Antenna tester

[Dean Hoffman]

I fix center pivot irrigation systems and am looking for an
easier way
to diagnose potential problems. The pivots are wire guided corner systems.
A picture here:

<https://www.bing.com/images/search?view=detailV2&ccid=Ga3B2hyh&id=A988F0919AAF5201499ABF2EA28817D134888F38&thid=OIP.Ga3B2hyh56Ol3zftxvSXHwHaDg&mediaurl=http%3A%2F%2Faz276019.vo.msecnd.net%2Fvalmontstaging%2Fimages%2Flibrariesprovider87%2Fproduct-pages%2Fproduct-page---child-2%2Fterrain-compensation_precisioncorner_corn_aerial_yorkne_june2012_003_hi_700x332.jpg&exph=332&expw=700&q=valley+corner+system&simid=608021412260020803&selectedindex=37&ajaxhist=0&vt=0>

OR: https://binged.it/2z61Xmt

The corner arm follows a buried wire and swings out in the corners
of a field picking up additional acres that a regular circle pivot will
miss.
The antennas I want to test are mounted like this below the black
tower box.
<https://www.bing.com/images/search?view=detailV2&ccid=yS99LIb7&id=A2FB8BA0C4386FC54F7EE2BF5B069E48A2176E0B&thid=OIP.yS99LIb7Lb-wWMkb2dSiZwHaFj&mediaurl=https%3a%2f%2fbigiron.blob.core.windows.net%2fpublic%2fitems%2f0b79d2467df9e61180c100155d7470d0%2f1995valleypivotwith2012cornersystem-41.jpg&exph=510&expw=680&q=valley+corner+system&simid=608052688166323060&selectedIndex=16&ajaxhist=0>

OR https://binged.it/2z4M1AX

The far left one angled down steers in forward, the far right one
angled down in reverse. The horizontally mounted one is the
safety/reference. It's helps with the steering and shuts the system down
if the machine gets off the wire.
We have to remove them to test them now. We energize the
transmitter, aka oscillator, for the buried wire then set a new antenna
directly over and perpendicular to the guide wire. We remove the
suspect antenna and put it in the exact place as the new one and compare
readings. Typical readings using our Fluke meters with a dummy load
are 20 mv or so. Link to picture of antenna:
https://imgur.com/5reAjEp
I'd like to be able to test the antennas in place and without
having to energize the buried wire transmitter. The transmitters are
powered by 120 vac. Energizing the transmitters sometimes requires
starting a diesel engine that powers a three phase generator. That can
be a problem in cold weather and just getting to them in snow can be an
issue.
My idea was to use 12 volts from an accessory outlet on an atv. I'd
make some sort of a wand to hold against the antennas that would
energize the antenna so I could take a reading similar to what I see
normally.
The antennas run at 833, 1000, or 1200 hz. I found this gizmo and
thought it might be useful:
<http://www.audiowind.com/pdf/R-102.pdf>
My idea is to put three of these gizzies in some sort of box and set
each one to one of the three frequencies. Put three outlets on the box
then plug the wand into whichever one matches the antennas I want to test.
Is this at all workable? Is there something better, maybe
something ready made for the job?


Thanks

 

[Jasen Betts]

On 2019-08-22, Dean Hoffman <dh0496@windstream.net> wrote:

We have to remove them to test them now. We energize the
transmitter, aka oscillator, for the buried wire then set a new antenna
directly over and perpendicular to the guide wire. We remove the
suspect antenna and put it in the exact place as the new one and compare
readings. Typical readings using our Fluke meters with a dummy load
are 20 mv or so. Link to picture of antenna:
https://imgur.com/5reAjEp

what is written on the label?

My idea was to use 12 volts from an accessory outlet on an atv. I'd
make some sort of a wand to hold against the antennas that would
energize the antenna so I could take a reading similar to what I see
normally.

Automotive electric power is sketchy, the smaller the vehicle the worse it
gets, you don't want accidentally bust your test equipment.

The antennas run at 833, 1000, or 1200 hz. I found this gizmo and
thought it might be useful:
http://www.audiowind.com/pdf/R-102.pdf

Page1 and page2 disagree about which version is A and which is B so
take care when ordering.

for those playing along at home that appears to be a CD4060 chip set-up
to oscillate in the audio range, but they have pixelated the markings
in the PDF.

