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HF Antenna Setup Questions

This topic contains 2 replies, has 2 voices, and was last updated by  Gabe, K6YAH 1 year, 3 months ago.

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  • #8621

    Gabe, K6YAH
    Participant

    Hi!

    Had a great time at the party yesterday :). I have some questions. I just ordered myself a Carolina Windom 80m-10m antenna. It’s 131′ long, and will just fit on my property (which is 150′ wide). I am overwhelmed by the choices of coax, connectors, etc, and honestly I’m not sure what I would need.

    I was thinking of getting a 100′ spool of coax and a bag of 10 PL-259 connectors from Quicksilver Radio (qsradio.com), where I am also getting my window pass-through plate. However per the questions below I’ll go elsewhere if it makes sense.

    On to the questions:

    * Is RG-8X a good coax for this project? I’m guessing I’ll have to run <30ft to the antenna (I don't yet know exactly the best position for it)
    * Does someone have a coax crimper I can borrow? It’s a pretty expensive part, and I don’t imagine I’ll use it all that often.
    * How do I know the connectors I’m getting are high quality? I’ve heard that connectors and the crimp quality are the highest sources of loss/noise, so I’d like to spent a few extra bucks where it’ll count.
    * Same question for coax – what’s a good source?
    * Any other parts I should be getting myself?
    * And lastly: is there anyone who would be willing to help do the install once everything is delivered? I have the week of the 18th (and of course the prior weekend) off, and am hoping I can get everything delivered by then.

    Oh and equipment-wise I have an icom 7000 with an antenna tuner (I forget the exact name but it was made especially for the 7000).

    Thanks for your help! I’m excited to finally up my antenna game. While I’m at it, I might as well put up a 2m antenna :).

    #9980

    David, KM6DOV
    Participant

    http://www.w4rp.com/ref/coax.html This is my favorite page for RF attenuation by cable type.
    http://www.fab-corp.com/pages.php?pageid=5 shows power drop per a given dB.

    RG-8X will drop between 0.5-2.5dB per 100′ and the dB loss scales linearly with the cable length. Worst case, you’re <1dB at the highest frequency for your new HF antenna.

    VHF has near double the loss. If you’re running it any more than about 15′, you might consider something thicker like LMR-400. Particularly if you ever plan to use UHF.

    A couple weeks ago, my main mast UHF/VHF feed line failed. It was 50′ of RG8-X, which drops 2.35dB @ 150MHz or 41% of the power. That turned my 50W transmission into 30W out the antenna. Factor in the SWR loss and it’s less than that. Upgraded to LMR-400 and I’m getting closer to 40W out. But the main lesson learned here was the root cause of the failure. I didn’t use sealing tape on the connector, and water got in.

    I got my cable from MPD. My window feedthrough is the “big one” from MFJ that has 4 UHF, N, F, balanced line, and random wire terminals as well as 12V, ground, and a passthrough port for an antenna tuner or other cable that needs to be snaked through the window. I screwed a terminal strip to the wood on the feedthrough for ground connections from each piece of equipment and drove a copper rod bonded to the rest of the house grounding right outside the window. If you’re concerned with reducing connector loss and noise, go with silver plated connectors and perhaps a gold center pin. If you don’t mind soldering, that will make a better connection to stand the test of time.

    Good luck with your antenna projects. If you need a hand with anything, just ask. I’m off work from the 23rd to the 8th, or I could help on weekends. I have a crimper and a stripper you can use.

    #9981

    Gabe, K6YAH
    Participant

    Hey David – thanks for the tips and the offers of help.

    I am going to put together an order now for RG8-X. I think my run will be something like 15-20ft for VHF and I have a 100W transmitter. If I change my mind and want to buy some LMR-400, it’ll be really easy to run a new feed line. Hopefully everything will get here this week and I can start tinkering over the weekend.

    Angelo offered me use of his tools off-list also. He lives across the street from me, but I really appreciate your offer.

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