>Rich Measures writes:
>> - - - Does the circuit in which the 4cx1600 is used have a grid
>> terminating R? If so, is there an inductor in series with said R? If
>> so, how much L? tnx.
>
>Hi Rich
Hello, Rich, de Rich.
>It looks like Ray, QRO, added the resistor after 1995 as a mod. It
>also has an inductor in series but the value is not marked in the drawing.
>Why do you ask?
*** - - Because an inductor in series with the grid terminating R does
three things:
the good: 1. Reduces 10m SWR by cancelling grid XC with XL.
the bad: 2. Increases level of anode to grid VHF feedback signal
arriving at grid.
the ugly: 3. regeneration may take place, usually during a contest, of
course.
- Note -- the source of the VHF feedback signal is the damped-wave
ringing which takes place at the anode resonance when anode current
increases or decreases.
- Thus, it may be that the bang was the end result of a regeneration at
the frequency of the anode resonance. This resonance can be measured
with a dipmeter on either side of the DC-blocker-cap. The reason for
the bang is that VHF is blocked by the low-pass HF tank, so it has no
place to go, runs amuck, and a HV-to-gnd arc may take place..
>
>Point of interest about converting these amps to a pair of 4CX800's:
>
>Very easy to do as the sockets are mounted on an easy to remove plate.
>However, I have both flavors of Ray's amps and a pair of 800's are
>NOT the same as one 1600. Not by a thousand watts.
>
>Both the QRO 2500 (2x4CX800A) and 3K (4CX1600B) amps run
>1500 watts out all day and are fine contest amps so the day I do
>have to convert the 3K's to 2500's will not be too painful, just sad.
>
>73 Rich KL7RA
>
>
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