$50.00
SKU: US0833

$50.00

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Heathkit HM-102 RF Power Meter

The HM-102 is perhaps one of the most popular accessories Heathkit ever made. They sold zillions of them. The HM-102 is a RF power meter that will measure up to 2000 watts of RF. The HM-102 will also measure the Standing Wave Ratio between the transmitter and the antenna. The HM-102 is designed for use with 50-ohm transmission line only. The removable pickup can be placed up to six feet from the meter. No external power is required for the HM-102. There is very little that can go wrong with the HM-102 meter. The first place to start looking for trouble is to check the cable between the pickup sensor and the meter box. If the pickup sensor is not already removed from the HM-102's cabinet, do so. After the sensor is removed open the metal box by removing all the metal screws. Be careful you don't break any of the wires between the two SO-239 connectors on the inside. The pickup coil is very fragile. Be sure you don't break its wires. Set your VOM to the Rx1000 range. Connect the black lead from your VOM to the minus side of the HM-102 meter. (Note many VOMs reverse the polarity of their test leads when in the ohm range. If you don't get the required results, simply reverse the probes.) Set the HM-102's meter switch to the 200-watt scale. Now, with the red lead of your VOM, touch pad "F" on the sensor board. The meter should deflect upward. If it does not, reverse the VOM's leads and try again. If the wire is not broken between the sensor and the meter, the meter's needle will deflect. Set the HM-102 meter switch to the 2000-watt position. Place the VOM lead on the "G" pad. The meter should deflect. Set the meter to SWR. With your probe, touch the "C" pad. The meter should deflect. Pull the SWR meter out. Probe pad "B" with the VOM. Again, the meter should deflect. If you find any of the tests do not produce a meter deflection, suspect an open wire between the sensor and the HM-102's meter. If you find no breaks in the wire, then the meter in the HM-102 may be defective. Set the calibrate switch to the normal position.


To test the HM-102, you'll need a transmitter that will produce up to 100 watts and a 50-ohm dummy load. Connect the HM-102 to the dummy and the transmitter. Set the HM-102 control to read 200 watts. Apply RF on the 40-meter band from your transmitter. The meter should deflect. Drop the transmitter and switch over to the 2000-watt position. Again, apply power from the transmitter. You should see the meter deflect again. If you don't see the meter move in either position, suspect diode D1. Also, check to see if the calibrate/normal switch is loose. After years of use the slide switch will become loose. Take a needle nosed pliers and gently squeeze the metal tabs on the switch. Don't squeeze too much, or you won't be able to move the switch. A quick spray of contact cleaner on this switch is a good idea, too. If the SWR section is not working, check diodes D2 and D3. Also, the slide switch on the SWR sensitivity switch may need to be tightened up and or cleaned. Other than the three diodes listed above, there is very little that can go wrong with the HM-102 power meter.
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