High Quality Ground Block ..where to find one?

[Punkitup]

Do any of you nice folks have any on-line sources for high quality grounding blocks? Preferably something that would allow for pass-through of two or more coax runs. I am looking at using CommScope 5781 Quad Sheild RG6 and I figure it is little use using a cabel tested to 2.2ghz and then connecting it to a grounding block that is not of the same quality.

Also I am wondering what you guys think is the relized advantage of using a Quad sheild over a dual shield [foil & 60% braid] in runs of 50ft.??

For runs of 100ft at 2.2ghz the attenuation figures from CommScope are....

9.7db for model 5730 [dual shield]

9.0db for model 5781 [Quad shield]

Peace-James/N8SBU

 

[waydwolf]

*rolls eyes*

    Okay, pretend you're a cable parts distributor. You take a ground block and put it to a spectrum analyzer used in cable, tuned pretty much from 5Mhz to at least 806Mhz and for good measure, you go to 1000Mhz.

    Good results? Advertise it as broadband digital cable ready and say "Rated to 1000Mhz!".

    Now let's say you're a satellite parts distributor. You take the SAME ground block and put it to a spectrum analyzer, this time looking from 950Mhz or so and sweeping straight on through to the top end of the stacked band at 2050Mhz and for good measure, you go to 2100Mhz.

    Good results again! Advertise it as digital satellite ready and say, "Rated to 2100Mhz!".

    Get the picture? Unless the ground block uses a barrel with a tremendously badly designed seizing pin, badly cast or machined threads, useless dielectric material between the seizing pin and body, then it will likely sweep just fine all the way to 3Ghz or better which you aren't going to need to deal with in DBS.

    Even Radio Shack would have to actually try hard to screw up a ground block and make it only able to carry analog cable.

 

[Mike500]

Check out this auction on Ebay;


http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=32848&item=3008509267&rd=1


There is a difference. They have much better contacts and more contact surface area.

[waydwolf]

Originally posted by Mike500
Check out this auction on Ebay;


http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=32848&item=3006349 104&rd=1


There is a difference. They have much better contacts and more contact surface area.

    I've seen these before. As I said before, unless the barrel is truly badly designed or made, and it passes a sweep which many others have before all the way through to the top of the band you're concerned with, and it has not been contaminated or corroded, then it will work fine.

    They point out the gold color ground blocks. Let's start there.

    I can tell you as a machinist that there is zip, zero, nada special about the ground block body. It is one piece of conductive metal alloy totally surrounding the stingers at each end and seizing pin in between. No magical precision aerospace manufacturing, just a hunk of metal that's usually cast although some are stamped metal combined with a separate barrel that is held with a nut.

    Give me a Bridgeport, a lathe, a tap and die set, and I'll build you a backyard aluminum and bronze melting foundry on top of it to turn out some of the spiffiest ground block bodies you ever saw. Heck, I'll send them out to be laser engraved with my company logo on it and if I really want to be a wise ass, gold plate the thing. If I wanted to be evil, I'd make them out of berylium copper alloy and play up the special precautions needed to make these "gems of modern engineering".

    The only thing important about the body would be the metal composition versus the composition of the fittings, although I'm sure some heckler would bring up gallium, mercury, plutonium, etc. which you're not making blocks out of for obvious reasons. Anyhow, when metals are electrified in a corrosive environment, which Earth's environment is especially with pollution, you tend to get electrolytic/galvanic corrosion effects.

    Dissimilar metals joined together and electrified corrode even worse. Copper can migrate right out of bronze alloys to form copper chloride and copper oxide crystals on the surface. In cable, we see road salt on the taps all the way into spring. Don't ask how it gets twenty five feet up. Just know that sort of thing causes more broken tap ports than you can shake a stick at.

    It wouldn't matter if you made the block out of pure osmium and coated it with platinum and inscribed the name "Cartier" on it, although there'd be legions of gullible people in Hollywood waiting to buy them for twelve million dollars a piece.

    As long as it is one solid piece of metal, the threads mesh properly with the fittings, and the fittings are properly applied to good coax, your leakage will be very low and relative to the signal you're dealing with nil.

    Next is the actual part that matters most next to the tightening of the fittings to the barrel, the seizing pin construction. I've installed many many hundreds of ground blocks and never had one fail when new. Some merely were doing cable that maxed at under a 1000Mhz and others were stacked installations going to 2050Mhz. Not a problem and the block in the worst case was one hundred ten feet from the dish.

