Base Can you detect RF currents flowing on your antenna system?

Marconi · Oct 21, 2020

Here is a video entitled, "The effect of a 1:1 balun on a resonant dipole." Check-out this Common Mode Currents test idea on the feed line and elsewhere using some better testing tools.

Long ago I tried checking this idea out several times...and I never was able to see an difference in the methods I tried...just using my radio, SWR meter.

I did see a difference using an RF Field Strength Meter, but those results seemed to vary from time to time, and I could never figure that out.

Alexis Mercado · Oct 21, 2020

Interesting video. Probably that will apply to endfed antennas as well.

Marconi · Oct 21, 2020

Alexis Mercado said:
Interesting video. Probably that will apply to endfed antennas as well.

Well Alexis I agree.

This guy had to use some antenna that was prone to CMC. I think most antennas that are discussed here on the forum are probably end fed, like the A99 and Imax seem to be the most guilty actors in CB radio.

Maybe if he had used an end fed antenna like a CB'er might use to test...then maybe we would have seen much more of a difference, and thus suggesting maybe the test might have been enough for us to tell...just using our radio system with a meter.

I tested and did not use high tech equipment, but I could not tell any difference as I noted earlier. Frankly I didn't really see much difference in the video test either, but some folks will surely say that tone he injected was loud an clear and could make the difference in some contacts not being heard.

Alexis, I recall another video by a forum member in England, I think. If I can find it I will post it too. It was using FM and the test was 2 way, comparing signals using an Imax and A99, I think.

I think it was Conor, not sure though, and he was not testing for noise, but part of the conversation was talking about noise, and I could see it and hear it happening.

Thanks for the response.

Marconi · Oct 21, 2020

Here is a post by CB590 reporting an obvious difference in his signals with and without a choke.

Noise floor testing

Marconi · Oct 21, 2020

Marconi said:
Alexis, I recall another video by a foum member in Eagland, I think. If I can find it I will post it too. It was using FM and the test was 2 way, comparing signals using an Imax and A99, I think.

I think it was Conor, not sure though, and he was not testing for noise, but part of the conversation was talking about noise, and I could see it and hear it happening.

Here is the video Alexis and it clearly shows the noise floor and the TX signals compared. The operator is PennG0VQY.

bob85 · Oct 21, 2020

Eddie,
we talked about current probes years ago,
I made one that got crushed & another that should be kicking around somewhere that uses a clamp on ferrite,

https://www.w8ji.com/building_a_current_meter.htm

having no box & no pcb to perturb the currents makes them very easy to break when you close a drawer & other items push against them,

you don't need to calibrate it if you just want a relative reading, "is that better or worse"

The video you posted demonstrates ( not just words on a forum ) why you don't want metal masts ground wires & unchoked coax connected to your antenna & also near a noise source

.

Marconi · Oct 21, 2020

bob85 said:
The video you posted demonstrates ( not just words on a forum ) why you don't want metal masts ground wires & unchoked coax connected to your antenna & also near a noise source.

Here is another video that is sorta' simple in a way I tend to prefer, but he only reports results on a simple drawing. It does not show real testing or comparisons, but I think Steve does a really good job of explaining how and what he did.

EFHW Installation Summary or Is your feed line part of the antenna?

Here is the link.

binrat · Oct 21, 2020

Marconi said:
Here is a post by CB590 reporting an obvious difference in his signals with and without a choke.

Noise floor testing

He was using a 9:1 without a counterpoise. To me that is very problematic from my experience. IMHO a counterpoise would reduce it some.

The Howler · Oct 23, 2020

The video you posted demonstrates ( not just words on a forum ) why you don't want metal masts ground wires & unchoked coax connected to your antenna & also near a noise source

.

How would not grounding metal masts, work out with the National electrical code?

bob85 · Oct 23, 2020

My mast is grounded but the antenna is not connected to the mast so i only have one ground for the equipment,

multiple grounds made in different places such as your ground rods & your house electrical system ground back at the sub station can be dangerous in the event of a local lightening strike & certain fault conditions that can cause your homebrew earth to carry high current that could burn the shack down,

I know Hams that live in council owned housing who were caught using their own ground rods when the council did work on the house electrical systems,
the council remove them & warn you not to make your own grounds because of our regulations,
property insurance can be invalidated if you do your own thing

its recommended that you use fiberglass masts or trees to support antennas & ground free installs to minimise the risks,

stick to code for where you live.

