There is are several reasons:
1. My power supply is happier at higher voltage
2. Less drive needed thus allowing non 1:1 input SWR direct cathode
connection with LC tank across it.
3. Main reason....
The Q of a L network is the square root of the ratio of input and
output impedance.
At 5 Kv the plate impedance is around 5kohms and thus I have a Q
of about 10
which I would consider the minimum Q for the output tank circuit.
The typical B&W 850 tank is many times greater than that.
73
Bill wa4lav
At 07:27 AM 1/3/02 -0500, you wrote:
>Why does everyone insist that the 4-1000 needs in excess of 5kV to run legal
>limit? I have built several that easily put out 1500W with only 4-4.5 kV
>and 100W from a solid state rig. Am I just using good tubes vs. ones near
>the end of life? Probably.
>
>I would use bandpass coax stubs to keep harmonics down with only an "L"
>network.
>
>Mike, W1NR
>
>
>-----Original Message-----
>From: owner-amps@contesting.com [mailto:owner-amps@contesting.com]On
>Behalf Of Peter Chadwick
>Sent: Thursday, January 03, 2002 3:59 AM
>To: amps@contesting.com; 'wlfuqu00@uky.edu'
>Subject: RE: [AMPS] Building new 4-1000A amp
>
>
>
>I used an L network in a marine tx many years ago: the antenna load for test
>purposes in the 1.6 - 3.8MHz band was 10 ohms in series with 250pF, so an L
>network gave adequate harmonic rejection. The working Q came out at 15 in
>that
>case, so the losses were manageable. We sold several hundred of them, so I
>guess
>they can't have been too bad.
>
>I gather from what's been said here in the past that you need 5 or 6kV on
>the
>plate, but I guess you knew that already.
>
>73
>
>Peter G3RZP
>
>
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>
>
>
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