SMD Dummy Load BNC Kit

$12.00

Want to try SMD for the first time but don’t want to try a big project with tiny parts?

This small QRP sized dummy load was designed as a learning tool for SMD soldering by using larger 2512 resistors for the dummy load portion. The 50 ohm load will operate from 500KHz to 30MHz with an SWR of less then 1.1:1 at power levels up to 20W under short durations. Usable at up to 225MHz with an SWR of less than 1.3:1. The circuit also includes a small tap for using an oscilloscope and a detector circuit for use with a DMM (or Arduino) to monitor your signal. The detector part of the circuit a SOT-23 type part, which are one of the next common smaller sizes. We’ll leave 0805 and smaller parts to other projects ?

Also available with an SMA female connector.

Manuals:

SMD-Dummy-BNC-Manual

 

3 in stock

SKU: SMD-DUMMY-BNC-K Category:

Description

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BNC Board

Large parts are used for easier first time building

Board Bottom

BNC Kit

Kit Package

SMA Version

Load Duration and Tap/Meter outputs

Power
In(W)		 Power
Dbm		 Power
Vrms		 Tap(Vrms) Meter (V)
JP1 Open		 Meter (V)
JP1 Shorted		 Max
Time(S)		 Notes
0.001 0 0.224 0.018 0.0001 0.0003 Unlimited
0.0025 4 0.355 0.028 0.0002 0.0028 Unlimited
0.010 10 0.70 0.055 0.005 0.029 Unlimited
0.063 18 1.58 0.138 0.098 0.158 Unlimited
0.250 24 3.54 0.275 0.318 0.395 Unlimited
0.500 27 5.00 0.406 0.555 0.635 Unlimited
1.000 30 7.07 0.557 0.850 0.950 Unlimited 100F at 30 seconds
2.500 34 11.20 0.898 1.370 1.570 >3 Minutes HOT 140F at 30 seconds
4.000 36 14.10 1.140 1.810 1.950 >3 Minutes HOT 160F at 30 seconds
6.000 38 17.50 1.490 2.460 2.560 120 HOT 180F at 30 seconds
10.000 40 22.40 1.860 3.140 3.210 90 Melts solder in 100 seconds
15.000 42 28.00 2.170 3.690 3.820 45 Melts solder in 60 seconds
20.000 43 31.60 2.475 4.230 4.330 20 Melts solder in 30 seconds

SWR

Frequency
Mhz		 Return Loss
Dbm		 SWR
1.80 -28.94 1.08:1
10.13 -28.78 1.08:1
18.10 -29.21 1.08:1
29.70 -28.11 1.08:1
52.00 -28.58 1.08:1
70.00 -27.14 1.10:1
148.00 -18.38 1.28:1
225.00 -14.82 1.45:1
450.00 -6.31 2.88:1

Chuck Carpenter, W5USJ, has a simple modification to change the modified the meter output to a peak detector.

(Thanks Chuck!)

You will need:

  • Germanium or low voltage Schottky diode such as a 1N5711, D101 can also still be used
  • 100nF (0.1uF) Capacitor
  • 100pF Capacitor
  • Jumper wire

Procedure:

  • Remove D101 or use at R125 (below)
  • Replace R123 with a jumper wire (a .01 ohm resistor shown in picture)
  • Replace R124 with a .1uF (104) and 100pF (101) capacitor in parallel.
  • Replace R125 with a 1N5711 diode (or any diode with a low Vf and high Vr) or place D101 here.
    • For the 1N5711 (Vr=70V, Vf=0.41V) place the banded end toward the outside of the PCB.
    • For the BAT54 (Vr=30V, Vf=0.3V) place the single pin side (pin 3) toward the center of the PCB and pin 2 (pin facing toward center of board) to the other PCB pad. You will need a couple small wires to connect the pads to the BAT54.
  • Note: R121 and R122 are omitted in the picture for the Oscilloscope tap and can still be used.

 

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Additional information

Weight 2 oz
Dimensions 6 × 5 × 1 in
Configuration

Kit, Assembled

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