I know nothing about Russian tubes and prefer to remain that way (-;
Carl
KM1H
----- Original Message -----
From: "Roger" <sub1@rogerhalstead.com>
To: "Carl" <km1h@jeremy.mv.com>
Cc: <Amps@contesting.com>
Sent: Thursday, July 15, 2010 11:58 PM
Subject: Re: [Amps] Size of Parasitic Chokes
> 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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>
>
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