URM 120
 

I just got a Struthers wattmeter/SWR meter at a hamfest, but no papers.

Does anybody here have the instructions/service manual or would know where
to get it??

Thanks Uwe

I have had one for several years. There is not much to it. Just be sure to
remove the "shipping and storage" wire from the back of the meter if it is
there before using it. It is a piece of springey bare wire across the meter
terminals. It may not be on your meter. Very nice meter but the meter is
very much dampened. It will take a while for it to reach the maximum value.
Just pop in the slug that you need for the range and power level. It is the
meter that has a SWR adjustment knob on it you turn it to the neasuerment
jposition and find a range where it is off scale, then adjust to full scale
and then turn the slug 180 deg to get the SWR. Or you could find a chart
the Bird meter uses and get the swr off the chart for the ammount of forward
and reverse power.

"Uwe" wrote in message
...
I just got a Struthers wattmeter/SWR meter at a hamfest, but no papers.

Does anybody here have the instructions/service manual or would know where
to get it??

Thanks Uwe

I have had one for several years. There is not much to it. Just be sure to
remove the "shipping and storage" wire from the back of the meter if it is
there before using it. It is a piece of springey bare wire across the meter
terminals. It may not be on your meter. Very nice meter but the meter is
very much dampened. It will take a while for it to reach the maximum value.
Just pop in the slug that you need for the range and power level. It is the
meter that has a SWR adjustment knob on it you turn it to the neasuerment
jposition and find a range where it is off scale, then adjust to full scale
and then turn the slug 180 deg to get the SWR. Or you could find a chart
the Bird meter uses and get the swr off the chart for the ammount of forward
and reverse power.

"Uwe" wrote in message
...
I just got a Struthers wattmeter/SWR meter at a hamfest, but no papers.

Does anybody here have the instructions/service manual or would know where
to get it??

Thanks Uwe

Well, mine apparently has a little problem. The knob on top, which lets you
select the power level, that knob turns a cam which raises or lowers the
sensing element. Very nifty mechanism.
Now in my meter the shaft which holds the know spins in the cam and so
obviously nothing happens. So I took the hole thing apart and fixed that
problem and in the process you wish you had the description or maintenance
instructions which would give you the exact distance of the sensing element
for each power range etc.

So thats why I was asking.
And the thing is built beautifully, thats for sure, I just seem to have to
recalibrate mine.
Maybe somebody else here has some documentation for the device.

73 Uwe

in article , Ralph Mowery at
wrote on 5/1/04 10:03 AM:

I have had one for several years. There is not much to it. Just be sure to
remove the "shipping and storage" wire from the back of the meter if it is
there before using it. It is a piece of springey bare wire across the meter
terminals. It may not be on your meter. Very nice meter but the meter is
very much dampened. It will take a while for it to reach the maximum value.
Just pop in the slug that you need for the range and power level. It is the
meter that has a SWR adjustment knob on it you turn it to the neasuerment
jposition and find a range where it is off scale, then adjust to full scale
and then turn the slug 180 deg to get the SWR. Or you could find a chart
the Bird meter uses and get the swr off the chart for the ammount of forward
and reverse power.

"Uwe" wrote in message
...
I just got a Struthers wattmeter/SWR meter at a hamfest, but no papers.

Does anybody here have the instructions/service manual or would know where
to get it??

Thanks Uwe

Well, mine apparently has a little problem. The knob on top, which lets you
select the power level, that knob turns a cam which raises or lowers the
sensing element. Very nifty mechanism.
Now in my meter the shaft which holds the know spins in the cam and so
obviously nothing happens. So I took the hole thing apart and fixed that
problem and in the process you wish you had the description or maintenance
instructions which would give you the exact distance of the sensing element
for each power range etc.

So thats why I was asking.
And the thing is built beautifully, thats for sure, I just seem to have to
recalibrate mine.
Maybe somebody else here has some documentation for the device.

