Saturday 23 November 2019 – I had planned to participate in the WIA VHF-UHF field day, however the forecast temperature is 33 degrees C (hot) and we have a thick red dust haze (hot northerly winds blow red dust from central Australia) which isn’t good for the respiratory system. So the plan for today is to construct a lightweight PVC hand-held telescopic 2 element 2m (145 MHz) yagi using two pairs of TV rabbit ear antennas as the elements. Approximate directional gain is 5dB.
- 1 metre length of 21.6 mm PVC water pipe, inside diameter is 18 mm (cut to length later). You can use a variety of lightweight materials for the boom.
- 1 * Plastic end cap – boom end cap at the handle end
- 1 * 1 metre length of RG58AU/CU Mil Spec coax – trim later
- 2 * telescopic TV rabbit ear antennas 80cm long (31.5 inches) online purchase
- 4 * solder tabs
- 1 * short length of solid copper wire
- 2 * M3 20 mm screws, nuts and washers
- 2 * M4 35 mm screws, nuts and toothed washers
- 1 * 50 ohm 4 hole BNC chassis socket and a solder tab
- 2 * M3 10 mm screws, nuts and flat washers
- 1 * 55 mm length of 20mm x 3mm aluminium bar
- 5 * cable ties
- 1 * 510 mm x 6mm dowel
2el 2m yagi dimensions @ 145 MHz. Start with the following dimensions and adjust the length of the telescopic elements evenly for a low VSWR.
2 element 2m yagi antenna in the extended position, element pacing is 406 mm (16 inches) 0.2 wavelength (λ).
BNC socket mount – 20 mm x 3 mm aluminium bar bent to form an L-bracket
Adjust the driven element length for your favourite 2m frequency. I plan to set my version to 145 MHz midway between 144 and 146 MHz.
Example: VSWR @ 146 MHz
Adjusted for 145 MHz – make the driven element a slightly longer on each side
With the operating frequency set, fold back the driven elements and mark the boom at the tip of the telescopic elements with a permanent marker. You now have a permanent reference for the length of the driven element. (Update 27 November 2019) Next make up a 510 mm (20.07 inches) length of 6 mm (1/4 inch) dowel as a measuring stick for each half of the reflector elements. Measure from the center of the PVC pipe. When not in use, store the dowel inside the PVC pipe, don’t forget the end caps. 🙂
510 mm length of 6 mm dowel. You can also scribe a mark on the dowel to the length of the driven elements.
I plan to use this 2el 2m yagi antenna for 2m SOTA activations on 144.2 MHz SSB and 146.5 MHz FM simplex. 5 dB directional gain is approximately 3 times the input power.
Have fun constructing your own hand-held 2el 2m telescopic yagi antenna. Total weight is 250 grams (8.8 ounces).
Last update: 27 November 2019