TSGARC – A short history

In September 1987 I joined the Thornbury Radio Club as I had recently passed the Radio Amateurs Examination (RAE), in those days we met in the upstairs hall of the United Reformed Church (URC).

We had a variety of radios at our disposal and a large hall, so if conditions allowed we were able to have smaller meetings around the hall; CW in one corner, a radio operating in another and maybe a group stood nattering about all things Amateur Radio, oh and computers were just making themselves known so we were also looking at packet radio and amateur television broadcast and receive.

But now for a short history.  The Thornbury Radio Club was formed in early 1980 by Alan Jones G8AZT after running the first RAE in Thornbury.  This, however, was not the first club in Thornbury.  During the late 60’s and early 70’s there was a club that met, as it happens, at our current location, the Chantry.  This club obtained the callsign G4ABC but when the club ceased it passed to a couple of members in Chipping Sodbury where it remained unused.  But during the 1980’s it was offered to the newly formed Thornbury Radio Club.  During the club’s expansion in the 80’s members also joined from area’s a little further afield: Wotton, Dursley, Yate and Chipping Sodbury.  To reflect this larger catchment area the club changed its name to the Thornbury and District Radio Club.  But in the early 2000’s the government disbanded Avon county and replaced it with South Gloucestershire, so the club again changed its name to reflect this new division, becoming the Thornbury and South Gloucestershire Radio Club.

We were a club of about 40 members in the late 80’s and into the mid 90’s. Then we started to lose members, either because they were moving away or because the stage after retirement caught them up. So for the period from then until about August 2008 we struggled on with a nucleus of about 12 to 15 members, then we had to vacate the hall for refurbishment, so for nearly 9 months we were offered the HQ of GX0WOI the local Scout radio station at Woodhouse park. Finally in May 2009, we were able to move back into the newly finished URC Hall! But it was not a good period as the hall had been finished with aluminium clad insulation boards in the roof, a highly gloss laminate floor and shiny gloss walls, the echo and cold feeling made it impossible to do anything resembling radio activities, so we were forced to find alternative accommodation.

Finally in August 2009 we were able to rent on a long term but weekly paid rental the Tudor Room in the Community Association premises, this just worked with 10 members but was not ideal. Over a period of time we negotiated the installation of both VHF and HF antenna’s, so things improved and we were gaining new members. The search began again for a larger room, after talks with the Chantry staff, it was agreed that we could trial the Buckingham Room in November and December of 2012, finally, in January 2013 we negotiated a similar deal for this room as we had for the Tudor room although it was about £4 per week dearer. A team exercise one weekend saw us transfer the antenna feed points to the Buckingham room.

Today the Buckingham room is the home of the Thornbury and South Gloucestershire Amateur Radio Club (TSGARC) where it meets each Wednesday evening.  Click here for further information.  Being one large room it has space to accommodate the club which continues to grow and now has 35 members.

Many thanks to Alan G8AZT for information about the earlier clubs.

Stan G0RYM

Back to the Future. Part 2

I could not resist the name of this article, it seemed so obvious 🙂

I’ve been in the radio room this afternoon listening to the 2m VHF band, calling CQ on CW and listening to the beacons.  The Scottish beacon, GB3ANG in IO86mn near Dundee has been perfectly readable for extended periods which is pretty amazing for a station using a 4 element Yagi and 20 watts.

http://www.youtube.com/watch?v=j8TYKrmpfrY

Andrew
G0RVM

Back to the Future…

Back in the 80’s I received my first amateur radio license, a ‘B’ license as it was back then entitling me to use, if I recall correctly, bands above 30 MHz only.  We didn’t have 6m and 4m band allocations then so it meant 2m and 70cms were the bands of choice for me and the majority of other ‘B’ license holders.

So I started with 2m and 70cms SSB and my interest was soon peeked by space communications with Oscar 10 etc.  Those early Oscar’s were excellent as, if I recall correctly, they where in elliptical orbits which meant that they appeared to hang in the sky for some time, not shooting overhead as do satellites in lower more circular orbits.  Their transponders were just like big SSB repeaters in the sky and I worked all over Europe.  Happy days.  But working those Oscars was not that easy especially at Acquisition of Satellite (AOS) as they were pretty far from the Earth so a good station was needed.  My station grew to a 2m, 9 element crossed Yagi; a 70cms, 19 element crossed Yagi, both circularly polarised; azimuth plus elevation rotators and mast head preamplifiers.  The radio was a Yaesu FT-736 which I only sold last year…It was a wonderful radio.

