Autek Research, PO Box 7556, Wesley Chapel, FL 33545 USA.
(813) 994-2199
www.autekresearch.com
WM1 DELUXE COMPUTING SWR/WATTMETER
COMPUTING SWR. WHAT SETS THE WM1 APART !
The WM1 Meter doesn't make you stare at crossed needles or make adjustments
or do any calculations to read SWR. Instead, like magic, it shows SWR
instantly and continuously. So it's a snap to do SWR plots, adjust antenna
tuners, or just glance at the SWR occasionally to see that it's still low.
Even when you vary power drastically, such as when adjusting a tuner,
the SWR reading virtually ignores the power changes.
Just tap the key on CW, or say a word into
the mike and you see your SWR instantly in the peak mode.
You can easily adjust a tuner while talking on SSB using the the peak mode.
AVERAGE OR PEP
The extensive electronics in the WM1 incorporates true peak detectors
accurate to 0.1% using op-amps. In contrast, other meters often use just
diodes with significant variable voltage drop and questionable accuracy.
Switching to the AVERAGE
position yields average power. However, the peak decay is sufficient to
follow most power changes, and many leave the meter in the peak position
at all times.
LOW POWER(QRP) OR HIGH
The meter has 3 full-scale ranges of 20 , 200 and 2000 watts.
Half scale on each range is 5 , 50 , and 500 watts. So the meter is ideal
for 5 watt CB or QRP,normal 100 to 150 watt ham rigs, or 1500 watt high power.
Just select the proper range. The meter is also quite usable at 1 watt
for super-QRP, except that SWR will read a little low.
Range switching is done with 1% resistors, so when
the meter is calibrated at, say, 100 watts, it will be within 2% in power
at 10 watts and 1000 watts.Note: Reads power up to 2000 watts at 1.5-30 MHZ, but limited
to 100 watts at 50 MHz.
The meter will not be damaged by overloads. For example, applying 2000 watts
on the 20 watt scale will peg the power meter, but the electronics limit
current into the meter, so there is no damage. Remember, when you buy a WM1
you're buying a unit that has been "field tested" for over a decade, and it is
NOT easy to damage!
REMOTE RF HEAD
Virtually all other meters put the coax connectors on the back of the
meter itself. Although this is less expensive, the heavy coax tends to
drag the meter across the table when moved. With the WM1, you connect
the coax to the remote head which is wired through a 4 ft. flexible wire
to the main unit. Most people simply drop the coax behind the operating
table, eliminating an eyesore also. You'll appreciate the remote head.
ACCURATE
Its accuracy compares with a $300+ lab standard at full or half scale,
and includes a meter scale specifically designed for its frequency and
power range, not a compromise for various "slugs." So, it's much more
accurate
at the low end of each scale. And, of course, its total cost
is comparable to the cost of just one slug!
RUGGED. A CLASSIC DESIGN
Its case is made of a special rustproof steel, welded at stress points, and
so strong you can stand on it! The meters are large..
2-3/8 inches across. It's designed to last for decades.
The WM1 was originally designed in 1986.In the Autek tradition, we
took the time and did it right the first time, and there have only
been minor
changes since. In 1991, we compensated the RF head to make it usable to
54 MHz. Lately, we made the peak power decay a little faster in response
to requests. Lastly, we added lighting on both meters in 1999.
Thousands of WM1's are in use worldwide. It's time tested and the
most popular unit of its type. We may be biased, but we really don't
think it has any competition. You can pay a lot more and still not
get computing SWR or any better accuracy. Many have told us it's the
favorite piece of equipment in their station!
OTHER CHARACTERISTICS
Power accuracy 5% of full scale; 10% of reading down to 0.2 full scale.
Typically usable even at 1 watt or less on the 20 watt scale.Indicated
SWR drops a little at low power, but typically less than 10% at 10 watts
and 3:1 SWR. Frequency range is 1.5 - 30 Mhz for full power and accuracy, and usable
to 54 MHz,except limited to 100 watts there. (The SWR may read a little high at 54 MHz.. up to 1.3 or so.)
Negligible insertion loss. Inline meter is left in line at all times.
The unit runs from 8 to 18 VDC at approx. 100-200 ma, most current being
drawn by the meter lights. A 115 VAC AC adaptor (wall transformer) is
included free. Handsome light-dark grey styling.
6-3/8 x 3-3/4 x 3 inches deep. See the excellent review in Nov. 1989
QST. (We cannot send you the review due to copyright laws. QST sells
them.)
COMMENTS ABOUT MODIFICATIONS
Many owners have lengthened the 4 foot remote cable to as long as 30 feet
or more. Since the cable carries little current this works fine.
However there is a danger of RF being picked up on the cable.
This makes the readings inaccurate, and is usually obvious. (The power
meter might move backwards, for example.)
Although the unit is heavily bypassed,and the cable is shielded,
a lengthened remote-head cable
may need RF chokes or beads on each wire, including the ground wires
in the cable.
This modification is especially popular with those using an amplifier
mounted near a tunable antenna, e.g. in the rear of a vehicle. By
extending the cable, the RF head can be mounted between the amplifier
and antenna, and the main unit mounted at the drivers position to
observe SWR. Because the cable is near the grounded vehicle metal chassis
in this situation, owners usually have no RF pickup problems.
Some have also asked about extending the range to 3000 watts.
This can be done by adjusting the power calibration pot (see WM1
instructions supplied with the unit.) so the unit reads 2/3 of the
true reading. However, long key down periods and high SWR's should be
avoided since the 1/2 watt 33 ohm resistors in the RF head will be
overheated. (We have never seen a case of high power causing a failure
of the WM-1 RF head, but 3000 watts is pushing the envelope.)
DISCLAIMER We are providing this information as an
aid to owners, but wish to emphasisize that we in no way warrant the results.
Specifically, if, in our opinion,any modifications cause
the unit to fail, the warranty
is not valid. We also cannot do any modifications at the factory.