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K3 keying an amplifier

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fserota

K3 keying an amplifier

Is there anything about the voltage or current on the keying line that would prohibit putting the K3's key line in parallel with an ICOM's keying line so I would not have to switch between the two when sharing an amplifier?

In other words, could I just use a "Y" connector to connect the two transceivers to the keying line on my amplifier (Alpha 9500)?

Thanks in advance,
Fred, K3BHX
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Scott Ellington

Re: K3 keying an amplifier

You might have a problem when only one rig is powered up, with the unpowered one pulling down the key/control line. The K3 is OK, as both outputs are open drain/collector. If that's also the case with the ICOM, the "Y" connector should work. If the ICOM has a pull-up resistor, or anything except an open drain/collector connected to that control line, there could be a problem.

Scott K9MA

On Feb 16, 2011, at 1:29 PM, Fred Serota wrote:

> Is there anything about the voltage or current on the keying line that would prohibit putting the K3's key line in parallel with an ICOM's keying line so I would not have to switch between the two when sharing an amplifier?
>
> In other words, could I just use a "Y" connector to connect the two transceivers to the keying line on my amplifier (Alpha 9500)?
>
> Thanks in advance,
> Fred, K3BHX
> ______________________________________________________________
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Scott Ellington
Madison, Wisconsin
USA

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P.B. Christensen

Re: K3 keying an amplifier

> You might have a problem when only one rig is powered up, with the
> unpowered one pulling down the key/control line. The K3 is OK, as both
> outputs are open drain/collector. If that's also the case with the ICOM,
> the "Y" connector should work. If the ICOM has a pull-up resistor, or
> anything except an open drain/collector connected to that control line,
> there could be a problem...

In that case, a Schottky steering diode can be used on the Icom key line. A
1N914 or 1N400X series may be fine but I've seen instances where the higher
diode junction voltage prevents the line from going low enough to circuit
ground potential. Not sure how sensitive the Alpha 9500 is to that effect.
I agree with Scott that the K3 should be fine with its open-drain on the
MOSFET switch.

I don't see this issue very often on the amp key line -- I do see it often
when trying to use a single CW keyer, feeding multiple transceiver's in
parallel, due to the use of pull-up resistors on the paddle key line.
Again, Schottky steering diodes used for isolation at the input to each
transceiver's CW key line solves the problem.

Paul, W9AC

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HarrytheHam

Re: K3 keying an amplifier

In reply to this post by fserota

CONTENTS DELETED

The author has deleted this message.

Scott Ellington

Re: K3 keying an amplifier

In reply to this post by P.B. Christensen

I don't think the diode isolation will work in this case.

Scott K9MA

On Feb 16, 2011, at 2:36 PM, Paul Christensen wrote:

>> You might have a problem when only one rig is powered up, with the
>> unpowered one pulling down the key/control line. The K3 is OK, as both
>> outputs are open drain/collector. If that's also the case with the ICOM,
>> the "Y" connector should work. If the ICOM has a pull-up resistor, or
>> anything except an open drain/collector connected to that control line,
>> there could be a problem...
>
> In that case, a Schottky steering diode can be used on the Icom key line. A
> 1N914 or 1N400X series may be fine but I've seen instances where the higher
> diode junction voltage prevents the line from going low enough to circuit
> ground potential. Not sure how sensitive the Alpha 9500 is to that effect.
> I agree with Scott that the K3 should be fine with its open-drain on the
> MOSFET switch.
>
> I don't see this issue very often on the amp key line -- I do see it often
> when trying to use a single CW keyer, feeding multiple transceiver's in
> parallel, due to the use of pull-up resistors on the paddle key line.
> Again, Schottky steering diodes used for isolation at the input to each
> transceiver's CW key line solves the problem.
>
> Paul, W9AC
>
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P.B. Christensen

Re: K3 keying an amplifier

>I don't think the diode isolation will work in this case.
>
> Scott K9MA

If the Icom used an amp key line from an NPN transistor with an open
collector and a high value (e.g., 10K) pull-up resistor to a positive supply
rail, then all one needs is a steering diode added to the Icom key line
configured with the cathode to the junction of the Icom's collector and
pull-up resistor. The diode's anode points to the Alpha 9500. The K3 with
its MOSFET output simply parallels the 9500 key line. It doesn't care.