Of course with those antenna’s it was perfectly possible to work terrestrial communications too.  I made contacts across the UK and Europe using sporadic E and Tropospheric propagation.  Those were exciting times indeed as not only was amateur radio new, to me, but it was such fun learning about different types of propagation, satellite communications and having great fun talking to people.

Ok, so by now some of you will be asking – what is the point of this article?  Well, bear with me…  I learnt Morse code and in the early 90’s received my ‘A’ license.  Soon afterwards the world changed as I started doing radio professionally for a few years.  This removed all interest to do amateur radio stuff when I got home from work.  Anyhow, time passed and I started to operate on HF talking to people all over the world – it was fascinating – I learn’t lots more.

With solar cycle 24 rapidly fading and with the real possibility that cycle 25 may be no better, probably worse, I’ve been looking back and found myself comparing my V/UHF experiences with those of HF.

My conclusion is that HF is fun, its pretty easy to work stations across the UK, Europe and further afield depending on your station.  Take a minute and think about that, especially the ‘depending on your station’ bit.  Do you have the space to erect, for example, a 9 element Yagi for the 20m band?  I’m seriously impressed if you do 😉  I bet most of us are using simple HF antenna’s and we are constrained by space, interference and the cost of erecting a high-performance HF station.  But move on up to VHF and things get so much easier.  I bet many of us could erect a 9 element Yagi for the 2m band and mount it several wavelengths above ground too….  Such an antenna will cost a tiny fraction of its HF equivalent; its small, light and easily rotated too.  Interference does certainly exist above HF but its nowhere near as bad.  But, FM repeaters and modes such as D-Star aside, VHF is dead these days I hear you say?  I cannot deny that it is much quieter than in the 80’s and 90’s but its still a happening place…  Its perfectly possible to work stations using phone and data modes across the UK and into Europe when propagation is flat.  All those exotic data modes are present and in active use too, people are exploiting Tropospheric propagation, meteor scatter, satellite communications, auroral propagation to name a few.

So its back to the future for me, the HF antenna is now down and until I receive my new VHF antenna I’ve elevated one of my original 9 element Yagi’s.  Already I’m hearing beacons GB3ANG in Scotland, GB3VHF in Kent and GB3SSS in Cornwall.  I even worked an old friend towards London using CW (RST:559) and Olivia with 20 watts.  Who says VHF is line-of-sight. 🙂

I guess you realise the message by now…. V/UHF is lots of fun, you can work DX, high-performance stations are much more achievable than on HF and you learn lots.  Amateur radio is so much more than HF, FM, repeaters, D-Star etc.  So, why not explore our higher bands?

Andrew
G0RVM

Royal Signals Visit

On Saturday 29th September the Thornbury and South Gloucestershire Amateur Radio Club visited the Royal Signals museum at Blandford Forum. The visit was instigated by Rex, Peter and John who provided CW coaching to the general public at the 2014 Bristol International Balloon Fiesta as part of a BBC World War one exhibit.

Royal_Sigs_Mus

A good day was had with many exhibits to be viewed from the early semaphore systems and the reasons why to modern day encrypted systems as used in Afghanistan.

The on-site Cafe served us very well with mid-morning snacks and an excellent three course lunch hihi.

In addition to the museum a well stocked gift shop allowed members to purchase gift items and also some equipment as used by the services today. Some members also visited the Camp shop where more equipment was available.

Royal_Sigs_Group

Four vehicles travelled to Blandford as a single vehicle and a loose format convoy carrying 12 people. My thanks to the drivers.

M0ZMB
Paul

 

Website directory

How many people know that our website has a members directory?  You do, great 🙂  But do you know what can be done with it?  No, read on….

Unsurprisingly our directory contains a list of all members and their contact information. 😉  All members receive a login account to the website when they become TSGARC members.  This account can be used to publish articles or news items, such as this, but also to access the directory.  When a website login account is created or removed the directory is also updated to ensure they are both aligned but unfortunately its a manual two-step process.  Website updates to create member accounts and ensure the directory is aligned are performed by the Secretary or Webmaster, if you spot a problem with the directory please let them know.

