[TowerTalk] 160M vertical dipole ?

[Robert Harmon]

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 at 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 at luxfamily.com> <mailto:jim at 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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