Elecraft

K3 external qro keying line

Classic

List

Threaded

14 messages Options

Barry, Stephen

K3 external qro keying line

I’m a long time builder/operator of an early K2 (s/n 377) and have considered going for the K3/10.

I would use my SB220 occasionally for more power since I can get approx. 200 watts with 12 watts in.

The question I have is there a PA key line available from the basic K3? Or, is that circuitry on the KPA3 subassembly?

If so, has anyone found a way to key an amp with the basic K3?

I enjoy reading the list serve and the good advice from some of the O/T submitters such as W2FPR, AC7AC and N0SS. Thanks

guys.

I’d ask the Elecraft guys but I don’t want to bother them while they’re cranking out K3s.

73.

Steve/AE2G

Greg - AB7R

Re: K3 external qro keying line

Barry,

The key out line on the K3 on not on a sub assembly, it is on the main RF board.

Im not sure of the relay on the SB220 but I suspect you may need to use one of
those AmpKeyer interfaces that the HeathGuy or Ameritron sells just to be safe...or
brew your own. It depends on the voltage requirement of the amp's relay.

-------------------------
73,
Greg - AB7R
Whidbey Island WA
NA-065

On Thu Feb 12 7:13 , "Barry, Stephen" sent:

>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>Iâm a long time builder/operator of an early K2 (s/n
>377) and have considered going for the K3/10.
>
>Â
>
>I would use my SB220 occasionally for more power since I can
>get approx. 200 watts with 12 watts in.
>
>Â
>
>The question I have is there a PA key line available from
>the basic K3? Â Or, is that circuitry on the KPA3 subassembly?
>
>If so, has anyone found a way to key an amp with the basic K3?
>
>Â
>
>I enjoy reading the list serve and the good advice from some
>of the O/T submitters such as W2FPR, AC7AC and N0SS.Â Thanks
>
>guys.
>
>Â
>
>Iâd ask the Elecraft guys but I donât want to
>bother them while theyâre cranking out K3s.
>
>Â
>
>73.
>
>Â
>
>Steve/AE2G
>
>Â
>
>Â
>
>
>
>
>
>

W8ZN

Re: K3 external qro keying line

I've seen numerous posts about the PTT output line on the K3 and using older amps. Yaesu's, Kenwood's, Icom's all share the same issue.

Unless you are running QSK and need instant keying, I would suggest adding a small 12v relay inside the K3 that the solid state device keys and presents the user with a set of dry, isolated contacts that can handle positive, negative and up to 250v DC or AC. I have added this to several K3's to protect the switching transistor from eventual destruction. Once again, if you are using QSK, solid state due to it's fast switching time is your only option.

Yes, it means touching your K3 with a hot soldering iron, but it's a "pay me now or pay me later" thing, sooner or later it will blow the switch if you are hooking up older or HB amps that use other than low current positive keying voltages.

Terry

----- Original Message -----
From: "Greg - AB7R" <[hidden email]>
To: [hidden email], '[hidden email], "Stephen'" <[hidden email]>
Sent: Thursday, February 12, 2009 10:18:50 AM GMT -05:00 US/Canada Eastern
Subject: Re: [Elecraft] K3 external qro keying line

Barry, The key out line on the K3 on not on a sub assembly, it is on the main RF board. Im not sure of the relay on the SB220 but I suspect you may need to use one of those AmpKeyer interfaces that the HeathGuy or Ameritron sells just to be safe...or brew your own. It depends on the voltage requirement of the amp's relay. ------------------------- 73, Greg - AB7R Whidbey Island WA NA-065 On Thu Feb 12 7:13 , "Barry, Stephen" sent: > > > > > > > > > > > > > > > > > > >I��m a long time builder/operator of an early K2 (s/n >377) and have considered going for the K3/10. > >�� > >I would use my SB220 occasionally for more power since I can >get approx. 200 watts with 12 watts in. > >�� > >The question I have is there a PA key line available from >the basic K3? ��Or, is that circuitry on the KPA3 subassembly? > >If so, has anyone found a way to key an amp with the basic K3? > >�� > >I enjoy reading the list serve and the good advice from some >of the O/T submitters such as W2FPR, AC7AC and N0SS.�� Thanks > >guys. > >�� > >I��d ask the Elecraft guys but I don��t want to >bother them while they��re cranking out K3s. > >�� > >73. > >�� > >Steve/AE2G > >�� > >�� > > > > > >
______________________________________________________________ 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 external qro keying line

Terry,

For those who prefer not to touch the K3 with a soldering iron, an
external 12 volt relay is a good solution. Obtain the power from the
K3 12VDC OUT jack and use KEYOUT to key the relay. It accomplishes
the same thing and retains the ability to use QSK in the future without
'undoing' the internal relay.

