If one wants to get to the bottom of locally varied TX performance, the
final answer lies with establishing a personal monitoring site.
The problems with simple (aka cheap) RF field strength meters are
potentiometers, meters with non-linear scales, and poor/sparse graticules,
and an antenna that collapses and extends, and has to be hand-held.
You will need a power meter that reads in watts, best a digital power
meter. And you will need a partner for measurements. You will need
communication devices. Cellphones or Family Radio Band transceivers, or
whatever passes for that in country of residence.
Buy a cheap FS meter, and then go to work. You are going to severely modify
this unit.
First, get rid of the collapsible antenna, replace if with a 0.5 meter
piece of BARE, SOLID COPPER wire soldered to the terminal INSIDE the
instrument. Solder a 0.5 meter wire to the bottom of the case. Use plastic
or teflon sleeve where you need to keep it from touching in the instrument.
Find a place where you can stand up a piece of PVC pipe permanently that is
10-20 meters away from trees and conductors like ground wires on power
poles, metal buildings etc. Drive a long rod or metal fence post into the
ground as far as you can. Cut off all but 0.6 meter above ground. Slide the
PVC pipe over the rod to support the rod and make it self-standing. Remove
the pipe
Attach the wires and unit to the pipe with tape to start. Tape the wires to
the pipe often enough that the wire cannot move.
Set the potentiometer to mid range.
Key your transceiver and your main antenna with 50 watts or some lower
level that you can safely run key down for extended times.
At the pipe adjust the potentiometer until you get a mid-scale reading that
is exactly on a half-scale-ish graticule.
You must be well away (10 meters is good) from pipe to measure and you may
find it helpful to use bird binoculars to read the scale.
You will have to repeat this process, because your body changes the
measurement when you get near the instrument.
Take the pipe down and without touching the potentiometer, measure the
potentiometer resistance. Replace the potentiometer in the circuit with a
combination of fixed value non-inductive resistors that fairly closely
match the value from the potentiometer.
Do NOT use switches anywhere. When you are done you should have a
hard-soldered instrument, with NO adjustments, with NO contacts to go bad,
and with a fixed, soldered in antenna that does NOT adjust. Put the
instrument back up on the rod.
Get some help. One of you watches the FS unit outside, 10 meters away, with
binoculars, the other keys the transceiver and records the power output.
Key the transceiver, and adjust power output until the outside person tells
you the meter is exactly on the half-scale. Record the power output for
exact half scale power. Keep a small book with all your readings, times and
dates, power levels, weather, dampness, etc, anything you suspect may be
bearing on your performance. Different powers levels for reference reading
on the meter
When you are not measuring, take the pipe and meter inside and store it in
a dry place, and short the two antenna wires near the case with a clip
lead. This is to prevent banging the meter when running high power and not
actually using the meter.
The readings in the book will give you measurements convertible to dB's
which are just as accurate as your power meter.
Trust me, lab grade equipment certified repeatable measurements is very
expensive, and costs more than a lot of entire ham shacks.
Your readings may not explain what is going on to you, but posting those
here will likely stir up helpful discussion.
73 and good luck.
Guy K2AV
On Sat, Feb 24, 2018 at 12:44 PM, Herbert Schoenbohm <
herbert.schoenbohm@gmail.com> wrote:
> Jack, Last night in the CQ 160 SSB contest I called CQ for hours and only
> worked a few stations mostly within a few hundred miles. Eu's were coming
> in but none heard me. Also, I could not hold a frequency anywhere. I did
> work LU2DKT and a few PY's. It was brutal trying to work anyone with 100
> watts. On my IC-7300 spectrum display, the band was loaded with signals
> and some very strong. I was pointless to call them as they just CQ'ed back
> in my face. These were stations I never had a problem working before. As
> far as you fresh water is concerned just consider it a good insulator and a
> reasonable way to absorb your power like a resistor connected to the feed
> point. In Minnesota, (W0VXO) I put a vertical about 100 feet out in the
> shallow portion of a big lake and had to struggle to work anyone. However
> when I was an engineer for WIRA in Fort Pierce, FL we had the AM tower out
> in the Indian River at the end of a pier. The water was very very brackish
> as an inlet to the Atlantic. There are about 16 radial at the base an
> weighted with concrete blocks to the river bottom. It worked very well
> according to an FSM at a mile and was well above what was expected. The
> only problem we had was that the base current would change as the tide
> would rise and fall.
>
> It will be interesting to see when your field dries out
>
> Herb Schoenbohm, KV4FZ
>
> On Sat, Feb 24, 2018 at 1:07 PM, Jack Henry via Topband <
> topband@contesting.com> wrote:
>
> > I was struggling to be heard in the contest last night. Only 4 stations
> > were worked and they needed repeats. All readings in the shack were
> normal
> > and I was hearing many stations with moderate signals. The only thing
> that
> > was different was that we were irrigating the grass. The grass is
> > irrigated by flooding from a small canal that is on the edge of the
> > property. The canal is fresh water fed from an Andean river. There was
> > about a quarter of an inch of water visible over the mowed grass. I am
> > wondering if the water is effecting the antenna performance.
> >
> > I do not have a super station and only run 800W. The antenna is a 45
> foot
> > vertical T loaded at the top. There are 32 radials 60 to 80 feet in
> length
> > of different type wires. All are insulated with various materials and
> are
> > buried about an inch below the soil level.
> >
> > Anyone have any experience or knowledge on this. The soil is drying now
> > in the blistering sun so maybe we will see if there is any improvement
> > tonite.
> >
> > Thanks. Jack OA4TT
> >
> > Sent from my iPad
> > _________________
> > Topband Reflector Archives - http://www.contesting.com/_topband
> >
> _________________
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