JIMMIE wrote:
On Mar 28, 11:45 am, ken scharf
wrote:
JIMMIE wrote:
On Mar 22, 4:25 pm, "Unca Pete" wrote:
I'd think an old Ohmmite Z-50 would be ideal. Wonder
what the value in uH was?
Pete
I thought about a Z-50. I have one I use on a 6 Meter amp using a pair
of 6146Bs. I didnt know if it would work with the 4cx250s or not.
6.8 uh rings a bell but Im not sure.
Id rather wind my own if it will keep me from having to pull out the
credit card and pay more shipping than what the thing cost.
Jimme
Any choke that is not self resonant at 50MHz and has enough inductance
to give an impedance at least 10 times the plate load resistance will
work. It, of course, must be able to handle the required voltage and
current. The form can be ceramic, Teflon, or any material that does not
absorb RF at 50 MHz. An air wound choke will work too, but would have to
be wound with thick enough wire to be self supporting, and it might be
hard to meet the other requirements with this type of construction.- Hide quoted text -

- Show quoted text -

OK I made a coil per the instructions I mentioned and placed it in
parallell with a 50 ohm resistor and connected it to my antenna
analyzer. There is a big spike in the SWR at about 75 Mhz. I assume
this is the self resonant frequency of the coil. Is this far enough
away from 50Mhz to use as a plate choke?
That's half an octave away. Good enough.
I would install the choke in the circuit and without applying power or
drive put a gird dip meter to the choke and double check for resonance
again. IF resonance at 50 mhz is detected, swing the tank capacitors to
make sure you are just detecting resonance in the tank circuit coupled
through the choke. If that is what you see, it's OK.