If the Icom is unpowered or powered, a Schottky steering diode will isolate
the pull-up resistor while still allowing the driving transistor's junction
to pull low enough to ground. An unbiased or unpowered NPN open-collector
switching transistor should not pull to ground potential if the rig is
powered down.

The only remaining obstacle is that when the Icom is powered down, the Alpha
9500 key line would see 10K resistance through the pull-up resistor to the
power supply positive rail. Powered down, that rail may be close to ground
potential. So, whether a steering diode alone will work is really a matter
of: (1) the value of the pull-up resistor; and (2) whether the Alpha 9500's
key line circuitry is sensitive to high-impedance switching. No problem if
the Alpha uses a photo-transistor on the input key line, for example. But
if say a pair of both pull-up and pull-down resistors are used ahead of a
CMOS gate, then the value of the resistors need to be known.

If a steering diode still doesn't work, then a separate switching transistor
can be used, using an open-collector without a pull-up resistor -- or a
MOSFET without a pull up on the drain.

Paul, W9AC

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Joe Subich, W4TV-4

Re: K3 keying an amplifier

In reply to this post by HarrytheHam

The same thing can be accomplished with any 2 x 2 or 2 x 4 audio
switcher - left/right become PTT and ALC. Radio Shack and most
consumer electronics stores have a reasonable selection of A/V
switches generally for less than the cost of a case, switch and
the connectors.

73,

... Joe, W4TV

On 2/16/2011 3:43 PM, HarrytheHam wrote:

>
> Fred,
>
> I run a Kenwood TS-590S and the K3 with my Tokyo Hy Power HL-1.2Kfx amp. I
> take the keying and ALC lines from both rigs and connect them to an LDG
> ALK-2 switch (2 port switch) and then connect a set of "common" keying and
> ALC lines from the LDG to the amp. Works just fine.
>
> Harry WE1X
>

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Scott Ellington

Re: K3 keying an amplifier

In reply to this post by P.B. Christensen

Sorry, I still don't think it will work reliably with the ICOM unpowered, if it has a pull-up resistor, etc. However, the ICOM may in fact be open collector/drain, in which case there's no problem. Might be worth checking.

Scott K9MA

On Feb 16, 2011, at 3:48 PM, Paul Christensen wrote:

>> I don't think the diode isolation will work in this case.
>>
>> Scott K9MA
>
> If the Icom used an amp key line from an NPN transistor with an open
> collector and a high value (e.g., 10K) pull-up resistor to a positive supply
> rail, then all one needs is a steering diode added to the Icom key line
> configured with the cathode to the junction of the Icom's collector and
> pull-up resistor. The diode's anode points to the Alpha 9500. The K3 with
> its MOSFET output simply parallels the 9500 key line. It doesn't care.
>
> If the Icom is unpowered or powered, a Schottky steering diode will isolate
> the pull-up resistor while still allowing the driving transistor's junction
> to pull low enough to ground. An unbiased or unpowered NPN open-collector
> switching transistor should not pull to ground potential if the rig is
> powered down.
>
> The only remaining obstacle is that when the Icom is powered down, the Alpha
> 9500 key line would see 10K resistance through the pull-up resistor to the
> power supply positive rail. Powered down, that rail may be close to ground
> potential. So, whether a steering diode alone will work is really a matter
> of: (1) the value of the pull-up resistor; and (2) whether the Alpha 9500's
> key line circuitry is sensitive to high-impedance switching. No problem if
> the Alpha uses a photo-transistor on the input key line, for example. But
> if say a pair of both pull-up and pull-down resistors are used ahead of a
> CMOS gate, then the value of the resistors need to be known.
>
> If a steering diode still doesn't work, then a separate switching transistor
> can be used, using an open-collector without a pull-up resistor -- or a
> MOSFET without a pull up on the drain.
>
> Paul, W9AC
>
> ______________________________________________________________
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P.B. Christensen

Re: K3 keying an amplifier

Sounds like a wager for some beer money! :-))

