[MAMS] 7289 operating voltages

[Danny Pease]

Thanks Mark, I'll check to see what he has. I know it is an older unit but I
don't know that he has ever said who manufactured it.

Danny NG9R


-----Original Message-----
From: mams-bounces at mailman.qth.net [mailto:mams-bounces at mailman.qth.net] On
Behalf Of MARK K8MD
Sent: Monday, December 03, 2012 8:06 PM
To: Mid-America Microwave Society
Subject: Re: [MAMS] 7289 operating voltages

Dan I hope that's not  one of the GrantPass Cavities. I found with a
microwave detector that it was leaking RF all over Ham Shack.  The solution
was take conductive copper tape and the seal the  cavity. I was see only 90
watts then the power jumped to 250W Key down my amp has 1100VDC when
transmitting idle is 1400 VDC. I don't care about the  current and use a
zener for bias and key the amp as N6CA does and about 12watts drive  Mark,
K8MD

--- On Mon, 12/3/12, Danny Pease <dpease at adams.net> wrote:

From: Danny Pease <dpease at adams.net>
Subject: Re: [MAMS] 7289 operating voltages
To: K9EA at arrl.net, "'Mid-America Microwave Society'" <mams at mailman.qth.net>
Date: Monday, December 3, 2012, 3:20 PM

Thanks Dan,

Jerry has both 500 watt and 250 watt 400 to 1000 MHz elements, both read the
same (doesn't mean either one is close though). The 250 watt element is very
close at 532, not sure how close at 1296 though. I do have a fairly t 5 watt
element and a couple of Narda couplers, maybe I'll look to see what I can do
with those.

He has tried a couple of different NOS Eimac tubes with the same results.
The last I heard he was going to try a third tube.

What I can gather from him is the bias seems to read higher when unkeyed
that when keyed, one reason I would like someone voltage measurements from
working amplifiers

I have read Chip's article and along with everything else I have found,
never seem to mention actual bias voltage measurements.

Thanks

Danny NG9R


-----Original Message-----
From: mams-bounces at mailman.qth.net [mailto:mams-bounces at mailman.qth.net] On
Behalf Of Dan Michnay
Sent: Monday, December 03, 2012 10:54 AM
To: Mid-America Microwave Society
Subject: Re: [MAMS] 7289 operating voltages

Dan

Checkout the article written by N6CA in QST( A Quarter Kilowatt amp for
1296) some years ago and in several issues of the ARRL handbook. Also see
his website for update info. I have one of his amps and in my experience
there is a great variability in what Po you can get vs the individual tube.
Some are much better than others. He recommends using only Machlett tubes by
the way.

I can usually get about 125 watts at around 300 Ma with roughly 1100 volts
on the plate. Another issue is the accuracy of the power meter you are using
but you probably have that covered. My stuff is not up and operating right
now or could get more definitivenumbers.

GL and 73
Dan K9EA
On 12/3/2012 10:47 AM, Danny Pease wrote:
> I am in need of some real world operating parameters for a single 7289 
> in grounded grid on 1296. Plate current and voltage, grid current and 
> voltage (both keyed and in standby) and efficiency.
>
> WJ9G has a single tube cavity amp and is only seeing about 90 watts 
> out with
> 8 watts of drive, plate voltage is 1200 VDC at 300 milliamps. I would 
> expect to see more than 150 watts given the drive level and input power.
>
> He has set the bias to get 25 milliamps of idle current but has not 
> actually measured what the actual bias voltage is when keyed.
>
> Any real world measured numbers would be a great help in trouble 
> shooting his output issue.
>
> Thanks
>
> Danny NG9R
>
>
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