Andy, G4JNT, has produced an interesting writeup of his 500KHz beacon project. This can be found at http://www.g4jnt.com/500kHz_beacon.pdf
Stewart/G3YSX
Monday, December 28, 2009
Sunday, December 27, 2009
Web SDR
A number of us are familiar with the webSDR at University of Twente. This is a multi-user SDR that runs on 80m, 40m and 20m. This has now been expanded to a world wide network. This program is a beta test, but the authors say that when these beta tests are successful, the software will be made available publicly on this site. That is very exciting news indeed.
Stewart/G3YSX
PS for a short time only one of the receivers is currently set up for 0..20KHz (it was set up for the Christmas Eve SAQ transmission on 17KHz), so if you have ever wondered what it's like down there, now is a good time to find out.
Stewart/G3YSX
PS for a short time only one of the receivers is currently set up for 0..20KHz (it was set up for the Christmas Eve SAQ transmission on 17KHz), so if you have ever wondered what it's like down there, now is a good time to find out.
Sunday, December 20, 2009
CARC Shack Familiarisation Wed 23 Dec
A very Merry Christmas to all readers of the CARC blog. As part of the work being conducted in the CARC shack and up on the tower we thought it would be a good idea to keep members up to speed on the changes. Therefore we propose a hands on session in the shack this Wednesday evening.
To start things off we plan to have a introduction for new members or a revision for existing members on the operation of the HF station. We'll be looking at the basics including operation of the FT1000MP, the role of the computer for logging and SteppIR antenna control. We'll also have a segment looking at how to tune the amplifier.
As there are still a few changes that need to be made, this will be a good chance to take on board suggestions for the future.
In the first place we'll concentrate on the simple modes, SSB and CW. In future sessions we'll look at the wide range of data modes which the shack can operate, also the VHF and UHF side of the shack.
I look forward to seeing you all there from 7.30pm onwards.
73
Mike
G0KAD
To start things off we plan to have a introduction for new members or a revision for existing members on the operation of the HF station. We'll be looking at the basics including operation of the FT1000MP, the role of the computer for logging and SteppIR antenna control. We'll also have a segment looking at how to tune the amplifier.
As there are still a few changes that need to be made, this will be a good chance to take on board suggestions for the future.
In the first place we'll concentrate on the simple modes, SSB and CW. In future sessions we'll look at the wide range of data modes which the shack can operate, also the VHF and UHF side of the shack.
I look forward to seeing you all there from 7.30pm onwards.
73
Mike
G0KAD
Saturday, December 12, 2009
CARC Oscilloscope Evening Wednesday 26th August
Following on from the success of previous CARC member-participating events, such as the RF power meter, Morse key and receiver evenings it was decided to devote an evening to that great and trusty friend of scientists, electronics engineers and amateur radio enthusiasts, the oscilloscope.
This magical piece of equipment comes in many forms and guises, from simple low budget models costing less than £200 through to high-end top of the range laboratory models, which will set you back thousands. In between of course is a vast range of oscilloscopes to satisfy all types of requirements. These are prices for new equipment. Most amateurs make do with second hand scopes to meet their budget and typical applications.
So what does an oscilloscope actually do? Well, for a start it has a calibrated screen (graticule) or display, (older models used a CRT, modern ones are LCD or LED) on which you can measure frequency, time and shape of a waveform. If it has more than one channel, and four channels are quite common, it will measure a number of waveforms at the same time so that you can for example compare input and output waveforms to and from an amplifier. It is an extremely useful piece of test equipment for signal tracing and faultfinding.
The oscilloscope permits signal voltages to be viewed, usually as a two-dimensional graph of one or more electrical potential differences in the vertical (y) axis plotted as a function of time or of some other voltage in the horizontal (x) axis. Whilst a scope displays voltage on its vertical axis, any other quantity that can be converted to a voltage can also be displayed. Some more advanced scopes are designed as a main frame with space to fit additional modules or sub-units such as RF and AF spectrum analyser.
The scopes on display on the club evening varied in age and specification and included products manufactured by Tektronix, Philips, Fluke, Gould Advance, Hameg, Hewlet Packard and not forgetting a very nice miniature scope designed some years ago for commercial manufacture by Adrian Wood G3VJM.
The evening was well attended, and with plenty of models on display for people to play with, (see photos below), plus some additional boxes such as function generators and signal generators to provide input voltages and waveforms.
John Longhurst G3VLH
Welcome to Ray M0RXJ and Janet 2E0JXR who stopped by for the evening
A nice Tektronics 465B
Adrian G3VJM with a scope that he designed as one of his first jobs as a young engineer
Richard G4ANN and Peter G3LEG checking out a nice storage scope
The Philips PM3240 - a popular scope in its day
Adding a spectrum analyzer to scope makes a useful piece of test equipment
Annual General Meeting Agenda : Wednesday 27th January 2010
Notice is hereby given that the Annual General Meeting of the Crawley Amateur Radio Club will be held on Wednesday 27th January 2010 at 20.00. The meeting will be held in the Clubhouse, Hut 18, Tilgate Forest Recreational Centre, Crawley.
