the 572B has 160 watts plate dissipation each.
A pair around 320,.
Now saying that there are some issues about the tubes and plate dissipation.
These are radiation cooled tubes needing air blown on the plate and pin
seals to
keep them from cracking.
Oddly enough they are usually surrounded by good shinny aluminum which
in turns
reflects a lot of the infrared back into the envelope. If the inside of
the cabinet was painted
black the tubes' plates would be cooler. We illustrated this the other day
when one of my
fellow employees tried to pull a fast one on someone after I explained why
the "laser" thermometer
read a temperature above room temperature. The thermometer , the laser is
just used for pointing,
was reading something near his body temperature. It was seeing his
reflection in the aluminum
plate. The emissivity of shinny aluminum is very small but it is very
reflective. He told a fellow co-worker
that something was wrong with the thermometer because it read almost room
temperature when he was
looking at the bottom of a cold Pepsi can. But seemed fine when measuring
his body temperature or that
of objects in the room. Well the co-worker was me, I guess he forgot that
I had explained it to him a few
years ago.
Glass is usually fairly small in the near infrared because it is
transparent. The emissivity not only is
a measure of the ability of an object to emit radiation but also to absorb it..
I believe it was the T-368 transmitter that had an aluminum
chimney around the 4-400A but it
was black anodized. I guess they they did not want to use glass. For the
same reason you have flat
black plates in these tubes.
Anyway, I think a lot of amplifiers with glass envelop tubes would be
more reliable if the
the metal surfaces around the tubes were black.
Well, I have to get back to work. I am working a bit late tonight.
73
Bill wa4lav
At 06:20 PM 3/12/2009 -0400, you wrote:
>Carl,
>
>Can you send us some of whatever is in the water up there? Because the
>SB200's in this part of the world are sure in need of that magic elixor.
>
>What's the plate dis of a pair of 572b? Something like 360w? Maybe
>that is the answer to my question on the other subject of anode dis
>limits...
>
>Clearly a sample size of 250 sb200 converted to 6m service is an
>extreeme case (given the tubes start running out of gas at 30mhz more or
>less) - and a large sample set of 200 statistically is very significant.
>
>If that tube will work at 2x the plate dis in the north east, then I
>surely should be able to get the similar multiplier from my conversion
>project here in the fly-over country.
>
>73/jeff/ac0c
>
>Carl wrote:
> > My 2 cents anyway. :)
> >
> > Yep, I agree with the above<G>
> >
> > In my experience with converting around 250 SB-200's to 6M I can
> > unequivocally say that a majority still have the original Cetrons
> > installed and will run 700W + key down on 6M on a 240V AC line. A bit
> > less on 120V.
> >
> > Your milage may vary.
> >
> > Altho I feel the 4 x 810 project is a wasted effort it is possible to
> > do it with 4 x 813's and cover 160-10M.
> >
> > Carl
> > KM1H
> >
> >
> > ----- Original Message ----- From: "Jeff Blaine"
> > <keepwalking188@yahoo.com>
> > To: "George Knight" <gkve3ltu@sympatico.ca>
> > Cc: <amps@contesting.com>
> > Sent: Thursday, March 12, 2009 3:21 PM
> > Subject: Re: [Amps] 810 Amplifier
> >
> >
> >> George,
> >>
> >> You may want to consider a trio of GI7B (less complicated) or perhaps a
> >> 4cx800 (more complicated) if you run something other than SSB. These
> >> ceramic tubes are far more durable than the glass counterparts in my
> >> experience.
> >>
> >> I bought 3 sets of 572b last year in a test to determine the actual life
> >> of the 572b vs. duty cycle because the data for contempary versions of
> >> the 572b are hard to come by. None of the tubes could reach the 25 hour
> >> key-down accumulated time before reaching 500w output for the set. I
> >> have seen the stories of guys with 500w out on a 25 year old set of
> >> tubes in a SB200, but that is clearly the excepiton and not the rule.
> >> The 572b at 1200w out of a set of 4 is really something that can only be
> >> sustaned in the long term if conditions are perfect and the winds are at
> >> your back.
> >>
> >> So while your mileage may vary, I can say categorically that at 1200w
> >> out as the goal (meaning net average power, not PEP or peak or
> >> whatever), the 572b set of 4 will do it. But just not for very long.
> >>
> >> My 2 cents anyway. :)
> >>
> >> 73/jeff/ac0c
> >>
> >>
> >> George Knight wrote:
> >>> Thanks to all who contributed. Although there is a lack of
> >>> unanimity in the responses, I think I will go ahead with the
> >>> project. In the event that it turns out to be a total failure, it
> >>> will be quite easy to change the sockets to accept 572B tubes and
> >>> get into the 1200 watt output class.
> >>> '73, George, VE3LTU.
> >>> _______________________________________________
> >>> Amps mailing list
> >>> Amps@contesting.com
> >>> http://lists.contesting.com/mailman/listinfo/amps
> >>>
> >>>
> >>
> >> _______________________________________________
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> >> http://lists.contesting.com/mailman/listinfo/amps
> >
> >
>
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