ATX-1080 SWR

The weather was quite rainy today but it cleared up during the afternoon. I decided to go outside with the FT-817 and the ATX-1080 antenna to make some SWR measurements. I also wanted to se how reliable the built-in SWR meter of the FT-187 actually is.

Started out on 40 meters. I could hear a lots of stations and it did indeed make a huge difference, whether there was a radial attached to the rig or not: When I attached the radial to the tuner chasis, the signals went from S0 to S9!

Starting out with the factory settings, i.e. 128cm telescope length, I got the following measurements:

7.000 1.3 3 3.0
7.010 1.3 3 3.0
7.020 1.3 3 3.0
7.030 1.3 3 3.0
7.040 1.3 3 3.0
7.050 1.3 3 2.7
7.060 1.4 3 2.5
7.070 1.4 3 2.5
7.080 1.4 3 2.2
7.090 1.45 3 2.1
7.100 1.5 3-4 2.0

The output power using a dummy load was 5 watts. I then tried to adjust the telescope length and at 121 cm the SWR got down to 1.25, appr. 2 bars on the FT-817, and it was flat across all the CW section. Not bad.

The factory settings on 30 meters were not good. With a telescopic length of 51.5 cm, the FT-817 goes bananas and the HIGHSWR flag is blinking. I then tried to adjust the telescope and with 35.5 cm the SWR was down at 1.0 all the way between 10.100 and 10.150 MHz.

On 20 meters the factory settings were cool. SWR was flat 1.0 on the whole CW section and rising slowly: 1.1 @ 14.070, 1.2 @ 14.150 and 1.3 @ 14.350

So, we can at least learn two things from this:

  1. Always adjust the telescopic length to obtain best SWR.
  2. Always deploy the telescopic section from the bottom, that is, it seems to be better if the thin parts are collapsed instead of the the thick parts.


Author: Alexandru Csete

Embedded software engineer in the satcom industry during the day. Radio amateur and SDR hacker during the night.