Re: Topband: [TowerTalk] New N6LF Ground Probe Designs
On 3/4/2024 10:48 AM, GEORGE WALLNER wrote: Salt water, salt marshes, alkaline soil, soil with a high water-table should be good. What could be considered a "high water table"?? My water table is maybe 110 - 120 feet down; but if it were shallower, like maybe 30 feet, I might be concerned about the soil over it not being "stiff" enough to rigidly-support a free-standing tower's pedestal dug down some 8 - 10 feet 8-O Steve, K0XP _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: [TowerTalk] New N6LF Ground Probe Designs
Salt water, salt marshes, alkaline soil, soil with a high water-table should be good. George On Mon, 4 Mar 2024 18:11:34 - "Roger Kennedy" wrote: But what is GOOD Ground for RF? I've always presumed that the reason I do so well for DX with a horizontal 160m Dipole is because the Ground conductivity is POOR . . . so my Dipole is effectively a lot higher. Plus I have always wondered how deep below the surface the ground matters, when it comes to RF. (and especially on Top band, where the wavelength is so long) For these reasons I've always been very sceptical about Computer Modelling of a low Dipole on 160m. Roger G3YRO _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Topband: [TowerTalk] New N6LF Ground Probe Designs
But what is GOOD Ground for RF? I've always presumed that the reason I do so well for DX with a horizontal 160m Dipole is because the Ground conductivity is POOR . . . so my Dipole is effectively a lot higher. Plus I have always wondered how deep below the surface the ground matters, when it comes to RF. (and especially on Top band, where the wavelength is so long) For these reasons I've always been very sceptical about Computer Modelling of a low Dipole on 160m. Roger G3YRO _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: [TowerTalk] New N6LF Ground Probe Designs
On 3/2/2024 11:36 AM, Jim Brown wrote: On 3/2/2024 10:43 AM, Jeff Blaine wrote: I live in an area surrounded by farm lands and assume that the soil here is nice and conductive. But I have no idea what that really means. There is no definite correlation between land being farmed and RF conductivity. My QTH is classified as "Class 4" soil for Ag. purposes. That's the LOWEST rating. It is 100% clay from the surface down to 40 feet. There is a water proof hard pan layer down a foot or so below the surface. Even weeds don't grow well. Yet, it evidently has high RF conductivity. I'm not saying you couldn't have land that is good for both farming AND RF. But the two don't always go together. 73 Rick N6RK _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: [TowerTalk] New N6LF Ground Probe Designs
On 3/2/2024 10:43 AM, Jeff Blaine wrote: I live in an area surrounded by farm lands and assume that the soil here is nice and conductive. But I have no idea what that really means. This is a link to ancient FCC maps of soil conductivity to be used by AM broadcast stations. I would expect it to still be good in undeveloped areas. It's in quadrants. As a young EE student, I had a summer gig using them to plot contours for an application for a new station. http://k9yc.com/FCC-GroundMap.zip 73, Jim K9YC _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: [TowerTalk] New N6LF Ground Probe Designs
I think there are a couple of reasons I want to try this method. First is that it's a technically cool use of a VNA - which is my personal favorite gadget in general. I live in an area surrounded by farm lands and assume that the soil here is nice and conductive. But I have no idea what that really means. Maybe the area around here is not that conductive. Making a set of measurements would be a way to quantify that assumption. I do realize that this is a data point specific to the place you took the measurement. So taking the similar measurement around the area would give some idea of how much variation there may be. 73/jeff/ac0c alpha-charlie-zero-charlie www.ac0c.com On 3/2/2024 11:51 AM, Richard (Rick) Karlquist wrote: On 3/1/2024 10:44 AM, Brian Beezley wrote: Rudy Severns, N6LF, has updated his writeup on ground parameter measurement with several new probe designs. A ground probe and NanoVNA I'm not trying to take away anything from Rudy's excellent work, but he doesn't explain in the posted article what useful advantage we can derive from the measurements. It only gives a spot measurement of the top foot of soil. And the soil that matters is the soil at large distances from the antenna. It is unlikely that this probe could be used to survey all that area of land that isn't owned by the ham with the antenna. Also, I would prefer Rudy's previous method using a low 1/2 wave dipole. It covers more area and presumably would penetrate into the soil more than a foot. Another thing I would prefer is to simply put up a vertical and a dipole and A/B them for signal strength on various RBN stations. Finally, it is also possible to build a Beverage antenna and run a current probe along it as I have done and determined how fast it attenuates with distance. I know very well that my QTH is over highly conductive ground without ever using an OWL probe. 73 Rick N6RK _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: [TowerTalk] New N6LF Ground Probe Designs
On 3/1/2024 10:44 AM, Brian Beezley wrote: Rudy Severns, N6LF, has updated his writeup on ground parameter measurement with several new probe designs. A ground probe and NanoVNA I'm not trying to take away anything from Rudy's excellent work, but he doesn't explain in the posted article what useful advantage we can derive from the measurements. It only gives a spot measurement of the top foot of soil. And the soil that matters is the soil at large distances from the antenna. It is unlikely that this probe could be used to survey all that area of land that isn't owned by the ham with the antenna. Also, I would prefer Rudy's previous method using a low 1/2 wave dipole. It covers more area and presumably would penetrate into the soil more than a foot. Another thing I would prefer is to simply put up a vertical and a dipole and A/B them for signal strength on various RBN stations. Finally, it is also possible to build a Beverage antenna and run a current probe along it as I have done and determined how fast it attenuates with distance. I know very well that my QTH is over highly conductive ground without ever using an OWL probe. 73 Rick N6RK _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
