[Amps] 10 KW CCS ON 6M...USING THE 3CX-6000A7... PART 12

Thu Dec 1 12:46:10 EST 2022

Date: Thu, 1 Dec 2022 07:58:49 +0800
From: Alek Petkovic <vk6apk at bigpond.com>
To: amps at contesting.com
Subject: Re: [Amps] 10 KW CCS ON 6M...USING THE 3CX-6000A7... PART 12

<Yes, me too but I just can't get my head around that piece of bent
<copper strip being sufficient inductance for 6m.

<I have a bigger coil in my 2m amp and my 6m amp has quite a few turns.

<73 and thanks, Alek, VK6APK.

## The tube is run at 5.5 kv @ 3amps under load.  Plate load Z = 1019 ohms.
With a conventional PI network, the MINIMUM Q we can use is a whopping 24.
That results in an insane  79 amps of RF flowing through the conventional
tank coil. (all based on 51 mhz)

If a conventional  PI network is used,  (Q = 24)  software spits out:  (51
mhz)
C1  =  13.1 pf
L =  .20 uh
C2 = 266 pf

Ok, now we switch to the "L-PI' network  (Q = 11)    (51 mhz)  Plate load Z
is now transformed down to just  192 ohms. The anode to grid C + strays  +
the .13 uh 1st coil forms a step down L network.

1st coil  (between plate block caps and C1 main vac tune cap)  = .13 uh
C1 = 17.7 pf
L =   .12 uh
C2  =   227.6 pf.

I used a high tech version of Termans formula for strap length for required
inductance. And yes, those straps are the correct length for the required
inductance. The measured results are dead on with his formulae for
straps..IE:  'flat wire'.
https://chemandy.com/calculators/flat-wire-inductor-calculator.htm  (Here
is the mating round wire software.
https://chemandy.com/calculators/round-wire-inductance-calculator.htm)

The big advantage of the straps is... they have 2 x sides, which doubles
the RF current capacity.  IF the straps were wound into coils, the current
capacity is only 1/2...so  2" wide strap coils would have to be used.....
instead of the 1" wide arced straps we used.
If tubing coils were used, the tubing would have to be 1.27" in diameter.
The closest readily available copper tubing is 1.125" OD..and comes in 50'
rolls...and is an absolute bitch to wind.

In the next video, a temp 1019 ohm resistor will be wired from anode to
chassis..and analyzer on the output. Then caps tweaked for 1:1 swr  @ 51
mhz.  Then leave the tune + load caps alone, then sweep from 50-52
mhz...and then again, but wider extremes, till we find the 2:1  swr points.

Jim  VE7RF