Hi Carl,
I forgot to add the the following in the note I had planned on posting
to the reflector and hit reply instead of reply all.
Although I know you are not a fan of the RUSSIAN tubes, what about the
GU84B, the so called 4CX2500?
How stable and clean is it at 50 MHz?
On 7/15/2010 8:53 PM, Carl wrote:
> The YC-156 doesnt use a socket and hasnt shown any need for a suppressor.
>
I took too long composing/rephrasing the original post<:-))
> With a spectrum analyzer its rather easy to spot a parasitic and then
> design whats needed. Many of the big triodes are extremely stable.
> Tetrodes respond well to grid suppressors, adequate screen bypassing
> and with a Carborundum style plate suppressor.
>
> I cant say what these big tubes are like on VHF but Id be tempted to
> build a rather big cavity for 6M to get around the output C problem.
I realize that size of components get a bit more more precise and that
both stray C and L can be problems, but I'm not familiar with an "output
C problem". I also realize this reveals my lack of experience in VHF and
UHF.
> I believe that is used on the FM and TV frequencies.
>
I've been thinking the 4CX3000A7 would do a nice job using an adaptation
of the 2-meter amp in the last couple of handbooks.
Are there problems using these tubes in a "conventional Pi, or Pi/L
circuit on 6-meters?
What about current in the coupling cap?
> Is it worth the bother?
Depends on space and money.<:-))
I'd like to stay some where within, or at least near the size of most
conventional amps.
73
Roger (K8RI)
Carl
KM1H
----- Original Message ----- From: "Roger" <sub1@rogerhalstead.com>
To: <Amps@contesting.com>
Sent: Thursday, July 15, 2010 8:21 PM
Subject: [Amps] Size of Parasitic Chokes
> How do you determine the size of a parasitic choke for a given tube
> other than using "The Handbook" as a starting point and going with "cut
> and try" from there?
> Say with a YC156, 4CX3000A7, or 4CX5000?
> Unfortunately sockets for those 4CX tubes are a tad pricey (Look like
> the socket for a 4CX1500B on steroids.) I don't see all that many of the
> 3000's any more, but I have one and know of possibly a couple good ones
> for a reasonable price. I think that socket (and 360 watt filament) keep
> the price more reasonable. Course it takes a rather chunky filament
> transformer too. That tube would make some nice 6 meter and 2-meter
> amps!
>
> 73
>
> Roger (K8RI)
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