    The miniscule difference between this eBay block and the average block would amount to a difference so slight, you'd need an oscilliscope to see it. I presently work with a DirecWay installer company and they use the same ground blocks as for DirecTV and Dish and not a single problem or loss of performance because they didn't use the magic blue ground blocks.

    Consider that the stingers are not always uniform in size and frequently the tip is mashed and bent when the coax is cut and many installers do not bother trimming it but instead force the deformed thing in there, some leaving a stinger long enough to physically touch the other stinger through the hollow seizing pin. I guarantee I could destroy these so-called high frequency ground blocks in two minutes with bad installation practices.

    Contamination with water is a very good killer of any splices whether barrels or ground blocks. If the fittings are not applied wrench tight, and many people don't bother, then you're going to get water infiltration, and failure by corrosion, sooner rather than later.

    Since using a coffin flooded with sealant is good around splices on cable, it would also be nice to see such an animal for ground blocks but I haven't seen it so far although Thomas&Betts does have a groundblock and integral compression fitting in their catalog. Instead if the owner worries, I simply fill boots with silicone sealant and there's almost no water getting in ever and the cable will fail first.

    Once again, if you sweep test the ordinary ground block, it passes no problem all the way to 2050Mhz and past. Before this magical blue and silver ground block was offered, did no one ever do broadband/wideband? Of course they did. And they did them just fine. It's fools gold and you can prove this by checking out all the other wideband installs to see.

    The sad thing is, these claims are sales propaganda and not based on solid engineering evidence of superiority and bought because most people work along the lines of, "if a space shuttle is good, then a Federation starship would be better". I am not kidding when I say that cable techs have sold jumpers of RG-11 to people as "Monster Coax" and gotten fifty bucks in some cases for them and keep in mind, we're talking a jumper from the RF output to the television set, carrying one simple NTSC signal.

    In fact, a friend of mine and I briefly considered getting a gold electroplating kit, and plating some Gilbert Ultraseal fittings and using some Times Fiber colored head end cable and selling it as designer color coax jumpers, but we had an attack of ethics and went for a stiff drink instead.

    In satellite, not one month goes by some lady does not ask me for lemon yellow or hunter green instead of black or white cable and believe me if I had it, I'd charge more for it and play up that it could pass a sweep test way beyond any frequency her wiring would likely ever need to pass. I'd be as wealthy as some of my customers if I could.

    If this sort of thing continues, people will all be demanding Andrew Heliax pressurized coax and C-band sized dishes with amplifiers on top of it so they can maximize their signal(and I can almost laugh hard enough to choke at the thought of what some guys would charge to put that on a tripod mount).

    Actually, I regularly run into people in cable who DEMAND an amplifier for a single outlet that is less the twenty feet cable run from the tap at the lockbox on the theory that maximizing signal is a good idea no matter how you do it or what the point is supposed to be.

    Chasing diminishing returns is the sort of thing all sales departments will always encourage you to engage in.

 

[Punkitup]

Thanks for your replies fellas.

My reference to the swept test figures on the cable was probable misleading. And only meant to note the quality of the cable.

I was mostly interest in a ground block of quality mechanical construction. I will look into the Thomas & Betts block that was mentioned, thanks. Is this part of their Snap-N-Seal line? Can those connectors be assembled by hand and normal cable tools, or to you need their over-priced compression tool?

Any further web-links for quality grounding blocks?

Anyone want to tackle my cable question? I understand that the issue of attenuation is only relative in the end results to the usable signal you started with, but not knowing this the question still stands. To Quad or not to Quad?

 

[JayeDVXIII]

why does the wolf always roll his eyes when someone asks a tech question? Poor technical support/customer service skills? :-)

<runs>

[Tomsoundman]

I think he is tired of the bad information out there. His posts are very appreciated.

By the way, do I need a special antenna to receive OTA HD?

<runs too>

ha ha...

[Richard King]

The wolf talks sense. There are way too many scammers out there and it appears he is simply attempting to stop one of them. If it works, don't fix it.

[Mike500]

The design of a high frequency grounding block has very little to do with the outward appearance of the grounded casting. Any grounding block will sweep test for 3000 MHz upon initial installation.

The most important factor is long term conductivity in the center socket. Important factors include the contact area between the center conductor and the socket, the contact tension, the ability of the socket to maintain long term contact tension, and the compatibility of the contact material.

