Why did Heath kit die?
Charles Harpole k4vud@hotmail.com
> Date: Sun, 31 Jan 2010 19:25:59 -0500
> From: sub1@rogerhalstead.com
> To: garyk9gs@wi.rr.com
> CC: amps@contesting.com
> Subject: Re: [Amps] Good amp to buy
>
>
>
> Gary K9GS wrote:
> > This has been an interesting thread. Along the same lines.....I wonder why
> > someone doesn't offer a well engineered kit amplifier?
> The same reason Heath doesn't sell kits any more. Economics! Those who
> build are a very small number.
> > Basically a
> > modernized SB-220 possibly using different tubes?
> Actually the 3-500 is still the most popular tube, it's relatively
> inexpensive and fairly tame and with enough voltage it'll run the legal
> limit without straining.
> > Is there possibly some
> > FCC regulation preventing this??
> >
> >
> Nope! It would require the FCC's blessings just like the ones being
> sold, but that's the only requirement.
> However, how many hams do you know that you would be comfortable with,
> poking around inside your amp with all that high voltage? I have an
> idea that at least part of the problem is our litigious (sp?) society.
> Maybe not the ham, but relatives and next of kin. Even signed Waivers of
> Liability offer very little protection from the one signing it and none
> from the next of kin.
> > Maybe two models, a KW class and a legal-limit class.
> Heath did that for years and closed shop. Maybe there's now a niche
> market for something like these, but it'd likely be a small portion of
> the overall market for amps. Would the market be large enough to support
> those doing it? Most current amps are built by relatively small
> operations, so it'd have to be small as well. Maybe two or three hams
> could do it, but remember it would have to survive the cost of receiving
> the FCC's blessing and make enough money to keep the families of those
> involved happy. It takes business and market savvy as well as a
> thorough understanding of amps to do something like this. Then there is
> the problem of "how rugged an amp or amps would you sell in kit form?"
> There will always be those who will push an amp for everything it can do
> which may be well beyond the ratings of the tube(s) and/or power supply
> and then blame the manufacturer for providing parts of insufficient
> capability. It reminds me of the early 8877's that had higher gain and
> lower drive requirements. Some hams were driving them with the full
> output of their exciters as the tube would do it even though it could
> reach its design limits with something like 50 watts or less and those
> things will put out about 2200 watts. I believe it was Carl who said
> Some one was blaming it on parasitics.
> > Perhaps even a solid
> > state AMP.
> >
> >
> Solid state is a different animal. The transistors are expensive and
> very fragile. Given a big voltage spike and a tube will normally just
> ignore it. They might blush a bit if you drive them too hard, but
> recover quickly (most times) Even the expensive, high powered
> transistors can be wiped out from the static you pick up walking across
> the floor. Even a microsecond of too high a voltage will take them out
> and maybe no more than a few milliseconds of excess current. Even the
> large, high power transistors are small physically and that makes heat
> transfer to the heat sink problematic even when using exotic heat
> transfer compounds such as "Arctic Silver" which is expensive.
> I use it on CPUs and it's very effective. Given a legal limit amp you
> have to get rid of the heat through an area that is likely to be less
> than 2% to 5% of the radiator area on a single, small, power tube like
> the 8874.. So you parallel two transistors to run the power that one is
> capable of just to get enough area to safely transfer the heat. Even
> then the delta T is pretty high. Then run them push pull. The Tokyo
> Hy-Power HL-1.5Kfx gets 1KW PEP and CW output on HF from just 4
> transistors. I can purchase a much more rugged 4CX-1500 for less money.
> You will probably spend nearly as much on the protective circuits as the
> whole rest of the amp. The basic amplifier runs about the power level of
> entry level amps and costs about $3,000. To add the capability of
> running the legal limit with some excess capacity now called overhead,
> more than doubles the price.
> The no tune, instant on, auto band switching, legal limit amps are
> great, but they come at a price and not just the monetary one. They
> require a low SWR to get maximum power out and by low I mean less than
> (>)1.2:1, more often, less than 1.1:1. That means an antenna tuner and
> retuning even after minor excursions 20 KHz or so on 40 meters. Of
> course there is now the auto-tuner which is also fantastic and almost a
> necessity for solid state amps if you do much moving around on 160, 75,
> and 40 meters. OTOH I did it with a pair of MFJ 989C tuners and an
> antenna analyzer and it worked very well. Switch in the noise bridge,
> adjust tuner, switch back to amp with no additional tuning. No on the
> air signal required at all.
>
> There are some adventuresome hams (couple even here on the reflector)
> who are working on some solid state amps at the legal limit level. Even
> with help from some well known manufacturers it's a rather daunting task.
> > The kit amplifier would be able to purchase components in volume, keeping
> > the cost down.
> >
> > Anyone know how many amps Heathkit sold anyway?? I'll bet it was a lot.
> >
> We now live in a different society as hams and individuals. Would what
> worked then, work now. Remember Heath started out small and grew like
> crazy in size and offerings. Then the market dried up abruptly. This was
> about the same time the attendance for most swaps dropped off and became
> more tire kickers than really interested purchasers. This did not
> coincide with the economy dropping off either. It did coincide with
> what a couple of manufacturers did though. Whether by chance, I don't know.
>
> 73
>
> Roger (K8RI)
>
> > 73,
> >
> > Gary K9GS
> > ++++++++++++++++++++++++++++++++++++++++++++++++
> > K9GS
> > Gary Schwartz email: k9gs (at) arrl.net
> > Check out K9NS on the web: http://www.k9ns.com
> > Society of Midwest Contesters (SMC) http://www.w9smc.com/
> > GMDXA http://www.GMDXA.org
> > ++++++++++++++++++++++++++++++++++++++++++++++++
> >
> > ----- Original Message -----
> > From: "Edward Swynar" <gswynar@durham.net>
> > To: <Gary@ka1j.com>; <amps@contesting.com>
> > Sent: Wednesday, January 27, 2010 1:03 PM
> > Subject: Re: [Amps] Good amp to buy
> >
> >
> >
> >> "...What do you recommend as a good HIGH power amp?"
> >>
> >> **********************************
> >>
> >> "Roll y'er own!" I say...
> >>
> >> The venerable, tried & true 813 is still available both new, surplus, at
> >> Hamfests, etc. Two of these in parallel grounded-grid will give you
> >> 600-watts output, four will up the ante to 1.2-kilowatts.
> >>
> >> They're practically "free", too, compared to the prices of modern 3-500Zs,
> >> 8877s, etc.
> >>
> >> And don't let their high internal output capacitance scare you: there are
> >> ways to make them play just as efficiently on 10-meters, as they do on
> >> 160.
> >>
> >> ~73~ de Eddy VE3CUI - VE3XZ
> >>
> >>
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> >>
> >
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