Over the last few months the committee have authored Terms of Reference or ToRs for their roles. These record the responsibilities of members who undertake committee roles both currently and into the future on behalf of the TSGARC.
A little terminology: A role is a set of responsibilities, a member may choose one or more roles depending on the size of the roles.
The ToRs have now been uploaded to our website and may be found under the About menu option.
Andrew Gawthrope
Chairman
Our TSGARC Christmas meal was at the Anchor in Thornbury this year. It was well attended and everyone had a good evening. The food was great. I particularly liked the roast beef 🙂 Yum.
Big thanks to Stan, G0RYM for making it happen 🙂
Andrew
G0RVM
For some time I’ve been thinking about replacing the IC-706Mk2g in my pickup with a newer radio. The obvious choice was a IC-7100 as it has all the same connectors, including that for the AH-4 auto-coupler. As a bonus the radio is the same size and uses the same mount bracket. I had held off getting the IC-7100 for quite some time as I wasn’t convinced its ‘L’ shaped head was suitable for mobile use. Having owned it for a month I’m still not convinced but do like the radio and its odd shaped head unit is growing on me.
D-Star was not a selection factor for the IC-7100 purchase, but since the radio had this capability it seemed wrong not to give it a go 🙂 D-Star could be a news item in its own right, but suffice to say my experience thus far is not great. Several of the repeaters around the Bristol area have either migrated to alternate digital systems, don’t seem to be operational or are not connected to the D-Star network which undermines usefulness. As the memory channels in the radio are programmed with many, many repeaters, selecting one in the vicinity of my location whilst driving was tricky. But IC-7100 has the ability to receive NMEA data from a GNSS receiver and use geolocation information to identify repeaters in the vicinity of the radio that may be used. I was keen to give this a go but needed a source of NMEA data. Unfortunetly, the IC-7100 does not contain a GNSS receiver but it does present a three-pole, 3.5mm NMEA interface. The pins are: Ground, TxData and RxData.
Locating a suitable GNSS receiver was not as simple as it should have been as most nowadays implement either Bluethooth or USB as the physical interface rather than NMEA. However, some research identified the G-STAR IV from Globalsat. It does have an RS-232 physical interface and as NMEA is compatible with RS-232 at the physical layer it worked fine. However, the G-Star IV used a 6-pin mini-din plug rather than the more conventional 9-pin ‘D’ connector associated with RS-232 plus it required a +5V DC, 80mA power feed.
Clearly, it was necessary to construct an interface between the radio and the G-STAR IV receiver not only because the physical connectors were different but because a power feed was needed. After some investigation, I decided to use the +12V DC power from the truck batteries reduced to the level required using a small voltage regulator, 7805, circuit. This worked great providing a rock-sold power feed. A byproduct of connecting to the truck batteries was that the power was always ‘on’ and thus the GNSS receiver was powered and consuming current. So, my design included a power switch to remove the GNSS receiver from the power when not in use.
The interface unit was quickly assembled using a plastic case, suitable connectors and a small piece of Veroboard onto which the voltage regulator and some electrostatic smoothing capacitors were attached. A small red LED was also included for diagnostic purposes. This lit when power was being provided to the GNSS receiver. Once assembled it was tested on the bench using an oscilloscope to monitor the resulting NMEA data. This data appeared as a square wave of the correct frequency so I had a high confidence that all was working well.
The pictures in the article show the completed interface unit. I’m happy to answer any questions if someone has a need for something similar.
Footnote: Everything worked great on the bench, however, on migrating the unit to the truck I realised that Icom and rather annoyingly used a 3-pole, 2.5mm connector for the GNSS receiver. This meant the whole project was delayed whilst I sourced a connector which as it was at a weekend – Maplin Electronics. Making the cable really was a short job but it took another 4 to 5 hours to get everything working reliably as there was a weird mechanical failure on the centre tip of the 2.5mm connector resulting in an intermittent connection. I really don’t like Maplin these days and this experience only served to reinforce my view that their products are of the lowest quality.
Andrew
G0RVM
So, most members should be aware by now that the old 40m dipole has been removed and replaced with a new 40m dipole! The feedpoint 1:1 balun was also changed for good measure and sealed thoroughly for the winter.
But this is not the end of the work on the HF antenna, that was just task 1 😉 Task 2 consists of two activities and is planned for Spring 2017 once it dries and warms a little 🙂
Activity 1 will add elements for 30m and 20m expanding the 40m dipole into three parallel dipoles. This will result in a tri-band antenna that is resonant on 40m, 30m and 20m giving us a very useful antenna.
Activity 2 will replace the coaxial feeder between the radio room and the antenna feedpoint.
