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Re: [Amps] 4CX1500B's -- worth using?

Subject: Re: [Amps] 4CX1500B's -- worth using?
From: "Roger (K8RI)" <>
Date: Wed, 20 Jun 2012 22:06:27 -0400
List-post: <">>
On 6/20/2012 8:15 PM, Carl wrote:
> At 1000W PD the 1500B requires less air (18 vs 25)at virtually the same
> pressure drop (.23 vs .20).
> There is a huge increase going to 1500W.

The DX-2sp is a great example of that with its Chinese version the 
4CX1500B, the FU728F.  Run it easy and it'll just loaf along. Run the 
legal limit on high duty cycle and the blowers will kick into hi gear 
after a few minutes for a substantial increase in wind out the top and 
it's downright toasty! <:-))  I haven't seen any figures on IM compared 
to the 4CX1500B. They too are the same size and fit the same socket, but 
use a different filament voltage.  OTOH the FU728F will run 2200 W 
nominal and 2500 PEP out with less plate dissipation rating.  You have 
too set the bias, but you have to do that every time you change tubes.  
With the DX-3sp you have to set the bias on both tubes when ever 
changing so you can change just one tube without having to adjust both 

I like the idea of the 4CX1500A though. With the *mesh basket* is it 
still basically instant on? Also It'll go to 220 MHZ where the cut off 
for the B is 150 MHz.

What's a new 1500A cost now days?  I assume it fits the same socket as 
the B model although my data sheets show the SK-831 for the A while B 
just says 800 series.  The FU728F has a slightly larger centering pin 
requiring that the pin be turned down a few thousandths or replaced with 
one around 0.003 to 0.005 smaller.  The Chinese tube also has a 
different filament voltage.


Roger (K8RI)

> Carl
> KM1H
> ----- Original Message -----
> From: "k7fm" <>
> To: <>; <>
> Sent: Wednesday, June 20, 2012 7:04 PM
> Subject: Re: [Amps] 4CX1500B's -- worth using?
>> Then why does the new ACOM 1500 use the 4CX1000A
>> 1.  Cheaper
>> 2.  Manufactured by some companies that do not make the 4CX1500
>> 3.  Less filament current
>> 4.  Less air restriction, so a smaller blower can be used.
>> 73,  Colin  K7FM
>> _______________________________________________
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