73,
Don W3FPR

[hidden email] wrote:

>
> I've seen numerous posts about the PTT output line on the K3 and using
> older amps. Yaesu's, Kenwood's, Icom's all share the same issue.
>
>
>
> Unless you are running QSK and need instant keying, I would suggest
> adding a small 12v relay inside the K3 that the solid state device
> keys and presents the user with a set of dry, isolated contacts that
> can handle positive, negative and up to 250v DC or AC. I have added
> this to several K3's to protect the switching transistor from eventual
> destruction. Once again, if you are using QSK, solid state due to it's
> fast switching time is your only option.
>
>
>
> Yes, it means touching your K3 with a hot soldering iron, but it's a
> "pay me now or pay me later" thing, sooner or later it will blow the
> switch if you are hooking up older or HB amps that use other than low
> current positive keying voltages.
>
>
>
> Terry
>
>

P.B. Christensen

Re: K3 external qro keying line

In reply to this post by W8ZN

> "Unless you are running QSK and need instant keying, I would suggest adding a small 12v relay inside the K3 that the solid state device keys and presents the user with a set of dry, isolated contacts that can handle positive, negative and up to 250v DC or AC."

And bring 250VAC into the case of the K3? If a relay is used instead of a solid-state device, it should be located external to the K3 cabinet, especially with 100-250VAC key lines.

The output switching device from the K3 can already switch 200VDC at 5A. For those switching medium-voltage AC/DC amp key lines, or want additional rig-to-amp isolation, a more viable option is to use a solid-state external interface. There are several commercial interfacing products available in both assembled and kit form.

My personal favorite is the "KeyAll" from Jackson Harbor Press. It is optically-isolated from the rig and will switch 500 VAC/VDC at 2.5 A loads.

http://home.att.net/~jacksonharbor/keyall.htm

Paul, W9AC

k0wa@swbell.net

Re: K3 external qro keying line

HMMMM.... I thought the transistor on the K3 doing the switching is pretty tough. I guess we are talking about older amps and not the ones that use 12 volts to switch.

I have done the following to.... Radio Shack sells a 5v reed relay that is pretty darn fast and has good specs. I just used a dropping resistor from a 12 volt line in series with the reed relay and worked great for years. I think I used a 180 ohm resistor. Worked great. Not QSK, but I don't like QSK anyway. Messes with my head. HI

Lee Buller - K0WA

In our day and age it seems that Common Sense is in short supply. If you don't have any Common Sense - get some Common Sense and use it. If you can't find any Common Sense, ask for help from somebody who has some Common Sense. Is Common Sense divine?

Doug Faunt N6TQS +1-510-655-8604

Re: K3 external qro keying line

In reply to this post by Don Wilhelm-4

There are solid-state relays in a DIP-6 or a SOP-4 package that can fit most
places and are fast. Check out the NEC PS7113 or PS7141, and similar
devices.

73, doug

X_CMAE_Category: 0,0 Undefined,Undefined
Date: Thu, 12 Feb 2009 11:00:27 -0500
From: Don Wilhelm <[hidden email]>

Terry,

For those who prefer not to touch the K3 with a soldering iron, an
external 12 volt relay is a good solution. Obtain the power from the
K3 12VDC OUT jack and use KEYOUT to key the relay. It accomplishes
the same thing and retains the ability to use QSK in the future without
'undoing' the internal relay.