73 Uwe

in article , Ralph Mowery at
wrote on 5/1/04 10:03 AM:

I have had one for several years. There is not much to it. Just be sure to
remove the "shipping and storage" wire from the back of the meter if it is
there before using it. It is a piece of springey bare wire across the meter
terminals. It may not be on your meter. Very nice meter but the meter is
very much dampened. It will take a while for it to reach the maximum value.
Just pop in the slug that you need for the range and power level. It is the
meter that has a SWR adjustment knob on it you turn it to the neasuerment
jposition and find a range where it is off scale, then adjust to full scale
and then turn the slug 180 deg to get the SWR. Or you could find a chart
the Bird meter uses and get the swr off the chart for the ammount of forward
and reverse power.

"Uwe" wrote in message
...
I just got a Struthers wattmeter/SWR meter at a hamfest, but no papers.

Does anybody here have the instructions/service manual or would know where
to get it??

Thanks Uwe

"Uwe" wrote in message
...
Well, mine apparently has a little problem. The knob on top, which lets
you
select the power level, that knob turns a cam which raises or lowers the
sensing element. Very nifty mechanism.
Now in my meter the shaft which holds the know spins in the cam and so
obviously nothing happens. So I took the hole thing apart and fixed that
problem and in the process you wish you had the description or maintenance
instructions which would give you the exact distance of the sensing
element
for each power range etc.

So thats why I was asking.
And the thing is built beautifully, thats for sure, I just seem to have to
recalibrate mine.
Maybe somebody else here has some documentation for the device.


Here is a scan of the procedure. YOu have to hook up a 50 ohm dummy load
and a known accurate meter after the urm120. That is the test setup referred
to as fig. 6. There is no exect distance, just turn the screw tuil
calibrated against a known standard.



ET61O-AA-OMI-O1O/81':1 SE502


NOTE

A precision RF Wattineter or a Calorimeter of the desired
accuracy may be
substituted for Items d, e and f.

6-12. PROCEDURE. Perform the following steps to calibrate a
coupler-detector
assembly:

1. Connect the test setup shown in figure 6-1.

2. Rotate the knurled slide knob on the coupler-detector assembly so
that the
arrow on the power selection plate points toward the 50-ohm
termination load.

3. Position the power range knob on the coupler-detector assembly to
the power
range within which the calibration is to be made.

4. Remove the two screws (9, figure 7-2) that secure the power
selection plate
(10) to the slide knob assembly (12) , and lift the power
selection plate (10)
over the power range knob (7).

S. Apply power to the RF power source, making certain that the RI'
source is
operating within the frequency range of the coupler-detector
assembly.

6. Compare the reading of the wattmeter with the reading on the test
eguipsent
power meter, taking into account the coupling factor of the
directional
coupler at the frequency being used.

Rotate the power range knob approximately 15' from its normal
position in
order to line up the hole in the slide knob assembly (12, figure
7-2) with
the hole in the slide cam assembly (13). At each setting of the
power range
knob the hole in the slide knob assembly (12) is directly in line
with the
arrow on the power range knob.

Insert a 1/8-inch hexagonal (Allen) wrench through the holes until
the
tuning knob lines up as indicated in Step 7, into the socket of the
calibrating screw (11).

Turn the calibrating screw (11) clockwise if the power reading of
the
wattmeter is higher than the test equipment power mater,
counterclockwise
if lower.

NOTE

If the correct reading can not be obtained within a half turn 0f
the
calibrating screw, the diode must be replaced.

Reasemble the coupler-detector assembly.

"Uwe" wrote in message
...
Well, mine apparently has a little problem. The knob on top, which lets
you
select the power level, that knob turns a cam which raises or lowers the
sensing element. Very nifty mechanism.
Now in my meter the shaft which holds the know spins in the cam and so
obviously nothing happens. So I took the hole thing apart and fixed that
problem and in the process you wish you had the description or maintenance
instructions which would give you the exact distance of the sensing
element
for each power range etc.

