[Top] [All Lists]

[AMPS] 4CX1000A advice??

To: <>
Subject: [AMPS] 4CX1000A advice??
From: (Ian White, G3SEK)
Date: Sat, 14 Mar 1998 19:43:04 +0000
km1h @ wrote:
>On Sat, 14 Mar 98 05:44:02 -0800 Rich Measures <> writes:

>One of the "no hassle" untuned input circuits floating 
>>about recommends putting an inductor in series with the grid 
>>R to improve the 12m and 10m input SWR.  Doing so is an invitation to 
>  If Emtron, QRO, and Alpha do not use such a circuit,  
>> .   However, one does not know until one sees the circuit. 
>I do not know what they or Alpha use.

The 91B "absorbs" the input capacitance of the 4CX800As by making it act
as C2 in a pi-network. The tube input capacitance is about 100pF total,
and the fixed capacitors used for C1 are about the same value. Thus the
transceiver sees a 1:1 impedance transformation into the 50-ohm
terminating resistor. 

At all HF/VHF frequencies, the grids see the 50-ohm resistor connected
directly to ground.

73 from Ian G3SEK          Editor, 'The VHF/UHF DX Book'
                          'In Practice' columnist for RadCom (RSGB)

FAQ on WWW:     
Administrative requests:

<Prev in Thread] Current Thread [Next in Thread>