Mega - Ditto's...
Tubes are still the way to go unless you need your amp on battery power.
At ~ $50 each, the 4CX800 is hard to beat. For the money, they are a
better deal than the 3-500Z, even in it's heyday. If you purchase an extra
set of 800's at the get-go, you could very well be set for life.
Life's too short for QRP...
Steve - WG7K
----- Original Message -----
From: "Will Matney" <craxd1@ezwv.com>
To: <amps@contesting.com>
Sent: Monday, March 28, 2005 6:03 PM
Subject: Re: [Amps] Solid State HF High power linear amps
> Yup,
>
> Plus the solid state designs splatter something awful without a filter on
> the end. Most amateur amps have a switchable filter on the output
> (switchable between each band). Also, if you have a high SWR condition, a
> transistor is generally toast unless you have a bunch of safety circuitry
> to prevent it. A tube can handle the beating with no ill effects for a
> period of time. Some of the large ones I've seen using up to 32
> transistors had to use welding cable to supply the power due to the very
> high current involved. Most transistors for this frequency range (2-30
> MHz) run on 12-18 Vdc and just a few higher. The transistors were really
> designed to be used as a single push-pull stage even though they can be
> split and combined.
>
> If it were me, and were going to start a new one, I'd build using a couple
> of 4CX800's.
>
> Best,
>
> Will
>
> *********** REPLY SEPARATOR ***********
>
> On 3/28/05 at 12:13 PM David Kirkby wrote:
>
>>Prasad Agrahar wrote:
>>
>>>Group
>>>
>>>Once a very active ham, I have been inactive for many years.
>>>
>>Same here
>>
>>> I have
>>>started dreaming about getting back into this exciting hobby. Signs
>>>are clear that the day is fast approaching. I was a home brewer and I
>>>will still be one. My wish is to gather parts to build a decent HF
>>>high power linear soon.
>>>
>>>That made me wonder whether I must focus on building a tube (valve)
>>>amp or is there any other choice? Tubes are not made any longer. Tubes
>>>that are available in the market are old leftovers and soon, there
>>>will be no more.
>>>
>>>
>>There are still made. There are numerous manufacturers still in
>>business, with Eimac the best known, and probably the largest.
>>
>>>I noted that discussion on this group is mostly about tube (valve)
>>>amps. But it is fact that all commercial rigs are all fully solid
>>>state and with transistor finals. If so, why no one talks about
>>>building high power transistor amps? Is any one working on home
>>>brewing project? Is it the cost of transistors or is it the technology
>>>that makes it difficult?
>>>
>>One issue I see is that for very high power you are going to need either:
>>
>>a) Lots of transistors
>>b) One tube
>>
>>The chances of you finding the matched transistors on the surplus market
>>at sensible prices is very low. So you will probably have to buy
>>multiple devices at full commercial prices. There are numerous tubes,
>>like the YC156 (5kW) on the surplus market at very reasonable prices. I
>>think the cost of transistors/kW new will be more than the cost of
>>tubes/kW, but I have not priced them up.
>>
>>There are very few solid state designs for multi-kW published in amateur
>>journals. High power is usually obtained by combining the output of
>>various modules (more complexity). Motorola had some application notes
>>on reasonably high power. No doubt there are application notes from the
>>manufacturers of transistors that describe ways of getting high power. I
>>think you will find the design will be complex.
>>
>>Tubes are more rugged.
>>
>>High voltage power supplies for a few kW are easy to build, whereas 28 V
>>or so at 100's of Amps is no trivial task.
>>
>>There seems to be lots of good reasons tubes are more attractive for
>>amateur use at high power.
>>
>>--
>>Dr. David Kirkby,
>>G8WRB
>>
>>Please check out http://www.g8wrb.org/
>>of if you live in Essex http://www.southminster-branch-line.org.uk/
>>
>>
>>
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>
>
>
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