Carl,
I don't have any experience with the tube at 50mhz. But in my
particular case, on 10mhz, the efficiency had dropped down to something
like 40%. And that was with a matched input network. Like I say, it's
the water as our experiences are so far apart there must be another
factor in here to explain the delta.
I have a datasheet from "Husky" that is ancient. They spec a 2500V
service and have a mention of 225w plate dis. No mention of upper
frequency range but the data sheet is listed at 30 mhz in their
example. So I do beleive the old tubes are probably much stronger than
the current vintage of Chinese made units.
You make a very good point about the tune-up. And I am probably
underestimating the number of guys using SSB which by it's nature is
very easy on the tubes.
One thing I can say, again in my case only, the SB200 transformer is
really a star performer. I don't know what the CCS rating is (not
advertised that I could find) but Harbaugh told me it was 500ma @ 850v.
I have been using this one here in a variety of load situations over the
last 6 months and the TX will put out 700ma with only a minimal rise.
Even on RTTY contest run-mode data, I could go about 1 hour before the
exterior temp hit 50C and at that point I shut it down. I don't know
what the internal temp would have been but I was worried that I would
inadvertently hit a breakdown temp of one of the insulating materials
and fry the tx. No easy way to measure the core temp so I just picked
50C as the max point and called it safe there. I planned to replace
that TX with a custom unit and so have given it hell quite a lot and the
thing just keeps on performing.
Contrast that SB200 (1KW rated input) at 18lbs performance to the SB220
(2KW rated input) - built on the same core but with a slightly larger
stack. Weight 22 lbs. Fried that thing in about 15 minutes of
intermittent load testing.
While I don't think we will come together on the capability or endurance
of the 572b, I can say that in a pretty serious abuse condition, the
SB200 transformer is really a workhorse. And for a guy who wants a
cheap 2KV PS that would be pretty comfortable at up to about 650ma on
the plate, it's a good choice.
73/jeff/ac0c
Carl wrote:
> Jeff, its not the tubes that are fault in the SB-200. The culprit is
> in the input networks and that has been discussed in print and on the
> Internet over and over.
>
> On 6M I use an input that not only provides a 1.1:1 VSWR to the
> exciter but also allows the maximum power transfer to the tubes.
>
> Also since it is now a monoband amp there is no constant tuning up
> involved; once tuned leave it alone until you change antennas. Tuning
> probably ruins more tubes of any type than simply operating.
>
> In SSB/CW at a nominal 1200W input and 60% efficiency there is 480W in
> heat dissipated in the tubes. I wouldnt run a SB-200 at more than 800W
> INPUT for RTTY & digital. Besides the tubes the transformer isnt rated
> for continuous duty and a RTTY contest could smoke it if not derated.
>
> Carl
> KM1H
>
>
>
>
>
> ----- Original Message ----- From: "Jeff Blaine"
> <keepwalking188@yahoo.com>
> To: "Carl" <km1h@jeremy.mv.com>
> Cc: <amps@contesting.com>
> Sent: Thursday, March 12, 2009 9:46 PM
> Subject: Re: [Amps] 810 Amplifier
>
>
>> Carl,
>>
>> I need to get a well drilled then. Had one as a kid and that brings
>> back memories.
>>
>> And congratulations on getting the 572b's to sing. On the ones I've
>> seen (stock units), the roll-off in po as a result of drops in
>> efficiency at 15m and above is huge.
>> What is your secret for getting good efficiency out of these tubes at
>> that high frequency>
>>
>> 73/jeff/ac0c
>>
>>
>>
>> Carl wrote:
>>> Well, the water here comes out of a 660' deep well and has a bit of
>>> iron in it but none of that funny stuff you get from town water.
>>>
>>> Its very easy to get power from 572B's on 6M since they are full
>>> power rated to 54 mHz. I certainly wouldnt run RTTY or digital that
>>> way but CW/SSB doesnt bother them a bit. I test every conversion at
>>> 1 minute full bore key down; the plates get a bit of dark red near
>>> the end.
>>>
>>> Im not the only one who converts these either.
>>>
>>> Carl
>>> KM1H
>>>
>>>
>>>
>>>
>>>
>>> ----- Original Message ----- From: "Jeff Blaine"
>>> <keepwalking188@yahoo.com>
>>> To: "Carl" <km1h@jeremy.mv.com>
>>> Cc: "George Knight" <gkve3ltu@sympatico.ca>; <amps@contesting.com>
>>> Sent: Thursday, March 12, 2009 6:20 PM
>>> Subject: Re: [Amps] 810 Amplifier
>>>
>>>
>>>> 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
>>>>>>>
>>>>>>>
>>>>>>
>>>>>> _______________________________________________
>>>>>> Amps mailing list
>>>>>> Amps@contesting.com
>>>>>> http://lists.contesting.com/mailman/listinfo/amps
>>>>>
>>>>>
>>>>
>>>
>>>
>>
>
>
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