The directory lets members identify the contact information of other members.  But it also has two other nice features relating to email.  The first allows members to email another individual member directly via the website.  The second allows members to email an entire group of members.  Let me explain.  Each member has a role or position in the club.  Chairman, Treasurer, Webmaster are examples of positions but there are others too.  One really cool position is Members.  Emailing the Members position will send an email to all current TSGARC members.

Another example. Lets say you wanted to email the Treasurer but you’re not sure who that is.  Well, you can email the Treasurer position and let the directory and website work out who that is 🙂

In addition to simple information such as name, telephone, email etc the directory can contain other information such as a photograph.  So, if you have a photo you are invited to add it to your entry in the directory.  For an example see my entry 🙂

Access to the directory can be achieved by selecting the Member contact link from the TSGARC home page.  Its the first item on the SUB-MENU which is located towards the top right hand side.

Hopefully this short update is useful.

Andrew
G0RVM
Webmaster

RSGB national SSB field day

The RSGB SSB field-day takes place over the weekend of 5 & 6th of September.  I agreed earlier in the year to organise something but now realise I am not available that weekend so organising a field event is difficult.

Would someone else like to organise this event?

To take part in the contest our station would need to comply with these RSGB guidelines.

Andrew
G0RVM

TSGARC gets a radio room

TSGARC Radio roomAt his first annual general meeting (AGM) our chairman, Paul M0ZMB, stated he would like to see the club with its own shack.  So I started talking to the Chantry staff about a convenient store room located next to the Buckingham room where the club meets each Wednesday evening.  Unfortunately it was under a rental agreement with a local Girl Guide Company, who had no wish to either share the room with us nor move out.

It became somewhat demoralising on club evenings as those wishing to operate the club radios found it hard to hear their radio contacts due to others talking in the room, and vice versa.  I tried to reach the Guide Company by leaving a typed note under the door in February of this year.  It finally paid dividends, as in March a friend informed me that a) she was the responsible person for renting the store and b) she had just cleared out all their tents and camping equipment.  I presented myself at the Chantry on the following morning at 09:00hrs and commenced negotiations for the room.  I was shown it and had pointed out to me that there was “a serious damp problem”. 🙁

TSGARC Radio room prior to renovation

Undeterred I persevered with negotiations until June when proposals were presented to the Chantry which they accepted. 🙂 We would refurbish the room and paint as required for which we would get 2 or 3 months of rent free use until September when we would begin a monthly long term sole rental.  It took 2 of us about 6 days of effort removing damaged plaster only to discover there was no damp problem at all – it was mainly condensation from storing wet tents in a non ventilated room. 🙂

TSGARC Radio room prior to renovationWe repaired the damaged areas to a reasonable standard, added 2 coats of brilliant white emulsion on walls and ceiling, new carpet tiles on the floor and a dedicated electrical and data supply into the room.  Finally 2 weeks ago the furniture was provided by our chairman and moved in ready for operation, the chairman also rerouted the antenna feed points into the shack and all was ready for operation.  It only remains to box in the cables in the hallway where they pass across the ceiling.

At last, on the club night of the 29th July 2015 our first contacts were made from the new shack. It is worth adding here that we now have some 30 paid up members, all anticipating their use of the shack.

We have a working party planned to re-jig antennas and maybe add a new HF one sometime in the near future.

Those responsible for bringing this amazing project to fruition are Stan G0RYM the club Treasurer, Richard 2E0RES and Paul M0ZMB, for providing the furniture, moving the antenna’s and John M0HFH for transporting the furniture to the Chantry. The entire project has cost us less than £200, has added a new vitality to the club, and hopefully will allow us to take part in more field days, contests and generally have more contacts with Amateurs around the world.

My utmost thanks to Richard for all his help and for Paul and John for providing and moving equipment

Stan
G0RYM

Fox Hunting with a TDOA Antenna

In preparation for the pedestrian fox-hunt that happened a couple of weeks ago, I decided to take a look around for some antenna designs that I could build at home. I came across a blog post which showed off a Time Difference of Arrival (TDOA) antenna that someone had designed and built.