Both Thomas and Betts, Sirling Canada, and other manufacturers make both 900 Mhz and precision or high frequency grounding blocks and F81 barrel connectors. The high frequency ones cost two, three or four times as much as the regular ones. The center socket of a "cheap" socket is similar to the two contacts on a phone jack socket. Two linear flat areas contact the round surface of the center conductor at a small point or tangent. The high frequency sockets resemble a machined RS-232 socket. It is a machined seamless tube with a flared entrance funnel. There is a 360 degrees contact along a length of the inner diameter of the tube. These are called machined Mil-spec sockets. The cheap sockets are made of brass, and the machined sockets are made of phosphor bronze.

The use of RTV (room temperature vulcanizing) silicone rubber as a floodant for the socket is strictly prohibited by industry and military standards. I can remember from the '60's when working with aerospace contractors, when NASA started to use RTV to pot electrical connections. Silicone RTV hardens on the basis of a reaction of water or moisture in the air reacting with acetic acid or vinegar in the silicone compound. The combination of acetic acid and the two dissimilar metals in the connection will cause corrosion, since the set up becomes an electric battery.

The best foodant is 100% pure silicone grease. The pH is neutral. There is no acid in this material.

There is a difference.

[Mike500]

Originally posted by Punkitup
Thanks for your replies fellas.

My reference to the swept test figures on the cable was probable misleading. And only meant to note the quality of the cable.

I was mostly interest in a ground block of quality mechanical construction. I will look into the Thomas &amp; Betts block that was mentioned, thanks. Is this part of their Snap-N-Seal line? Can those connectors be assembled by hand and normal cable tools, or to you need their over-priced compression tool?

Any further web-links for quality grounding blocks?

Anyone want to tackle my cable question? I understand that the issue of attenuation is only relative in the end results to the usable signal you started with, but not knowing this the question still stands. To Quad or not to Quad?

&nbsp;


Try these sites:

http://www.mjsales.net/thomasbetts659.htm

http://www.mjsales.net/sns59.pdf

Be aware that the only tools that can be used to apply the integral connectors like the grounding blocks are the splices are the SNSIT or thr SNSUTL.

Any tool like the Cablematic, the LCCT-1, the IT-1000 or the Terminx will not work with these.

I'd only use quad shielded cable, if you have a long cable run. The extra shielding means more wire and better conductivity, and therfore less voltage drop to preserve upper voltage lnb switching.

The least expensive tool for installing Snap-N-Seal is the Sargent 8600esc;

http://www.jensentools.com/product/group.asp?parent_id=12430

There are several Snap-N-Seal kits listed on Ebay:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3006620412&category=15067

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=32848&item=3008449592&rd=1

The ones listed above include the 8600esc tool.

Hope this helps.

[Mike500]

Here are the Pro's and Con's on solid copper cable:

Most cable companies prefer "copperweld" or copper coated steel center conductors for drop cables. Solid copper stuff, although electrically more conductive for dbs systems, has less tensile strength, is subject more to kinking and neverthe less less durable physically. No longer available is "hard drawn copper" that they used to make, because copperweld serves the same purpose. Monster cable is made for fexibility. Quad shielded Monster cable would be ideal for long runs to reduce resistance and voltage drop to the lnb's and multi-switches. The center conductor is solid copper; so is the shielding braid. This increases conductivity and reduces voltage drop. The Archille's heel to this cable, however is that it is more delicate and requires better protection and more careful handling. Larger radii must be physically maintained. Stretching of Monster cable or any other soft copper conductor cable will change its conductivity and impedance. A stiffer copperweld higher tensile strength cable automatically maintains a wider radius and is less subject to redction of center conductor reduction in diameter and change in impededance from stretching.

Look at the "circuit limited" or "CL" rating stamped on the jucket of a good cable. If it is marked CL-3, it is a better cable than one marked CL-2. This rating relates to conductivity. The CL-3 can handle a higher voltage and current. Consequently, it has better conductivity, although its intended rating is not specifically meant for dbs use.

On account of the forememtioned, I prefer CL-3 rated copper coated steel center conductor RG-6 for dbs use, 60% shield, and preferbly, 90%. A cable like Times Fiber Lifetime with 90% shield and a light preservative or floodant is, by design, the ideal cable for both dbs and CATV.

[Mike500]

Another place to purchase Snap-N-Seal connectors:


http://www.starkelectronic.com/augat.htm

[Mike500]

Here is the difference between two F81 connectors with "f' connector sockets.

