[CQ-Contest] Help with a common mode choke

Arthur Peters K0ACP at arrl.net
Wed May 27 07:09:35 EDT 2015


Good morning:

I am building a couple of common mode chokes for multi-band antennas:

a) remotely tuned 490’ sky wire antenna

b) Husler BTV-6

Right now I will be limited to 100 watts but may go qro in the future, either
500 or 1500.

I am going to build a couple of common mode chokes using Jim’s, K9YC,
choke cook book: http://www.hamradio.me/charts/k9yc-choke-cookbook.html <http://www.hamradio.me/charts/k9yc-choke-cookbook.html>.

I have a some questions for the group:

1) I want the choke to work for 160 - 10 for both antennas (I’ll be adding
a 160m tuned radiator to the hustler in the future).  Using the recipie sheet,
my plan is to use:
   -16 turns on a single FT240-31 core for 1.8 - 5
   -14 turns on a single FT240-31 core for 3.5 - 10
   -12 turns on a single FT240-31 core for 14 - 30

Question 1: is this the correct approach?  

Question 2: what is the appropriate spacing between each choke?

Question 3: according to Jim’s tutorial, I should place the 14-30 Mhz
choke closest to radio, correct?

Question 4: is there a significant avantage over using RG316, over
RG174, over RG58 or bifilar?  It looks like the bifilar will be easier
to construct, but I recall reading that the Bifilar will have an
impedeadence of 90 ohms - not a show stopper, but less optimal than
the 50 of the coax solutions.

Question 5: My remote tuner is an iCom AH4 and it required a four-
conductor control line, I am assuming that  I should also run the control
line through the same arrangement — it will likely not fit on the same
toroids, so this will be a parallel arrangement.

Thanks for the assistance &

73,

Art
K0ACP at arrl.net



More information about the CQ-Contest mailing list