Organize and Share your Electronics the way you want. Sign-Up for a free account now. It takes only 30 seconds!

Loaded dipole for 20m

Loaded dipole for 20m

My HF-project has stalled since I do not have a decent antenna. I have limited space for a full-sized antenna on my roof. My friend LA8OKA has assembled a loaded 20m dipole, and I wanted to test a similar design so I could get on the air on 20m.

First I simulated the antenna in EZNEC+ 6.0. The antenna is about 6m with 9uH loading coils halfway on each dipole segment.

Above, the parameters in EZNEC. I created two coils at about 9uH, which I calculated as 0R+791j ohm.

This is how the antenna looks like in EZNEC.

The SWR minimum is 1.34 at 14.05 MHz, meaning that the antenna should be great for WSJT work at 14.0760 MHz.

Then I created the two coils using 32mm PVC and 23 turns of 1mm2 multicore copper wire. I calculated the inductance to be 8.8uH, and a prototype coil proved to be in the ballpark of the calculated value.

Picture of the coil (in the rain).

I used a cheap 1:1 China-Balun as the center isolator.

Then, I mounted the antenna on a test location on my balcony and tuned the antenna using a NWT150 scalar network analyser and a directional coupler.

The above picture show the test setup using the SNA, a directional coupler, and a 50 Ohm dummy load for calibration of the SNA.

The first sweep gave a minimum SWR of 2.0 at about 13.5 MHz. By shortening the antenna, the minimum moved to 14.07 MHz. Minimum SWR is still 2.0. I suspect that the antenna impedance somewhat below 50 ohm due to the loading coils. In addition, there was about 50cm of wet snow on the roof just 1m below the antenna when I did the measurements. This might affect the result, which deprives me from experiencing the holy grail of 1.0 SWR. 
The verdict: Honestly, I am not sure how good the antenna is, since I do not have anything to compare with. In addition, the band conditions on 20m has been really poor and my softrock only outputs about 1W. Hence the chances to obtain great DX is limited. Nevertheless, I have made a few contacts up to 2500 km.

Read more Here

Pinned onto

Related Pins

Tutorial: DHT22 sensor with a PICmicro
Tutorial: DHT22 sensor with a PICmicro
BQ24650 Based MPPT li-ion Battery Chage Controller With Software MPPT adjust and 3 Channel LED P ...
BQ24650 Based MPPT li-ion Battery Chage Controller With Software MPPT adjust and 3 Channel LED PWM dimming.
Play beautiful music on an Arduino thumb piano
Play beautiful music on an Arduino thumb piano
40 dB attenuator
40 dB attenuator
A multimeter heads-up display with Arduino glasses
A multimeter heads-up display with Arduino glasses
Robotic fish swims under Arduino control
Robotic fish swims under Arduino control
Arduino Xylophone
Arduino Xylophone
MPPT Solar Charger Testing
MPPT Solar Charger Testing
Design and Application Guide of Bootstrap Circuit for High-Voltage Gate-Drive IC
Design and Application Guide of Bootstrap Circuit for High-Voltage Gate-Drive IC
ESLOV is the amazing new IoT invention kit from Arduino
ESLOV is the amazing new IoT invention kit from Arduino
μPC1237 based 2 channel speaker protector
μPC1237 based 2 channel speaker protector
ESP8266 WeatherStation Color
ESP8266 WeatherStation Color
Keyless piano project using Arduino uno
Keyless piano project using Arduino uno
IoT Wardrobe
IoT Wardrobe
Automotive CAN Transceivers
Automotive CAN Transceivers
Restoring a vintage Xerox Alto day 8: it boots!
Restoring a vintage Xerox Alto day 8: it boots!
Sonicare toothbrush teardown: microcontroller, H bridge, and inductive charging
Sonicare toothbrush teardown: microcontroller, H bridge, and inductive charging
Reverse engineering a server CPU voltage regulator module
Reverse engineering a server CPU voltage regulator module
Building a sweet plastic MIDI controller
Building a sweet plastic MIDI controller
A DIY interactive book that uses digital gestures
A DIY interactive book that uses digital gestures

Top


Shares