My idea is to put three of these gizzies in some sort of box and set
each one to one of the three frequencies. Put three outlets on the box
then plug the wand into whichever one matches the antennas I want to test.
Is this at all workable?

Yeah, that should work, I'd go with battery power instead of plugging
into the ATV. those things will use less power than a portable radio
does, so you should get good battery life.

You can get audio jacks that have normally open switches inside them,
so you could have the socket turn the power on when you plug in

If I was doing it I'd use an LM555 instead of the CD4060
the 555 has a stronger output and is probably more frequency stable,
(but in the end that depends on the other parts on the board also
being stable)

(555 oscillator module) https://www.aliexpress.com/item/33017061992.html

What you describe is a specialised signal generator, your specialised
version is likely to be easier to use than a general purpose signal
generator.

at audio frequencies where this works the only practical antenna type
is a loop antenna, your buried anrtenna wires form a very large loop.

So for your wand you also need a loop. someting like several overlaid
loops of fine electric wire (preferably magnet wire).
maybe wound on a plastic jar lid, or on a hand reel, or some other
non-metallic frame.

It's going to need a resistor in series to not overload the oscillator,
about 100 ohms should be sufficient, maybe a add variable resistor too
so that you can adjust the power level.

--
When I tried casting out nines I made a hash of it.

 

[Dean Hoffman]

On 8/22/19 3:14 AM, Jasen Betts wrote:

On 2019-08-22, Dean Hoffman <dh0496@windstream.net> wrote:

We have to remove them to test them now. We energize the
transmitter, aka oscillator, for the buried wire then set a new antenna
directly over and perpendicular to the guide wire. We remove the
suspect antenna and put it in the exact place as the new one and compare
readings. Typical readings using our Fluke meters with a dummy load
are 20 mv or so. Link to picture of antenna:
https://imgur.com/5reAjEp

what is written on the label?

The frequency, part #, and the parent company.
Picture here:
<https://imgur.com/2VamZhG>

My idea was to use 12 volts from an accessory outlet on an atv. I'd
make some sort of a wand to hold against the antennas that would
energize the antenna so I could take a reading similar to what I see
normally.

Automotive electric power is sketchy, the smaller the vehicle the worse it
gets, you don't want accidentally bust your test equipment.

The antennas run at 833, 1000, or 1200 hz. I found this gizmo and
thought it might be useful:
http://www.audiowind.com/pdf/R-102.pdf

Page1 and page2 disagree about which version is A and which is B so
take care when ordering.

for those playing along at home that appears to be a CD4060 chip set-up
to oscillate in the audio range, but they have pixelated the markings
in the PDF.

My idea is to put three of these gizzies in some sort of box and set
each one to one of the three frequencies. Put three outlets on the box
then plug the wand into whichever one matches the antennas I want to test.
Is this at all workable?

Yeah, that should work, I'd go with battery power instead of plugging
into the ATV. those things will use less power than a portable radio
does, so you should get good battery life.

Good. That would make it handier to use too.

You can get audio jacks that have normally open switches inside them,
so you could have the socket turn the power on when you plug in

If I was doing it I'd use an LM555 instead of the CD4060
the 555 has a stronger output and is probably more frequency stable,
(but in the end that depends on the other parts on the board also
being stable)

(555 oscillator module) https://www.aliexpress.com/item/33017061992.html

What you describe is a specialised signal generator, your specialised
version is likely to be easier to use than a general purpose signal
generator.

at audio frequencies where this works the only practical antenna type
is a loop antenna, your buried anrtenna wires form a very large loop.

There is usually a twisted pair wire running from the center of
the field where the
control panel is to the edge of the field. It's connected to a single
wire running in a loop around the field where we want the corner arm to
run. It's probably close to 11,000 ft. of 14 awg. copper wire.

So for your wand you also need a loop. someting like several overlaid
loops of fine electric wire (preferably magnet wire).
maybe wound on a plastic jar lid, or on a hand reel, or some other
non-metallic frame.

What about using a potted solenoid valve coil? Some of those have
about 25 ohms resistance. Put it in series with that variable resistor?
They look like this:
<http://i.ebayimg.com/images/i/260291870099-0-1/s-l1000.jpg>

It's going to need a resistor in series to not overload the oscillator,
about 100 ohms should be sufficient, maybe a add variable resistor too
so that you can adjust the power level.

Thank you