I also wonder if there are fewer 'elmers' around these days and as such we're
slowly losing the culture of building stuff. There should be no excuse for
this in the days of this new-fangled interweb thingy, but here in the UK local
amateur radio clubs seem to be dying out so maybe fewer people see and help
debug each others' projects? I gained the confidence to start building stuff
because I knew other people locally who were home brewers and were helpful with
advice (G8ROU, G6ABU, GW3NWS, GW4LXO etc). But surely these days with the www
at our fingertips and a ready-made bunch of experts on this list to help
diagnose and fix problems it should be easier to home brew from scratch, kit or
no kit?
Contrary to what some people may say, you don't need a state of the art metal
workshop. The only metal working tools I use are a jigsaw, a file or two and a
drill. You can make decent cabinets and chassis like this with just sheet
aluminium, angle and a big bos of self tapping screws. Sure, I can't get an an
amazingly professional finish like Bob VK3ZL does but it's good enough for me.
What did surprise me was that when I bought a couple of large vacuum variable
capacitors on the fleamarket at Dayton and was carrying them around and back to
the car, I lost count of the number of guys with extra class callsign badges
who asked me what they were. Is there a message in there somewhere?
Dave G0OIL
-----Original Message-----
From: "Alek Petkovic" <vk6apk@bigpond.com>
To: "Charles Harpole" <k4vud@hotmail.com>
Cc: amps@contesting.com
Sent: 01/02/2010 01:48
Subject: Re: [Amps] why did Heath die?
That's easy to answer.
People don't wanna build stuff.
I have a table at our hamfest every year and I sell used and new bits
and pieces that hams can use in their construction projects . Mainly
amplifier and high voltage stuff.
Out every 100 people that go past, only 5 will look at the stuff and
2 will buy something. My prices are dirt cheap as my motive is not to
make money but rather give the builders in our small ham community
access to stuff that is hard to find and that they would have to pay
an arm and leg for elsewhere.
We all have too much money these days. There is no incentive for most
people to build when they can buy so easily.
73, Alek
VK6APK
At 08:37 AM 1/02/2010, Charles Harpole wrote:
>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
> > >>
> > >>
> > >> _______________________________________________
> > >> 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
> > >
> > >
> > _______________________________________________
> > 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
http://www.qrz.com/db/vk6apk
http://www.qrz.com/db/vk6py
_______________________________________________
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
|