FW: [Elecraft] K3 and StepIR/Icom PW-1

[Jerry Flanders]

I once blew up an unprotected amplifier's output circuit when a flaky 
antenna feed line opened with 1500 watts RTTY applied.  Prior to 
that, I didn't think I needed anything more than a hand on the drive 
level control to keep my amp safe.

Now I make sure the ALC is there so the amp can cut that drive within 
milliseconds if the antenna opens up again.

The K3 ALC fix is available from Elecraft. It works.

Jerry W4UK

At 12:00 AM 9/8/2008, Greg - N4CC wrote:
>Adam -- I guess it depends on the user.  Certainly having the ALC 
>connected (if it were compatible) would be preferred...but my point 
>is that saying " the K3 should not be used as an exciter for the 
>PW-1" [without ALC] is not entirely accurate.  it is possible to use 
>the PW-1 without ALC.  It can be done and done quite 
>safely.  Granted you lose a measure of protection but if you use the 
>K3 as I do -- where it recalls the drive setting by band, a unique 
>feature of the K3 -- it is less likely that not having the ALC 
>connected will ever be an issue.   If you change the power settings 
>frequently and are not careful to return them to the desired drive 
>level when operating the amplifier then your chance of damaging the 
>amp increases without the ALC.  Cheers.  73 de Greg
>
>At 10:53 PM 9/7/2008, you wrote:
>>Hi Greg,
>>
>>The PW1 uses the ALC loop as an essential part of its protective subsystem,
>>as described in the service manual excerpt  which I sent you. Any one of
>>several anomalous operating conditions (including over-drive and load
>>mismatch) will pull down the ALC line to reduce the drive. This is the
>>amplifier's first line of defence.
>>
>>I would never put an expensive piece of equipment such as the PW1 at risk by
>>connecting it to an exciter without a fully-functional ALC loop.
>>
>>Cheers for now, 73,
>>Adam VA7OJ/AB4OJ
>>
>>-----Original Message-----
>>From: Greg - N4CC [mailto:n4cc at alltel.net]
>>Sent: 7-Sep-08 19:05
>>To: Adam Farson
>>Subject: Re: FW: [Elecraft] K3 and StepIR/Icom PW-1
>>
>>I'm using the K3 with a PW-1 and the beauty of it is you don't need the ALC
>>if you use the K3's capacity to store the power level (drive
>>level) for each band.  Obviously if you use the K3 barefoot at 100 watts you
>>would have to be careful to turn it back down with the amp but I just leave
>>it at the saved settings that I have established for output for each band.
>>The proper drive level does vary somewhat by band.  You are right about the
>>ALC ..the K3 ALC is not compatible with the PW-1 and you should not connect
>>the ALC line between the two.  73 de Greg
>>
>>At 09:08 PM 9/7/2008, you wrote:
>> >  Hi Tom,
>> >
>> >The K3 should not be used as an exciter for the PW1 unless the polarity
>> >of its external ALC input has been changed from positive-going
>> >(original) to negative-going (range 0 to -4V). Failure to heed this
>> >warning will result in extensive damage to the PW1, necessitating
>> >costly repairs (as much as
>> >$1800!)
>> >
>> >http://www.ab4oj.com/icom/main.html#alc
>> >
>> >Cheers for now, 73,
>> >Adam VA7OJ/AB4OJ
>> >
>>
>>_______________________________________________