[Elecraft] Balun Questions

[Bob McGraw K4TAX]

Yep, good stuff.  Be sure of your budget before buying a roll.  It is a 
bit pricey.  Handles legal limit HF power with a reasonable SWR.

73
Bob, K4TAX



On 2/6/2016 7:10 PM, Robert Nobis wrote:
> I have used RG303/U for chokes.  A bit smaller diameter than RG400 (0.170 versus 0.195 inches). RG303/U has a solid copper center conductor that is silver plated.  The shield for RG303 is also silver plated copper. The jacket is Class 9 Teflon. Also the dielectric material is teflon.
>
> 73,
>
>
> Bob Nobis - N7RJN
> n7rjn at nobis.net
>
>
>> On Feb 6, 2016, at 17:49, Guy Olinger K2AV <k2av.guy at gmail.com> wrote:
>>
>> If one wants a small 50 ohm coax that will take QRO with a very large
>> margin and was *designed* for bending and use in aircraft wiring harnesses
>> then use RG400 to wind around your core. RG400 uses a fine stranded
>> silvered copper center conductor that is more flexible than its Teflon
>> dielectric. It has a double shield made from silvered copper strands.
>>
>> That's silvered strands whose silver sulphide patina or tarnish is
>> conductive as opposed to the green copper sulphate that separates copper
>> strands that have been water soaked.
>>
>> Wind the coil form with RG59 to get the length and buy just what RG400 you
>> need. You can buy brand new RG400 by the foot.  With the Teflon dielectric
>> you can solder the RG400 without worrying about melting it.
>>
>> Do it with the good stuff to start with and put it in your will.
>>
>> 73, Guy K2AV
>>
>> On Saturday, February 6, 2016, Ron D'Eau Claire <ron at cobi.biz> wrote:
>>
>>> Bob makes an excellent point. I've seen cases where even "solid" dielectric
>>> did that over time because, after all, it is not really solid. The
>>> dielectric is plastic so the coax can be bent.
>>>
>>> All coax has a minimum bending radius specification. Specific data is
>>> available on line but, in general, RG58 size cable usually has a minimum
>>> radius of 1 to 1.5 inches (2.5 to 3.8 cm) and RG8 size cable has a minimum
>>> radius of at least 2 inches (5 cm). Note that is radius. If you curl the
>>> cable into a circle the minimum diameter of that circle should be at least
>>> twice that or 3 to 4 inches (7.5 to 10 cm).
>>>
>>> It's not something I've found especially critical in HF applications at
>>> least around my shack, but tighter bends, which may not actually cause a
>>> short (yet), alter the impedance as the center conductor migrates toward
>>> one
>>> side so it is no longer equally spaced within the shield. This can be a
>>> serious issue in microwave and even UHF installations.
>>>
>>> 73, Ron AC7AC
>>>
>>>
>>>
>>> -----Original Message-----
>>> I would have concern that long term usage of RG-8X, being foam core
>>> dielectric material and bent in a tight radius, may allow the center
>>> conductor to migrate to the inside radius of the bend.  The Minimum Bend
>>> Radius for RG-8X is 2.50".     Thus the tight bend will allow the center
>>> conductor to short to the shield.  A solid core dielectric coax such as
>>> RG-303  is much preferred.
>>>
>>> 73
>>> Bob, K4TAX
>>>
>>>
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