[Antennaware] Very Low Dipole Radiation Resistance

[Gedas]

Hi Terry and thanks for your input. I realized I would have some 
additional complications & uncertainties if I were to go by measurements 
from the shack alone as I have already permanently installed within my 
PVC tubing a large CM choke. I could guess as to the length of that 
exact coax used but that affirms what you said about there being a lot 
of approximations involved either way. Any measurements and calculations 
based on them would already have a wider tolerance.

BTW, I made some more progress and walked out the two separate runs of 
very springy, coiled, and hard drawn wire....OMG was that ever fun. I 
had forgot how long 300' was for a single length of wire. It almost 
turned into a scene from the 3-stooges when I let the end slip out of my 
hand and it turned into a HUGE "slinky-mess" moving across the muddy 
lawn at 50 MPH LOL.

Anyway, I will be running 30-40W TPO in the shack and about 280' of coax 
to the feedpoint from the shack. Thanks agn 73

Gedas, W8BYA

Gallery at http://w8bya.com
Light travels faster than sound....
This is why some people appear bright until you hear them speak.

On 3/17/2019 9:40 PM, Terry Conboy wrote:
> I suspect you’ll be just as close by trusting the model.  Making measurements of antennas in the wild, especially one with so many lossy elements, is likely to involve a lot of approximations, too.
>
> Curious how much TX power you’ll be using.  Will you actually get close to the legal limit on 630m?  BTW, I’m waiting for you to fire up on WSPR so I can give you a signal/noise report.
>
> 73, Terry N6RY
>
>> On 2019 Mar 17, at 10:23 AM, Gedas <w8bya at mchsi.com> wrote:
>>
>> Right. I.e., in my case since we are talking about a short 600' inv-v antenna on 630m at 85' I get a calculated value for R(rad) of about 0.66 ohms.
>>
>> If I raise this perfect antenna model to approx 1/2-wave above a perfect ground I get ~16 ohms and at 1-wavelength above perfect ground ~17.3 ohms.
>>
>> My goal is to arrive at a somewhat accurate number for EIRP to ensure I am compliant with FCC requirements.
>>
>> I think I have two choices:
>>
>> 1. Should I trust EZNEC and return my ground type to real, add back in all my wire losses, and losses in my inductors etc and trust the finished dBi gain value provided by the program?
>>
>> 2. Or should I or do I need to install the finished antenna at height with all it's inductors and ohmic losses etc and try to make measurements of the antenna voltages and currents at the feedpoint in an attempt to calculate R(loss) ? I realize I will have to carefully take into account the impedance transformation due to the coax feeding the antenna since my measurements will be in the shack and not up on the tower top.
>>
>> Opinions or experiences anyone want to share?
>>
>> Gedas, W8BYA
>>
>> Gallery at http://w8bya.com
>> Light travels faster than sound....
>> This is why some people appear bright until you hear them speak.
>>
>> On 3/17/2019 12:23 PM, Edward Mccann wrote:
>>> Noting that the Rr varies as a function of height above ground.
>>>
>>> AG6CX
>>>
>>> Sent from my iPhone
>>>
>>>> On Mar 17, 2019, at 7:38 AM, Dave Cuthbert <telegrapher9 at gmail.com> wrote:
>>>>
>>>> Gedas,
>>>>
>>>> you are correct. The reported resistive part of the input impedance is the
>>>> short dipole is the radiation resistance.
>>>>
>>>>    Dave KH6AQ, formerly WX7G
>>>>
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>