[Amps] Why do tubes cost so much?
Carl
km1h at jeremy.mv.com
Tue Aug 31 09:26:39 PDT 2010
My modeling in the 90's with YO included reworking the CC A50-5S as 4 and 5
elements.
The gain difference between them and the original was only a few tenths when
optimized at the low end.
The optimized F/R of either went to 26 and 28dB respectively, up from 19dB
as built. In some noisy locations thats a big help.
The feed impedance of the wide spaced 4el dropped to 14-18 Ohms over the low
end while my modified 5el ran 32-34 Ohms, similar to stock and not requiring
messing with the gamma match. Numerous duplications have been built by
others of the 5el.
I can provide plots of all 3 iterations which have been verified with the
NEC provided in all versions of YO.
Amplifier related: They will take 1500W.
Carl
KM1H
----- Original Message -----
From: "Bill VanAlstyne W5WVO" <w5wvo at cybermesa.net>
To: "Carl" <km1h at jeremy.mv.com>; "[Amps]" <amps at contesting.com>
Sent: Tuesday, August 31, 2010 8:17 AM
Subject: Re: [Amps] Why do tubes cost so much?
> Well, no, I don't play with cars. I was always an electronics guy first
> and foremost, from an early age. I didn't even get a driver license until
> I was 18. LOL If it didn't directly contribute to ham radio, I wasn't
> interested.
>
> And it's true that my assumption regarding 6-meter yagis is low-end
> (50.0-50.5 MHz) weak-signal operation. Why on earth would you want a yagi
> antenna at 53 MHz? I mean, what's even there? Repeaters? (Don't get me
> started... ) If you really have a need for directable weak-signal repeater
> work at the high end of the band, model an optimized, high-efficiency yagi
> design for that frequency that can be mounted vertically polarized (i.e.,
> you design that into the model).
>
> As for the A50-5S, you can make it much better without extending the boom
> just by removing one of the excess parasitic elements and remodeling. It
> will have slightly more gain and a much better pattern. Same is true for
> their 6-element yagi (A50-6S). Remove one of the directors, remodel as a
> 5-el and optimize for best trade-off of pattern vs. gain. It too will be a
> much better antenna with fewer parasitic elements. Will it be as
> broad-banded? I have no idea, I've never even attempted to model a yagi
> for 6 meters above 50.5 MHz. I have zero interest in anything that's
> currently up there. Now, if they opened up the band plan a little so that
> the vast majority of 6m users weren't all jammed together into the bottom
> 300 kHz or so...
>
> Anyway, I suppose we should nip this VHF thread in the bud, as it's
> off-topic. I shouldn't have brought it up, but it seemed like an obvious
> example of the point I was trying to make. Maybe I was wrong. :-) Mea
> culpa.
>
> Bill W5WVO
>
> --------------------------------------------------
> From: "Carl" <km1h at jeremy.mv.com>
> Sent: Monday, August 30, 2010 19:07
> To: "Bill VanAlstyne W5WVO" <w5wvo at cybermesa.net>; "[Amps]"
> <amps at contesting.com>
> Subject: Re: [Amps] Why do tubes cost so much?
>
>> I guess you dont play around with vintage vehicles Bill. Reproducing old
>> parts is a huge and profitable business if the quality is there. Some
>> have the blessings of the Big 3.
>>
>> And it doesnt have to be that old either, anything from around 1971 and
>> earlier is fair game.
>>
>> Id almost think a 4-1000A could be built at home by a very talented
>> industrial modelmaker, not toy models.
>>
>> As far as the current CC 5el for 6M, that was PC designed and is pretty
>> decent considering the wide bandwidth it has to cover. A PC program cant
>> do much better on a 12' boom except optimize the F/R at the low end.
>> Anybody can run off a decent yagi for the low end CW/SSB operators.
>>
>> Carl
>> KM1H
>>
>>
>> ------ Original Message -----
>> From: "Bill VanAlstyne W5WVO" <w5wvo at cybermesa.net>
>> To: "Carl" <km1h at jeremy.mv.com>; "[Amps]" <amps at contesting.com>
>> Sent: Monday, August 30, 2010 1:33 PM
>> Subject: Re: [Amps] Why do tubes cost so much?
