SMD Dummy Load

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*** Prototype Special ***

 

SMA Version Large parts are used for easier first time building BNC Version
SMA Kit  

Kit Package

BNC Kit

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 tap and detector parts of the circuit uses 1206 and SOT-23 type parts, which are one of the next common smaller sizes. We’ll leave 0805 and smaller parts to other projects 🙂

Available with either an SMA or BNC female connector.

Manuals:

SMD Dummy SMA Manual

SMD-Dummy-BNC-Manual

 

This is a prototype run and a few changes needed to be made.  We were not happy with the meter circuitry as it was too easy to pop the diode at full power.  (It was not John-proof!)  A few part changes and a small modification of an additional part between C1 and ground is needed.  The part changes are included and can be seen in the pictures above – click to zoom in.  For that reason we are selling these prototype kits at our cost!

Kit $5

Assembled $9


Style



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 0.000 0.0000 Unlimited
0.0025 4 0.355 0.027 0.000 0.0025 Unlimited
0.010 10 0.70 0.054 0.005 0.030 Unlimited
0.063 18 1.58 0.147 0.099 0.159 Unlimited
0.250 24 3.54 0.293 0.322 0.395 Unlimited
0.500 27 5.00 0.500 0.660 0.720 Unlimited
1.000 30 7.07 0.707 1.000 1.110 Unlimited 100F at 30 seconds
2.500 34 11.20 1.120 1.700 1.830 >3 Minutes HOT 140F at 30 seconds
4.000 36 14.10 1.398 2.150 2.250 >3 Minutes HOT 160F at 30 seconds
6.000 38 17.50 1.770 2.610 2.850 120 HOT 180F at 30 seconds
10.000 40 22.40 2.250 3.400 3.670 90 Melts solder in 100 seconds
15.000 42 28.00 2.700 4.300 4.420 45 Melts solder in 60 seconds
20.000 43 31.60 3.040 4.910 5.000 20 Melts solder in 30 seconds

SWR

Frequency
Mhz
Return Loss
Dbm
SWR
1.80 -27.01 1.07:1
10.13 -28.45 1.07:1
18.10 -28.79 1.07:1
29.70 -25.61 1.07:1
52.00 -26.89 1.1:1
70.00 -25.1 1.1:1
148.00 -20.94 1.2:1
225.00 -16.87 1.3:1
450.00 -7.92 2.3:1

 

 

 

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