ME-165/G SWR-POWER METER 1.8–30 MHz

With internal dummy load and quiet-tuning facility

 10 jun 2011 With the original schematic.

SWR-POWER METER ME-165/G

The ME-165/G is manufactured by Barker & Williamson, Inc. (SWR-POWER METER ME-165/G, Radalab (STANDING WAVE RATIO-POWER METER ME165/G) and others as matching unit designed for use with T-368 400 W transmitter. This combination dummy load/SWR/power meter is an especially useful accessory to have for a ham.

Left: BARKER & WILLIAMSON's ME-165/G, right: RADALAB's ME165/G

ME-165/G

The matching unit is provided with:

1. Internal dummy load 50 Ω/600 W

2. Power-meter ≤ 600 W

3. SWR-meter

4. Quiet tuning facility

This schematic was drawn with the board as an example because the original diagram was not in my possession.

Meanwhile ON4FVQ gave me a copy of the manual and below is the original schematic with the 1N69A diode.

Wiring detail ME-165/G

DUMMY-LOAD 50 Ω

The dummy load (fig») used 12 × 600 Ω/50 W non-inductive 5% resistors in parallel to provide a 50 Ω/600 W load with a SWR of 1.5 or less up to 30 MHz. However when dissipating power in excess of 250 W limit the operation to intermitting on-off periods. Do not apply 600 W power for longer than 10 minutes. The matching unit can be damaged by the great amount of heat generated. For longer periods a ducted airflow should be used for the dummy load.

Stray inductances are tuned out with three capacitors on the input and the ends of the paralleled resistors.

PRINCIPE OF QUIET TUNING

In a quiet tuning device («fig) the full power is dissipated in a non-inductive resistor and a minor part of the power is used for a bridge circuit that permits direct readings of the SWR between the transmitter and its load (eg. Antenna or ATU). If one is matching his ATU or antenna the low power output will not be noticed by another ham. With the control switch in the SWR position the ME-165/G's output is only 50–100 mW and the transmitter is loaded with a perfect 50 Ω match. 1N277 can replace a defect diode.

MATCHING SEQUENCE

Two added switches.

Set the controls switch to the POWER position connects transmitting power to the unit and power output is indicated on the meter.

Set the switch to the ADJUST position and rotate the ADJUST control to obtain a full-scale meter reading. Do not keep the switch in that position any longer than necessary for meter adjustment.

Set the switch to the SWR position. The SWR between the transmitter and ATU or antenna may now be read and you may match your ATU for lowest SWR.

Finally set the switch to the OPERATE position and the transmitter output is connected directly to the load.

ACCURACY

If the power meter is well calibrated with R19 and C14 the accuracy of the scale is almost 5 % eg. better than most ham's SWR/PWR meters.

Calibration checks should be done with the front panel firmly pushed to the enclosure.

 

The SWR reading is not accurate due to the messy wiring from input to switch, from switch to dummy load and from switch to output. Replace the messy wiring by 50 Ω coax cable.

The null on 10 m can be improved when the two wires from switch to dummy load are bound together with tie-rap cable ties or plastic and waxed-linen lacing cords.

 

 

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