George,
Brian, K6STI, kindly sent this info on the N6LF gound probe.
The rods are 3/8" dia aluminum. I know what you mean about the soil in the
Phoenix area. I used to line in Phoenix.
My soil here isn't that great either. I am thinking about buying a 1/2" steel
copper clad ground rod from Home Depot
and making the two probe rods out of it. Will cost $13.00. Would probably
spend more that for aluminum rod................
http://ham-radio.com/k6sti/owl.htm <http://ham-radio.com/k6sti/owl.htm>
Bob
K6UJ
> On Jan 24, 2022, at 10:04 AM, George Skoubis <geo.skoubis@gmail.com> wrote:
>
> Bob,
>
> What are those probes made of? I have an Array Solutions VNA but I don’t
> think I can pound an aluminum probe in the ground here in AZ (Phoenix area).
>
> I have problems getting a 5/8” ground rod pounded in (I have a jackhammer
> ground rod driver).
>
> I’m guessing the ground conductivity is pretty horrible though. We built a
> guest house last year and there was no ground rod required, they had us put a
> 30’ copper UFER wire in the footing that comes up through the stem walls into
> the electrical panel.
>
> I’d be interested in putting the probes in the ground and leaving them
> there. Then take measurements every week to see if the rain has a big effect
> on the conductivity. For those of us with crappy conductivity it may be
> worth watering the “yard” before a 160 contest if the difference is big
> enough...
>
>
> Thanks,
>
> George / W7GES
>
>> On Jan 24, 2022, at 10:42 AM, Robert Harmon <k6uj@pacbell.net> wrote:
>>
>> John,
>>
>> Brian, K6STI, geve me some good info on using two probes and a VNA.
>> I havent used my Nanovna yet so it will be a learning experience.
>> I'm not very optomistic about my soil conductivity arund here though. From
>> what I have
>> read it isn't that good.
>>
>> 73,
>> Bob
>> K6UJ
>>
>>
>>
>>
>>
>>> On Jan 24, 2022, at 7:00 AM, John Simmons <jasimmons@pinewooddata.com>
>>> wrote:
>>>
>>> Bob,
>>>
>>> How are you going to test your soil conductivity? Megger or VNA?
>>>
>>>
>>> --
>>> 73,
>>> -de John "Curly" NI0K in rural Debs, MN USA
>>> Hamshack Hotline: 6100000271
>>> https://www.qrz.com/db/NI0K <https://www.qrz.com/db/NI0K>
>>>
>>> Robert Harmon wrote on 1/23/2022 4:59 PM:
>>>> Jim,
>>>>
>>>> I appreciate the feedback. I am going to test my soil conductivity to
>>>> see if I can get a handle on it. You got me thinking, how about if the
>>>> top and bottom horizontal
>>>> wires were T shaped rather than a single wire bent over ?
>>>>
>>>> Bob
>>>> K6UJ
>>>>
>>>>
>>>>
>>>>
>>>>> On Jan 23, 2022, at 11:00 AM, Lux, Jim <jim@luxfamily.com>
>>>>> <mailto:jim@luxfamily.com> wrote:
>>>>>
>>>>> On 1/23/22 9:46 AM, Robert Harmon wrote:
>>>>>> No I don't have a 260 foot tower :-) but thinking about this crazy
>>>>>> idea.
>>>>>>
>>>>>> My HDX590 tower is 90 feet fully extended. By attaching to the side of
>>>>>> the mast 15 feet up I can have an attachment point at 105 feet.
>>>>>> I am envisioning hanging a vertical dipole from the 105 feet point and
>>>>>> running the top wire horizontally 82 feet sloping down to a 30 foot mast
>>>>>> at the corner
>>>>>> of my property. Likewise on the lower end of the dipole 9 feet high and
>>>>>> going to the other corner of my property. This woud put the center of
>>>>>> the dipole about 57 feet
>>>>>> above the ground. I don't know how a dipole will work with the ends
>>>>>> bent this way but maybe it would be more efficient than a vertical with
>>>>>> a compromise radial field.
>>>>>> An option might be to make two big boy loading coils and shorten the
>>>>>> dipole.
>>>>>> What do you think of this idea ? Am I off my rocker ? hihi
>>>>> You're not off your rocker, but pay attention to the inherent problems
>>>>> with vpol being strongly affected by the soil properties in the area -
>>>>> particularly for low angles.
>>>>>
>>>>> What's interesting is that the directivity of a infinitely short dipole
>>>>> is 1.5 dBi, and a full size half wave is 2.15 dBi. So a shortened dipole
>>>>> with capacity hats, loading coils, or matching network will be pretty
>>>>> much the same (within a 1/2 dB) as far as the far field goes for the same
>>>>> center height.
>>>>>
>>>>> Your issues are going to be losses due to the fields interacting with the
>>>>> soil AND losses in your matching networks (whether at the feed or loading
>>>>> coils, or whatever). The radiation resistance is smaller, so the current
>>>>> in the antenna (for the same power) will be higher, so you get more IR
>>>>> losses.
>>>>>
>>>>> Those can be driven down by using bigger wires, etc.
>>>>>
>>>>> The other thing that happens is that the impedance will vary more
>>>>> quickly, so you might need an adjustable matching network.
>>>>>
>>>>> You might also look at making the bottom of the dipole a "cone" (even
>>>>> shortened), because that improves the matching bandwidth. Cones (and fan
>>>>> dipoles) are broader band than single wires.
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>>
>>>>>
>>>>>
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>>>>
>>>>
>>>>
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