[600MRG] 200 ohms

[Roger Graves]

Ben,

You have a great signal for your situation. What is your power?

Re. your question, get more vertical height, more capacitive top loading, longer radials.
When I raised my vertical from 30 to 40 ft there was a big improvement.
Try to extend the radials to the ends of your lot (and beyond if the neighbors allow). More may not help (unless you can get to use the other two 90 degree directions) until you get them longer.

The feedpoint resistance should go down as you do the above as an indication of effectiveness.

Are you using the calculator at
http://people.physics.anu.edu.au/~dxt103/calculators/marconi.php

Thanks for the QSO last night!

73,
Roger

On Nov 6, 2017, at 8:24 PM, Ben Gelb <ben at gelbnet.com> wrote:

> My small city lot features a single 30 ft tree, which is currently
> supporting my 30' x 30' inverted L (other end of the horizontal segment
> supported by a 20' fishing pole strapped to a fence post ... so maybe 25'
> in the air).
> 
> The tree is at the corner of the lot, so the radials are really just over a
> 90 degree sector (rather than a full circle around the vertical). I also
> only have 3 radials probably each about 20 ft long, with a 10' ground rod
> at the end of each one. There is also a 10' ground rod at the base of the
> vertical.
> 
> So, it ain't great. But is what it is on a small city lot.
> 
> Feedpoint impedance is ~200 ohms (and with 472khz.org antenna calculator
> estimating ~0.2ohm radiation resistance, thats an efficiency of maybe 0.1%,
> give or take).
> 
> So naturally I've been thinking about how to improve the setup. One thing
> is that the tree really is supporting the antenna (wire dragged right up
> over it). Its HV-insulated wire (20kV) to prevent any arcing to the tree
> and burning behavior (pre-HV wire version didn't fare too well, but the
> smolders have been successfully eliminated with the HV wire upgrade).
> 
> I guess I am wondering if the tree itself may be impacting the performance
> of the antenna (capacitive coupling to the tree?) and contributing to the
> high feedpoint Z, or if its really all just terrible ground that is to
> blame.
> 
> Your thoughts appreciated!
> 
> 73,
> Ben, N1VF
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