TDOA Antenna

A simple and effective fox-hunting antenna

How it works

The antenna relies on a timer, in my case a 555 timer, to generate an audible signal. I have mine calibrated to a frequency of 1kHz. This signal is level-shifted so that it goes between -4.5V and 4.5V. The use of a set of diodes causes the circuit to quickly switch between the two dipole antennas mounted to the unit (tuned to 145mHz). When the signal received by the two dipoles is out of phase, the receiver emits a tone. When the RF source is equidistant from both antennas (when you are pointing at the “fox”) the signals are in phase, causing the tone to disappear.

This design is fully functional regardless of how close you are to the source, providing an advantage over other antenna designs. The audible tone also provides a clear indicator of direction. However, the main issue is the fact that you get two readings, at 180° to each other.

Parts List

The list of components required is quite simple, so I had most of them laying around.

  • 555 Timer
  • 4.7K  Resistor
  • 100K Resistor
  • 2x 470Ω Resistor
  • 2x 0.01uF, 50V Capacitor
  • 10uF, 25V Capacitor
  • 0.001uF, 50V Capacitor
  • 4x 1N4007 RF Pin Diode
  • 2x 10uH Inductor Coil
  • RF Choke, 8 turns (salvaged from a motherboard)
  • SPST Switch
  • 9V Battery
  • 9V Battery Clip
  • Antenna wire (single core) or 4x Telescopic Antennas
  • 1.5M of RG-58 Coax

Build

When building the antenna, I used two blog posts for reference. You can find them here(pdf) and here. For some reason I ended up combining both of the designs, using the Bryonics.com design for the dipole circuits, and the 146970.com design for the rest of the circuit. This probably isn’t advisable, but it worked for me. Here is the circuit I used:

You can test the 555 timer circuit by hooking the output pin up to a speaker. You should hear a tone when power is supplied to the circuit. I started by breadboarding the timer circuit, and then moved it to veroboard for the final build. Once the circuit was complete, I zip tied the PTT button down on my PMR446 Walkie-Talkie, plugged the antenna into my Wouxun KG-UVD1P reciever, and tuned into the 446mHz signal. The antenna worked perfectly first time, providing a clear tone that faded out when I pointed the antenna at the radio.

For the physical construction of the antenna, I used some thick, single core, cable to make the dipole antennas, and mounted the whole thing on a 60cm long piece of wood. Lots of glue gun was used as I couldn’t be bothered to find some screws. I also drilled holes in the ends of the wood to poke the coax through. The dipole elements were attached using screws, and can be bent between a folded and deployed position.

CircuitEvaluation

I took the antenna out for the pedestrian fox-hunt that happened a few weeks ago. The antenna picked up the first signal very well, and the audio tone allowed me to find the direction of the transmission to quite a high accuracy. Unfortunately for me, I headed off into the wrong direction, as the antenna will give you two readings at 180° to each other. I had it running all evening, without the battery flattening. The RF choke fell off quite quickly, as I had not done a very good job with the soldering. I was also worried that the connection between the RX input coax and the board would break, so I would consider using a small connector in the future (such as an SMA socket). Overall the antenna worked very well, albeit sending us in the wrong direction! In terms of improvements, I would also like to mount the circuit board properly, and put it in an enclosure.

If anyone has any questions, or wants me to bring mine with me on a club night, just let me know.

-Peter Barnes

Cobwebb resonating. Part 2

Last week I wrote about recent work that identified where my G3TPW Cobwebb antenna was resonating on each of its five bands (20m, 17m, 15m, 12m and 10m).  Following on from that work G0MGM and myself spent a day recently adjusting my Cobwebb so that it was resonant around the SSB sections of each band and this article summarises that work.

The instructions supplied by G3TPW for his Cobwebb are excellent and identify the tuning effect of shortening/lengthening each dipole leg.  For reference I have identified these below:

Band Change
 20m  40kHz/cm
 17m  50kHz/cm
 15m  75kHz/cm
 12m  100kHz/cm
 10m  120kHz/cm

What the instructions omit is whether the dipoles interact, whether they should be adjusted in any sequence (e.g. 20m before 17m) and the impact of extending/reducing the gap between each dipole leg (spanned by the string) upon resonance.  These were all questions that were going through my mind prior to starting adjustment work and which drove the approach adopted.