First, the standard 900 Mhz one:

http://catv-cat.tnb.com/tnbcat/tnbcat/webcat_search_results_dsp2.build_category_home_pag e?p_catalog_code=LRC&p_category_hier_id=LRC40&p_div=D

Second, the precision one for 2200 Mhz and above:

http://catv-cat.tnb.com/tnbcat/tnbcat/webcat_search_results_dsp2.build_category_home_pag e?p_catalog_code=LRC&p_category_hier_id=LRC40&p_div=D

Notice that the precision splice only accepts pins or cablecenter conductors from between .032 to .040, which is 18 guage RG6 center conductor.

Who says that there is no difference?

[DoyleS]

I pretty much agree with Wolf. Saying a cable is sweep tested to 2.2 or 3 GHz means nothing unless you know what the results were. There are two factors that can affect your signal. The first is Insertion Loss. If the loss is too high you don't get enough signal and the receiver doesn't work. The insertion loss from a barrel connector in a ground block is going to be miniscule compared to the loss in cable which is rated in db per 100 feet. If a cable has 10 db of loss per 100 feet then it has .1 db of loss for 1 foot and correspondingly you could estimate that the barrel connector has less loss than a 1 foot piece of coax since it is only 1-2 inches long. Impedance is another item that can cause problems. Mismatched impedance causes reflections on the line which in turn gives multiple signals of the same information arriving at different times at the receiver as well as phase cancellation of the signal. Again magnitudes are important and this little connector would have to be off by a significant amount to cause any noticeable problem. If your cable run is only 50 feet you also will not be able to see the difference in signal of 9.7 db loss vs 9 db as it only amounts to .3 db at 50 feet. It is also unlikely that differences in the shielding between these two will make a difference. Foil is a good shield for reducing coupling between lines. If a cable is going to be flexed a lot then a higher quality cable is in order as the phase variation due to flexing can cause problems. In most permanent installations it is not a problem as ling as you don't start making small radii bends in your cables bend (1/2 inch or less depending on the cable. Stiff cables need larger sweeping bends. The cables often more critical for a UHF TV antenna installation since you are looking at Analog receivers where signal loss manifests itself as a fuzzy picture vs a digital receiver where the signal is either present or not.

Typically the Sweep measurements are made with Scalar or Vector Network Analyzers which have built in sweep generators and a calibrated tracking receiver to measure the signal strength. TDRs or Time Delay Reflectometers are also used and have the ability to look at discontinuities along the length of a cable.

..Doyle

[AntAltMike]

The eBay link in Mike500's post that alluded to the standard "gold colored" ground blocks did not say that the blocks were inferior because of their color or composition, but rather it attempted to identify the present incarnation of cheap ground blocks by their appearance. Someday soon, I expect the manufacturers of the standard, "gold colored" ground blocks to wise up and start making silver colored ones with blue plastic ends because they will be able to sell them for more, but for the time being, I believe I can reliably identify the cheap ones from the good ones by those non-causative identifying characteristics.

I'm all for ground blocks that are designed to make and maintain more reliable contact with the center conductor of the coax, but regrettably, I will never be able to independently ascertain how much better off I am by using them. I pay a little more for the Holland 2Gz splices and ground blocks because they claim to have a center conductor seizing mechanism that touches the center conductor all the way around, and that claim, coming from a reliable, albeit low-end, manufacturer, is enough reason for me to pay another maybe $.20 for barrel splices and maybe another $.50 for grounding blocks. But if someone using the name "Tru-Spec" (or Terk) tries to get me to pay the additional $.20 or $.50 for products about which similar claims are made, I probably wouldn't pay it, even though it might actually be the grade of product that I want.

There are high frequency splitters with a dark yellow-gold finish that were engineered for use in Europe that used to say 450-1,750Mz but which now say 450-2050Mz or 900-2050Mz. On my spectrum analyzer, when I feed stacked LNB signal into these, the signal strength drops off a cliff starting at about 1,800 Mz. By 2Gz, it may be down an additional 5 or more dB and the attenuation drop-off is irregular as well.

And by the way, those splitters choke channel 4 and cable channel 17 (which are harmonically related) like you wouldn't believe. Not that they claim to pass those frequencies, but I carelessly used some for cable TV splitters and got callbacks on all of them.