Today we have approximately 2.3dB of loss at 7.1MHz between the radio room and the antenna feedpoint. Assuming the coax is in the very best condition (which its not) and it’s RG-58C (Its an RG58 of some sort) this equates to about 54m of coax. That’s a 40% power loss on Tx and Rx. Replacing this with RG-213 reduces the loss to 0.9dB or a 19% power loss. An improvement of 1.4dB or 20% doesn’t sound much and its not but consider the situation at 14MHz. With RG-58C there is 3.2dB / 53% loss but using RG213 the loss is 1.3dB or 26%.
| Frequency | RG-58C | RG-213/U | Ultraflex-10 |
| 7.1MHz | 2.2dB | 0.9dB | 0.5dB |
| 10MHz | 2.7dB | 1.1dB | 0.6dB |
| 14.2MHz | 3.2dB | 1.3dB | 0.8dB |
Coax loss per 54m
To put this differently. The transmitter places 100W max into the feeder at 7MHz, 10MHz and 14MHz. With RG-58 the antenna receives: 60W, 54W & 47W respectively. Replacing with RG-213 results in: 81W, 77W & 74W. Using a better coax and one that does not cost much more than RG-213 the situation can be improved further. The overall difference of using something like Ultraflex-10 over RG-58 is definitely worth having and that is why activity 2 is so important.
The completed parallel dipole antenna will remain in its current location supported by the trees at either end. But supporting the end of the antenna elements will require two attachment points instead of the one we have today. Investigation has showed this is not a significant obstacle.
Thanks to Peter, G3LDO for the above diagram taken from his excellent book Backyard Antennas.
I really love this little movie from Essex Ham.
The Thornbury & South Gloucestershire Amateur Radio Club (TSGARC) has an active Foundation and Intermediate amateur radio training programme. We do this on Wednesday evenings from our clubhouse at the Chantry in Thornbury.
Myself G0RVM and Peter 2E0UAR attended the RSGB Convention in Milton Keynes this year. We left Bristol around 15:30hrs but got stuck in jam after jam. Towards the end of the journey ‘here comes another set of blue lights’ was becoming a bit of a joke! Fortunately we did arrive before the buffet dinner finished. It was a close thing tho as there where only a few slices of pudding pie left 😉
This was my first Convention and I must congratulate the RSGB for such a great event. The accommodation was good, the food and conference facilities excellent. It was educational to hear talks on a variety of subjects from speakers deeply knowledgeable in their subject. Access was free to those under 21yrs too – a great way of incentivising attendance by younger radio amateurs. Thank you RSGB.
In addition to the rooms hosting five parallel lecture streams there was a room with stands by Icom, Kenwood, the RSGB and of course, Martin Lynch who were the prime sponsor. Outside this room was a rather large trailer tower with HF antennas providing live signals for the exhibitors.
Proudly parked outside the front of the conference centre was Flossie, the mobile radio van of Camb-hams. Protruding through its roof was a Clark pneumatic mast with rotary HF dipole. The van looked excellent and a great way to get a portable setup to a distant location, setup and on-air with minimum fuss. As I have a pneumatic mast also it was good to swap experiences, finding we shared some of the challenges associated to these masts.
Some of my favourite talks over the weekend were:
I was really looking forward to “Best practice for VHF UHF DX” by Ian White GM3SEK but unfortunately Ian had to cancel. Maybe next year.
From the first talk identified above I learnt that we as radio amateurs are soon to have a ‘bend-pipe’ transponder in geostationary Earth orbit. Wow that is an amazing feat and I can’t wait till its operational. Amazing. The talk by Prof. Cathryn Mitchell was excellent being delivered superbly and hugely informative. It was interesting to hear how in 2015 space weather was identified in the UK National Risk Register with an impact of the same scoring as emerging infectious diseases, inland flooding, effusive volcanic eruptions, major industrial accidents etc. In fact, in 2015 the likelihood of a major space weather event occurring in the next five years was in the second from highest category.
I can thoroughly recommend attending the Convention and I know I will be booking my 2017 ticket as soon as they become available next year.
Andrew
G0RVM
Andrew, G0RVM will be giving a talk on VHF Propagation this Wednesday evening (5th Oct) starting at 19:45 hours.
The talk will be an introduction to the most common modes of propagation at VHF and their use by radio amateurs.
The RSGB 2016 Convention will be held at the Kents Hill Conference centre in Milton Keynes again this year on the 8th and 9th October. It is a weekend of lectures spanning many topics of interest to all radio amateurs. The RSGB have now released a draft programme for Saturday and Sunday which I have included here.
If you are under 21yrs you get free entry too. 🙂
Peter, 2E0UAR and I, G0RVM are going. Are you?
A short SDR video from a Friedrichshafen 2016 lecture. In the video Phil Harman, VK6PH outlines different SDR architectures their associated benefits/dis-benefits and has a look at future use of CUDA instead of FPGAs.
Strange hot weather but good conditions on 2m 🙂
Monday 5th and Tuesday 6th September very busy on 2m. At times tonight every 10kHz step and often 5kHz step was busy. Great to see/hear. Worked F8IQS in Caen on CW. His signal was easily 599!
Even bumped into another club member, Steve, M6JJV working contest from Berkeley 🙂
Andrew
G0RVM