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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