Wednesday, April 26, 2017

Step attenuator kit from K5BCQ

3dB switched in for 50 mW from R-Pi
Due to the incredible performance offered by WSPR with 100 mW I recently found myself in need of a step attenuator for further experimentation at even lower power levels.

I've known about the kits offered by K5BCQ for quite a while and am glad to report that a step attenuator is among them - the imaginatively named Attenuator Kit #13.

The kit was in my mailbox two days after ordering it. Assembly took under an hour and testing with my KX2 and OHR WM-2 wattmeter yielded impressively accurate results. I placed the attenuator inline and, with all switches off, power output was 10 watts. Switching in the 3 dB pad dropped power to exactly 5 watts. Other values of attenuation decreased the output to exactly what it should be.

There are two options available for switching in various levels of attenuation - slide switches or jumpers. I ordered the slide switches but should have ordered the jumper version since the slide switches don't perfectly fit the holes drilled into the circuit board. The slide switch pins (6 per switch, 9 switches) have to be bent into an ugly configuration to fit and the result doesn't look too good. As infrequently as changes in attenuation levels would be made, jumpers would have been adequate and would have made for a better-looking end result.

But it is dead-on accurate.

I am now (for the past 15 minutes) WSPRing on 20 meters with a ionosphere-scorching total of 50 milliwatts and am being heard in France and Switzerland.


  1. Hello John, I tried ordering from K5BCQ last week, but up till now no reply to my emails. How did you contact him?

    The attenuator was also on my shopping list. I will order it with jumpers now, so thanks for your review.

  2. It took a few days for me to get an initial reply too and then I noticed that the address on his website and that on his page were different so I emailed him at both addresses and got a quick reply. And as mentioned, the order arrived very quickly so he is fast to act on orders once he receives them.

    73 - John

  3. Thanks. I mailed him at both addresses, but no reply after a week. I'll try again. 73 de Hans