>"Hi all - can anyone tell me if there is a depth in ordinary soil that is
>too deep for radials.
>I have a field which is currently growing wheat - when we harvest this year
>I am thinking of digging down approx 1m and laying a new radial system.
>At this depth when I plough I will not touch the radials system - in fact 1m
>is really overkill unless I use the subsoiler which may get a bit close."
>Thanks from Dave G3RCQ
>Yes. Most books recommend no deeper than a "few inches" because if radials
>are beneath very much soil, every benefit of using radials is lost through
>losses above them.
>73, Roy K6XK
While that may be true as a general guideline, it needs to be tempered a
bit depending on the frequency and quality of the soil. On 160 meters
with average soil the depth of penetration is about 20 feet, which means
at that depth the current density is still about 37% of that at the
surface. So you could estimate the current density for your soil at the
depth you desire and figure out what the current density is. I think
the ARRL Antenna book has a chart of current density versus freq versus
soil quality, but I didn't research exactly how to calculate the loss
for an arbitrary depth.
Sure there will be some loss getting to any level below ground, but it
might not be too bad depending on exactly how deep you go.
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