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
After last nights excellent and informative talk by Gary on Network systems in which a 5G was mentioned, there is a talk at the RSGB meeting in Redland on Monday 28th November by Prof Andrew Nix (University of Bristol) on the 5g network being tested in Bristol.The Network uses Rediffusion infrastructure in the form of underground cabling bought by Bristol University for experimental purposes many decades ago.
Please see the Link to the event below
Well Wedensday 23rd November was a suprising talk by Garry (G7NVZ) on Networking because it should have happened next Wedensday 30th November.
Thanks Peter (M6KVA) for pointing it out. Shame he left it until after the talk to let me know 😉
So next week will be a programme planning / discussion night.
Just wanted to post this piece regarding how heartened I was to see so many old Amateurs returning to the hobby. In the past 3 weeks I guess I must have seen at least two or three per week (two today Weds 23rd) coming back to the hooby having posted on the Amateur Radio FB page.
Don’t let anyone tell you that Amateur Radio is dying. Its definately not and I have a feeling that this may be the start of a resurgance of interest. Goes hand in hand with Andrews post on the Introduction to Amateur Radio.
Way to go!
Mark 2E0RKM
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.
Yesterday myself, Andrew, Graham, Rex, John and John spent the day at the Chantry renovating the club’s antenna systems.
Our plan for the day was to inspect the existing antenna systems, replace a section of coax between the attic and balun and to install and tune the new 40m dipole.
Condition of existing antenna systems
Existing 40m dipole balun
The overall condition of the existing HF antenna was good, but clearly the self-amalgamating tape has suffered from UV degradation. This doesn’t appear to be a major problem however the antenna has only been up roughly 4 years, so the problem would get worse over time.
Existing VHF Co-linear
While on the roof we also inspected the existing VHF antenna. It is clear that it is not ideally placed, being blocked by the chimney stack as well as the Chantry’s satellite dish.
Replacing the coaxial cable
One of the jobs for the day was to replace the RG-58 coax run between the attic space and the existing balun with some superior Westflex 103. In order to do this, Andrew and myself had to climb into the attic in order to cut the existing cable and solder new UHF connectors onto it. This allowed us to replace the cable between the attic and the antenna. On completion we measured the loss through the cable using a 50Ω dummy load and power meter.
New Westflex 103 cable run
We measured the loss at just under 3dB at 7mHz. We measured 60W at the end of the cable with a 100W input. Currently we plan to improve this loss further by replacing the rest of the cable to the shack
Andrew getting ready to test the loss through the new cable
Installing and tuning the new 40m dipole
With the new coax installed, we now set to work installing the new antenna. Before we could putt the new dipole in place we had to let down the existing antenna. As the two ends were attached to trees, I volunteered to put my tree-climbing skills to use and lower the existing elements
Rex giving us a hand getting up the trees
With the antenna on the ground we attached the new dipole and hoisted it into the air. Following some tests with Andrew’s MFJ antenna analyser we deduced that the elements were too long. Following several rounds of tuning we reached a state where everyone was happy with the performance of the antenna.
New balun installed
We sealed the connections with self amalgamating tape and headed to the shack to have a listen to the band.
Performance
| Frequency (mHz) | Resistance (Ω) | Reactance (Ω) | SWR |
| 7.0 | 60 | 8 | 1.2 |
| 7.1 | 78 | 0 | – |
| 7.2 | 112 | 0 | 1.5 |
We also tested the SWR in the shack and measured an SWR of 1.4 at 7.2mHz. A quick sweep of the band picked up some loud and clear Morse, although this may be due to a contest that was running at the time.
Conclusion
We hope that the new 40m dipole continues to deliver excellent results. There are still improvements that need to be made to the club’s antenna systems, including:
I’d like to thank Andrew G0RVM, Graham, Rex G4RAE, John M3EQQ and John M0HFH for giving up their time yesterday to help the club. I had a great day and learned a lot throughout the process.
Peter Barnes
2E0UAR
Well its now official…sent off this morning and I am registered on the Advanced course in Jan with Steve Hartley in Bath. Work now begins although I have been reading the RSGB book now for a couple of months – take it everywhere..works for me. Strangely liking the Maths.
Mark 2E0RKM
