Broadcast - 28 September 2025
Last Wednesday night Geri VK2UTE dropped into the NTARC club rooms to say hello. But he ended up staying to watch the live REAST YouTube stream presentation on “How to use the RSGB calculator”. Following the presentation we partook of drinks, food and general calculator implementation chatter around the table. It was great to see you again, we hope you enjoy your last week back in Hobart. With a bit of luck we will see or hear you next trip over.
The club’s last technical night was a hands on follow up of the previous weeks REAST streamed presentation on the Vector Network Analyser. It’s amazing how prevalent these little units have become amongst the amateur fraternity over the last few years, almost as common as a multi-meter. The night got off to a surprise start with the arrival of Brenton VK7HP, who decided to travel down from the North West coast for the VNA evening. He also brought an assortment of antenna related items he had been designing and constructing recently.
He had made a stand-alone 1296 MHz band modular antenna assembly that could be used individually or on a multi arrays. The dual driven radiating elements are constructed using 2 by 9 mm flat copper strapping bent into the classic bow-tie shape. Each radiating element is mounted on a double split quarter wave balun which also incorporates a feed rod which was machined to different diameters providing multi stage impedance matching. The module is interconnected using a QMA RF connector mounted directly on the rear. All this came with pages of calculations and detailed construction details for us to peruse.
For testing on the VNAs we used the version with the single module mounted on a screen back reflector and incorporating a single director element. This was so recently constructed that evidently the paint had only finished drying during the trip over to the club rooms. This little antenna setup demonstrated the various VNA capabilities. It also proved to be very useful demonstrating, in real time, the proximity effect from objects on impedance and Smith chart plots.
Brenton also had a very impressive screen backed quad bay version using these dual driven element assemblies. All this was hand made with the possible exception of the Bunnings, very rigid, wire mesh shelf which was repurposed as an excellent screen backing. Mounted on the rear of the meshing was a four port power divider interconnected to each antenna module with a QMA patch lead. An N type connector was used for the main RF input. The quad power dividers were also made from scratch using copper tubing and rods plus some machined brass blocks. The whole assembly had the feel and looks of a commercial product.
For those interested, QMA connectors are “quick-connect” RF connectors and a variation on the conventional SMA while maintaining the same electrical properties. They are similar to the operation to the pneumatic quick connect air couplers. There is a simple push-and-lock mechanism that secures the connection and you simply pull-back the collar for disconnection, as opposed to a screw thread collar on the conventional SMA. These were used instead of standard SMA connectors because they were extremely cost effective, read that as free, Hi-Hi. Brenton had as many as he wanted simply by de-soldering them from a pile of discarded printed circuit boards. Plus they also came with a heap of recovered suitable short patch leads, a no brainer when it comes to recycling. QMA connectors have been available since 2003 and were extensively use in mobile phone base station equipment over the years. Just for interest N Type connectors are also available as a QN version, for quick release.
The night ended up being a fun, interesting hands on VNA night as well as an excellent show and tell from Brenton.
Mug Order - yes, we are talking about the white mugs for drinking out of, those that have our club logo on one side, personalised with your name and call sign on the other. We are placing another order so if you would like one then please email secretary@ntarc.net to place an order. Please specify what name is to be printed above the call sign. The final price will be about $12 depending on eventual quantity ordered.
As always pictures will be available on the NTARC Web site under “Blogs” for this broadcast. NTARC Blogs
UPCOMING EVENTS
On Air Test and Technical Net session - Every Wednesday, Test-Net and CW course on 3.580 MHz from 7 pm, then a Technical Net on 3.567 MHz from 7.30 pm till 8.30 pm. Your host for the evening is Nic VK7WW.
NTARC General Meeting - Wednesday 8th October at 7:30 pm. Held at Rocherlea Scout Hall, Archer Street, Rocherlea.
Club Room Technical night – This Wednesday the 1st of October and will commence at the usual time of 6.30 pm at the Club Room Archer Street, Rocherlea.
Coffee Morning - Held every Friday in the NTARC Club rooms. Time is from 10 am to noon.
Finally – If you have any items of news please email them to the Secretary at the following address news@ntarc.net all items to be received no later than 5 pm on the Friday prior to the Broadcast.
That’s all folks,
73, Stefan VK7ZSB.
