where we used a
toggle switch marked SEND on the old receivers which applied voltage
to the old Dowkey coax relay. Those had aux contacts for grid-bias
keying the old vacuum tubes transmitters.

Ed

------------------------------

Message: 6
Date: Fri, 17 Feb 2012 07:55:20 -0500
From: Don Wilhelm <[hidden email]>
Subject: Re: [Elecraft] K3 TX delay

Igor,

I understand your situation, but the application of PTT does not produce
any RF - nothing will hot switch.
When you "hit the key" (or for SSB begin talking), then RF is produced.
If you arrange your switching to be accomplished by either the PTT or
the K3 KEYOUT, and leave the K3 in non-VOX state, there is no need to
increase TX DLY to any other than the 8 ms default value and therefore
no shortening of CW elements.

73,
Don W3FPR

73, Ed - KL7UW, WD2XSH/45
======================================
BP40IQ 500 KHz - 10-GHz www.kl7uw.com
EME: 50-1.1kw?, 144-1.4kw, 432-QRT, 1296-?, 3400-?
DUBUS Magazine USA Rep [hidden email]
"Kits made by KL7UW" http://www.kl7uw.com/kits.htm
======================================
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