Ground Wire Mistakes?

[prcguy]

Did you bond the new ground rod to the house main ground rod as specified by NEC? If not that can be dangerous on several levels from causing the ground potential on the radio connected to that ground rod to be much different than everything else in the house. As a young person I did this and my one radio connected to the isolated ground rod had about 90 volts AC on the chassis and whenever I disconnected the antenna it shocked the heck out of me.

The other problem is if you were to get a lightning strike the different ground potentials can cause much more damage to equipment in the house. Its fine to experiment and see how grounding affects noise but I would not recommend leaving an isolated ground rod connected to your radios.

I used an outside ground rod (just outside the window) and saw one-half S-unit increase in signal with no apparent increase in noise. It's an incremental improvement, I think.

 

[KB2GOM]

Did you bond the new ground rod to the house main ground rod as specified by NEC? If not that can be dangerous on several levels from causing the ground potential on the radio connected to that ground rod to be much different than everything else in the house. As a young person I did this and my one radio connected to the isolated ground rod had about 90 volts AC on the chassis and whenever I disconnected the antenna it shocked the heck out of me.

The other problem is if you were to get a lightning strike the different ground potentials can cause much more damage to equipment in the house. Its fine to experiment and see how grounding affects noise but I would not recommend leaving an isolated ground rod connected to your radios.

I used a separate ground rod with no connection whatever to the house ground. The linked write-up I did for SWLing.com blog, I hope, made that clear.

Cheers, Jock

 

[MUTNAV]

For HF or SWL reception you have to consider signal to noise ratio is most important and absolute signal level is meaningless in most cases. So you ground your radio or coax and a signal goes up by half an S unit. What happened to the signal to noise ratio? If it got better, great, but did it get worse because connecting to a ground brought up noise and RFI and the increase on your S meter is really showing the noise increase?

In many if not most cases grounding your coax or radio to a grounding point in the house like the third prong of an AC outlet or the house ground rod brings in more noise because that point is common to all other electronic devices in the house that create RFI and noise. Noise doesn't know any better to travel to ground, the ground wires end up being a freeway for the noise to travel around the house distributing the noise to more places.

That is a good point... On some equipment I used to work on (taking up the good portion of a building) the designers had both a digital and an analog signal ground. I'm sure that arrangement is used on other systems as well.

I wasn't able to tell (at the time, so I don't know now), how everything was tied to a single point ground but kept signal grounds "isolated", maybe filters?

Thanks
Joel

 

[MUTNAV]

Ok.... One interesting (to me) question-idea about the grounding (obviously following N.E.C. comes first), but if you use a 1/4 wave vertical with a ground plane, and feed it with coax, the ground plane ends up being connected to the house ground system and all of its associated noise, but if its fed with twin lead, the ground plane radials AREN'T connected to the house electrical ground. Is this correct?

Thanks
Joel

 

[prcguy]

A ground plane as in radials or screen or whatever does not have to be directly grounded to work. They do work in conjunction with the vertical radiator to be the other half of the antenna. Placing ground radials on the ground will affect and detune them and introduce ground losses plus the surrounding earth will potentially increase the ground plane and influence the radiation pattern.

To meet NEC you would ground the coax from a distant ground plane in the yard and that will provide a DC ground path but not necessarily an RF ground. In some cases it will extend the ground plane, other cases it might bring noise from the house to the antenna then eventually your radio.

If you feed a ground plane with twinlead the antenna will still be a ground plane but the final grounding will be determined by how you feed the twinlead. If one side of the twinlead is grounded at a tuner or the radio then you have grounded your radials but now the twinlead is being operated in an unbalanced condition and you will loose some of its benefits. If its fed from a transformer or good choke balun then its balanced and a transformer will isolate the ground were a choke balun would leave you with a DC ground on the radials.

Ok.... One interesting (to me) question-idea about the grounding (obviously following N.E.C. comes first), but if you use a 1/4 wave vertical with a ground plane, and feed it with coax, the ground plane ends up being connected to the house ground system and all of its associated noise, but if its fed with twin lead, the ground plane radials AREN'T connected to the house electrical ground. Is this correct?

Thanks
Joel

 

[MUTNAV]

That was pretty much my understanding (for the most part)...

Since a tower is also required to be grounded to the ground ring (at / around) around the tower, it also becomes part of the radiating system?. I'm starting to think that twin lead (or Cat 5 ethernet cable for SWLing) along with transformers may be a better arrangement than using co-ax.

Thanks
Joel

 

[prcguy]

Last time I checked you can have lower loss with various types of coax and its more predictable than using cat5.

That was pretty much my understanding (for the most part)...

Since a tower is also required to be grounded to the ground ring (at / around) around the tower, it also becomes part of the radiating system?. I'm starting to think that twin lead (or Cat 5 ethernet cable for SWLing) along with transformers may be a better arrangement than using co-ax.

Thanks
Joel

 

[MUTNAV]

Last time I checked you can have lower loss with various types of coax and its more predictable than using cat5.

At MW / SW I thought that (and I'm not being a wise guy about this, my experience with noise mitigation is very limited, most of the stuff I've worked on was was pre-engineered) the noise that comes from other sources outweighs the losses of the feed-line.

Thanks
Joel

 

[MUTNAV]

This attachment is part of what I'm thinking of

Thanks
Joel

 

[MUTNAV]

And this would be technically a violation of N.E.C. since the ground rods are not connected with the 6 Ga wire?

Unless the coax braid is considered larger than 6 Ga, even then, it wouldn't be considered to be directly connected.

Thanks
Joel