73,
Don W3FPR

[hidden email] wrote:
>
> I've seen numerous posts about the PTT output line on the K3 and using
> older amps. Yaesu's, Kenwood's, Icom's all share the same issue.
>
>
>
> Unless you are running QSK and need instant keying, I would suggest
> adding a small 12v relay inside the K3 that the solid state device
> keys and presents the user with a set of dry, isolated contacts that
> can handle positive, negative and up to 250v DC or AC. I have added
> this to several K3's to protect the switching transistor from eventual
> destruction. Once again, if you are using QSK, solid state due to it's
> fast switching time is your only option.
>
>
>
> Yes, it means touching your K3 with a hot soldering iron, but it's a
> "pay me now or pay me later" thing, sooner or later it will blow the
> switch if you are hooking up older or HB amps that use other than low
> current positive keying voltages.
>
>
>
> Terry
>
>
______________________________________________________________
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

Tom Hammond-2

Re: K3 external qro keying line

In reply to this post by k0wa@swbell.net

The K3's T-R line output ("KEY OUT") can switch up to 200VDC @ 5A... so it will
easily switch the +120VDC @ 15-30mA from the SB-220.

However, it will NOT SWITCH a NEGATIVE T-R line voltage UNDER ANY
CIRCUMSTANCES!
Users with amps which offer a negative T-R line control voltage will have to
provide alternate switching (relay, or solid state).

73,

Tom N0SS

>phones, mic,
>line in, and line out

At 10:13 02/12/2009, Lee Buller wrote:

>HMMMM.... I thought the transistor on the K3 doing the switching is
>pretty tough. I guess we are talking about older amps and not the
>ones that use 12 volts to switch.
>
>I have done the following to.... Radio Shack sells a 5v reed relay
>that is pretty darn fast and has good specs. I just used a dropping
>resistor from a 12 volt line in series with the reed relay and
>worked great for years. I think I used a 180 ohm resistor. Worked
>great. Not QSK, but I don't like QSK anyway. Messes with my head. HI
>
>Lee Buller - K0WA
>
>
>
>In our day and age it seems that Common Sense is in short supply. If
>you don't have any Common Sense - get some Common Sense and use it.
>If you can't find any Common Sense, ask for help from somebody who
>has some Common Sense. Is Common Sense divine?
>______________________________________________________________
>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

John Lemay

Re: K3 external qro keying line

I can see reason for confusion here - the K3 Manual on page 17 describes the
"amplifier T-R relay keying output ...."

Maybe the wording could be clarified. I would certainly form a (incorrect)
picture in my mind of a small power relay, for which + or -ve switching
would be permissible.

John G4ZTR

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Tom Hammond
Sent: 12 February 2009 17:19
To: Lee Buller; Elecraft Reflector
Subject: Re: [Elecraft] K3 external qro keying line

The K3's T-R line output ("KEY OUT") can switch up to 200VDC @ 5A... so it
will
easily switch the +120VDC @ 15-30mA from the SB-220.

However, it will NOT SWITCH a NEGATIVE T-R line voltage UNDER ANY
CIRCUMSTANCES!
Users with amps which offer a negative T-R line control voltage will have to
provide alternate switching (relay, or solid state).

73,

Tom N0SS

>phones, mic,
>line in, and line out

At 10:13 02/12/2009, Lee Buller wrote:

______________________________________________________________
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

__________ Information from ESET NOD32 Antivirus, version of virus signature
database 3849 (20090212) __________

The message was checked by ESET NOD32 Antivirus.

http://www.eset.com

__________ Information from ESET NOD32 Antivirus, version of virus signature
database 3850 (20090213) __________

The message was checked by ESET NOD32 Antivirus.

http://www.eset.com

______________________________________________________________
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

Guy, K2AV

Re: K3 external qro keying line

The sentence does not fix whether the relay is in the amplifier or in the
K3. Perhaps:

"...is transistor output for keying amplifier T-R circuits, ONLY positive
voltages up to +200VDC @ 5A."

Could a future mod include a blocking diode for negative keying voltages if
the circuit will not sink high negative voltages without damage.

73, Guy.

