What is the point of a back of desk grounding bus? Does it fill any real
need, or is it just one of those feel-good things that's been around
forever?
Surely it's not to deal with anything related to lightning, because if that
were the case, then you've already failed by allowing lightning into your
shack -- the place to deal with lightning energy is outside the shack, not
behind your desk.
If it's to deal with noise and hum, then I don't see the point either,
because in my experience, a ground such as this makes noise and hum worse,
not better.
73, Jerry
On Thu, Mar 27, 2014 at 1:18 PM, Chris <EZRhino@fastmovers.biz> wrote:
> An even easier way to remove the static is with a 3M ohm resistor to
> ground.
> http://www.ad5x.com/images/Articles/Static%20Bleed.pdf
>
> Chris
> KF7P
>
>
>
>
>
> On Mar 27, 2014, at 1:11 PM, Patrick Greenlee wrote:
>
> > Clay, my Hy-Gain Hy-Tower vertical antenna is mounted with no concrete
> and no radials on top of a 36x72 metal barn (NICE COUNTERPOISE). The base
> of the antenna is at about 25 ft above grade. At over 75 feet it is by far
> the tallest thing around and so is a target for collecting static
> electricity.
> >
> > Neons (depending on which you use) typically ionize and conduct at about
> 60 volts depending on how bright the ambient light is shining on them.
> When they do conduct they make significant RF noise.
> >
> > I wrapped plenty of small copper wire around a scrap of PVC pipe. One
> layer of wire, adjacent windings no spacing and as neat as I could. I then
> inserted this RF choke into a larger scrap of PVC and waterproofed/sealed
> the ends with GE II silicone caulk (RTV) and then placed the choke across
> the ground and antenna feed at the location of the BALUN feeding the
> antenna.
> >
> > I looked up the necessary formulas for the size of the wire, number of
> turns/length, and diameter of the form to ensure I had more than enough X
> sub L at the low end of 160 meters. so that the RF choke would basically be
> seen as an open circuit to the RF on all 8 bands I use it on but of course
> be a short (or very low resistance) to static charges. The DC path to
> ground via the RF bleeds off static charges without the RF noise associated
> with gas discharge tubes such as neons etc.
> >
> > I have no illusions regarding the survivability of the DIY choke in the
> event of a direct hit but so far so good over a year into its life and it
> would be simple and cheap to replace it. I do not depend on it to handle a
> strike. I have store bought in-line coaxial lightning suppression devices.
> Since it drains charges down to the zero volt level I think it drains
> static charges that the tall (75 feet above grade to the top) gathers and
> reduces the likelihood of a direct hit.Should the antenna take a hit the
> choke will be toast and I'm out a dollar or so to replace it. Meanwhile,
> it is electrically quieter.
> >
> > I'm open for suggestions to improve my situation. Although the ham
> population in my zip-code has doubled in the last couple years (I took the
> other guy to the exam venue so he is a tad new to offer well seasoned
> advice) I still have to rely on books and the internet for getting ideas
> other than my own.
> >
> > Patrick NJ5G
> >
> >
> > On 3/27/2014 10:02 AM, Clay Jackson wrote:
> >> Very interesting discussion! Thought I'd share a little bit about my
> >> shack - we're in Eastern Washington, in the middle of what used to be a
> 90
> >> acre wheat field. I have a HyGain AV18HT (50' vertical) about 200'
> from
> >> the house, and then a couple of VHF antennas on 30' masts bracketed to
> the
> >> side of the house.
> >>
> >> When we had the house built, before the foundation was poured, I
> cadwelded a
> >> #2 copper wire to one of the rebars in the middle of the foundation and
> left
> >> it out. After the house was completed, I cadwelded that wire to an 8'
> >> copper rod, then ran #2 wire around the 3 corners of the house, with an
> 8'
> >> rod at each corner, all cadwelded - I also cadwelded that to the house
> AC
> >> "Safety" ground, which is just another piece of rebar tied to the
> foundation
> >> that comes up through the garage floor near the electrical panel.
