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Does anyone know what these things are? The seller doesn’t know what it is, and I don’t know what it is.. but there’s a total of 300 feet of it, and I’m thinkinking maybe it can be used to make a ground plane – at least I’m hoping so, cause the price is right
There’s 3 images attached
Anyone know?
Total posts : 45366From the shipping tag it appears that it is a length of Belden 8924 and another length of Belden 9422. You can get the specs by searching on this. You could also ask the seller if this is printed on the cable since Belden puts their name and number on their cable.
Neil
Total posts : 45366The 8924 cable is coaxial line with foil and webbed shielding. The center conductor is single strand copper.
The 9422 is a multi-conductor stranded cable use for control and instrumentation. It is not shield.
Total posts : 45366Thanks Marshall, but how did you find that? I did search before posting, and ran another search a moment ago, but found nothing! I’d like to take a closer look at the info.
So what’s your impression about utilizing this as ground plane material? We’re talking about 300 ft of it for about $50 (and it looks like a big conductor).
Alternatives I’m considering for about the same price…
1. 500ft of solid 12 awg ground, and stripping the jacket off (whew), or
2. 100ft of solid 8 awg already bare, and making only 10 radials, and then adding to it gradually as I get more copper.If I had enough money left I’d just buy several hundred feet of bare wire, but for now I want to get the best ground performance (on the roof) that I can get for about $50
So what you think?
Oh, concerning the Beldin, the guy said:
The end tips that you see, they are of some kind of metal material, and then it is just one long flexible cable after that, is it attached it doesn’t slide throughout.
I purchased this from the Iowa DOT. It is new in the box. The one pictured has part number BL 8924 and BL 9422.
This sale is for one, but I have 14 with different model numbers. Thank you.
Total posts : 45366Rich, I am not Marshall but I will offer my comments. Though any metallic conductor will function as a ground radial, for the money you will be better off buying some #12 or #14 solid or insulated wire. The foil covered web wrapped wire will not be as good a conductor. Due the the skin effect the RF current will be on this outside metal. The foil is not very conductive and if the wrap wire is aluminum (don’t know if this is) it will not perform as well as copper.
The unshielded multiconductor wire should be OK for this use.
Though bigger is better the difference you will gain with #8 as compared to #12 or #14 wire is not worth the cost in my opinion.
Neil
Total posts : 45366Ground “radial” wire need not be very big/thick to do the job. Even 12-14 ga. is a bit stout for Part 15 uses. Stranded “bell wire” is sufficient for what we need (22-18 ga.). If you install a single earth ground conductor of 6-8 ga. connected directly to at least one ground rod, you are pretty well grounded for lightning or static discharge. The ground radials are for the antenna to work the best it can for the ground conductivity of your area.
One not about lightning safety. If your antenna gets hit by lightning, the size of the ground conductor won’t really matter. Lightning gets to make the rules for what burns and what doesn’t. Please refer to lightning grounds in the ARRL Antenna Book for further study.
The ground radials are the current return component of the antenna system and greatly effect the initial launch of signal from the antenna. This effect is most noticeable within 100 feet or so. beyond that, the ground conductivity surrounding the antenna out several miles takes over. So, if your communities soil conductivity is not very good, ground radials will help; but only to a point of marginal return in signal strength and range.
I found the specs on the Belden wire by “Googling” Belden and the cable numbers. I wouldn’t use either for ground radials.
Total posts : 45366Over the years I’ve always thought that safety is a good idea, but upon deeper thought I’d like to review what is meant when we talk about “lightning safety.”
We could mean safety of the equipment, which I have no doubt is true, but maybe we also mean safety of any nearby humans. Or maybe, safety of the whole electrical system in the entire house.
For a hundred years I’ve occupied buildings with old wiring which does not have the third ground wire, and except for an actual lightning strike once which damaged a Ramko mixer board, there’s been no trouble.
Define safety in the way it’s being used here in these discussions.