----- Original Message -----
From: "John Lemay" <[hidden email]>
To: "'Tom Hammond'" <[hidden email]>; "'Lee Buller'" <[hidden email]>;
"'Elecraft Reflector'" <[hidden email]>
Sent: Friday, February 13, 2009 5:54 AM
Subject: Re: [Elecraft] K3 external qro keying line

>I can see reason for confusion here - the K3 Manual on page 17 describes
>the
> "amplifier T-R relay keying output ...."
>
> Maybe the wording could be clarified. I would certainly form a (incorrect)
> picture in my mind of a small power relay, for which + or -ve switching
> would be permissible.
>
> John G4ZTR
>
>
> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of Tom Hammond
> Sent: 12 February 2009 17:19
> To: Lee Buller; Elecraft Reflector
> Subject: Re: [Elecraft] K3 external qro keying line
>
> The K3's T-R line output ("KEY OUT") can switch up to 200VDC @ 5A... so it
> will
> easily switch the +120VDC @ 15-30mA from the SB-220.
>
> However, it will NOT SWITCH a NEGATIVE T-R line voltage UNDER ANY
> CIRCUMSTANCES!
> Users with amps which offer a negative T-R line control voltage will have
> to
> provide alternate switching (relay, or solid state).
>
> 73,
>
> Tom N0SS
>
>>phones, mic,
>>line in, and line out
>
>
> At 10:13 02/12/2009, Lee Buller wrote:
>
>
>>HMMMM.... I thought the transistor on the K3 doing the switching is
>>pretty tough. I guess we are talking about older amps and not the
>>ones that use 12 volts to switch.
>>
>>I have done the following to.... Radio Shack sells a 5v reed relay
>>that is pretty darn fast and has good specs. I just used a dropping
>>resistor from a 12 volt line in series with the reed relay and
>>worked great for years. I think I used a 180 ohm resistor. Worked
>>great. Not QSK, but I don't like QSK anyway. Messes with my head. HI
>>
>>Lee Buller - K0WA
>>
>>
>>
>>In our day and age it seems that Common Sense is in short supply. If
>>you don't have any Common Sense - get some Common Sense and use it.
>>If you can't find any Common Sense, ask for help from somebody who
>>has some Common Sense. Is Common Sense divine?
>>______________________________________________________________
>>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
>
> __________ Information from ESET NOD32 Antivirus, version of virus
> signature
> database 3849 (20090212) __________
>
> The message was checked by ESET NOD32 Antivirus.
>
> http://www.eset.com
>
>
>
>
> __________ Information from ESET NOD32 Antivirus, version of virus
> signature
> database 3850 (20090213) __________
>
> The message was checked by ESET NOD32 Antivirus.
>
> http://www.eset.com
>
>
> ______________________________________________________________
> 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 external qro keying line

Guy,

I do not understand your confusion. The statement is that KEYOUT can
key up to +200VDC @ 5A. It does not matter whether there is a relay in
the K3 or not (it actually is a HEXFET), that statement specifies the
limits that the circuit in the K3 can handle.

The path will be a closed circuit on keying the K3 and will be open
circuit during receive.

The voltage and current as well as the polarity are determined by the
device (usually an amplifier) to be keyed. One can measure the
requirements with a DMM - measure the voltage at the amp's PTT input -
if it is positive and less than 200 volts, all is OK so far, but there
is one other step - put the DMM in current measurement mode and connect
the DMM to the amp PTT input again - if the current is less than 5 amps,
the K3 KEYOUT can handle it. The conditions must be less than the
KEYOUT maximum for voltage and current, and the voltage polarity must be
positive. Those are the maximum ratings that the K3 switch can handle.

73,
Don W3FPR

Guy Olinger, K2AV wrote:

> The sentence does not fix whether the relay is in the amplifier or in the
> K3. Perhaps:
>
> "...is transistor output for keying amplifier T-R circuits, ONLY positive
> voltages up to +200VDC @ 5A."
>
> Could a future mod include a blocking diode for negative keying voltages if
> the circuit will not sink high negative voltages without damage.
>
> 73, Guy.
>
>

David Cutter

Re: K3 external qro keying line

In reply to this post by Don Wilhelm-4

That's a good thought and provides instant isolation, but have some thought
about the back emf off the coil - it could exceed the rating of the keying
transistor. I measured 800V on a very fast scope many years ago from a reed
relay. Just sticking a diode across the coil will slow it down a lot, so,
some experimentation with zeners and resistors will get the situation
optimised. I once used a separate keying transistor and relay and found
that a small cap from the base to the collector did the job quite well by
slowing the off rise time, so the transistor absorbed a bit more power but
gave good control.

