Thursday, November 8, 2012

RF Attenuator Kit

As we get into winter I'm starting to get back into some amateur radio projects. I recently built an RF attenuator kit  from Hendricks QRP Kits.

It's a nice simple attenuator that supports from 1 to 41 dB of attenuation with 50 ohm input and output impedance and can handle up to about 5 watts of power and is good to at least 30MHz. It's based on
a circuit in the ARRL Radio Amateur's Handbook.

Front View

Rear View
It only contains resistors and switches but comes with a nice silk-screened PCB and a metal case with decals for labelling the switches. It went together in an hour or so not counting the time spent waiting for the coats of Krylon clear coat finish to dry.

I plan to use it for a couple of applications. I have an RF signal generator built from a kit that has a fixed output. This will allow me to adjust the output level in 1 dB steps from 100% down to about .02% output level.

The other application, which it was designed primarily for, is to adjust the output level of a QRP transmitter so you can work at lower power levels with the flip of a few switches. The rear panel has a label which lists the percentage of output level and power output for 1W and 5W input) and various switch settings.

In may also come in handy when testing and calibrating ham radio and communications receivers.

1 comment:

Grant McDuling said...

Seems like a nice piece of kit. I have many Hendricks kits and I think I need one of these. Thanks for the post, Jeff.