To Station Ground or Not to Station Ground

Discussion in 'General Technical Questions and Answers' started by KC1KDG, Sep 14, 2018.

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  1. KC1KDG

    KC1KDG Active Member QRZ Page

    New ham operator here. By all means tell me everything I'm doing wrong!

    My setup is as follows:

    shack is on second floor
    ICOM 7610 transceiver
    deep-cycle marine battery for power
    two coax lines fed crudely out the window and into the trees
    two commercial dipoles, 20m and 40m, relatively low, 1:1 baluns I assume

    With this setup I have had some fun indeed, including a handful of SSB voice contacts in Europe and the US. So no complaints about performance at this point.

    The battery power is temporary until I replace a faulty DC power supply. As described, the entire system is ungrounded and so floats. When I connected my computer to the transceiver this morning, the performance of the system (on 40 m anyway) greatly increased. It's tough to quantify, but the overall effect was at least 3 S units of increase in signal to noise ratio.

    My limited understanding at this point is that this is likely due to common mode noise finding its way into the transceiver, perhaps on the outside of my coax. When I connected the computer, I provided a low impedance path to earth though the transceiver chassis, across the USB cable, into the computer chassis and from there through the electrical safety ground and ultimately to the earth though the grounding point (the copper water service entry in my basement). I think we'll all agree this isn't a desirable path for this current to flow.

    For the moment, the most pressing question I have is: What accounts for the enhanced performance? Does my theory hold water? There seems to be a lot of anecdotal information on the web regarding not needing a station ground if you have balanced antennas (like my dipoles fed via baluns). So in my newbie frame of mind I am trying to understand what is going on here. I'm an electrical engineer by training so don't hold back with any technical explanations.

    Thanks for any info!

    -Jim
     
  2. KA9JLM

    KA9JLM Ham Member QRZ Page

    I would go down from the antenna to a ground rod, Then run the feed line up to your station.

    That will help to keep your station from being half of the antenna. Keeps lightning out of the shack too.

    The benefit is worth the extra small coax loss.

    Enjoy.
     
  3. KC1KDG

    KC1KDG Active Member QRZ Page

    Thanks for the suggestion. If I understand lightning protection, at least a little bit, I would want to bond that ground rod to my electrical systems's ground point, lest I create a path for a step potential between the two ground points. I guess the simplest example of this would be a lightning strike to ground that puts the two rods at very different potentials. This can send current between the rods, which means through the safety ground in the house, equipment chassis, the coax shield between the equipment and station ground. Everything and everyone in the house is at risk for exposed high potentials, and it could also start a fire. Have you heard of this sort of concern?

    Thanks,

    -Jim
     
  4. KA9JLM

    KA9JLM Ham Member QRZ Page

    True.

    That is the correct way to do it.

    1 rod is better than none.
     
  5. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    Those bad things couldn't happen if absolutely nothing in your ham station is connected to ground inside the house; unfortunately, that's nearly impossible.

    Bonding the electrical utility ground to any other ground (rod) you install isn't just a good idea, it's required by the National Electrical Code, which is written almost entirely to help prevent fires. This isn't difficult to do. Easiest way, and the one I prefer anytime it's possible, is to bring cables in from outside to inside right next to the electrical service panel, where that utility ground already exists, or below that where its ground connection is located -- makes this "bonded connection" really easy to accomplish.:) For an upper floor hamshack, I bring cables in at ground level and then run them upstairs "inside" the house, which is always possible but may be a bit of work (drilling, pulling wires, etc).

    The "enhanced performance" you describe when you added an accidental ground to your station via your computer should absolutely never happen. My guess is you had (or have) a bad "ground side" connection between your dipole(s) and your rig -- possibly a bad coaxial shield connection at a connector along the line somewhere.

    A 1/2-wave, center-fed dipole doesn't need any kind of "ground" to work perfectly, and adding one anywhere along the cable length, including right at the "rig" itself, should not change anything.
     
    K7TRF and N0TZU like this.
  6. KC1KDG

    KC1KDG Active Member QRZ Page

    That's great advice for bringing the cables in near the service entrance - that's easy to do in my situation.

    I'll investigate the accidental grounding affecting performance a bit further and report what I find.

