Herein lies some of my problem, I get different numbers with different
calculators..
I would figure they would be close...of course, 970 to 1.2k isn't that far
off BUT!
some formula's want "Q"..I input 12.5 to be in the middle..
now, screen supply solid so far, using the tetrode boards for both screen
and control grids.
will double check.
tune cap to me says out to antenna AFTER tank coil
Load cap to me says after PLATE before COIL.
screen grid 365v watching the current into it.
control grid -65v watching no meter movement for current.
plate volts from 2300 unload to 2100 load 500w out steady.
I know I ramble :)
sorry. still new to electronics after 32 years. lol i'm going to switch to
solid state..!
----------------------------------------------------------------------------
-------------------
Peter Voelpel df3kv
<mailto:amps%40contesting.com?Subject=%5BAmps%5D%20Tank%20value%20problems%2
0and%20grid%20current&In-Reply-To=0D7AAF2377484516AAC90C2E2768F968%40telecas
tfiber.local> at t-online.de writes....
To see 1.5KW output your anode current must be around 1.2A if you have 2100V
on the plate.
Your load Z will be about 1-1.2kOhm, so on 80m (3.5MHz) your coil should be
about 5.7µH, not 3.7 and never 7.2µH on 3.8MHz.
Tune cap setting will be about 400pf and the load padder should be at least
1200pf.
Your writing is not clear when you talk about grid current, screen current,
tune cap and load cap.
Screen current drop and grid current drop are somehow different as well a
1000pf tune cap or a 1000pf load cap.
Remember, with a tetrode amp you need to tune with your tune cap for maximum
screen current and tune your load cap for specified screen current.
Normally that setting gives the desired output.
then
Bill, W6WRT dezrat1242
<mailto:amps%40contesting.com?Subject=%5BAmps%5D%20Tank%20value%20problems%2
0and%20grid%20current&In-Reply-To=0D7AAF2377484516AAC90C2E2768F968%40telecas
tfiber.local> at yahoo.com writes
I haven't used a GU-74b before, but I have used a 4CX1000A and a
4CX1500B and I think they would be similar in operation.
It is normal for a tetrode's screen current to vary a lot with
different drive levels. It can go either negative or positive
depending on drive level and plate loading. The important thing is
that screen VOLTAGE should be constant. Do you have a regulated screen
supply?
Second, what plate impedance are you designing for? I figure with 2100
VDC on the plate, current will have to be about 1.2 amps for 1500
watts output. Is that what you are planning for? Using the factor of
1.8, plate impedance would be about 970 ohms. Given that, my G4AXX
spreadsheet gives 80 meter values of C1 = 467 pF, C2 = 1856 pF and L1
= 5.28 uH for a Q of 12. Are those values about what you are figuring?
73, Bill W6WRT
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