Bernard ZL2BD gave a talk on how to safely switch between RX and TX antennas on your rig and demonstrated the circuit (which is probably not suitable for break-in keying). This circuit would allow us to use our active antenna or mag loop antenna on RX and our standard antenna on TX. The MFJ unit above is an alternative approach.
He also demonstrated a simple phasing circuit that works with two RX antennas to reduce noise levels or to peak a signal. Steering of a two antenna array throughout 360 degree is possible. Two active antennas can be used, or in fact, any two antennas spaced less than 1/4 wavelength apart can be steered (on RX) to reduce unwanted noise and maximise forward gain.
The following articles relate to the workshop:
Receive Antenna Phasing and Noise Cancelling Explained
Our regular meeting in September 2019 (at Mike ZL1AXG QTH) was the opportunity for members to bring out their home construction projects to be judged in the annual Blackwood Cup competition. The right to hold the cup has been contested since 1930 (won that year by ZL2BC)!
There were three entries in 2019:
George ZL2AG – Artificial RF Ground Unit. George explained that Trevor ZL2AKW being on the thirteenth floor of a building needed to remove the noise from nearby audio speakers. He explained how the unit was constructed, how it operated, etc. supported with some written papers.
Mike ZL1AXG – Control Console. Mike talked about easier control of the transceiver by the unit he had constructed. The unit sits between the microphone and transceiver. The unit has 5 push buttons and 1 switch. With the press on one button, it can select a CW or Voice Keyer function depending on the mode used. The fourth button replaces the PTT button on the microphone.
Bernard ZL2BD – Station T/R Switch and Phasing Unit for Receive Antennas. Bernard talked about the first unit including how protection is provided from RF on Transmit going to the Receive Active Antennas. Bernard then explained how the phasing unit can be used with a mix of two receiving antennas.
The winner for the Blackwood Cup in 2009 was announced as George ZL2AG for his Artificial RF
On Tuesday 10 September, a combined Wellington branches meeting held at Branch 42 HQ welcomed the three councillors (Daniel and Ben in person, and Phil on the end of a cellphone). Members from all six Wellington region branches were present including three from Branch 50 NZART. The meeting primarily focussed on the challenges that NZART faces in terms of retaining and expanding membership (and amateur radio more generally), and how to improve the relationship between NZART and members. Those attending appreciated the willingness of Daniel to travel to Wellington especially to meet with local amateurs, and to openly discuss the challenges.
The second shed workshop on Active Antennas involved a construction day … with soldering irons out and smoke from the burnt plastic wafting through John ZL2XY’s QTH.
The kit was made available to all Branch 50 NZART members wanting to build an active antenna. This involves two enclosures – the active RX unit at the antenna site – where the whip antenna is mounted and powered over coax, and the shack unit that provides for the power over coax. Assemblers found they were able to build about half of the circuit in the allotted time, and the rest will be done at their own QTH.
With the next shed workshop on 6 October 2019 at Bernard ZL2BD’s QTH will focus on antenna switching and phasing of two RX antennas to reduce or eliminate noise. This is a logical follow on and should be of heightened interest with club members getting their active RX working over coming weeks.
Type 504 Active Antenna Kit - Construction notes (updated 9 Sept)