10 kw CCS on 6M..using the 3CX-6000A7...Part 5.
https://www.youtube.com/watch?v=EFgPEcMdmyQ
<https://www.youtube.com/watch?v=EFgPEcMdmyQ&fbclid=IwAR2i1mGPEdZpHa88nHgOau-I0nPQAfsm9_PB-Jnt6u2D2qITHfMkN7an4ow>
Here the very unique method of constructing the filament choke is shown.
Instead of paralleling 2 x identical 40 amp fil chokes..... (made from 8 ga
magnet wire on 8" long x .5" type 43 ferrite rods), a new method is used.
The new method uses a string of Fair-rite ...... 'type 43 full flat cable
cores' . These are oval shaped cores, that are 1.53" wide x 1.024" tall x
1.126" long. Inside dimensions of the oval shaped hole are 1.03" wide x
.51" tall.
The max size pair of power cables that will fit inside is 1-0 RW 90 power
cable. (170 amp CCS, and 600 vac rated). I verified this already months
ago, and the pair of 1-0 cables just slides in comfortably.
For this 6M amp, double insulated 4 ga, and fine stranded wire was used
(600 vac rated). 4 ga wire will easily handle the 79 amps of fil current.
Each bead has a Z of aprx 125 ohms @ 50 mhz. 5 x cores are used which = 625
ohms, which is ample, considering the 3CX-6000A7's input Z is 50 ohms. Typ
you want the Z of the fil choke to be quadruple the input Z. (Heath's
SB-220 used a 9 uh fil choke = 197 ohms of XL @ 3.5 mhz).
For lower freq operation, more cores can be used.
The Z of each oval core per Fair-rite is as follows.
2mhz - 25 ohms
4 mhz - 30 ohms
10 mhz - 75 ohms
21 mhz - 100 ohms
30 mhz - 115 ohms
50 mhz - 125 ohms
For operation down to 160m, a minimum of 8 x cores are used, which equates
to a total length of 9". For larger tubes like the 3CX-10,000A7 / 15,000A7,
those tubes have a lower input Z, aprx 32-35 ohms...and a minimum of 6 x
cores are required.
More is better of course. Typ the fil choke is oriented across the width of
the chassis, between the input fil connectors at one end of the rear
apron...and the tube at the other end. This method works good on typ 19"/
24" wide rack setups.
With this 6M amplifier, the 5 x beads are flipped 90 degs, and the length
to the socket is very short. Fil V is measured at the socket
(via a pair of RF chokes). The 7.0 vac fil V at the cold end of the fil
choke will be rectified into 8 vdc for powering the opto-isolator, used to
key the myriad of vac TR relays. Fil V will be controlled via a variac,
located in lower box #2.
Fair-rite info. https://www.fair-rite.com/.../miscellaneous-suppression.../
<https://www.fair-rite.com/product/miscellaneous-suppression-cores-2643167851/?fbclid=IwAR1fruWjot5OB_h-gGq_XwiSE31jnZhwYBTcwQ3zlu3DcTtLgPkgXcWvXEY>
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