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14 Mar 19 – Arduino Update by Martin, M0XMP

The evening began with a YouTube video by Randy, K7AGE who gave part one of his introduction to Arduino.

Martin then followed with an explanation of what he wanted to achieve and how he went about it.

On display was a large Mag-loop aerial and it was pointed out that tuning by hand wasn’t an option, not only because it’s not healthy to be near a transmitting loop, but that the tuning changes when the operator moves away from the aerial. Martin produced an ordinary TV remote handset and explained how he used the Arduino to decode the output from each button. That output was then used by the Arduino to control a stepper motor which turned the tuning capacitor and thereby achieved a degree of remote control. Martin explained the programming needed to achieve this outcome. However, he felt the tuning didn’t have the feedback necessary for fine tuning as he listened to the background noise rising and falling on his rig. He did admit to have previously tried using a servo to turn the tuning capacitor and felt that offered a better feel to achieve resonance since using a knob for tuning in place of the TV remote offered better feedback.

Martin felt that both methods had led to considerable scope for experimentation in mechanical and computer science.

7 Mar 2019 – Making your antennas work

This evening’s discussion was all about how members choose and maintain their antennas. A variety were talked about. Most members are using wires, either dipoles, doublets or untuned and tuned lengths, but there was one notable inclusion of two verticals which were home brewed by spiral winding wire around  the vertical support and feeding above ground level and having sloping radials. This has proved to be a very successful arraignment for working real DX with low power.

For maintenance, various products were suggested for anti-corrosion connections and protection against moisture ingress.

Discussions continued through the tea break before members headed for home.

28 Feb 2019 – Background Noise, a discussion

It seems that most amateur radio operators experience noise or QRM at some time or another. Fortunately, most is short lived and can be tolerated, however, some interference can be more destructive and blocks out all transmissions. Those need to be found and dealt with, if possible.

Members took turns describing their problems and, at times, playing sound samples. Methods used to minimise noise and interference were discussed. This discussion has resulted in more input and participation from members than any subject so far.

Next week’s subject is almost a follow on from this, when we will discuss how to Make Antennas Work.

21 Feb 2019 – Apps for Radio Amateurs

This evening we had a short discussion about the possible use of applications for smart phones or tablets that might be useful in amateur radio.  After a short on line search, numerous sources and types were found. Some apps could provide CW training and practice, as well as providing a read out. Numerous apps were able to provide propagation reports as well as solar data.

An app for smartphone can access the EchoLink network to almost anywhere in the world, using either WiFi or cellular 3G.  Although not Amateur Radio in the usual sense, the network is only available to licensed amateurs and can be useful on holiday or for those amateurs who do not have access to equipment and aerials.

More information for Android phones apps can be found at: http://www.g0hwc.com/android_apps.html

 

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.