So thats why I was asking.
And the thing is built beautifully, thats for sure, I just seem to have to
recalibrate mine.
Maybe somebody else here has some documentation for the device.


Here is a scan of the procedure. YOu have to hook up a 50 ohm dummy load
and a known accurate meter after the urm120. That is the test setup referred
to as fig. 6. There is no exect distance, just turn the screw tuil
calibrated against a known standard.



ET61O-AA-OMI-O1O/81':1 SE502


NOTE

A precision RF Wattineter or a Calorimeter of the desired
accuracy may be
substituted for Items d, e and f.

6-12. PROCEDURE. Perform the following steps to calibrate a
coupler-detector
assembly:

1. Connect the test setup shown in figure 6-1.

2. Rotate the knurled slide knob on the coupler-detector assembly so
that the
arrow on the power selection plate points toward the 50-ohm
termination load.

3. Position the power range knob on the coupler-detector assembly to
the power
range within which the calibration is to be made.

4. Remove the two screws (9, figure 7-2) that secure the power
selection plate
(10) to the slide knob assembly (12) , and lift the power
selection plate (10)
over the power range knob (7).

S. Apply power to the RF power source, making certain that the RI'
source is
operating within the frequency range of the coupler-detector
assembly.

6. Compare the reading of the wattmeter with the reading on the test
eguipsent
power meter, taking into account the coupling factor of the
directional
coupler at the frequency being used.

Rotate the power range knob approximately 15' from its normal
position in
order to line up the hole in the slide knob assembly (12, figure
7-2) with
the hole in the slide cam assembly (13). At each setting of the
power range
knob the hole in the slide knob assembly (12) is directly in line
with the
arrow on the power range knob.

Insert a 1/8-inch hexagonal (Allen) wrench through the holes until
the
tuning knob lines up as indicated in Step 7, into the socket of the
calibrating screw (11).

Turn the calibrating screw (11) clockwise if the power reading of
the
wattmeter is higher than the test equipment power mater,
counterclockwise
if lower.

NOTE

If the correct reading can not be obtained within a half turn 0f
the
calibrating screw, the diode must be replaced.

Reasemble the coupler-detector assembly.

Thank you Ralph, were did you get that document?
Some of the info one could guess, but some items will be helpful when I try
to calibrate the two plugs which had a problem. It is certainly worth
maintaining this piece of work.

73 Uwe







in article , Ralph Mowery at
wrote on 5/1/04 5:13 PM:


"Uwe" wrote in message
...
Well, mine apparently has a little problem. The knob on top, which lets
you
select the power level, that knob turns a cam which raises or lowers the
sensing element. Very nifty mechanism.
Now in my meter the shaft which holds the know spins in the cam and so
obviously nothing happens. So I took the hole thing apart and fixed that
problem and in the process you wish you had the description or maintenance
instructions which would give you the exact distance of the sensing
element
for each power range etc.

So thats why I was asking.
And the thing is built beautifully, thats for sure, I just seem to have to
recalibrate mine.
Maybe somebody else here has some documentation for the device.


Here is a scan of the procedure. YOu have to hook up a 50 ohm dummy load
and a known accurate meter after the urm120. That is the test setup referred
to as fig. 6. There is no exect distance, just turn the screw tuil
calibrated against a known standard.



ET61O-AA-OMI-O1O/81':1 SE502


NOTE

A precision RF Wattineter or a Calorimeter of the desired
accuracy may be
substituted for Items d, e and f.

6-12. PROCEDURE. Perform the following steps to calibrate a
coupler-detector
assembly:

1. Connect the test setup shown in figure 6-1.

2. Rotate the knurled slide knob on the coupler-detector assembly so
that the
arrow on the power selection plate points toward the 50-ohm
termination load.

3. Position the power range knob on the coupler-detector assembly to
the power
range within which the calibration is to be made.

4. Remove the two screws (9, figure 7-2) that secure the power
selection plate
(10) to the slide knob assembly (12) , and lift the power
selection plate (10)
over the power range knob (7).