    Thanks!

    -Jim
     
  7. KC1KDG

    KC1KDG Active Member QRZ Page

    Well, I don't see the enhanced performance now, which is puzzling. When I did see it it was rather early before 40 m had really opened up, and only a few strong signals were visible on the band scope. I tried it a number of times and attempted to gauge the signal strength and background noise levels. Of course I couldn't turn off the AGC, which might have helped trying to quantify the effect. I believe I can slow down the AGC a great deal on the IC7610 with a custom time constant so maybe that will help.

    My guess is these sorts of mysteries are part of what makes the hobby fun. I'm sure some would disagree!
     
  8. KI4AX

    KI4AX Ham Member QRZ Page

    Jim:

    What are you going to do with your feed lines during lightning storms? Do you plan to operate during storms or leave your equipment connected to your antennas during storms? Or, are you going to disconnect your feed lines during those events, and lay the lines down on the floor of the shack?

    Generally speaking, neither of those options will provide protection from lightning. Leaving the feed lines connected to your rig puts your equipment between the lightning bolt and ground. Disconnecting the lines and laying them on the floor of the shack leaves the lightning bolt to find it's own way to ground. Which could be through your appliances, stereo, phone system, (you if standing nearby) etc.

    My suggestion would be to install a separate ground rod for lightning protection, connect it to a grounding block inside the shack, and attach your feed lines to the ground block when not operating. Do not bond this ground rod to any others. The ground block can be home brewed or purchased. I made one out of 2-1/2" copper tube with SO-239's soldered to it. Also soldered to the block are two #4 solid copper wires which are soldered to a 16' ground rod (two rods welded together). The run from block to rod is about 3 ft. This forms a direct path from antennas to ground.

    I know there will probably be those out there that disagree with this. Yes, bonding your station ground to the electrical system ground is a good idea for many RF reasons. But, not necessarily for lightning. I have dealt with a devastating lightning strike in the past so I speak from experience. Since installing a ground block, and keeping my feed lines connected to it when not operating, I have not experienced another destructive lightning strike despite the fact that I live in or near the lightning capital of the U.S. I do believe my antennas have been hit (or near hit) several times since then but there has been no adverse effects.

    Dan KI4AX
     
  9. KC1KDG

    KC1KDG Active Member QRZ Page

    Hey Dan, thanks for all the advice. I'm very aware that my biggest priority is lightning protection, and that it will require grounding the antenna shields at the entry to the house, presumably with lightning arrestors for protecting the center conductor as well. I'm pretty sure that NEC requires such grounding to be bonded to the electrical systems's safety ground, and for good reasons such as keeping all grounds at the same potential, or at least close to the same potential by providing a low impedance path between multiple grounding points outside the building. Otherwise you are encouraging step potentials (lightning induced, wiring faults like a neutral wire connected or shorted to the safety ground) to drive current through your house. I'm really pushing the envelope of what I understand here, but there you go.

    I'm contemplating professional help (a qualified electrician) to help in the matter, which I know is counter to the ham radio DIY ethos, but I'm not really willing to take a chance that I've understood everything I should in such an important aspect of my setup, and really don't want a code violation to get in the way of a claim I might have to make if I should experience damage to due lightning or other covered events. And I don't want to die. Or have my house burn down. Or have my shack trashed, etc.

    Since what I've heard about bonding being good and required for lightning protection deviates from your advice, I'm very interested in hearing more about how lightning damaged your shack. Did you have a shack ground rod bonded to your electrical system's grounding point? If so, why do you feel it contributed to the destructiveness of the strike you experienced? Really trying to understand what can happen. Thanks!

    -Jim
     
  10. KV6O

    KV6O Ham Member QRZ Page

    A separate ground is a bad idea. It's not about the strike hitting your antenna, it's about any nearby strike hitting a tree, pole, fence, shed, whatever - and propagating thru the ground. Since the earth is a pretty poor conductor, you will have voltage gradients, which can easily reach several thousand volts per foot. When your ground is properly bonded, the ground potential rises and falls as one - like riding a wave in the ocean. If you have 2 grounds, now you have a voltage difference that you have brought into your shack that can easily be kilovolts. No direct strike needed.
     
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