73

David
G3UNA

----- Original Message -----
From: "Don Wilhelm" <[hidden email]>
To: <[hidden email]>
Sent: Thursday, February 12, 2009 4:00 PM
Subject: Re: [Elecraft] K3 external qro keying line

> Terry,
>
> For those who prefer not to touch the K3 with a soldering iron, an
> external 12 volt relay is a good solution. Obtain the power from the
> K3 12VDC OUT jack and use KEYOUT to key the relay. It accomplishes
> the same thing and retains the ability to use QSK in the future without
> 'undoing' the internal relay.
>
> 73,
> Don W3FPR
>
> [hidden email] wrote:
>>
>> I've seen numerous posts about the PTT output line on the K3 and using
>> older amps. Yaesu's, Kenwood's, Icom's all share the same issue.
>>
>>
>>
>> Unless you are running QSK and need instant keying, I would suggest
>> adding a small 12v relay inside the K3 that the solid state device
>> keys and presents the user with a set of dry, isolated contacts that
>> can handle positive, negative and up to 250v DC or AC. I have added
>> this to several K3's to protect the switching transistor from eventual
>> destruction. Once again, if you are using QSK, solid state due to it's
>> fast switching time is your only option.
>>
>>
>>
>> Yes, it means touching your K3 with a hot soldering iron, but it's a
>> "pay me now or pay me later" thing, sooner or later it will blow the
>> switch if you are hooking up older or HB amps that use other than low
>> current positive keying voltages.
>>
>>
>>
>> Terry
>>
>>
> ______________________________________________________________
> 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 external qro keying line

David,

The back emf pulse from a relay occurs when the coil circuit is opened,
and its polarity is opposite that used to operate the relay. A properly
connected diode should 'swallow' the back emf, and a capacitor in
parallel with the coil should reduce the amplitude of the pulse.
Any delay introduced by the diode and capacitor will be on the trailing
edge and will not normally introduce significant delay on the leading edge.

Anyone adopting this scheme would not be operating QSK, so any
additional delays introduced will not be significant.
Those desiring QSK operation should consider fast relays (vacuum relays)
or solid state switching devices for their amplifier switching.

73,
Don W3FPR

David Cutter wrote:

> That's a good thought and provides instant isolation, but have some thought
> about the back emf off the coil - it could exceed the rating of the keying
> transistor. I measured 800V on a very fast scope many years ago from a reed
> relay. Just sticking a diode across the coil will slow it down a lot, so,
> some experimentation with zeners and resistors will get the situation
> optimised. I once used a separate keying transistor and relay and found
> that a small cap from the base to the collector did the job quite well by
> slowing the off rise time, so the transistor absorbed a bit more power but
> gave good control.
>
> 73
>
> David
> G3UNA
>
>
> ----- Original Message -----
> From: "Don Wilhelm" <[hidden email]>
> To: <[hidden email]>
> Sent: Thursday, February 12, 2009 4:00 PM
> Subject: Re: [Elecraft] K3 external qro keying line
>
>
>
>> Terry,
>>
>> For those who prefer not to touch the K3 with a soldering iron, an
>> external 12 volt relay is a good solution. Obtain the power from the
>> K3 12VDC OUT jack and use KEYOUT to key the relay. It accomplishes
>> the same thing and retains the ability to use QSK in the future without
>> 'undoing' the internal relay.
>>
>> 73,
>> Don W3FPR
>>
>> [hidden email] wrote:
>>
>>> I've seen numerous posts about the PTT output line on the K3 and using
>>> older amps. Yaesu's, Kenwood's, Icom's all share the same issue.
>>>
>>>
>>>
>>> Unless you are running QSK and need instant keying, I would suggest
>>> adding a small 12v relay inside the K3 that the solid state device
>>> keys and presents the user with a set of dry, isolated contacts that
>>> can handle positive, negative and up to 250v DC or AC. I have added
>>> this to several K3's to protect the switching transistor from eventual
>>> destruction. Once again, if you are using QSK, solid state due to it's
>>> fast switching time is your only option.
>>>
>>>
>>>
>>> Yes, it means touching your K3 with a hot soldering iron, but it's a
>>> "pay me now or pay me later" thing, sooner or later it will blow the
>>> switch if you are hooking up older or HB amps that use other than low
>>> current positive keying voltages.
>>>
>>>
>>>
>>> Terry
>>>
>>>
>>>
>> ______________________________________________________________
>> 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
> ------------------------------------------------------------------------
>
>
> No virus found in this incoming message.
> Checked by AVG - www.avg.com
> Version: 8.0.237 / Virus Database: 270.10.23/1953 - Release Date: 02/14/09 18:01:00
>
>

David Cutter

Re: K3 external qro keying line

Agreed. It's good to bring out these things so we are aware of ALL the
ramifications of doing things, you never know who's monitoring this channel.

