Mt St Leonard VK3-VC006

It was forecast to be a fine cloudless day, so headed off to Mt St Leonard.  Arrived at the car park about 9:30 in thick fog and had a shorter than expected walk up the track to the summit. When I got to the top the fog was just starting to lift and from the lookout there was a sea of fog just below from the lookout.

Path to the summit

The path up to the summit is basically a road, so no problems here, its only about 1.5km up the road.

For a 7MHz antenna, I set up an end fed half wave using the squid pole as a centre support.   Had a bit of trouble finding something to keep the squid pole supported and in the end I used a few bungy chords to strap it to a large rock.

Squid pole with end fed inverted V half wave

At one end of the inverted V dipole, the matching box is directly connected.

The matching box worked well and didn’t need any counterpoise at all for a 1:1 match.  The matching box was made from a toroid transformer and a tuning capacitor from Jaycar (RV-5728 $2.75).   See photo for internals of matching box.  The turns ratio on the T-50-2 toroid (minikits) is 1:8 with 4 turns on the transceiver end and 32 turns for the antenna end.  This gives an impedance of around 8 squared times 50 or 3200 Ohms.

Matching box insides

The switch connects the one side of the antenna end back to the coax ground.  As the impedance of the antenna is high, the capacitance of the feed coax outer and radio etc. is sufficient ground.  If using the radio as a ground causes issues, the switch can disconnect it and a separate counterpoise can be used from the black terminal.

Schematic of the tuner

The 20 metre long 7MHz dipole’s end connects to the red terminal.  A squid pole supports the centre of the dipole, one end is pegged to the ground via an insulator and the other end connects to the matching box.

Antenna wire and match box

The antenna wire and match are pretty compact and take up less space than the previous vertical antenna, tuner and ground radials.

To tune the antenna, the capacitor is tuned for maximum noise then fine tuned for minimum SWR.

Based on the article by AA5TB

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1 Response to Mt St Leonard VK3-VC006

  1. Pingback: EFHW Antenna Tuner 2 | VK3YY

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