Total posts : 45366Carl,
I can give you my opinion and experience. When I mention lightning safety, the true meaning is probably lightning effects suppression safety equipment and circuits. To totally eliminate the the effects of a direct or peripheral strike for most consumer grade equipment is NOT possible. Safety grounds in radio deal primarily with lightning suppression, anti-shock and ground-loop issues.
Lightning safety grounds normally consist of several 8 foot long copper plated ground rods spaced 12 feet apart and connected by 0 or 00 ga. cable. The cables are attached to the roads with an exothermic device called Cad-Weld. Some broadcast stations use 4 inch wide heavy gauge copper strap instead of heavy copper cabling.
There has been extensive debate and research as to whether lightning initiates on the ground or in the cloud. Most lightning suppression equipment and hardware is for the purpose of directing and lessening the effects of the energy in the strike.
The only way to totally protect electronic equipment in a lightning storm is to disconnect the equipment from the AC service mains and antennas. Using antenna designs that have a direct path to ground helps to protect feed lines and associated tuning circuits. But, nothing protects like a disconnect.
If you were to take a look at a piece of Romex house wiring, notice the thickness of the insulation and the spacing of the conductors. A static discharge or a lightning strike would jump across the insulation or spacing with little effort. And the third conductor on the power pole is neutral which is hooked to ground at some point. So, if lightning hits the power lines, the energy will be conducted directly into the house or building electrical system. Metal Oxide Variistors (MOV) can help to suppress some of the energy and help protect equipment. Many well built power strips have these devices built in them.
When dealing with NEC code and electrical wiring practices, you will need to ask a licensed and certified electrician.
Total posts : 45366Marshall, your description of the safety situation is valuable, and I especially take note of the “disconnection is best” advice. So we come up to this question:
During electrical storms I always shut down all electronic equipment, but leave it plugged into the wall socket. Would it be better to pull the plug?
Total posts : 45366At our Regional Dispatch Center, the equipment is Motorola. Motorola has very strict specifications regarding static discharge/lighting protection at their installations.
Our Comm equipment room is below grade. It includes dispatch console interface equipment, telephone/911 equipment, data servers, etc. There are no antenna cables entering the room, however there are other communication cables, i.e. telephone, fire alarm, fiber optic, etc. All local radio equipment is located on the 2nd floor and connectivity to the County 800 mHz trunked radio system is via fiber optic cable to a microwave link site about 4 miles away.
Motorola requires a stranded 4 awg “halo” mounted around the room above the equipment rack height. Each equipment rack and other stand alone equipment is attached to the “halo” with a separate stranded 4 awg cable. Even the metal door frame and each electrical conduit entering the room. There are NO SHARP BENDS in the “halo” or separate grounding wires, only gentle bends with at least a 12″ radius. The whole room is on a 2 stage UPS with backup generator.
The “halo” is grounded directly to the electric service entrance ground point some 100 feet away. The “halo” itself is not a complete loop around the room, rather it starts and ends on the same wall but the ends are not connected together.
Motorola has a design specification number (R56) for this. I’ll bet the book for that is fairly large. They offer a 4 day R56 training class for $1900.
Total posts : 45366Even 12-14 ga. is a bit stout for Part 15 uses. Stranded “bell wire” is sufficient for what we need (22-18 ga.). If you install a single earth ground conductor of 6-8 ga. connected directly to at least one ground rod, you are pretty well grounded for lightning or static discharge. The ground radials are for the antenna to work the best it can for the ground conductivity of your area.
Sufficient for what we need. – My understanding is; the larger the wire the stronger the return, even if minuscule (as is all aspects of Part 15). I thought that every little thing you do to improve your output, was just that; an improvement.
Your telling me it’s overkill to use a stronger conductor for the ground plane. Marshall, I don’t understand where your coming from. I’m sitting the transmitter on a flat roof, one floor up from the sidewalk.. I thought the whole concept of a groundplane was to create a ground where there is none. So I opted to try to get the biggest copper wire I could to build, you know what, a groundplane.
