Antenna Grounding Advice

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KJ6EWX, Feb 12, 2018.

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  1. KF5LJW

    KF5LJW Ham Member QRZ Page

    There are a lot of them. Try Google search term " Antenna Surge Arrestor". Pay attention to connector type. Many of them use "N" and you likely are looking for PL259. They look like what you see below. The one on the left is a N fitting, while the other two are PL259.

    upload_2018-2-12_23-20-24.jpeg upload_2018-2-12_23-20-50.jpeg [​IMG]
     
  2. KJ6EWX

    KJ6EWX Ham Member QRZ Page

    Thanks KF5LJW, turns out those are what I was looking at.
     
  3. KM4VOW

    KM4VOW Ham Member QRZ Page

    Lots of great advise and opinions thus far. Lightning protection is peace of mind that you have addressed the concerns as best possible. Nothing will protect you from a direct strike, but the odds of a direct strike are so low that you probably have a better chance winning at the lottery. HOWEVER, its the nearby strikes that you need to prepare for and protect against as the odds are much higher of an occurrence.

    Personally, I agree with the idea of the ground rod directly below the antenna. Rent a 6" core drill for 1/2 a day and cut a core out of the concrete below the antenna (where you showed coax 2 route entering the crawl space). Sink 1-2 eight foot ground rods there, bond together and then bond to the electrical service panel via the crawl space. On the wall above these ground rods, hang a metal cabinet and bond it to the grounds below it. In this metal cabinet created a bulkhead out of an aluminum bracket (or very rigid copper) that shorts the shield to the ground rods and/or install an arrestor after the bulkhead. I purpose of the metal cabinet is create sort of a faraday cage at the entrance to your shack.

    Depending on future expansion (a second vhf or uhf for DSTAR) or even HF, you might want to consider pulling an extra feed or two into this metal cabinet from your radio. As an additional protective measure, you could install an antenna switch at this location (I like the Ameritron RCS-10L that will short to ground when the relay has no voltage applied) or a cheap DPDT relay with a 12vdc coil that shorts the antenna center and shield together when no 12v is present and makes up the contacts when 12v is applied. For both, you would just run cheap phone or network cable to control this from the shack when you power on your power supply for the station. Shorting out the antenna center to ground should help with nearby lightning as it eliminates the static charge buildup when the wind blows that attracts lightning to your antenna in the first place.

    I personally ran 3 feeds from my radio bench to this metal cabinet and already use all 3 feeds. 1-vhf/uhf for my local repeater radio, 1 vhf/uhf for a DSTAR radio and the 3rd is my HF feed to a remote location where my HF antennas are on the RCS-10L. In the metal cabinet, all are bulkhead grounded, then lightning arrestors. On the HF, it also has a current isolator to remove RF as one of the my HF antennas is an end fed. I LOVE the isolator and would highly recommend it if you have an end fed down the road as it cleans up the received signal extremely well and 100% eliminated the RF I was getting in the computer at my radio bench.

    NO! I am no expert, not an electrician or an engineer, nor have I been installing antennas for years. I would suggest that you continue to read and research until you decide what is the best approach (if any) you are going to take to negate the possibility of lightning affecting your station and home. Oh, and get the best coax you can afford... I ended up using LMR400 and I've been pretty happy with it thus far.

    Good luck to you and welcome to the hobby!
     
  4. KJ6EWX

    KJ6EWX Ham Member QRZ Page

    Thanks for the advise. I’ll need to find out where my underground drainage pipes run before thinking about a second rod. Also will need to check local codes, my city is a PIA as we found out during construction.

    For route 1 I will need about 100ft of cable, would LMR-195 be sufficient?
     
  5. KM4VOW

    KM4VOW Ham Member QRZ Page

    Check out this chart that compares diff coax at 100' based on frequency. http://www.w4rp.com/ref/coax.html

    Hopefully it will help you to decided what you can afford and what your results will be based on that decision.
     
  6. K7TRF

    K7TRF Premium Subscriber QRZ Page

    For VHF and UHF use I'd go with LMR-400 or RG-213. LMR-195 has substantial losses at 144 and 440 MHz.

    From the data sheets:
    LMR-195 loss per 100' at 450 MHz: 7.8dB = 16.7% of your transmit power reaching the antenna
    LMR-400 loss per 100' at 450 MHz: 2.7dB = 53.7% of your transmit power reaching the antenna
     
  7. KF5LJW

    KF5LJW Ham Member QRZ Page

    Only you can decide what is sufficient. In other words how much loss you are willing to take in the wallet and signal. Keep in mind loss varies greatly from manufacture to manufacture. Great example is 9913 which is a RG8 type. Belden 9913 has 1.8 dB/100 feet @ 200 Mhz while generic RG8 is 2.7 dB/100-ft. Another example is say LMR 195 like you mentioned. There is LMR 195 made by Times Microwave, and then there is LMR 195 made by any other manufacture will not be equal.

    The number you want to look at with your antenna is 444 Mhz or IMO 500 Mhz as a baseline. Example LMR 195 at 450 Mhz has a loss of 7 dB/100-ft which IMO is unacceptable as that equates to roughly 80% signal loss, or 100 watts out of the radio gets 20 watts at the antenna. Minimum I would be looking at is LMR 400 is 2.8 dB/100-ft @ 450 Mhz.

    It comes down to what your wallet thinks. What anyone else thinks means nothing.
     
  8. KJ6EWX

    KJ6EWX Ham Member QRZ Page

    Wow that loss is substantial, I guess LMR-400 is the ticket.

    Can anyone recommend a good online supplier?
     
  9. W1GHD

    W1GHD XML Subscriber QRZ Page

    What purpose do multiple ground rounds serve, when driven within a 6 inch circle?
     
  10. K8MHZ

    K8MHZ Ham Member QRZ Page

    That would depend on if they are next to each other, or coupled together in such a manner as to make a single 16' ground rod.
     

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