[TowerTalk] Back of desk grounding buss

[n4zkf]

Building a site. Big or small.

http://www.radioandtrunking.com/downloads/motorola/R56_2005_manual.pdf

2-19
3-17
4-44

You will get the hintŠ.


73 Dave n4zkf
e-mail: n4zkf at n4zkf.com
web: http://www.n4zkf.com
AR-Cluster node: 145.05 Mhz. or telnet://dxc.n4zkf.com:23
CC-Cluster node: 145.07 Mhz. or telnet://ccc.n4zkf.com:7373
Packet BBS: 145.05 Mhz.-14.098 Mhz. or telnet://bbs.n4zkf.com:6300
BPQ Node: 145.05 Mhz.-14.098 Mhz. (n4zkf-5)
SEDAN Node: 145.770 Mhz. (n4zkf-7)
N4ZKF/R 147.375 Mhz. Tone 103.5






On 3/22/14 12:04 PM, "Gary Schafer" <garyschafer at comcast.net> wrote:

>
>
>> -----Original Message-----
>> From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of
>> Jim Lux
>> 
>> Wide flat strips have low AC *resistance* because of skin effect, but
>> the inductance isn't much different from a round wire.
>> 
>> AC resistance is *very important* in applications like RF grounds for
>> commercial broadcast antennas, because resistance = heat = lost power =
>> lost money, so they use flat ribbon.
>
>But lightning energy peaks around 1 MHz where low AC resistance is
>important.
>
>> 
>> Flat ribbon/strip has a high surface area to volume ratio, and AC
>> resistance is all about surface area for RF because of skin effect, so
>> if you're paying by the pound for the copper, it's the best deal.
>> 
>> Inductance just isn't strongly affected by the shape of the conductor.
>> The NBS monograph by Rosa (from 1907, it's one of the first ones
>> published) has all the formulas.
>> 
>> Flat strips don't have markedly lower inductance for a fairly simple
>> reason..
>> 
>> Consider your ribbon as a bunch of parallel wires.  Each of those wires
>> has some inductance L, and you'd think that putting N inductors with
>> inductance L in parallel would give you an inductance of L/N.  But the
>> problem is that those wires are right next to each other, so they have a
>> significant mutual inductance (the magnetic field of wire #4 is tightly
>> coupled to wires #3 and #5 next to it, etc.).  That tight coupling means
>> that the inductance of the parallel combination just isn't that much
>> lower than of one wire.
>> 
>> The inductance of two parallel inductors is:
>> (L+M)/2
>> where L is the inductance of a single inductor and M is the mutual
>> inductance.
>
>Yes flat strap has mutual inductance across its width but isn't mutual
>inductance considerably lower with a flat strap than separate parallel
>wires.
>
>73
>Gary  K4FMX


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