[Elecraft] Balun Questions

[Bill Frantz]

I just completed a 160/80M common mode choke made from 6 type 31 
cores. Each core is 1/2" inside diameter, 1" outside diameter, 
and 1" long. (12.5mm, 25mm, 25mm). There are four windings of 
RG58 and I think this design is in agreements with Jim Brown, 
K9YC's RFI-ham.pdf. The choke hangs just below the feed point of 
my 160M dipole/80M inverted V. The antennas are at 44' (12M). 
The choke appears to work well and seems to have knocked the 
noise levels on 160M down an S unit or two. I was able to hear 
and work DX during the CQ contest further away than before.

The cores are separated by about an inch each and the total 
diameter of the windings is about 8 inches (200mm). I don't 
think you need to wrap tightly to the cores.

I have no test information, lacking equipment.

73 Bill AE6JV

On 2/7/16 at 9:03 PM, rmcgraw at blomand.net (Bob McGraw K4TAX) wrote:

>I am speaking of the radius of the coax bend.   To have a coax 
>bend radius of 3" the torroid would be huge.......the size of a 
>large coffee can.  A 3" OD, x 1.5" ID   torroid would typically 
>have a winding radius of less than ~1", even with 2 stacked 
>cores.    For my "ugly balun" project I use 4" ID PVC which has 
>an OD of ~4.5" and which provides a bend radius of 2.25".

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