This discussion pertains only to poorly designed AMPS. There should be no
voltage sag and the amps should be ccs at 1.5 kw out (in the US). If digital
modes are contemplated, 5 to 10 KW amps in class A mode are necessary.
On 9/24/10 1:14 AM, "Jim Thomson" <jim.thom@telus.net> wrote:
> Date: Thu, 23 Sep 2010 16:45:28 -0700
> From: "Bill, W6WRT" <dezrat1242@yahoo.com>
> Subject: Re: [Amps] Pulse tuning
>
> On Fri, 24 Sep 2010 06:23:51 +0800, Alek Petkovic <vk6apk@bigpond.com>
> wrote:
>
>>
>> That's exactly my point. You keep presenting my argument for me.
>>
>> By tuning up at 100% duty, your are not tuning to 100% output because
>> your voltage has sagged.
>>
>> With pulse tuning at 30% for example, you eliminate that voltage sag
>> problem and you are tuning much closer to that ideal 100%.
>
> REPLY:
>
> No, you are missing my point. By tuning up at 100% and getting some
> voltage sag, when you go to a lower duty cycle like SSB you have less
> sag and more headroom. Thus less likely to splatter, and equal or
> slightly more power output.
>
> Bill, W6WRT
>
> ## say what ? Not a chance. Tune up with say 1200-1500w out
> CXR, VS pulse tuning with a 20-30% duty..and watch the diff on
> the pep wattmeter.
>
> ## if you pulse tune to 1.5 kw pep out, then switch to SSB, you will be dead
> on.
> If you tune to 1.5 kw, with a CXR, then switch to ssb, B+ is no longer
> sagging..and
> PO is up a bit. Amp was never tuned up for the higher power,cuz of the lower
> duty
> cycle. IF you had gone back and pulse tuned it, you would have seen the po
> increase
> to 1600-1700w pep. With the amp pulse tuned to 1600-1700w pep out, and
> drive
> reduced, so amp is putting out only 1.5 kw pep, now you do have some
> heardroom.
>
> ## if u insist on tuning with a cxr, at least, when done, overcouple the
> loading a bit, till
> the po drops 2% [30w]. Now you have effectively got the loading where it
> should be.
>
> Jim VE7RF
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