[TowerTalk] Back of desk grounding buss

[Patrick Greenlee]

Thanks so much for posting the Moto site guide. A breath of fresh air.  
When there is a group grope debating the number of angels dancing on the 
head of a pin it is good to use a microscope and just count the buggers!

Patrick NJ5G


On 3/22/2014 11:13 AM, n4zkf wrote:
> 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 hintS(.
>
>
> 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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>>
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