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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