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2 Meter J-Pole Grounding and Installation

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KK4HYS, May 20, 2012.

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  1. KK4HYS

    KK4HYS Ham Member

    Hi everyone,

    I'm a new ham and I just recently installed my KB9VBR 2Meter J-Pole. This is my first antenna ever and it has been very fun to install. It took me quite a bit of research and time before I could finally begin the installation so I thought I would share what I learned with others who may end up starting out their first antenna install.

    First, let me start out by saying that I live in Florida. Since Florida has a very high rate of lightning strikes, I decided grounding my antenna was a high priority for me. You can see in the image below Florida is the lightning capital of the U.S.

    map.jpg

    As I began to research I came across several good free articles (PM me if you'd like a link) on what is required for proper grounding. The more complicated your set-up the more complicated your grounding (and costly) will be. Fortunately, all I needed was a simple Coax cable to run into my room since I am using a hand held tranciever (HT).

    Based on the design of my house and the location of the house grounds, I decided to mount the antenna to the side of the house for simplicity. Although, I would have preferred to mount it on the side of the 2nd story of my house for the extra height. This would've increased my expenses by requiring a lot more cable and would've made grounding the antenna more complicated. As a result, I went for a simple side house install. Fortunately, the mast is tall enough with the antenna attached to still reach above the 2nd story roof of my house. Its also far away enough to avoid any interference.

    I still haven't finished the install as I still have to drill a hole through the wall into my room to run the final coax cable but everything else is pretty much done.

    List of most (not all) Materials used:

    1. LMR-400 Cable
    Purchased 2 runs. 1 is 30 feet long and the other is 25 feet long. Both have PL259 connectors.
    I chose this cable since I will be running very low power (standard HT 5 watts) until eventually get an amp I wanted the least amount of loss. I also figure that the cable is just as important as the antenna. If I want to get a large distance (which I do) I can't be cheap on cable.

    2. KB9VBR 2Meter J-Pole

    3. Coax-Seal
    This is used to make sure no water/moisture enters the cable/feedpoint.

    4. Copper Plate
    The copper plate was used as the single point ground (SPG). My lightning arrester was attached to this. I ordered it from Grainger. Part# 2AAD1
    I would've ordered a smaller one (length wise) but they didnt have anything smaller. So I ended up cutting this (pictured below).

    5. Non-metal Electrical box
    Purchased this at Lowes. Cheap and easy to work with.

    6. Lightning arrester/surge protector
    I finally decided upon (after lots of research) the polyphaser IS-50UX-C0. Everyone should do research before purchasing one. Make sure it fits your application (freq wise). I'd also read reviews on any arrester before you buy it.

    7. Antenna Mast
    I purchased a 10ft aluminum pole from Lowes.

    8. 24" Clearance Y-Wall Mount
    These are the brackets that actually hold the antenna. They sell some on ebay but I found it a little cheaper after some searching.

    9. Ground cable
    20 feet of #4 THHN Cable from Lowes. I wish I could've gone with #2 but its too costly. Some people say that #6 will get the job done but bigger is almost always better.

    10. Metal Bracket
    The overhang at my house was 2 feet (24 inches) wide so my uncle and I had to fabricate some brackets to get an extra 2 inches of clearance since the largest Y-Wall mount was exactly 24inches. You'll see what I mean in the pictures below.

    11. Ground brackets.
    Bought these at lowes. One was mounted to the SPG and another to the actual antenna.

    12. Copper couplings

    13. Tapcon scews (to drill through concrete)

    14. Self-tapping screws

    15. Bolts, washers, and self-locking nuts.

    Tools:

    I forgot all the tools used. In truth, they were my uncles and he did most of the hands on work since he is 100x more handy than me. Some of the tools used were:

    1. Small electric saw
    2. 18v cordless Drill & bits
    3. High-powered corded drill.
    4. wrench/wratchet and socket
    5. Mapp Gas torch, soder, and Flux
    6. Screw driver

    0Box.JPG

    The box used.

    0Mast.JPG

    The mast.

    1CutBrackets.JPG

    The random bracket purchased to give us clearance.

    2Flux.JPG

    Flux being put on the antenna to soder the couplings on. My uncle says the the flux draws in the soder, giving you a better connection and more surface area sodered. Also clean the surface of the area before placing the flux by using an abrasive thing to remove any surface impurities (very important).

    3Coupling.JPG

    Coupling being placed on. This will prevent the antenna from wiggling in the mast.

    5Soder.JPG

    Soder being placed on.

    6Mark.JPG

    Measuring. Marking where the self-tapping screws will go.

    7Drill.JPG

    8Drill.JPG

    Drilling them in.
     
  2. WB2WIK

    WB2WIK Premium Subscriber

    Is there a question in there, somewhere?:eek:

    BTW, the coax isn't just as important as the antenna. Not even close.

    On VHF, what makes antennas work is "height."

