>
>
>-----Original Message-----
>From: Mike Sawyer <kc4slk@csrlink.net>
>To: measures <2@vc.net>; Steve Thompson <rfamps@ic24.net>; AMPS
><amps@contesting.com>
To: <amps@contesting.com>
>Date: 20 September 2000 21:38
>Subject: Re: [AMPS] Some tube questions...conversion to H2O cooling
>
>
>>
>>Yes, but at the same time, your also adding Cg. Which is usually minute with
>>one tube but begins to add up with several.
>>Mike(y)
Even with only two tubes, ignoring Cg on 15m and 10m is not good
engineering practice because it typically results in too much SWR for an
exciter to deal with . The solution is to tune out the grid reactance
with a small roller coil. This way the input SWR will be virtually
perfect on all frequencies -- even if ten tubes are paralleled.
>For hf use, you could try a swamping resistor per pair, and then split the
>drive with wideband transformers.
>
For 4cx 250Bs, with c. 100w drive, a 12.5 ohm grid swamper and a 4 to 1
input transformer is about right.
later, Steve
>
>>----- Original Message -----
>>From: measures <2@vc.net>
>>To: Steve Thompson <rfamps@ic24.net>; AMPS <amps@contesting.com>
>>Sent: Wednesday, September 20, 2000 12:40 PM
>>Subject: Re: [AMPS] Some tube questions...conversion to H2O cooling
>>
>>
>>>
>>> >
>>> >
>>> >-----Original Message-----
>>> >From: Bob Duckworth <wb4mnf@atl.org>
>>> >To: amps@contesting.com <amps@contesting.com>
To: <amps@contesting.com>
>>> >Date: 19 September 2000 15:25
>>> >Subject: [AMPS] Some tube questions...conversion to H2O cooling
>>> >
>>> >
>>> >>
>>> >>I'm curious.
>>> >>How do I figure out how much current I can squeeze through a tube.
>>> >>Lets use the 4cx250FG for example.
>>> >>
>>> >>4cx250FG
>>> >>It's heater draws 14 watts.
>>> >>The max plate voltage is 2KV and it's rated
>>> >>as a 500W input tube.
>>> >>Plate dissapation is 250W.
>>> >>
>>> >>If I can keep it cool, how much plate current can I expect to run
>>> >>before there are not enough electrons coming off the heater?
>>> >
>>> >
>>> >The most I've ever known of is running them in real cut off class C with
>>> >about 400mA of anode current key down. The user had a source of really
>>good
>>> >ones that took 3kV in cutoff and 2.7kV key down. Output from a pair was
>>in
>>> >the 1.5kw region, and they lasted around a year of regular skeds. For
>EME
>>or
>>> >MS cw use, transmit duty is about 60%, and there's 50% rx time so the
>>anode
>>> >dissipation isn't compromised.
>>> >
>>> >At $10 each, I'd stick to 2kV, 250mA and just put more in parallel.
>>> >
>>> good idea, Steve. Paralleling tubes is a lot easier than most builders
>>> think. As RL decreases, more Tune-C is naturally needed to maintain a Q
>>> of c. 10.
>>>
>>> cheers
>>>
>>> - Rich..., 805.386.3734, www.vcnet.com/measures.
>>> end
>>>
>>>
>>> --
>>> FAQ on WWW: http://www.contesting.com/FAQ/amps
>>> Submissions: amps@contesting.com
>>> Administrative requests: amps-REQUEST@contesting.com
>>> Problems: owner-amps@contesting.com
>>>
>>
>>
>>--
>>FAQ on WWW: http://www.contesting.com/FAQ/amps
>>Submissions: amps@contesting.com
>>Administrative requests: amps-REQUEST@contesting.com
>>Problems: owner-amps@contesting.com
>>
>
>
>--
>FAQ on WWW: http://www.contesting.com/FAQ/amps
>Submissions: amps@contesting.com
>Administrative requests: amps-REQUEST@contesting.com
>Problems: owner-amps@contesting.com
>
>
- Rich..., 805.386.3734, www.vcnet.com/measures.
end
--
FAQ on WWW: http://www.contesting.com/FAQ/amps
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
|