On Fri, 14 Nov 1997 14:31:37 -0500 (EST) Jeffrey Maass
<jmaass@freenet.columbus.oh.us> writes:
>
>We are feeding our 2-wire Beverages with RG6, and want to place RF
>chokes
>at the feedpoints to prevent errant signals on the shield from making
>their way into the receiver.
>
>We are currently testing 12-14 turns (as many as will fit) of RG6
>through an FT240-77 ferrite core close to the feedpoint. Is this
>sufficient/effective? Another core?
>
>Thanks / 73,
>
>Jeff Maass
Jeff, I use the 77 mix for all kinds of RX level RFI suppression (never
in a Beverage xfmr) and am generally pleased with the results. If you
happen to notice increasing common mode rejection as you run out of
winding space then go to one of the smaller cables. I use RG-179B/U 75
Ohm Teflon cable here because I wound up with a 5000' reel for zip at a
local junk yard.
Perhaps Tom or others could offer opinions on using another impedence
cable for this purpose. RG-141, 178, 188, etc are all very small 50 Ohm
cables that show up at surplus prices. Or vice versa with the RG179.
I'm not sure how many turns around whatever core will do strange things
to the desired impedence back at the radio when you start mixing 50 and
75 Ohm cables.
GL Carl KM1H
(jmaass@freenet.columbus.oh.us) Amateur Radio
>K8ND
> USPSA/IPSC # L-1192 NROI/CRO NW of Columbus Ohio
> 25000 Members in 2000!
>
>
>
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