Braided antenna wire and lightweight coax

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by W4LKR, Aug 1, 2018.

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  1. W4LKR

    W4LKR Ham Member QRZ Page

    I recently discovered segmented dipoles. They're popular with SOTA activators and I hope to join their ranks later this summer. I'd like to homebrew a segmented dipole but I am confused about something I read. Apparently there is a kind of wire that's basically a braided copper tube sandwiched between insulating material. There's an insulating core running through the center of the braid and a jacket on the outside. Just curious if anyone has ever heard of this? Does it offer any benefits for building wire dipoles?

    Second question - I'd like to carry some lightweight coax for SOTA. I've used RG8X for island and NPOTA activations. Is there anything lighter that's a good compromise between weight and shielding? I'll be operating mostly 5W - 15W with it.

    Thanks.
     
  2. KC8VWM

    KC8VWM Ham Member QRZ Page

    I have constructed my own SOTA link dipole antenna and it works great.

    When operating portable antennas in the outdoors, every dB counts. I find a good compromise between feed line loss and carrying around the extra bulk of larger low loss feed line is LMR-240 cable. It's basically the same diameter size as RG-58 but exhibits attenuation losses similar to much larger diameter RG-213 cable.

    For example, losses per 100/ft.

    RG-213 at 50 MHz = 1.6dB
    LMR-240 at 50 Mhz = 1.7dB

    LMR-240 datasheet: https://www.timesmicrowave.com/documents/resources/LMR-240.pdf

    Some SOTA operators like to use RG-174 because it's really thin and lightweight, but I think it's rather lossy and I personally wouldn't use it for anything beyond a very short run myself.

    I am not sure I am correctly understanding the kind of "wire" you are describing, so I can't answer that part of the question.

    73
     
    Last edited: Aug 1, 2018
    NH7RO likes this.
  3. W4LKR

    W4LKR Ham Member QRZ Page

    KC8VWM, thanks for the feedback. I have run LMR-240 from my backyard dipole into the shack and I may have some left over.

    Another question I have is how much feedline I should be using when I setup an inverted-V for a summit activation. I see a lot of SOTA guys erecting their dipole with a "squid pole", basically a telescoping fiberglass mast about 12' or 15' high. Let's say it's 15' high. How far away from the antenna does my operating position need to be?
     
  4. KC8VWM

    KC8VWM Ham Member QRZ Page

    I carry a run that's 30 feet long. I found this to be about the perfect length for use with my 20' tall squid pole and for many other portable antennas for that matter. It's just the right length for many different operating position scenarios I have encountered.

    The SOTA dipole is never installed on the very thin whippy section at the very top of the squid pole anyways. It's always going to be installed more like 18' up on the pole.

    Here's a photo of this SOTA link dipole installed on a 20' squid pole with LMR-240 attached.

    IMAG0957_1.jpg
     
    Last edited: Aug 1, 2018
    NH7RO likes this.
  5. NH7RO

    NH7RO Ham Member QRZ Page

    While I agree on the LMR-240 suggestion if you really need to go with light weight try RG-316, barely thicker than RG-174 but much less lossey.
     
    KC8VWM likes this.
  6. W4LKR

    W4LKR Ham Member QRZ Page

    Thanks for the photo. I've honestly never seen a squid pole before but I'm guessing they're available at my local bass pro shops.

    Are you guying the pole with the antenna itself?
     
  7. KF5FEI

    KF5FEI Ham Member QRZ Page

    Squid pole = Jackite pole or crappie pole. One brand name is Shakespeare Wonderpole. (There is another Wonderpole that makes flag poles)
     
    KC8VWM likes this.
  8. KC8VWM

    KC8VWM Ham Member QRZ Page

    As KF5FEI points out, these kind of fishing poles go by different names. Some people call them squid poles, other people call them fly fishing poles, crappie poles etc.. etc.. I just call them a transportable telescopic pole that's 20 feet tall :)

    Yeah the SOTA dipole antenna is pretty much guying the fishing pole too. The pole is basically self supporting at this height. After all, it's just a tall fishing pole and hardly weighs anything at all.

