Guy:
Thanks for the info.
New to this topic, but find it fascinating.
Will research to earlier posts to get up the speed.
73,
AG6CX
Sent from my iPhone
> On Dec 26, 2016, at 3:40 PM, Guy Olinger <k2av@contesting.com> wrote:
>
> On Mon, Dec 26, 2016 at 3:45 PM, Edward Mccann via TowerTalk
> <towertalk@contesting.com> wrote:
>> As far as the "Measurement they are, and Measurements they is, and we're
>> stuck with them," I would also be interested in the measurements, and look
>> forward to learning more about this.
>
> Really not much to learn. UV and likely outdoor wetness turned THHN
> into a MEASURED linear resistor at RF.
>
>
>
> What IS complicated is how so many clearly have some kind of stake in
> it NOT being true.
>
>
>
> Measurements and test method posted several times in prior posts. It's
> not a secret.
>
> Radial effective series resistance test, with UV deteriorated
> insulation, showed 81 ohms resistance per 1/8 w radial at 1.83 MHz.
> Old radials replaced with bright new bare wire in less than an hour,
> **only thing different is the wire**. Bright shiny bare copper
> measurement is down to 18 ohms per radial. With 4 radials, effective
> series resistance of four radial system would be OLD: 20.25 ohms and
> NEW: 4.5 ohms. This level of loss would be like inserting a 15 ohm
> resistor between the coax center conductor and the vertical wire.
>
> The test is done by initially separating all the individual radial
> wires from each other and the common point. The radials measured need
> to be identical length. They need to be very close to or at 90 or 180
> degree orientation from each other.
>
> With compass orientations for illustration of concept and angles
> between measured wires only...
>
> The N radial is connected to the S radial at the center. The E radial
> is connected to the W radial at the center.
>
> The SO239 center conductor is connected to the N-S junction and SO239
> shell to E-W connection. Measure. This is two radial pairs. Each pair
> is two radials in parallel. The two radial pairs are then in series.
> Divided by two and then multiplied by two, the result is the average
> effective series resistance of a single radial.
> Of which hopefully only a tiny percentage is R loss in the wire.
>
> For equally long and spaced radials, the effective series resistance
> of the radial system is then the test result divided by the number of
> radials.
>
> Use an instrument that can reliably measure the R value separate from
> the X value. Best done with more modern graphing instruments, where
> the design takes R and X seriously. This test cannot be done with an
> SWR meter.
>
> Measured on several instruments, all readings very close, including an
> old MFJ 259x. The AEA VIA analyzer was recently repaired, calibrated
> and certified by their lab. This instrument is reliably within a
> percent of the AIM 4170.
>
> Readings on the identical radials for the other phased vertical were
> within 5% of the first radial set, both the deteriorated measurement
> and with new bare copper. The second set, of course, is over a
> different patch of back yard.
>
> Surface, per se, of old copper wire appeared a quite dull bronze
> color, not greenish, with small etch lines, similar to the gripping
> surface of basketballs and footballs, with the little mounds and
> valleys, except much smaller mounds.
>
> 73, Guy K2AV
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|