The Pd was specified at 24/7 commercial AM/FM service. Obviously ham SSB/CW
doesnt even come close nor does ham RTTY/digi unless its also 24/7
Carl
KM1H
----- Original Message -----
From: "Sam Carpenter" <sam@owenscommunication.com>
To: "'Roger (sub1)'" <sub1@rogerhalstead.com>; <amps@contesting.com>
Sent: Thursday, May 26, 2011 10:37 AM
Subject: Re: [Amps] 4-1000A Pi-Output-Load-Control & RTTY
> Isn't the "real" plate dissipation much, much higher than 1kw? Even the
> 3x3
> is 3x4. I have always been told that you can treat it like a 4k
> dissipation
> tube.
>
>
> -----Original Message-----
> From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
> Behalf Of Roger (sub1)
> Sent: Thursday, May 26, 2011 3:01 AM
> To: amps@contesting.com
> Subject: Re: [Amps] 4-1000A Pi-Output-Load-Control & RTTY
>
> On 5/25/2011 3:04 PM, Bill Fuqua wrote:
>> On HF a 4-1000A should run a good 1.5kW , even more, continuously.
>> Red glowing plate is normal. In fact when in idle with 5500 V on plate
>> in
>> GG they glow
>> brighter than when driven to 1.5kW output. Unless there is some reason
>> why
>> the efficiency is low, they should operate 24/7 with a full gallon
>> output.
>> 73
>> Bill wa4lav
>>
>
> If the tube has enough emission to run it, a 1000 watt plate dissipation
> at 60% efficiency should be capable of 1.67KW out without exceeding the
> plate dissipation. As Carl said, cooling is important and if efficiency
> is below 60% it's time to get it back up there. Just divide the plate
> dissipation rating by the percent. IOW for a 1500 watt tube dissipation
> the tube should be capable of 1500/0.6=2500 watts. But there are tubes
> like the 4CX1500B which I understand will not come near the 2500 out due
> to lack of emission.
>
> Now I have a FU728F with only a 1200 watt dissipation rating, BUT it's
> capable of 2500 PEP out. As SSB has a duty cycle of only 20% this is no
> where near hitting the 1200 watt dissipation. The tube is capable of a
> 2KW nominal output. At 60% efficient that works out to an input of 3,333
> watts - 2000W = 1333 watts dissipation. which is 133 watts over the
> listed plate dissipation. Boost the air flow a bit (might get a bit
> noisy) and you are still within the capability of the tube. How well
> it'd hold up running that much emission I don't know.
>
> I've never used a 4-1000A, but am looking at picking up a pair of good,
> tested ones locally along with a stack of 813's and 3-500s. I think a
> 4-1000A should be capable of, or close to, matching anything a "pair" of
> 3-500s can do.
> Except I had forgotten how little the 3-500s look when compared to a
> 4-1000A<:-)) I haven't heard what the club plans yet, but a few of them
> are likely to show up at the next swap if club members don't take them
> all. As there are few of us running QRO I think there may be a few
> available. I'll know more in a couple weeks.
>
> BTW at work (in the old days) we used to run a pair of Amperex tubes
> that looked like 3-500s on steroids (bout the size of a 4-1000A but with
> a graphite plate). They were a low Mu triode, convection cooled with a
> tad over 6KV on the plate running about 6 KW, link coupled into a wide
> range of impedances.
>
> One of the locals pulled the guts out of one of those and built up a
> 4-1000A in it. He used to claim he may not have had the most powerful
> amp, but it was likely the largest and heaviest KW around. <:-))
>
> 73
>
> Roger (K8RI)
>
>> At 11:58 AM 5/25/2011 -0400, w3hvq wrote:
>>> Gents/Ladies,
>>> Just a suggestion if running a 1-1000A and the bright red plate
>>> bothers you as it does me. I know, many think that this tube should
>>> always run with a plate red because its built for it. All I know is
>>> that
>>> my HB amp's tube is still in perfect condition after 15 years of mostly
>>> "black-plate use" here at station W8OHT.
>>> My suggestion is based on my happy experience in the recent Volta
>>> RTTY contest. For good results in this DX contest, as is in most,
>>> almost
>>> full RF output is required from the amplifier when using a 4-1000A
>>> linear
>>> into a poor-man's inverted ell on 40 meters at night, for example. My
>>> tube's biasing is fixed at about 10 vdc as I recall.
>>> When my homebrewed Pi loading control (ex-HRO-receiver variable
>>> with
>>> all sections-in-parallel) was set the same for RTTY as for SSB or CW, my
>>> tube's plate went from black to full red (not yellow) by the time my
>>> longest contest exchange macro had completed its canned message: (his
>>> call 599 Q# Q# - 05 05 his-call). Since I couldn't allow my favorite
>>> pet
>>> tube to undergo such treatment, I reduced the drive from the K-3 to
>>> about
>>> 11 watts. A cheap old RF watt meter on the antenna line indicated about
>>> 300 watts to the antenna (with no appreciable reflected power). Due to
>>> noisey nitetime conditions on 40m this output signal was enough to get
>>> DX, but only with frequent repeats.
>>> So I made an effort to see if I could lighten the loading control
>>> to
>>> result in more RF voltage on the plate of the subject tube and thereby
>>> get the same output with less DC plate current. The HRO loading control
>>> had been indicating a reading of 200, but now I could put amplifier in
>>> tune and use more drive power (45 watts), yet experienced no RF voltage
>>> break downs (frying sounds) in the amplifier's output circuit (the HRO
>>> loading dial now indicated 25 (a much higher output pi loading capacity,
>>> i.e., lighter loading). Now turning the tuning capacitor always yielded
>>> a much easier-to-adjust dip and there was only slight-redness in the
>>> plate at the very end of contest transmissions. Now the output RF
>>> meter
>>> indicated 850 watts output to the antenna and the longest sending macro
>>> for the contest resulted in plate redness only during the final second
>>> of
>>> these hundred-percent-duty-cycle transmissions. So "Mission
>>> accomplished". No more contest messages had to be repeated.
>>> FYI,
>>> John, W8OHT
>>> _______________________________________________
>>> Amps mailing list
>>> Amps@contesting.com
>>> http://lists.contesting.com/mailman/listinfo/amps
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