    You can simply lean it up against something, or if you like you can sandwich it between a rock and your backpack to hold it upright or something. lol

    Yes, I got it from Bass Pro... It's a 20' "Black Widow" model.

    Here's the product link: https://www.basspro.com/shop/en/bnm-black-widow-crappie-rod

    This is what my 20' pole looks like collapsed down, ready to carry. This photo is using a different type of portable antenna though. Incidentally, in this photo you can also see the RG-316 coax cable Jeff, NH7RO was talking about earlier. I still prefer using LMR-240 instead of RG-316 unless carrying less weight is a super critical requirement. In most situations, it's really not "that" critical. In terms of signal performance, LMR-240 is going to work better anyways because it's almost as good as using RG-213. :)

    IMAG0847.jpg
     
    Last edited: Aug 2, 2018
  9. KJ4ADN

    KJ4ADN Ham Member QRZ Page

    Second question first:
    We've had very good luck with AIM802 coax, CA192FLEX has been a good compromise between Size, Loss and Weight @ 20 meters.
    https://www.air802.com/CA195FLEX-CABLE-BULK-REEL-LMR195UF-IDENTICAL/
    The lowest frequency it's rated at, 30MHz 2.3db per 100ft... I'm guessing (not testing), it's going to be about 1db per 100' @ 14MHz, even less at 7MHz.
    Weight is 2.1 lbs per 100ft. Given a 1/2wl @ 14.2MHz is about 51ft, that would add about 1lb to your SOTA load.

    The new Times Microwave LMR-lite195 is even lighter, 1.47lbs per 100' - they switched from copper to aluminum braid (note, you'll be using CRIMP connectors), and with a 80VF, it'll save you a just a little in length and 4-5oz in weight.

    As a site note, I built a LOT of antenna systems (for packing, SOTA & portability), and found it's best to stick with the crimp connectors the cable manufacturer recommends.
    Aluminum shielding is wonderful, but aluminum braid is NOT. .. nope, not for cables that get wound up, unwound, connectors subject to lots of portable use, on and off - mechanically... eh... the 4-5oz weight savings, verses mechanical connection failures - I'd rather crimp to copper braid (or soldier). We also use double wall, adhesive heat shrink to both seal the crimped "barrel" and coax sheath to keep out dirt & moisture. Even with DOZENS of setups & take downs per year, the longest lasting cable is none-of-the-above, but some Blue 75ohm network coax, going on 5 years of door pinching, walked over, tight bends... but, it's just too much weight.

    In my experience, AIM802 cables are the best for weight, low loss, ruggedness & price (make sure you buy the FLEX). Their CA195FLEX has been our favorite - in that size/weight/performance class, especially for SOTA, 20~40 meters & lower. People often say, "wow, what is that stuff - it's so light!?"

    I like this stuff: https://messi.it/en/home.htm but the PRICE....! At some point you've got to be honest, "How long is this going to last, and is the extra $ worth it?"
    With that in mind, coax wears out faster than anything else - $$ cost really leads me back to AIR802 coax as the best overall.

    First question:
    Build a 40-20-30 close spaced fan Dipole out of copper clad steel wire.
    https://www.amazon.com/gp/product/B009L88JQY/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
    This stuff is Great! Look for reviews like this: "This wire is stranded but although the wires "look" like they are copper from the pictures they are only copper COATED wires." It makes thin, strong antenna wire that'll flex a little better than solid stuff... not bad for less than 4 cents a foot - and it's nearly invisible in the air (peel it apart).

    KJ4ADN - Bill
     
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  10. W4LKR

    W4LKR Ham Member QRZ Page

    Thanks for the photo, that's really slick looking. Are those fly fishing reels with antenna wire on them? I'm glad you posted this because it perfectly illustrates the kind of antenna wire I'd like to find, assuming it exists. I want something that is really flexible so it can be coiled, wound or even reeled up without keeping that shape. For US Islands I've been using some braided copper I ordered from AES years ago. It works fine but it's not flexible. It wants to retain the coiled shape it came in and I'm constantly fighting with it during setup. I want a coated wire that will fall into a pile, kind of like an extension power cord does if you coil it on the floor.
     

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