*At least for now, even if we could afford one of the Big Gun Solid State
Amps. I would hope that we would have the good sense to stick with an Amp
which runs 1 or 2 of the 3-500ZG Triodes. They are as tough as Nails. How
can you argue with a system that with proper care, will run a lifetime.
The
tubes in our SB-220 are Original. This means that they are approaching
their Fortieth Birthday. We recently replaced the Capacitors and Relay.
The
Amp was still working Great when we did this Preventative Maintenance.
And
Even a Cave Man with Knives and Bear Skins can repair the Amp if needed. *
* 73
from Wade/KJ4WS*
On Sun, Aug 10, 2014 at 12:01 PM, Robert <rmcgraw@blomand.net> wrote:
Many to most design parameters do change radically when converting from
BIPOLAR to MOSFET devices.
I seen to think MFJ does have their products in the reach of the average
ham. I find typically they offer reasonable designs, reasonable quality
at
reasonable prices. Maybe it's the hams average reach that needs
adjusting.
The days of the SB-200 and SB-220 KIT prices are long gone.
Good quality amps, those that are clean and don't spew garbage across the
bands, require good design and good quality parts. Then add a high duty
cycle and it places more demand on the designs and the parts choices.
73
Bob K4TAX
Sent from my iPhone
> On Aug 9, 2014, at 5:38 PM, Brian Carling <bcarling@cfl.rr.com> wrote:
>
> So maybe the Hercules can be converted to use MOSFETs. Seems like it
should be possible.
>
> I also think MFJ needs some competition on MOSFET linear amplifiers to
get the price point within reach of the average ham.
>
> There is just not a good reason why so many linear amplifiers should
cost $3500 to $9500 when you look at the parts cost and manufacturing
cost.
>
> [/SOAPBOX]
>
> Best regards - Bry Carling
>
>
>
>> On Aug 9, 2014, at 5:24 PM, Douglas <sparks06524@yahoo.com> wrote:
>>
>>
>> Date: Sat, 9 Aug 2014 10:12:45 -0400
>> From: Brian Carling <bcarling@cfl.rr.com>
>> To: "k9yc@arrl.net" <k9yc@arrl.net>,
>> Discussion of Ten-Tec Equipment
>> <tentec@contesting.com>
>> Subject: Re: [TenTec] Hercules 444 amp
>> Message-ID: <86F80EE5-1044-42AA-9641-D8859123467B@cfl.rr.com>
>> Content-Type: text/plain;
>> charset=us-ascii
>>
>> Seems like a lot of RF power transistors are similar, so it
>> should not be too difficult to find a substitute.
>>
>> Best regards - Bry Carling
>>
>> ------------------------------------------------------------
>>
>> Ah - but it is hard to find a substitute. The Ten-Tec factory can't
find one.
>>
>> There were only a few designs of 250 to 300 watt 50V bi-polar power
transistors made. The remaining ones are hard to get and have an HFE that
is too high. Several such transistors have been totally discontinued.
Motorola for example is out of that business. M/AComm bought some of
their
designs but in general bi-polar RF transistors are considered passe. RF
MOSFETS are now the name of the game.
>>
>> Per another poster: I've not had trouble with the power supply
>> drifting
upward with temperature rise. Perhaps they solved that with compensation.
>>
>> 73,
>>
>> Doug/WA1TUT
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