K2/100 Keying a Drake L-4B

[ny4g]

Hi Elecrafters,
I am ready to key my Drake L-4B using my K2/100 but I read from a previous post:
"If you already have the KPA100, look on the rear panel and you will see an RCA jack marked "PA KEY OUT" between the ground connection and the power connector - this will allow you to key your external amplifier directly - but only if your amplifier has a positive voltage for its keying line.  If  your amplifier uses a negative voltage keying circuit (like the Collins 30L-1 and some others) you will need to construct an external circuit to key the amp.  73 --don n4hh K2/100 #2028 "
Does the Drake use a negative voltage for the keying (line)?
If it does what modification do I need.   I installed the Soft-key mod made by Harbach. I am not sure whether that converts the Drake to positive voltage keying.
Any help is appreciated.
Ariel    
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[Mike WA8BXN]

A simple way to find out is turn the amplifier on and measure the voltage on
the keying input on the amplifier, noting the voltage and its polarity. Next
switch your multimeter to measure current and connect it to the same place
on the amplifier. The amplifier should key and you will see how much current
needs to be switched by the radio. This procedure should work with any
amplifier.

 

73 - Mike WA8BXN

 

 

 

 

 

-------Original Message-------

 

From: Ariel Jacala

Date: 08/04/13 07:57:01

To: elecraft reflector

Subject: [Elecraft] K2/100 Keying a Drake L-4B

 

Hi Elecrafters,

I am ready to key my Drake L-4B using my K2/100 but I read from a previous
post:

"If you already have the KPA100, look on the rear panel and you will see an
RCA jack marked "PA KEY OUT" between the ground connection and the power
connector - this will allow you to key your external amplifier directly -
but only if your amplifier has a positive voltage for its keying line. If
your amplifier uses a negative voltage keying circuit (like the Collins
30L-1 and some others) you will need to construct an external circuit to key
the amp. 73 --don n4hh K2/100 #2028 "

Does the Drake use a negative voltage for the keying (line)?

If it does what modification do I need. I installed the Soft-key mod made by
Harbach. I am not sure whether that converts the Drake to positive voltage
keying.

Any help is appreciated.

Ariel
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[Don Wilhelm-4]

Ariel (and all),

I don't know the specifics of that amplifier, but one can make a quick
measurement to find the answer for yourself.
Turn on the amplifier and measure the voltage at the amp's Keying input
with your DMM.  Is it positive or negative?  How large is the voltage?

If you are concerned about the keying current, set the DMM to measure
current.  The amplifier will key, and the meter will indicate the
current that is developed.

73,
Don W3FPR

On 8/4/2013 7:56 AM, Ariel Jacala wrote:
> Hi Elecrafters,
> I am ready to key my Drake L-4B using my K2/100 but I read from a previous post:
> "If you already have the KPA100, look on the rear panel and you will see an RCA jack marked "PA KEY OUT" between the ground connection and the power connector - this will allow you to key your external amplifier directly - but only if your amplifier has a positive voltage for its keying line.  If  your amplifier uses a negative voltage keying circuit (like the Collins 30L-1 and some others) you will need to construct an external circuit to key the amp.  73 --don n4hh K2/100 #2028"
> Does the Drake use a negative voltage for the keying (line)?
> If it does what modification do I need.   I installed the Soft-key mod made by Harbach. I am not sure whether that converts the Drake to positive voltage keying.
> Any help is appreciated.
> Ariel  
>

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