Paul, W9AC

----- Original Message -----
From: "Scott Ellington" <[hidden email]>
To: "Elecraft Reflector" <[hidden email]>
Sent: Wednesday, February 16, 2011 5:10 PM
Subject: Re: [Elecraft] K3 keying an amplifier

> Sorry, I still don't think it will work reliably with the ICOM unpowered,
> if it has a pull-up resistor, etc. However, the ICOM may in fact be open
> collector/drain, in which case there's no problem. Might be worth
> checking.
>
> Scott K9MA
>
>
>
> On Feb 16, 2011, at 3:48 PM, Paul Christensen wrote:
>
>>> I don't think the diode isolation will work in this case.
>>>
>>> Scott K9MA
>>
>> If the Icom used an amp key line from an NPN transistor with an open
>> collector and a high value (e.g., 10K) pull-up resistor to a positive
>> supply
>> rail, then all one needs is a steering diode added to the Icom key line
>> configured with the cathode to the junction of the Icom's collector and
>> pull-up resistor. The diode's anode points to the Alpha 9500. The K3
>> with
>> its MOSFET output simply parallels the 9500 key line. It doesn't care.
>>
>> If the Icom is unpowered or powered, a Schottky steering diode will
>> isolate
>> the pull-up resistor while still allowing the driving transistor's
>> junction
>> to pull low enough to ground. An unbiased or unpowered NPN
>> open-collector
>> switching transistor should not pull to ground potential if the rig is
>> powered down.
>>
>> The only remaining obstacle is that when the Icom is powered down, the
>> Alpha
>> 9500 key line would see 10K resistance through the pull-up resistor to
>> the
>> power supply positive rail. Powered down, that rail may be close to
>> ground
>> potential. So, whether a steering diode alone will work is really a
>> matter
>> of: (1) the value of the pull-up resistor; and (2) whether the Alpha
>> 9500's
>> key line circuitry is sensitive to high-impedance switching. No problem
>> if
>> the Alpha uses a photo-transistor on the input key line, for example.
>> But
>> if say a pair of both pull-up and pull-down resistors are used ahead of a
>> CMOS gate, then the value of the resistors need to be known.
>>
>> If a steering diode still doesn't work, then a separate switching
>> transistor
>> can be used, using an open-collector without a pull-up resistor -- or a
>> MOSFET without a pull up on the drain.
>>
>> Paul, W9AC
>>
>> ______________________________________________________________
>> 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
>
> Scott Ellington
> Madison, Wisconsin
> USA
>
>
>
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John Seney

Re: K3 keying an amplifier

In reply to this post by fserota

K3 keys Alpha 9500 plug-n-play full break-in sweet!

73

WD1V

Sent from my iPhone
John Seney
603 785-2413

On Feb 16, 2011, at 2:30 PM, Fred Serota <[hidden email]> wrote:

Lu Romero - W4LT

Re: K3 keying an amplifier

In reply to this post by fserota

Or a composite video A/B switch.

I have been using a Radio Shack composite/S-Video one in two
out Stereo audio and video switch to delegate amplifier key
lines, footswitch and Paddles between my primary K3 and my
secondary TS570 for a few years now.

The S-Video lines switch the paddles between each radio's
Microkeyer, while the video and audio RCA cables switch the
footswitch send to the Microkeyers and the key lines from
the rigs to the amplifier.

Snazzy thing, a sloping front panel in silver and gray
plastic with big rectangular hard to miss delegation buttons
that came with custom labels.

I even have a spare set of RCA jacks that might be pressed
into service for something else, like big fat red "this
radio is enabled" LED lamps... Well, maybe not :)

Cost a total of I think $4. I have seen other similar
things at WalMart and Target.

-lu-W4LT
K3 # 3192

Message: 9
Date: Wed, 16 Feb 2011 16:52:50 -0500
From: "Joe Subich, W4TV" <[hidden email]>
Subject: Re: [Elecraft] K3 keying an amplifier
To: [hidden email]
Message-ID: <[hidden email]>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

The same thing can be accomplished with any 2 x 2 or 2 x 4
audio
switcher - left/right become PTT and ALC. Radio Shack and
most
consumer electronics stores have a reasonable selection of
A/V
switches generally for less than the cost of a case, switch
and
the connectors.

73,

... Joe, W4TV

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