[Amps] The ongoing 4CX250B verbage!

[R at contesting.com]

On Apr 4, 2006, at 2:52 AM, Jerry Muller wrote:

> Although you couldn't tell the difference between a 4CX250 and an 8877,
> anyone operating near you in frequency could. The triodes are MUCH 
> cleaner
> in terms of IMD than the tetrode. The 3rd order IMD performance of the
> 4CX250 is not much better than -20dB where the 8877 is about -38dB.

In AB1, with heavy loading (little screen-I) and 2400v on the anode, 
I've measured a bit better than 30db TIMD below PEP.
>
> This is coming from someone who has run and still owns a pair of 8930s 
> for
> 432, a single 8930 for 220 and a pair on 2M. I'm not planning on 
> putting the
> 2 and 432 amps on the air again if you're interested. I've already got 
> an
> 8877 for 2 and I'm building a GS35B for 432.
>
> 73, Jerry K0TV
>
> ----- Original Message -----
> From: <exray at bellsouth.net>
> To: <Amps at contesting.com>
> Sent: Monday, April 03, 2006 10:00 PM
> Subject: Re: [Amps] The ongoing 4CX250B verbage!
>
>
>> 4CX250B tubes will reliably run 500W out for a pair( observe the 
>> AN/URC-32
>> or its commercial cousin the KWT-6). If you must have more try three, 
>> as I
>> recall, (AN/ARC-58 or TRC-75). This was 1 KW output autotune on the 
>> back
>> of a jeep.
>>
>> These military radios had to operate under rather stringent (read
>> horrible) conditions. And guess what....these " relics " did just 
>> fine!
>>
>> Yes there are better tubes available today...but the old 4CX250 
>> family is
>> the granddaddy of all of them. If you come across a pair, and they 
>> should
>> be inexpensive,  there are many good designs which have been published
>> thru the years.
>>
>> Frankly, I doubt you could tell the difference between 3 4CX250Bs and 
>> an
>> 8877 except for the rattle of the change still in the pocket of the 
>> guy
>> with the 4CX250B rig! He can then spend money on an antenna and feed 
>> line
>> where it really counts!
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>
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>



Rich Measures, 805.386.3734, AG6K, www.somis.org