> >>
> >> I have a DX Engineering Entry Panel, and my #2 copper wire terminates in
> >> that panel, with the wire clamped to the aluminum plate inside the
> panel.
> >> All of my antennas except the vertical enter through that panel, through
> >> lightning arrestors bolted to the panel. The VHF antenna masts are
> mounted
> >> in a pipe sleeve buried at least 4' into the ground, and there's an 8'
> >> ground rod at each mast, cadwelded to the round-the-house ground wire.
> >>
> >> The HyGain Antenna is mounted on a 6x6x6 block of concrete - the "legs"
> were
> >> clamped to the rebar in the concrete, and I left one of the pieces of
> rebar
> >> above the concrete, to which I clamped the antenna ground and lightning
> >> arrestor at the base. The AV18HT feeds the tower at the base (the legs
> sit
> >> on insulators); and so I have a box with 8 neon bulbs in it connected
> >> between the tower and ground as a static discharge.
> >>
> >> In the shack, I have a 6' strap of 2" wide copper braid, bolted to a 6'
> >> long 2" copper pipe that sit on the back of my operating table. All
> of my
> >> gear is connected to that pipe with 1/2" or bigger copper braid. The
> >> operating table frame is constructed of 1x1 steel tubing, and that's
> also
> >> connected to the ground pipe. All of my power comes through a
> generator
> >> backed set of 3 UPS, 1 1500VA and 2 450VA.
> >>
> >> So far, I haven't had any DIRECT strikes; but, last year, we did get a
> >> strike about 100' from the base of the tower that was pretty intense -
> no
> >> damage to any of the rigs or other devices.
> >>
> >> Clay
> >> N7QNM
> >>
> >> -----Original Message-----
> >> From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of
> Jim
> >> Brown
> >> Sent: Sunday, March 23, 2014 9:37 AM
> >> To: towertalk@contesting.com
> >> Subject: Re: [TowerTalk] Back of desk grounding buss
> >>
> >> That experience counts for lightning protection of commercial
> installations
> >> with big budgets, setups that don't change, no local analog audio, and
> in a
> >> broadcast environment, balanced audio. But that's not most ham
> stations. We
> >> have limited budgets, we do everything ourselves, we change our setups
> as we
> >> try new things, buy new gear, have lots of stuff interconnected, like
> >> computers, rigs, amps, audio processors, SO2R boxes, and all of the
> >> interconnections are UNbalanced.
> >> Moreover, if it's FM broadcast, cellular, or VHF/UHF 2-way, most of
> those
> >> antennas are high in the air and have nulls in the direction of the
> >> equipment, whereas our antennas often produce significant field
> strength in
> >> our shacks.
> >>
> >> Those interconnections, especially analog audio, is one big reason why
> >> chassis-to-chassis bonding is far better than running individual wires
> to a
> >> common point (or bus bar).
> >>
> >> And there is nothing about that chassis-to-chassis bonding that is less
> good
> >> than individual wires to a common point. Remember that with those wires
> to a
> >> common point, we still have a loop to create magnetic coupling -- it's
> >> formed by the interconnections between the boxes and those long wires
> to the
> >> common point.
> >>
> >> 73, Jim K9YC
> >>
> >> On 3/23/2014 8:44 AM, Jim Lux wrote:
> >>> Your experience is probably more relevant. Especially with reference
> to
> >> commercial practice.
> >>> My thing is more about the theory behind the recommendations, which is
> >>> often buried in the mists of history. Sort of like 468/f
> >>>
> >>> On Mar 23, 2014, at 3:53, n4zkf<towertalk@n4zkf.com> wrote:
> >>>
> >>>>> I didn't put a rover on mars but I do grounding on cell and
> >>>>> broadcast sites for a living working in telecom. Does that count?
> >>>>>
> >> _______________________________________________
> >>
> >>
> >>
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> >>
> >>
> >
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> >
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