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Re: [Amps] Tubes vs. Solid State (was) Expert Amps 2K-FA: Any Opinions ?

Subject: Re: [Amps] Tubes vs. Solid State (was) Expert Amps 2K-FA: Any Opinions ?
From: "Roger (K8RI)" <>
Date: Sun, 29 Apr 2012 23:37:52 -0400
List-post: <">>
On 4/29/2012 9:35 PM, Joe Subich, W4TV wrote:
>   >>  A well designed amplifier using 8 VRF-2933 or a pair of the Motorola/
>   >>  Phillips 1200W TV transmitter "bricks" could be done commercially at
>   >
>   >  I don't want a 1200 watt amp that has to be derated for digital.
> 8 x VRF-2933 or 2 x 1200 W Motorola/Phillips "blocks" are not a 1200W
> amplifier.  2 x VRF-2933 do 600W brick on the key in the KPA-500.  Both
> configurations I listed will do 2 KW CCS with reserve gain given the
> proper cooling system design.

But, I'd have to build a system to use them as components including band 
switching with LP filters.

>> FCC rules mean I have to import a 2KW nominal, 2.5KW PEP amp to have
>> an amp that will run the legal limit any mode key down.
> Yes, and by law US Customs should impound your amplifier until you can
> provide the FCC approval documents for it (it does not fall under the
> "one off" exemption since it is a commercial product).  Fortunately,
> Customs is not designed to look for individuals importing their own
> amplifier.

I was told for my own use, I could import, or build an amp and It does 
not have to be FCC approved.  It is perfectly legal to build a 4CX3000 
for each band as they did away with the One off rule as well.

The main stipulation is that the manufacturer does not have a US 
distributor, or outlet.  For instance, Array Solutions imports and sells 
Acom amps. They can not sell me an amp that is not FCC approved because 
they have a US outlett, IE Array Solutions.  They could sell me one that 
is approved, but I would have nothing to gain as well as no service from 
Array Solutions.

OTOH I'd bet the manual tune Alpha with a pair of 4CX1000s will easily 
do that as well as it is not computer controlled.

>> I can currently go from a 1.1:1 to a 1.3:1 and see no difference in
>> output. I could not do that even at 1.2:1 with the SS amp.
> Then the amplifier in question was not particularly well designed.
> A properly designed solid state amplifier should be able to handle
> a modest amount of QSY ...

The SS amp would let me cover the whole band without retuning, but it 
would roll back the output power as the SWR went up.
The tube amp does not roll back the output. IIRC the SS amp was down 
about 200 watts at 1.2:1. It's been a couple of years.


Roger (K8RI)


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