I'd be very interested to hear how you managed to achieve that, and how
you measured it. I've never measured any air-cored coax choke that
achieved 500 Ohms (or more) over a 33:1 frequency range; less than 6:1
is more usual.
The results for air-cored chokes I've measured are shown at the bottom
of this table:
http://www.karinya.net/g3txq/chokes/
As you can see, the choke with just 25 turns of RG58 on a 4.25"
diameter form had dropped below 500 Ohms by 21MHz - so I've no idea how
you could maintain >500 Ohms out to 60MHz with 40 turns.
I'm also puzzled how you managed to get 40 turns of RG58 in a 6" winding
length?
Steve G3TXQ
On 29/10/2014 22:41, Hans Hammarquist via TowerTalk wrote:
Myself, I am using a air wound coil, 40 turns of RG58 on a 4 1/2" D, 6" L
cylinder as the choke. No, it is not hanging in free air but is well supported. End up to
work well from 1.8 to 60 MHz. Has a Z=500 Ohm at 1.8 MHz and 60 MHz.
Best 73 de,
Hans - N2JFS
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