The reactance, resistance and impedance data presented in Part 1 was collected using my MFJ-259b antenna analyser.  The MFJ-259b is a basic analyser and does not have any capability for data logging or data export necessitating the collection of data at multiple manually sampled frequencies.  This process was laborious and constrained the number of samples it was practical to collect and thus the accuracy of the overall result.  As I foresaw the need to resample each of the five bands for each single adjustment, it clearly, was not going to be practical to use the MFJ analyser.  Fortunately, a good friend, G0MGM, has a miniVNA analyser that can auto-sweep a band, log the results and export them in a CSV formatted file, which we later imported into Microsoft Excel. This capability made it practical to capture data samples, visualise and analyse the impact on each band of every change.

All graphs in this article may be enlarged by ‘clicking’ upon them.

Baseline

Because a different analyser was used, two new sets of baseline data were captured with the antenna at 3m and 8.5m above ground.  The lower height represents the  height of the antenna when my mast is retracted.  The baseline data presented in this article is that sampled at 8.5m.  Measurements were taken in the radio room at the end of the RG-213 coax feeding the antenna.

20m (Baseline)17m (Baseline)15m (Baseline)12m (Baseline)10m (Baseline)

It is interesting comparing the baseline results above with those captured previously using the MFJ analyser and presented in Part 1.  It should be noted that the comparison was performed with the antenna at the same height, with the same coaxial feeder, but on different days, that the weather was similar and that on both occasions the antenna and its surroundings were completely dry.  Furthermore it should be noted scales and colours vary thus some interpretation is required.

Adjustment

Based on experience of adjusting a Butternut HF-6V antenna, now made by DX Engineering, and a need to start somewhere, the decision was made to sequence adjustments from 20m, progressing to 10m.

After analysing baseline results it was decided to adjust the 20m, 17m and 15m elements.  Starting with the 20m element we reduced the length of each leg by 2cm and resampled data across each of the five bands.  Results showed that the change had a positive impact, raising the 20m resonant frequency by the amount expected with little or no change on any of the other bands.  This was good news and was the first indication that there was little interaction between the five elements. We then repeated the process removing a further 2cm from each leg.  Again the results were the same. i.e. the change on 20m was that expected and there had been little or no change on the others.  The graph below is the final result of the two changes.

20m band (Final)

Next the 17m dipole element was adjusted, reducing each leg by 2cm.  The process of sampling across all five bands was repeated and again it was found that the change had no significant effect upon the frequency of resonance for the other bands.  This really gave confidence that each element could be adjusted independently and that no sequence of adjustment was necessary.

Only one change was necessary and it raised the resonance point to the frequency required.

17m Band (Final)

Sticking with the original plan, although it was almost certain by now, the 15m element was adjusted reducing each leg by 1cm.  This raised the resonant frequency to that required.  This time some minor changes were noted to the point of resonance on the other bands, however, the change was very small.

The changes to 20m, 17m and 15m had necessitated the retying of the string between there individual leg elements.  The string between the unchanged elements had remained unchanged and it was now observed that there was noticeably more slack in the wire at the leg ends for those elements.  It was thought that this additional slack may be causing the very small changes observed.

15m Band (Final)

With changes complete the results from sampling each of the five bands were analysed and found to be acceptable so again the antenna was lowered and the length of string on the unchanged elements reduced so as to tighten the wires slightly.  The change in string length was small but afterwards it was noted the resonant frequency had raised a little on those band elements.  This was expected as reducing the gap between each leg end adds capacitance.

The results for 12m and 10m are shown below.

12m Band (Final)10m Band (Final)

Conclusion

Adjusting the Cobwebb proved to be much simpler than expected.  Results showed that each dipole element could be adjusted without impacting other elements and that adjustment need not take place in any particular sequence.  It was also found that frequency change per cm as specified by G3TPW in his instructions was accurate.

In writing this article it was realised that it would have been useful to capture the length between the ends of each element leg.  i.e. the string length.  When these can next be measured I will update this article with the information.  Describing the tautness of the elements is difficult.  They are neither taut nor slack, but ‘just right’.  i.e. there is a little movement of the wire.  Perhaps it is better to describe by stating that their tautness does not deform the cross shape of the fiberglass spreading arms.

Key to the success of the adjustment work was the miniVNA analyser and its ability to visualise and log sampled data.  Without it, what took approximetly 5hrs would have taken much longer.

Finally, thanks to Rob, G0MGM, for his assistance and his miniVNA and enjoy the bottle of sake 😉

Andrew
G0RVM