338_MtRushmore · Oct 23, 2020

bob85 said:
My mast is grounded but the antenna is not connected to the mast so i only have one ground for the equipment,

multiple grounds made in different places such as your ground rods & your house electrical system ground back at the sub station can be dangerous in the event of a local lightening strike & certain fault conditions that can cause your homebrew earth to carry high current that could burn the shack down,

I know Hams that live in council owned housing who were caught using their own ground rods when the council did work on the house electrical systems,
the council remove them & warn you not to make your own grounds because of our regulations,
property insurance can be invalidated if you do your own thing

its recommended that you use fiberglass masts or trees to support antennas & ground free installs to minimise the risks,

stick to code for where you live.

The problem with sticking to code is most people would have to rebuild much of their utility infrastructure in their home to be compliant while still having adequate performance. When someone decides to meet code they realize they will have to add many ground loops and that they are so far out of compliance they scrap the whole idea. For example, who is actually going to replace a 16awg RX antenna just to meet code at 14awg? Who is going to purposely add ground loops in their shack to meet code? Once you realize you are out of compliance it just makes it easier to give up.

bob85 · Oct 23, 2020

our regs have changed a few times over the years, what was acceptable once is no longer to code, at one time the council did not remove your homebrew ground setups.

The DB · Oct 23, 2020

338_MtRushmore said:
The problem with sticking to code is most people would have to rebuild much of their utility infrastructure in their home to be compliant while still having adequate performance. When someone decides to meet code they realize they will have to add many ground loops and that they are so far out of compliance they scrap the whole idea. For example, who is actually going to replace a 16awg RX antenna just to meet code at 14awg? Who is going to purposely add ground loops in their shack to meet code? Once you realize you are out of compliance it just makes it easier to give up.

It has been a while since I read any of the codes so I could be wrong, but from what I understand, you don't need loops in such a setup, its just that all the grounds need to be connected to each other, and there is a very good reason for that. I am not aware loops being required in such a setup. I am aware of an antenna grounding method that uses a loop that goes around the antenna structure to maintain a common earth potential in the region around said structure, but in that case both sides of the loop attach at or near the same point, so that loop is more or less ignored by RF.

bob85 said:
our regs have changed a few times over the years, what was acceptable once is no longer to code, at one time the council did not remove your homebrew ground setups.

Hey bob, do you by chance live in a building with a floating ground system? I know many buildings over there use such a system these days. Over here we still use the traditional earth grounded electrical utilities. What needs to be done for each setup is different.

The DB

bob85 · Oct 23, 2020

DB
my mains supply is old at this place mid 60's,
the earth goes into the armored cable feeding the house, it disappears through the concrete raft the house is built on and under the front lawn to the electrical main under the sidewalk which is about 25 years old,

as far as I know it terminates at a ground in the local sub station about 275 yards from me,
all metal things like taps, radiators, outlet sockets & gas pipes are grounded to that cable,

im not sure but i think we have 3 different systems here depending on how old it is.

The DB · Oct 23, 2020

That is definitely different than it is here. All houses, unless they have a really old electrical system (such as knob and two, which was phased out around 1930), have a ground rod immediately under the electrical meter, and other services such as cable connections are also connection directly to this ground rod. Further, many telephone poles have have wires running down under the earth (as they are bare wires I assume they are earthing wires?), so the typical house has several ground connections between them and the substation, and this isn't factoring in all of the other houses and their ground rods that are connected to said power lines that are en route. From what I understand it is like this across the US.

I would guess that in your case the goal is to keep the electrical lines from dealing with lightening strikes directly, while in my case the system is designed to dissipate said strike as much as possible over a wide area?.

I wonder, do you have more buried electrical cables than we have? I don't see the setup you have being as feasible with overhead wires unless they took other precautions as well...

All this being said, I am not an electrician, so there may be more to all of this than I realize...

The DB

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Base Can you detect RF currents flowing on your antenna system?

Marconi

Usually if I can hear em' I can talk to em'.

Alexis Mercado

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Marconi

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Marconi

Usually if I can hear em' I can talk to em'.

Marconi

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