    Almost anyone with 45+ years experience on VHF as I have (and so do many) would agree the most important things on VHF are:

    1. Height above ground
    2. Height above ground
    3. Height above ground
    4. Antenna design
    5. Coax loss.

    1-3 are very important.:p
     
  3. KK4HYS

    KK4HYS Ham Member

    9Attach.JPG

    attaching the ground mount.

    9Attach2.JPG

    10Finished.JPG

    All done.

    10Soder.JPG

    Added soder to the end of the ground cable. This will prevent the wire from spreading out when screwed in.

    11SoderEnd.JPG
    12look.JPG
    15GBarMarked.JPG

    Marking the bar to mount in the SPG box.

    16PrepBox.JPG

    Preping the box so the screws don't cause mounting problems. Also drilling the holes for the mounting.

    17BarReady.JPG

    Everything attached to the SPG bar.

    18Box.JPG

    Drilling holes for the coax cables to enter/leave.
     
  4. KK4HYS

    KK4HYS Ham Member

    19BoxMounted.JPG
    20Mounted.JPG

    The box mounted.

    21MountedMast.JPG
    1BracketsDone.JPG

    Y-Wall Bracket Mounted along with the custom brackets to give me clearance.

    22Antenna.JPG

    Antenna on the roof. You can see one of the towers with a repeater I like to hit in the background :)

    23WrapSeal.JPG

    Coax Seal on the feedpoint to avoid moisture/rain.

    23AllMounted.JPG

    All done :cool:

    My appologies if I put too many pictures. I love pictures when I look up how to do things because it saves me from having to guess. Hope this post helps someone else out.
     
  5. WB2WIK

    WB2WIK Premium Subscriber

    Once you get some experience installing antennas I think you might realize all the weatherproofing on the coax connector isn't nearly as important as preventing water from getting into the connector via its receptacle (the female UHF connector mounted on the antenna itself) and I didn't see anything in the photos indicating that was handled.

    However, good job on making a coax loop just below that point: That should prevent water which intrudes from coming all the way down the coax and contaminating all of it. That's done well, and is really required of almost all outdoor antenna installations.
     
  6. KB4QAA

    KB4QAA XML Subscriber

    Great photos!

    Beware to expect significant corrosion due to dissimilar materials where your copper plumbers' delight is attached to the aluminum pole. Probably the easiest fix is to use a piece of doweling or broomstick to keep the two components separated.

    b.
     
  7. KK4HYS

    KK4HYS Ham Member

    I didn't realize I wasn't allowed to start a thread without a question. I assumed I was being helpful :)

    I understand what you're saying that the coax loss is not as important as the antenna, but I disagree. If you are using a HT (as I am) with only 5 watts of power and have long runs of cable, the coax can be JUST (if not more so) as important as the antenna.

    I do agree that the height of the antenna is more important than either the coax and antenna.
     
  8. KK4HYS

    KK4HYS Ham Member

    On the famale, are you reffering to the back of it? Or the side where the PL259 connector actually connects. You're correct about the back side, I didn't think I had to cover that side too. Should I go ahead and cover it with coax seal?

    The loop at the top is a balun loop to prevent the RF going down and yes it was also done with the intention of preventing water from coming all the way down, JIC.

    Thanks! What about painting them? Would that do the trick?
     
  9. KB4QAA

    KB4QAA XML Subscriber

    Yeah, painting would probably work.
     
  10. K9SAT

    K9SAT Ham Member

    I have this same type of installation for my Jpole for local 2m repeaters ant it works well.
     
  11. KB5UBI

    KB5UBI Ham Member

    We sure can't fault your enthusiasm. I assume you are working FM and looking for a non-directional antenna.

    Have you thought about constructing a simple center fed vertical dipole or a full wave loop? Nether would have the ground dependance problems of the J-Pole.

    If you still want the J-Pole, I would suggest balanced feeding it at the 200 ohm point with a 4:1 co-ax balun easily constructed with an electrical 1/2 wave length of co-ax (approx. 27").

    Do not forget W2WIK's height rule. Nothing beats height for 2 meters.

    KB5UBI
     
  12. KK4HYS

    KK4HYS Ham Member

    I have thought about making a dipole. I might make one later on.

    I don't understand what you mean about ground dependance? I was under the impression a J-pole doesn't need to be grounded. I'm only grounding it for lightning protection.
     
  13. K9ZMD

    K9ZMD Subscriber

    No sweat, note that Steve did put a smiley after his comment. Although questions are the norm here, this forum doesn't actually require questions. In fact, some of the best threads I seen here have been sans questions . . . just descriptions of completed work & a few pics. You're in good company.
     
  14. K9KJM

    K9KJM Ham Member

    Here is a link to an article with some tips on how to do lightning protection on a low budget:
    http://www.scribd.com/anon-849269/d/14868226-lightning-protectiontaming-thors-thunderon-a-budget

    You already have the MAPP gas torch, Just get some true "hard silver solder" sticks and you can do good connections that are MUCH better than using plain soft low temperature lead/tin, Or the low temperature plumbing type silver solder.