Like you say, “The ground radials are for the antenna to work the best it can for the ground conductivity of your area.”Why oh why is a thicker, stronger and more resonant wire not the better thing to use for radials?
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Oh, I didn’t go for the Belden wire. I ended up snagging a ‘Buy it Now’ for 9.99 + 10 shipping.. 350ft of wire. Sweet deal.. Well, I think it was..
The sellers short description with a picture of 2 reels of wire:
I have some left over hook up wire from Olympic 150ft white 16awg 26/30 105c 600v, and approx. 200ft red 14Awg 41/31 105c 600v Rohs complaint, it is always good to have extra! unused.Please don’t tell me this $19 deal was a poor choice!
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One other thing.. While I was reading the lightning lecture I could not get an image out of my mind; Have you ever watched lighting from space? (a filmed image on the video screen of course). There was an interesting program, probably on the History channel, that was talking about how surprising it was when scientist first watched lighting in action from space, and it showed film of the earth from space with a lighting storm occurring – not in a specific local of globe, but stretching massive areas. And It didn’t look like a bunch of individual stabs of light like we see here, it looked like it was a one thing.. you know, I can’t describe it, I mean perhaps it was not all that spectacular, but it impressed me.
And that’s what I kept seeing in my head while I read your lightning discussion.
Total posts : 45366Rich,
Let me try to clear up your confusion. There are, in AM broadcast, three different ground systems at work in the stations.
1) AC earth ground, usually configured as a “star” ground system. All ground conductors are supposed to go to a single earth ground; no daisy chaining of conductors. Every conductor terminates at the same point or ground rod system. This ground system can carry a large amount of current during a fault in the circuits.
2) An antenna lightning ground system consists of at least one (or multiples) 8-12 foot ground rod with hefty gauge wire, cable, braid or strap (usually copper) connected between ground and the ground side of the feed line or tuning unit. Most antennas have a spark gap (Johnny Balls) to suppress static or lightning energy stored on the antenna; one side of gap on the antenna, the other connected to ground. The current carried by this system is huge (sometimes mega-amps) and the conductors need to be up to the task or they will burn in to. The spark gap drains some of the energy off directly to ground. Some Part 15 transmitters have gas discharge capsules in the output circuit to help protect the transmitter.
3) Ground radials, or the ground plane, are the return side of the antenna circuit. Electricity needs a negative pole and a positive pole (circuit potentials) for current to flow. With RF, the alternating current flows in a circuit. The radials/ground plane compose the other side of the complete circuit with the antenna (radiator). Because this system works with the current produced by the transmitter, Part 15 systems don’t require large gauge wire. Remember, the input to the transmitter should not exceed 100 milliwatts, or 1/10th of a watt. The output is quite a bit less because of the inefficiency of the antenna system. Small gauge wire (bell wire) is O.K. here. And finally, smaller conductors have a higher inductive reactance and force high frequency lightning energy to the lightning ground system.
The confusion comes when we blend all three of the systems into one. However, for construction and operational purposes they all serve a different purpose.
In Part 15 broadcasting, the ground radials are almost NEVER resonant because they are way too short. The shortest, somewhat resonant, length for a radial for 1700 KHz would be 73 feet long (1/8th wavelength). Unless the roof you are installing your transmitter on is 150 feet square, ground system resonance will not come into play. Ground radials this long would get at least raised eyebrows from an FCC inspector these days. See the Part 15 rules.
I have seen the lightning space video you mention. For other “way cool” videos, you might see if the University of Colorado researchers still have their lightning videos still posted. In slo-mo you can actually see the lightning strike initiate. Lightning research has always been fascinating, even since the experiments done by good old Ben Franklin.
Total posts : 45366Bookmark it!
