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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