All posts by G4YRF

14 Feb 2019 – Aircraft Communications by Don, G4LOO

Don started by pointing out that most people think only of air to ground voice communications as being the sum total of the use of radio. There are, however, many other types of radio signals in use, beside voice there is radar and data.

Don went through the communications used to help the pilot know his location and point to the destination. Following that, Don detailed radio used for instrument landings indicating the aircraft position with regard to the runway, the glide slope and markers at three critical distances to landing. But, it was also pointed out that important information can be automatically transmitted to indicate position, aircraft operating parameters and aircraft ‘health’ to ground stations. During long flights, including overseas trips, automatic transmissions can be made to satellites designed to work with the aircraft information.

The question was asked as to why signals of this sort couldn’t be used to locate a plane that had gone off the radar map. The answer being that the transmitting units, in this case, must have been turned off. The next question was why be able to turn the system off and the answer is that they must be turned off when on the ground to stop multi transmissions from various planes interfering with those in the air.

Don showed a diagram of a typical airliner pointing out the locations of various antennas, there can be over twenty!

Tipical antenna locations

7 Feb 2019 – Construction Contest Winners Talk

First up was Martin, M0XMP who won the kit class section of the contest with his QCX 5w CW transceiver. This kit supplied by QRP Labs is very complete and the downloadable instructions, all 142 pages, were described as ‘like Heathkit’ on steroids!  Martin showed his copy with each part described and followed up with a colour illustration as to where and how it should be fitted.

Martin was especially pleased the unit came with a built in signal generator and alignment tools as well as a voltmeter, RF power meter and frequency counter so the builder does not have to have a workshop full of test equipment to get it going.  Martin demonstrated the unit decoding CW and it was pointed out that it can also be used for stand alone WSPR transmissions.

All this is very impressive for the modest price being asked. See all the details at:  www.qrp-labs.com               or watch a video at: https://www.youtube.com/watch?v=6zlCuPq2aNA

close up of part of instructions with red squares showing where to insert 100 nF capacitors

 

Don, G4LOO won the Weekend Special with his very simple project used to locate dislocated buried radials. The idea came originally from a published article which could easily be adopted and implemented. Don found that rabbits had been chewing the ends of his buried radials at the central connection point at the base of his four square antenna. Using this unit Don could  walk along  the area over the radial and carrying a small MF radio taped to the end of a cane (like a metal detector) could listen for a null and thereby detect the broken wire.

Radial pattern for 80m four square antenna

31 Jan 2019 – Antenna Modelling by Gareth, M5KVK

Sample Plot using MMANA-GAL

On a very cold evening on the last day of January, we were expecting some snow but members turned out to hear Gareth present his introduction to antenna modelling. He stated he would give a gentle introduction to modelling back garden antennas. The presentation was not meant to be the definitive guide to modelling antennas but more of what you might achieve. Gareth stated that modelling is not too difficult, provided you don’t expect perfection. It can provides a lot of insight into how your antenna works and provide a good basis for making improvements.

He then went on to list the programmes available, either free or ‘paid for’ and explained what can be expected from each. One that he tried was MMANA-GAL which was provided on a CD with the RSGB’s “Introduction to Antenna Modelling” by Steve Nichols, G0KYA.  This free programme does have some limitations but can be useful as a start.

Next examined was EZNEC, not free, but there is an EZNEC Demo which is free but limits the complexity of antennas you can analyze.  Gareth also mentioned  ‘Transmission Line Details (TLD)’  which calculates SWR and loss for lengths of transmission lines of different types, a good addition to antenna modelling situations.

A live demo then followed with several examples, one of which was Ian’s massive doublet, 360 feet long and up 60 feet. The doublet ends are supported at 46ft and 29.5ft high, the system is fed with 400 Ohm ladder line.  Although the PC took a while to compute, the result showed that matching would be possible on all bands, 160 to 10m, with the best match on 20m.

Gareth said Part 2 would focus on a practical application of this software.

24 Jan 2019 – Construction Contest

Members judging entries

This year’s Construction Contest saw sixteen members attending to judge six projects. The categories entered were projects from a Kit and Weekend Projects. There were no entries this year in the Major Project class nor the Novice category. Members present on the evening judged the projects and two winners were found. The winner in the Kit Class was Martin, M0XMP who submitted a very well built QCX 5w transceiver kitted by QRP Labs. Along side his entry, but not entered, was a loop aerial used to show the rig operating.

Photo by M0XMP of his QRP 5W rig
Judges at work!

Don, G4LOO submitted the winner in the Weekend Special class. It’s a buried radial tester from a published design by Tony, VA3AVR. The unit is basically a  means of injecting an RF signal into the buried wire to find if it’s entire length is still connected to the earth being used by a vertical antenna.

Don’s Project

10 Jan 2019 – Video Evening

The story of WRTC2014, an Olympic styled radio contest comprised of  59 competing teams from 29 qualifying regions around the world. Competitors represented 38 different countries.

This video was edited and produced by James Brooks, 9V1YC, James took advantage of 9 roving video teams to capture the action at headquarters and out in the field, artfully telling the WRTC2014 story using the participants’ own words.

3 Jan 2019 – Welcome back

This was our first meeting after the holidays and members had the chance to tell of their radio activities over the period.  Later tea and biscuits brought the session to an end.

13 Dec 2018 – Mince Pie Evening

For our last meeting before the holidays, members met for a Mince Pie Evening. Pies were warmed up in the oven and tea or coffee was served.  The turnout was good considering the near zero temperatures outside.

Meetings will resume on 3 Jan 2019 with a ‘welcome back’ get-together.

6 Dec 2018 – Antique and Unusual Electrical Equipment, Bring your own!

Last evening 23 members attended a meeting with a bit of a difference. Members were asked to bring in antique or unusual electrical equipment and tell everyone a bit about what they had brought.  There were commercially produced radios from a private collection which dated from the start of broadcasting till after WWll, some working. Other displays were more recent but very much the ‘out of the ordinary’ type. All had rather interesting pasts

29 Nov. 2018 – Video evening

This evening we watched a video from the RSGB 2018 Convention featuring a talk by Tim Duffy, K3LR from West Pennsylvania. Tim has engineered a station over the last twenty seven years or so that is perhaps the number one Multi-Multi contest stations in the world!  We saw mast after mast loaded with an unbelievable number and size of antennas.  As Tim once said when he was giving a short demo on 20m SSB and a station in Sweden couldn’t believe Tim was only running 100w. You can’t understate the power of 24 elements which makes 100w sound like 1500w.

It’s not possible to include all Tim’s station details here, but you can search for K3LR or K3LR antenna fly-by to see for yourself.  It’s very impressive.

AA7BQ photo during his visit (check QRZ.com, K3LR for more)