----- Original Message -----
From: "Jeff Blaine" <keepwalking188@yahoo.com>
To: "Carl" <km1h@jeremy.mv.com>
Cc: <amps@contesting.com>
Sent: Friday, March 13, 2009 5:47 PM
Subject: Re: [Amps] 810 Amplifier
> 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.
Something is definitely wrong with your water Jeff. What is your input
circuit? Its easy to have a good match to the exciter and a poor
transfer to the tube. Just about any output tank circuit will work, 30M
isnt much above audio <G>
>
> 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.
Yeah, I have the same one from O'Malley, dated 1963 I think. Seems a few
enterprising hams were rebranding Cetrons and trying to get some SSB
action. Taylor built the tube for AM modulators and then AM disappeared
almost overnight. Cetron twisted Heathkits arm to use it at HF and the
rest is history.
So I do beleive the old tubes are probably much stronger than
> the current vintage of Chinese made units.
Agree about current ones but less than a year ago I could beat on the
Penta's and never had a failure. Same with their 3-500's.
>
> 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.
The 30% duty cycle goes up into the CW range with processing.
>
> 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.
Dahl lists it as 800V/500ma in an old catalog.
> 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.
You got more nerve than Id have! Ive tweaked 900W out of a pair of
Pentas once and 800 many times on 6M, Needless to say I didnt keep them
there for long and advise the customers to back off on the drive.
Get back to me with that 30M info, something is amiss.
Carl
KM1H
>
> 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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