S. Apply power to the RF power source, making certain that the RI'
source is
operating within the frequency range of the coupler-detector
assembly.

6. Compare the reading of the wattmeter with the reading on the test
eguipsent
power meter, taking into account the coupling factor of the
directional
coupler at the frequency being used.

Rotate the power range knob approximately 15' from its normal
position in
order to line up the hole in the slide knob assembly (12, figure
7-2) with
the hole in the slide cam assembly (13). At each setting of the
power range
knob the hole in the slide knob assembly (12) is directly in line
with the
arrow on the power range knob.

Insert a 1/8-inch hexagonal (Allen) wrench through the holes until
the
tuning knob lines up as indicated in Step 7, into the socket of the
calibrating screw (11).

Turn the calibrating screw (11) clockwise if the power reading of
the
wattmeter is higher than the test equipment power mater,
counterclockwise
if lower.

NOTE

If the correct reading can not be obtained within a half turn 0f
the
calibrating screw, the diode must be replaced.

Reasemble the coupler-detector assembly.

Thank you Ralph, were did you get that document?
Some of the info one could guess, but some items will be helpful when I try
to calibrate the two plugs which had a problem. It is certainly worth
maintaining this piece of work.

73 Uwe







in article , Ralph Mowery at
wrote on 5/1/04 5:13 PM:


"Uwe" wrote in message
...
Well, mine apparently has a little problem. The knob on top, which lets
you
select the power level, that knob turns a cam which raises or lowers the
sensing element. Very nifty mechanism.
Now in my meter the shaft which holds the know spins in the cam and so
obviously nothing happens. So I took the hole thing apart and fixed that
problem and in the process you wish you had the description or maintenance
instructions which would give you the exact distance of the sensing
element
for each power range etc.

So thats why I was asking.
And the thing is built beautifully, thats for sure, I just seem to have to
recalibrate mine.
Maybe somebody else here has some documentation for the device.


Here is a scan of the procedure. YOu have to hook up a 50 ohm dummy load
and a known accurate meter after the urm120. That is the test setup referred
to as fig. 6. There is no exect distance, just turn the screw tuil
calibrated against a known standard.



ET61O-AA-OMI-O1O/81':1 SE502


NOTE

A precision RF Wattineter or a Calorimeter of the desired
accuracy may be
substituted for Items d, e and f.

6-12. PROCEDURE. Perform the following steps to calibrate a
coupler-detector
assembly:

1. Connect the test setup shown in figure 6-1.

2. Rotate the knurled slide knob on the coupler-detector assembly so
that the
arrow on the power selection plate points toward the 50-ohm
termination load.

3. Position the power range knob on the coupler-detector assembly to
the power
range within which the calibration is to be made.

4. Remove the two screws (9, figure 7-2) that secure the power
selection plate
(10) to the slide knob assembly (12) , and lift the power
selection plate (10)
over the power range knob (7).

S. Apply power to the RF power source, making certain that the RI'
source is
operating within the frequency range of the coupler-detector
assembly.

6. Compare the reading of the wattmeter with the reading on the test
eguipsent
power meter, taking into account the coupling factor of the
directional
coupler at the frequency being used.

Rotate the power range knob approximately 15' from its normal
position in
order to line up the hole in the slide knob assembly (12, figure
7-2) with
the hole in the slide cam assembly (13). At each setting of the
power range
knob the hole in the slide knob assembly (12) is directly in line
with the
arrow on the power range knob.

Insert a 1/8-inch hexagonal (Allen) wrench through the holes until
the
tuning knob lines up as indicated in Step 7, into the socket of the
calibrating screw (11).

Turn the calibrating screw (11) clockwise if the power reading of
the
wattmeter is higher than the test equipment power mater,
counterclockwise
if lower.

NOTE

If the correct reading can not be obtained within a half turn 0f
the
calibrating screw, the diode must be replaced.

Reasemble the coupler-detector assembly.