Total posts : 45366Marshall’s post are always good – especially when you can understand what he’s saying! (he’s oft over my head).
Mr. Marshall,
In Part 15 broadcasting, the ground radials are almost NEVER resonant because they are way too short. The shortest, somewhat resonant, length for a radial for 1700 KHz would be 73 feet long (1/8th wavelength).But Marshall, a often quoted link on on the forums is http://www.theradiosource.com/articles-techtalk-powerplane.htm ‘Groundplane TechTalk in which they recommend using 62 10 foot radials of 12awg wire connected to a 6 gauge inner copper ring, for the upper band.
But your saying it would require 7 times that length to have any effect, – so, is their recommendation then bogus information?
Correct me if I’ve misunderstood, but it seems like your suggesting that as far as part15 is concerned, ground radials are a waste of time, pointless, and of no benefit.
Now, I don’t really think that’s what your saying, but it is what it sounds like to me.Elaborate a bit please..
Total posts : 45366Rich,
The article you and others have cited is for a “licensed” radio service called Information Service Radio which is operated by government entities and agencies (not Part 15). This design, when used for a Part 15 ground system, will likely exceed current FCC rulings and cause NOUO’s. The 3-meter rule would, specifically for the Rangemaster, not allow for what would be a ground radial system and ground lead in excess of the maximum length (3-meters).
The transmitter and antenna are very nearly at the maximum already. Even tech tips on the Rangemaster web site recommend a ground radial system. However, in the last few months, an additional recommendation by Hamilton of adding a filter device to the ground lead to reduce the signal. Two different versions of the filter have been developed and available for sale. In the case of KENC, the FCC tech lab tested the device with findings that the filter didn’t reduce the additional radiation sufficiently to warrant keeping the transmitter on the air. The FCC ordered two transmitters out of three to be shut off. The SStran doesn’t seem to have the same issues with the FCC inspectors.You mention resonance. Resonance is a technical term that means when a radio frequency circuit possesses zero reactance. That further means that the capacitive and inductive reactance cancel each other out, leaving just the pure resistance of the load, or radiation resistance. Because ten foot radials are so short, in comparison to the length needed to resonate, their efficiency is very low. However, even with a very low efficiency, the more short radials there are (to a point) the greater the signal launch from the antenna. If the intrinsic ground conductivity of the area is very low, the signal beyond several hundred feet will be poor no matter how extensive the ground system is. The amount of power radiated by a real world Part 15 antenna is realistically in the single digit nano-watt range under average conditions. And finally, resonance is NOT impedance matching the transmitter output to the antenna feed point. Matching simply brings the individual impedance values closer to each other for the purpose of better energy transfer from one to the other.
The effect of a good ground radial system for the Rangemaster transmitter (from my own experience) is a very solid near-filed signal (within several hundred feet), improved audio quality, higher modulation with less distortion and sharper, more defined peak tuning.
“…ground radials are a waste of time, pointless, and of no benefit.” Nothing could be further from the truth. In Part 15 broadcasting with a Rangemaster transmitter, there is a balance each operator must find between what the FCC requires to be legal and what improvements can be made to have a useful community-wide AM signal. Recent history has demonstrated that a good faith effort on the part of the station/transmitter operator may not be enough to keep it on the air. So, I am forever optimistic about the future of low and micro power unlicensed operation, balanced by the presence of the FCC and the ever present possibility of the NOUO.
My mention of the gauge or thickness of the wire used is merely to assist in not spending a pile of money on copper wire that simply isn’t necessary. By using the minimum gauge of wire, you save money and get the job done safely. Copper is very expensive at today’s prices. You ever wonder why radio station transmitter sites are vandalized and the copper is taken? It’s expensive.
I have built very extensive grounding systems for 100 kilowatt FM and 50 kilowatt AM stations where there is a lot of stray electricity. A good ground system is for more than just getting the signal out there. Why “over build” a ground system for one tenth of a watt?
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