Jeff -- I have seen Eimac data sheets where the (g-g config)
feedback-C and the output C were inadvertently swapped.
On Oct 15, 2004, at 8:53 PM, jeff millar wrote:
Art...
Let's put this back on the reflector...it's getting interesting.
All the data sheet from the gda.pl site list values like
input C 10 pF
output C .05 pF
Transfer C 5 pF
But the data sheets at nd2x.net generally look like
input C 10 pF
output C 5 pF
Transfer C .05 pF
Note the swapping of values between ouput C and Transfer C values
Going to the Eimac web site and looking at the 8877 data sheet clears
this up. The values swap around between grounded grid and grounded
cathode. Feedthrough and Transfer C measure the same thing.
Capacitance Grounded Cathode
Input
Output
Feedthrough
38.5 pf
0.1 pf
10. pf
Capacitance Grounded Grid
Input
Output
Feedthrough
38.5 pf
10.2 pf
0.1 pf
So... make a table of all the Grounded Grid transfer C we can find for
these tubes
GI-6B 0.2 - 0.3 pF
GI-7B 0.055 to 0.095 pF
GS-9 0.04 pF
GI-46B
GS-31 0.12 pF
GS-35 0.12 pF
8877 0.1 pF
It doesn't appear that any of the various web sites have data on the
capacitance for the tube...which is a bit strange. But since someone
built a 432 Amp with the GI-46b, it probably doesn't have the special
feedback wires like the GI-6B.
A very interesting little bit of investigation.
jeff, wa1hco
Arthur Moe wrote:
Jeff,
You might want to look here:
http://www.mif.pg.gda.pl/homepages/frank/sheets/018/g/GI7B.pdf
http://www.mif.pg.gda.pl/homepages/frank/sheets/018/g/GI46B.pdf
Note that Transfer "C" is 4.0-5.2 for the GI7B and 5.1-6.4 for the
GI46B, the 46 only 1.1 to 1.2 more
Art
KB7WW
jeff millar wrote:
Interesting...do you think there's a typo on the data sheet?
jeff
Arthur Moe wrote:
All,
If you look around these sites you will find VHF amplifiers using
these tubes. One
is a commercial builder in europe. See mid power list.
http://www.pollak.sulinet.hu/elektro/pa_rev/pa_rev.htm#mid_vhf
http://www.westparknet.com/business/ham%20shop/GI46Bamp.htm
http://www.qsl.net/ok2zi/pa432.html
Art
KN7WW
Bob the advertisement says the GI-46b is a variant on the GI-7b.
But
its interesting to read the description of the GI-6B, particularly
the
transfer capacitance (http://nd2x.net/gi6b.html). Lets compare
transfer
capacitance
GI-6B 0.25 pf wires from cathode to anode to make it
oscillate
GI-7b 0.075 pf good to microwave frequencies
GI-46B 5.1 pf wow
(http://www.tubes.ru/techinfo/TransmittingPulseTubes/gi-46b.html)
So it look to me like they used the tube as a power oscillator in
UHF/microwave application and include extra transfer capacitance to
simplify the external cavity design.
I belive the statement that the tube is the last generation of
small
triode and it's the most advanced design. But its not suitable
for UHF
and probably not for VHF. But in an HF amplifier in Grounded
Grid, it
works fine.
jeff, wa1hco
Bob Bruno - K2KI wrote:
Are there any examples of an amp that has been built using the
GI-46B tube. I see a guy on eBay selling them rather cheap I
think.
Anything that I should know about this tube that might steer me
away from getting one?
73, CUL
Bob Bruno - K2KI
k2ki@starc,org
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Richard L. Measures, AG6K, 805.386.3734. www.somis.org
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