    The good stuff goes by names like "Silfoss" "Silvalloy" etc. And is used by air conditioner repair shops. One stick will do lots of connections.

    http://www.ebay.com/itm/15-silver-W...845?pt=LH_DefaultDomain_0&hash=item2ebe3689ad

    (The connections that should be hard silver soldered, Or "brazed" are for any lightning conductors, Not the antenna itself.)
     
  15. WB2WIK

    WB2WIK Premium Subscriber

    The "problem" with the j-pole design is common mode currents are almost impossible to eliminate, and they generally detract from performance. If you mount it on a conductive mast, that mast is absolutely guaranteed to become part of the antenna; if you don't (and use an insulated support), then the common mode current flows back down the outer surface of the transmission line shield and radiates. If everything is perfect, this can sometimes benefit performance, but you'd have to be really lucky for that to happen; usually it detracts, as the radiation causes field cancellations at various angles and can make the antenna have "less than zero" gain.

    A good ground plane antenna with a lot of radials does't have this problem; even better is a ground plane made with a cone-shaped decoupling sleeve like the old AEA "Isopole" design. That was darned near perfect at minimizing common mode and maximizing desired radiation. It's also a very simple antenna!
     
  16. KB5UBI

    KB5UBI Ham Member

    A DC ground and RF ground are not the same. The J-Pole is not a balanced antenna. Any object near the antenna will disturb the radiation pattern and impedance. To eliminate most of the common mode currents in a J-Pole design, one must feed the antenna with a balanced feed. Simple to do with a 1:4 coax balun.

    Check out this link:
    http://n-lemma.com/calcs/dipole/balun.htm

    Instead of soldering a SO239 to the antenna, use an additional half wave length of coax to construct a 1:4 balun. Assuming you don't have an antenna analyzer, you can move the parallel connection points up from the original feed point to a point where your SWR is lowest. This should be the 200 ohm point. You will find the J-Pole will now come to life.

    For your next project, may I suggest a vertically polarized full wave loop. It's not omnidirectional having deep nulls off the ends but will show considerable gain over a J-Pole in most directions. Best of all, it's very cheap to construct with schedule 40 PVC, copper wire and a 1/4 wave length of RG-59.

    KB5UBI
     
  17. WB2WIK

    WB2WIK Premium Subscriber

    True, the j-pole is really a silly design because it wastes space and doesn't work as well as other stuff that would occupy the same area. Hams are almost the only ones to use this design. Commercial (LMR) VHF antennas almost never do.

    W1BX (founder of Cushcraft) found a way to make a j-pole 20" shorter in length and perform exactly the same way when he designed the "Ringo" antenna back in the late 1960s. That still has the same common-mode problems, but at least it doesn't waste space.

    With a 2m j-pole, the first 20" or so doesn't do any radiating, so it just sucks up space and materials for no particular reason.

    I think the design should go down in the annals of "worst jokes.":p
     
  18. WA7PRC

    WA7PRC Ham Member

    Ditto. There are better performers. The Hustler/New-Tronics G3-144, G6-144 and G7-144 are three good designs.
     
  19. KB5UBI

    KB5UBI Ham Member

    Correct.

    The first 19" is a 1/4 stub to change impedance from several thousand ohms to somewhere around 50 ohms. Then to add to the problem, we feed it out of balance without a gamma match or true current balun. An 82 inch hunk of wire across the coax would have more gain. That is why I asked to OP if he was interested in a center fed half wave or quad. Both are more predictable and cheaper to build.

    If the OP doesn't need 360 degrees of coverage, my vote would be for a full wave loop. For less than $5 worth of PVC, Coax and wire, he could actually have some gain, broader bandwidth and lower noise. With the addition of another loop 90 degrees out of phase, he could have an omnidirectional with gain.

    Anyway, I am happy to see his enthusiasm for the hobby and the fact he built his first antenna.

    KB5UBI
     
  20. KK4HYS

    KK4HYS Ham Member

    lol oh believe me I caught the sarcasm... I was teasing right back..hence my own smiley face..

    Thanks for the link! I was actually looking for those at Lowes but didn't find any. I had read they were basically required for any sort of lightning protection as opposed to the usual soder which will easily melt off!

    In the end, it made no difference because we used a screw connector to attach the wires. Thanks for the heads up though!

    Thanks KB5UBI, I'll take all that into consideration. I'm led to believe with a ferrite choke on the coax near the feed point that should take care of any of the RF from traveling down the coax.

    I wanted to clarify something though, I know next to nothing about antennas. I don't have an antenna analyzer and I have no idea what the difference is between half-wave's, full-waves, etc. I remember reading about it when studying for the exam but the memory was quickly erased (and probably insufficient to begin with) after i passed the exam. This J-pole was purchased and all I did was install it. I've never built my own antenna but after I get the hang of this J-pole I'll definitely look into your suggestion.

    lol oh well.... I gotta start somewhere

    I don't need something omni-directional but I prefer it. Truthfully, I need something that will get at least 50 miles on 50watts (once I get my in-line amp).

    Based on the reviews I've read of this particular J-Pole, this antenna can do it.

    But it sounds like there are a few j-pole haters on this forum lol.....which is causing me to have doubts...
     
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