back to attenuators

N0ZYC Hybrid Attenuator:




This is my hybrid attenuator. The rotary switch selects between bypass, -20db, -40db, and the offset
attenuator. Offset attenuators suffer from a "donut" area around the fox where the signal overloads
the radio but is still too weak to be picked up with the attenuator in-line at it's lowest attenuation.
The addition of bypass and -20/-40 attenuators allows useful attenuation in all situations. (until you get
so close to the transmitter that it's "air mixing" with the mix signal inside the box, simply bypassing
whatever variable mix control you have)

The rotary switch also controls power to the offset attenuator board, only turning it on when selected.

There's a 7.4v LIPO rechargeable battery installed, with an external port for charging. RF connections
are made using 1.13mm micro coax, which is not fun to strip, but great for small enclosures. Use of
strain-relief is essential when working with micro coax like this. Hot glue was used to secure the
connections on the rotary switch, attenuator board, and BNC jacks.

Every effort was made to RF-proof this attenuator, to maximize performance. A BNC coupler is used to
mount the attenuator directly to the antenna jack on the radio. (usually an HTX-202) It's based off
KC9ON (3rd Planet Solar)'s offset attenuator, though I have swapped the 4mhz crystal with 2mhz.


1 prototype

2 second build

aluminum box ($6 at Ali Express)



last updated 09/19/2023 at 12:47:11