>>
>>
>>> This is an interesting thread in terms of manufacturing and marketing
>>> "philosophy" (if you will). When you're looking at a tube that has been
>>> around for a while, you're basically looking at a post-maturity product.
>>> That doesn't mean that the demand for the product is lessening, just
>>> that it has stopped increasing and the product has stopped evolving to
>>> more efficiently meet increasing demand. You reach a "good enough"
>>> balance point where you're going to be meeting current and future demand
>>> and are making your margin. Why try to change anything when all your R&D
>>> resources are 100% absorbed working on future products?
>>>
>>> Another case in point is the family of Cushcraft VHF yagi antennas,
>>> which have been marketed essentially untouched for decades. The designs
>>> go way back before computer modeling, and they basically suck (most
>>> notably the 12-foot 5-element 6m yagi). Many people, including myself,
>>> have redesigned them using computer modeling and vastly improved their
>>> performance. Cushcraft could obviously do the same thing. But do they?
>>> No. They're in the post-maturity phase of these products, and it is
>>> simply not worthwhile for them to put one more DIME into them for R&D.
>>>
>>> I think there may be some axioms at work here.
>>>
>>> Axiom #1:
>>> You can make more money selling something new than selling something
>>> old.
>>>
>>> Axiom #2:
>>> If you make something old better with new technology, to the marketplace
>>> it's not something new, it's still something old. See Axiom #1.
>>>
>>> Axiom #3:
>>> If you ARE making money selling something old that really isn't very
>>> good, but it is absorbing zero dollars in engineering overhead, just
>>> keep selling it, and don't put another DIME into it to make it better.
>>> See Axiom #2.
>>>
>>> Bill W5WVO
>>>
>>>
>>> --------------------------------------------------
>>> From: "Carl" <km1h at jeremy.mv.com>
>>> Sent: Monday, August 30, 2010 13:04
>>> To: "Jim Tonne" <tonne at comcast.net>; <amps at contesting.com>
>>> Subject: Re: [Amps] Why do tubes cost so much?
>>>
>>>> I read somewhere (years ago so dont quote me) that tubes with extremely
>>>> close grids such as the 3CX800 and 1500 have yields around 20%. You
>>>> would
>>>> think that after all these years companies would have better technology
>>>> available to assemble.
>>>>
>>>> Setup times should be controlled also, I just suspect that Eimac doesnt
>>>> care
>>>> since they still have the bulk of the market that will pay whatever it
>>>> costs.
>>>>
>>>> Carl
>>>> KM1H
>>>>
>>>>
>>>> ----- Original Message -----
>>>> From: "Jim Tonne" <tonne at comcast.net>
>>>> To: "Frederick Mott" <fredmott at zoominternet.net>;
>>>> <dezrat1242 at yahoo.com>;
>>>> <amps at contesting.com>
>>>> Sent: Sunday, August 29, 2010 9:40 PM
>>>> Subject: Re: [Amps] Why do tubes cost so much?
>>>>
>>>>
>>>>>
>>>>> I think that Bill and Fred have summarized things
>>>>> nicely.
>>>>>
>>>>> But I also suspect that the "tiny" tubes like a 6BA6
>>>>> are assembled in a relatively (if not entirely) automated
>>>>> operation. And I chose the 6BA6 because of how the
>>>>> first grid is formed, with that nonuniform winding.
>>>>>
>>>>> The "big" tubes - those with 100 kW or more of plate
>>>>> dissipation - offer the same challenges that the 1000
>>>>> watt tubes do but are simply scaled up and are
>>>>> larger in every respect and so probably relatively
>>>>> easier to build. The cost of materials in those huge
>>>>> tubes is probably significant. So is warranty cost.
>>>>>
>>>>> - JimT W4ENE
>>>>>
>>>>>
>>>>>> I have often wondered why big tubes cost so much.
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> Amps mailing list
>>>>> Amps at contesting.com
>>>>> http://lists.contesting.com/mailman/listinfo/amps
>>>>
>>>> _______________________________________________
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>>>>
>>>
>>
>>
>>
>
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