[Amps] Re K3

[Fern]

Jim:
      Where in the world are you getting your misinformation from re the K3? 
You don't own one so quit running the darn radio down. Most of us ham don't 
run any more than the legal power of 1500 watts so there's no need for a 200 
watt exciter. I happen to have Icom, Kenwood and Yaesu rigs and by far, the 
K3 has them all beat without a doubt. It would be nice if people would quit 
running down equipment that they don't even own. I've been in the 
communications business for over 50 years with owning my own business for 
over 25 years so I think that I have a bit of an  idea as to what I'm 
talking about as I have on my disposal all of the test equipment to check 
this all out.
    The output power on the K3 is just over 120 watts dc (key down on mine) 
not 100 W pep as you stated. 99% of legal hf amplifiers don't require any 
more than 100 watts to drive them to full 1500 W allowed power. No offense 
Jim, I'm just stating the facts.
Fern

----- Original Message ----- 
From: "Jim Thomson" <jim.thom at telus.net>
To: <amps at contesting.com>
Sent: Friday, August 17, 2012 7:57 PM
Subject: [Amps] K3 spike problem


> Date: Thu, 16 Aug 2012 14:11:02 -0700
> From: Jim Brown <jim at audiosystemsgroup.com>
> Subject: Re: [Amps] K3 spike problem
>
> On 8/16/2012 5:59 AM, Joe Subich, W4TV wrote:
>> In addition, if Charlie is using external ALC (he does not say) and
>> has the K3's power control set too high, he will see the spike due
>> to ALC time constants*in the amplifier*.
>
> It should be noted that when high quality rigs like the K3 are used to
> drive a power amp, amplifier output power should be set by using just
> enough drive power, NOT by setting drive power higher and using ALC to
> reduce it. For at least 30 years, Ten Tec has recommended AGAINST using
> ALC with their rigs and power amps in this manner. The only good reason
> for using ALC between a power amp and a transceiver is to protect the
> amp in case of a failure in the antenna system.
>
> ###  Unless the amp has a front panel adjustable ALC  control knob,
> it won’t work anyway.  Also, the alc time constant in the  amp  HAS
> to match the alc time constant in the XCVR..and NONE of em do..
> so don’t waste your time.
>
>
>
>
> In an excellent applications note on the topic, Tom, W8JI, noted that
> many rigs produce a spike of their full power output when their drive
> level is set well below full power. For those rigs Tom recommends a
> passive attenuator between the rig and the amplifier. The K3 is NOT one
> of those rigs -- indeed, it is quite well behaved. It's also one of the
> cleanest rigs on the air.
>
> ###  IOW, if the amp requires 50 watts of drive, then use a 3 db pad 
> between
> the xcvr and amp, then run the xcvr at 100 w output.   IE: the pad is used 
> to
> control the power output, and not any control in the amp.  If 25w drive 
> required,
> then a 6db  pad is  required.  Any pad is a PITA.   The 3db pad has to be 
> rated
> for at least 50 w CCS.   The 6 db pad has to be rated for at least  75 
> watts CCS.
> Then you also lose   3-6db on RX... which is the last thing you want.
>
> ##  a simpler approach to adjustable po  is to just put –9vdc across a 50 
> k
> pot...then feed 0-9 vdc (neg)   into the alc buss  on the xcvr.   Crank po
> control on xcvr to max... then adjust pot for desired output..from 0-max.
> No alc time constants to mess with,  since you have already developed the
> alc voltage  with your –9vdc source.   And no spike problem.
>
>
>
> ##  The K3 is NOT a clean xcvr on ssb.   It has typ lousy imd... like –29 
> db pep
> for IMD3.   That’s on a par with sweep tubes from the 70’s.   It only does 
> 100 w
> pep out, and I require a  200-250w pep put xcvr..so no K3 on my desk.
> Ten tec  needs to go back to the drawing board, and
> build a competitive xcvr.... not one that’s  suited  for cw only + grid 
> driven
> tetrodes.
>
> Jim  VE7RF
>
> 73, Jim K9YC
>
> _______________________________________________
> 

π