[TowerTalk] Modeling vs Experimenting
Jim Rhodes
jim at rhodesend.net
Thu Sep 12 11:52:08 EDT 2019
Experimenting can give you an antenna that works well, modelling can tell
you why (and even how to improve it).
Jim Rhodes
K0XU
On Thu, Sep 12, 2019, 08:26 Jim Thomson <jim.thom at telus.net> wrote:
> I use both methods. The problem being in a residential neigbourhood
> is I am surrounded by other homes, some with well grounded wire mesh
> below stucco siding, then the usual myriad of neighbours attic +
> house wiring, copper plumbing, then miles of single and 3 phase
> commercial AC power, utility poles,
> lamp standards, sloping ground, trees, miles of asphalt streets,
> concrete and asphalt driveways, hundreds of metal cars. Miles of telco
> and cable company lines.
> And soon to be installed 5G network.... with ants mounted every
> 100-300 yards. One nearby home just installed a ton of solar
> panels. Some homes are now installing
> metal roofs.
>
> How do you propose how to implement HFTA with the above ???
> Loads of clay below the pristine lawns too. Forget the lousy ground
> for a minute, there is so much junk
> in the nearfield, and farfield, how can any software even begin to
> factor a fraction of these extraneous items? Same deal with nec2
> and nec4. Sure, the say proposed yagi, etc,
> can be designed in free space.... then modeled above sloping... poor
> to average ground. Good luck with trying to correlate software
> results ...with reality. Trying to compare
> RX + TX signals with nearby hams is an exercise In futility. One
> night Im louder, the next night, local buddy is louder. Change
> directions, and it all changes again. Change bands,
> and its a whole new ballgame. Huge differences in band condx, when
> trying to compare with stations 100 miles north of me.
>
> They have a sign up at NASA that sez...... one test is worth a 1000
> opinions. Want to see how good your CM choke is, measure the RF
> current with a clamp on RF ammeter in several
> places on the coax, then again around the home and shack, plus
> misc stuff. Then swap CM chokes, and repeat the test. Its a eye
> opener.
>
> Later.... Jim VE7RF
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