There are some fast, small, non-vacuum relays that can be speeded up with a
little circuitry.

73

David
G3UNA

----- Original Message -----
From: "Don Wilhelm" <[hidden email]>
To: "David Cutter" <[hidden email]>
Cc: <[hidden email]>
Sent: Sunday, February 15, 2009 1:37 PM
Subject: Re: [Elecraft] K3 external qro keying line

> David,
>
> The back emf pulse from a relay occurs when the coil circuit is opened,
> and its polarity is opposite that used to operate the relay. A properly
> connected diode should 'swallow' the back emf, and a capacitor in parallel
> with the coil should reduce the amplitude of the pulse.
> Any delay introduced by the diode and capacitor will be on the trailing
> edge and will not normally introduce significant delay on the leading
> edge.
>
> Anyone adopting this scheme would not be operating QSK, so any additional
> delays introduced will not be significant.
> Those desiring QSK operation should consider fast relays (vacuum relays)
> or solid state switching devices for their amplifier switching.
>
> 73,
> Don W3FPR
>
>
> David Cutter wrote:
>> That's a good thought and provides instant isolation, but have some
>> thought about the back emf off the coil - it could exceed the rating of
>> the keying transistor. I measured 800V on a very fast scope many years
>> ago from a reed relay. Just sticking a diode across the coil will slow
>> it down a lot, so, some experimentation with zeners and resistors will
>> get the situation optimised. I once used a separate keying transistor
>> and relay and found that a small cap from the base to the collector did
>> the job quite well by slowing the off rise time, so the transistor
>> absorbed a bit more power but gave good control.
>>
>> 73
>>
>> David
>> G3UNA
>>
>>
>> ----- Original Message -----
>> From: "Don Wilhelm" <[hidden email]>
>> To: <[hidden email]>
>> Sent: Thursday, February 12, 2009 4:00 PM
>> Subject: Re: [Elecraft] K3 external qro keying line
>>
>>
>>
>>> Terry,
>>>
>>> For those who prefer not to touch the K3 with a soldering iron, an
>>> external 12 volt relay is a good solution. Obtain the power from the
>>> K3 12VDC OUT jack and use KEYOUT to key the relay. It accomplishes
>>> the same thing and retains the ability to use QSK in the future without
>>> 'undoing' the internal relay.
>>>
>>> 73,
>>> Don W3FPR
>>>
>>> [hidden email] wrote:
>>>
>>>> I've seen numerous posts about the PTT output line on the K3 and using
>>>> older amps. Yaesu's, Kenwood's, Icom's all share the same issue.
>>>>
>>>>
>>>>
>>>> Unless you are running QSK and need instant keying, I would suggest
>>>> adding a small 12v relay inside the K3 that the solid state device
>>>> keys and presents the user with a set of dry, isolated contacts that
>>>> can handle positive, negative and up to 250v DC or AC. I have added
>>>> this to several K3's to protect the switching transistor from eventual
>>>> destruction. Once again, if you are using QSK, solid state due to it's
>>>> fast switching time is your only option.
>>>>
>>>>
>>>>
>>>> Yes, it means touching your K3 with a hot soldering iron, but it's a
>>>> "pay me now or pay me later" thing, sooner or later it will blow the
>>>> switch if you are hooking up older or HB amps that use other than low
>>>> current positive keying voltages.
>>>>
>>>>
>>>>
>>>> Terry
>>>>
>>>>
>>>>
>>> ______________________________________________________________
>>> 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
>> ------------------------------------------------------------------------
>>
>>
>> No virus found in this incoming message.
>> Checked by AVG - www.avg.com Version: 8.0.237 / Virus Database:
>> 270.10.23/1953 - Release Date: 02/14/09 18:01:00
>>
>>