[Amps] 4CX1500B

[Carcia, Francis A HS]

You also need a good step attenuator in line with the second receiver input
because most receiver S meters are bogus. The only one I have ever seen that
has any kind of calibrated scale is a good working R390A. 

-----Original Message-----
From: R.Measures [mailto:r at somis.org] 
Sent: Thursday, September 22, 2005 10:22 AM
To: robert briggs
Cc: Amplifiers
Subject: Re: [Amps] 4CX1500B


On Sep 21, 2005, at 3:28 PM, robert briggs wrote:

> I have received several query's about the Super Cathode Drive method 
> on my 4CX250 B amplifiers.
> The amplifier's take around 100 watts of drive power for 600 watts 
> output.
> When the drive input is correctly matched the Grid ("screen" ) current 
> is 1 to 3 Ma with the amplifier loaded.Anode voltage 2500 vdc.
> Idle current for a pair of tubes is 25 to 30 Ma.
> According to Orr in his note's "QST July 1967 IMD 3rd order would be 
> -46 db 5th order
> 49 db.I have no measuring equipment to confirm this.

The main tool needed to measure total IMD is a second SSB receiver -- 
preferably one with a double-filter -- tuned c. 4KHz above or below the 
signal being measured.

> The point I am trying to establish is whether this setup would be 
> applicable to the 4CX1500B.

The 4cx1500B already has low IMD in grid-driven config.

> Bob VK3ZL..
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>
>

Richard L. Measures, AG6K, 805.386.3734.  www.somis.org

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