CHA TD Broadband Terminated Dipole 

This is the Chameleon CHA TD. It’s a Broadband terminated dipole operating from 160 through 10 meters without a tuner, and 50Mhz with a tuner. My primary use for this antenna is Automatic Link Exchange or ALE.

Where they CHA TD fits in
Each radio ALE station uses a callsign or address in the ALE controller. When not actively in communication with another station, each HF SSB transceiver constantly scans through a list of bands and frequencies, listening for its callsign. Moreover, the ALE controller selects the best available frequency by sending out brief digital selective calling signals for about 15 seconds containing its callsigns. This is called sounding, and is very similar to a beacon in APRS. Since sounding and scanning can happen across frequencies and bands (band hopping) an antenna system capable of instantaneous communications without a need for user intervention on any of the ALE bands/frequencies is desired.

So far I’ve been pretty astonished with this antenna. It’s mounted in inverted-v configuration from my tower at the moment. I also plan on finding the best configuration for use as a field station antenna. The user guide can be downloaded from the Chameleon website. It has lots of antenna configurations, to suit a variety of applications. There are also many configuration ideas on the HFLink website.

160-10m SWR
I initially deployed this antenna incorrectly, leading to some very wrong SWR readings. A few minutes troubleshooting with chameleon and the problem was solved. The wide SWR sweep looks pretty good now. It also looks very similar to the SWR plots that chameleon publishes themselves. Now we know the plot results are attainable by anyone deploying this antenna correctly.

Band by band SWR
Looking at the results one band at a time they actually look much better than they did in the whole HF band sweep.

System Components

  • Matching transformer 
  • Antenna elements and wire winders
  • 300kohm resistors
  • Counterpoise wires and wire winders
  • Carrying case
  • Ground stakes

After deploying this antenna for the first time, I immediately went back to Chameleon and said “please make a lightweight, 20 watt version of this antenna”. There are giant mega-corporations who make Broadband terminated dipoles for non-governmental organizations and Aid agencies deployed around the world. Many of them still rely on HF Communications. So it is an effective design! From amateur radio perspective I would kill to have a lightweight version of this antenna to carry and deploy man portable, in the field. Still the antenna as it exists is a magnificent beast, which is definitely being overlooked by the amateur radio community.

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