I went to a seminar at WSNet in 1997 or 1998 when the parts industry was just becoming conscious of the marketability of 2Gz products, and I saw some splitters there in which the 2Gz label had been plastered over the 1,450Mz label, and it could be readily peeled off. Some even had the stickers on upside down, such that the port labels of "input" and "output" didn't even line up with any ports.

I always buy the cheapest coax and have never have any trouble with it, even though I deal with more stacked LNB signals than do most of you. I wouldn't pay one dollar more to have it "sweep tested" to 2Gz because I don't think that anyone would know how to make coax that passed a 1Gz sweep test but failed a 2Gz sweep test even if they wanted to. I use 60% shielding with single foil.

But, on the other hand, I enjoy the luxuries of being able to engineer my installations to parameters in the middle of the operating ranges of the components I use, I have test gear to evaluate system performance and lots of parts to shotgun with if anything doesn't work as well as I expect it to. Maybe if I had to work with a typical residential installer's more modest inventory and limited technical resources, I'd care more about whether it was worth paying extra for some incalculably slight reduction in product failure rates. Maybe I'm just spoiled.

[Punkitup]

In the end I decided I wasn’t going to go overboard on cable for the DBS. Just to prove I know what going overboard is, have a look at what I use for my AMATEUR SATELLITE (http://www.amsat.org/amsat/news/wsr.html) setups, ANDREW HELIAX (http://www.andrew.com/products/trans_line/heliax/default.aspx). For cable I decide to go with 500ft. of Quad Shield from CABLE X-PERTS (http://www.cablexperts.com/) a reliable company who I have dealt with for Amateur Radio supplies. It’s their item number CXP006Q (http://www.cablexperts.com/cfdocs/cat.cfm?ItemGroup=5&amp;itmsub=0&amp;bskt=0&amp;USA_ship=1&amp;c=0 ) have a look and see if you think I did all right, it will arrive Friday. For grounding blocks I have not yet decided, I am looking around, including Mike500's eBay offerings, thanks for the link Mike. And thanks very much to the rest of you folks for taking the time to supply me with links. One thing I would feel comfortable in suggesting. There is a lot of crossover application between technologies in different forms of hobbyist electronics, don't forget to have a look at the many Amateur Radio supply houses when looking for a item. As a rule they have been in business for many years, and being that they service a relatively small but very tuned in segment of the market, they have reputations to uphold (please excuse the prior pun). And who knows you might find a new hobby to sink countless dollars into, Rod AC6V (http://www.ac6v.com/) has a site with tons of links....Peace - James/N8SBU

[Mike500]

Looks like a good quality cable. As an amateur radio operator, you know that workmanship and preparation is important. Since switching voltage is very important, the additional wires in quad shielded cable will be beneficial for all future needs.

[Punkitup]

Originally posted by Mike500
Looks like a good quality cable. As an amateur radio operator, you know that workmanship and preparation is important. Since switching voltage is very important, the additional wires in quad shielded cable will be beneficial for all future needs.

&nbsp;

Thanks Mike. Interestingly enough, I think it safe to say that in most amateur satillite systems switching is still preformed seperate from voltages applied to the feedlines, at least in home-brew setups. Pairs of Yagi antennas [2 transmit/2 receive] are set up 90degrees out of phase with each other. Right hand or Left hand Circular Polarization is then selected through a 12volt relay placed in line at the phasing harness, usually on the cross boom supporting the antennas. Your biggest concern with feedlines [coax] becomes losses, be it from the cable at VHF, UHF and so called SHF frequency or at connectors, N-type connectors being the optimal choice. Low noise on receive and effective radiated power [ERP] on transmitt mean everything.

Just for anyone who is reading this note and wondering what this guy is talking about [and probable why it is somewhat off-topic..HaHa]. There are many Low Earth Orbit satillites up there built and launched with funding&nbsp;from private citizens for the purpose of radio comunication with each other [vocie/data]. Unlike the satillites for DBS these birds are closer to the earth and appear to move across the sky, so your antenna must use a pair of rotors to track the AZ-EL as the bird passes your view. It is really great fun for a nerd such as myself. Oh, and there are two other birds you can track, and if you are lucky enough get a chance for a quick chat with, the International Space Station or the Shuttle ( God bless &amp; keep them), every flight has a least one licensed amateur onboard.

Or if you have enough time, money and space try Moon Bounce, where you bounce your signal off the Moon, no, I mean it honestly.

Well I think&nbsp;this has&nbsp;pretty much run it's course...thanks all.

Peace - James/N8SBU

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