The Agenda for the meeting is as follows:
1. Apologies for Absence
2. To approve the minutes of the Annual General Meeting held on the 30th January 2008.
3. To discuss any Matters Arising.
4. To receive the Chairman’s Report for the year ending 31st December 2008.
5. To receive the Audited Balance Sheet and Accounts for the year ending 31st December 2008, together with the Hon. Treasurer’s Report and to pass a resolution adopting the Accounts.
A copy of the Audited Balance Sheet and Accounts for the year ending 31st December 2008 will be available at the meeting
6. To pass a resolution fixing the subscriptions for the year ending 31st December 2009.
7. To elect for the year ending the 31st December 2009:
1. The Chairman
2. The Vice Chairman
3. The Hon. Secretary
4. The Hon. Treasurer
5. The Hon. Newsletter Editor
6. Up to five Committee Members
8. Any Other Business
BY ORDER of the Committee
Malcolm Harman (G3NZP)
Hon. Secretary
Note : All paid-up members for 2009 are entitled to attend and to vote at the meeting and to nominate Officers and Committee Members.
The Agenda for the meeting is as follows:
1. Apologies for Absence
2. To approve the minutes of the Annual General Meeting held on the 30th January 2008.
3. To discuss any Matters Arising.
4. To receive the Chairman’s Report for the year ending 31st December 2008.
5. To receive the Audited Balance Sheet and Accounts for the year ending 31st December 2008, together with the Hon. Treasurer’s Report and to pass a resolution adopting the Accounts.
A copy of the Audited Balance Sheet and Accounts for the year ending 31st December 2008 will be available at the meeting
6. To pass a resolution fixing the subscriptions for the year ending 31st December 2009.
7. To elect for the year ending the 31st December 2009:
1. The Chairman
2. The Vice Chairman
3. The Hon. Secretary
4. The Hon. Treasurer
5. The Hon. Newsletter Editor
6. Up to five Committee Members
8. Any Other Business
BY ORDER of the Committee
Malcolm Harman (G3NZP)
Hon. Secretary
Note : All paid-up members for 2009 are entitled to attend and to vote at the meeting and to nominate Officers and Committee Members.
CARC Visit to the British Vintage Wireless and Television Museum 31 October 2009
On October 31, Club members Stewart (G3YSX), Richard (G4ANN) with XYL Trisha, Malcolm (G3NZP), Brian (G0IOE) and Peter (G4FYY) enjoyed an excellent visit to the home of Gerry Wells, vintage wireless restorer extraordinaire at his home/museum in Dulwich South London. Gerry, now in his 80th year, has been collecting and preserving vintage wireless since the late 1960’s and opened his home as the Museum proper in 1974. Today, the Museum includes vintage television as well as wireless and the intervening years have seen the collection extend beyond the house into purpose built workshops and out buildings at the bottom of his spacious garden.
There is nothing unusual on the outside of the house to hint at extraordinary treasures that lay within. Gerry’s house is one in a large Victorian terrace and the outside appears like any other in the street. The first clue that things might be somewhat different inside came when Gerry opened the front door wearing a white lab coat and we glimpsed for the first time row upon row of wooden wireless cabinets occupying every visible surface in the hall and disappearing into shadows up the stairs. Gerry welcomed us into a large front room where we were surrounded by yet more wireless and early televisions (including the very first television) for a preliminary cup of tea and a chat. This was an opportunity to get to know a little about Gerry’s life-long passion for wireless that began when he was just 4 years old. We learned how Gerry started collecting and repairing old wirelesses that he could not bear to see consigned to the scrap heap. We also learned about Gerry’s commercial success in manufacturing valve audio amplifiers and in vintage wireless restoration. In the latter case, [quote] ”it was like shooting fish in a barrel”.
Throughout this discussion, my attention was drawn to the most enormous audio horn behind Gerry’s chair that, from where I was sitting, appeared to be growing out of the back of Gerry’s head. Seeing our interest, Gerry moved his chair to reveal a very large wind-up gramophone on which he put a ’78. The volume and fidelity surprised us all.
Gerry was born in this house that is now the museum and has lived here all his life. These days his bedroom is on the ground floor for reasons that became apparent when he led us up stairs past more mahogany cabinets on more shelves to more rooms where beds no longer had any fitting place. Shelves upon shelves of wireless lined every wall. The landings also carried their share. Surely, here must be at least one of every type of British wireless ever made. And being the passionate restorer that Gerry is, most if not all were in working condition.
The visit to the workshops in the garden revealed yet another plethora of wireless history. There were rooms of glass cabinets containing hundreds of valves and components. Another room was lined with cabinets of drawers bursting with every spare part imaginable. Some rooms were punctuated with wireless and TV chassis. Yet another room was given over entirely to mains transformers. At one time, Gerry manufactured his own ‘R’ valves in these workshops. Today, one of the larger work areas is a classroom equipped with test benches where invited school children are encouraged to discover the magic of wireless for themselves.
We eventually returned to the house for a final cuppa (courtesy of Trisha who seemed to be able to find her way around any kitchen) and a wind-up discussion on the bygone era of wireless. Thank you Gerry for making the day such an interesting one.
Special thanks to John, G3VLH for organising the day, (and who, in the event, wasn’t able to make the visit) and to Richard G4ANN for transporting us all in his people carrier.
See the Museum’s web site at http://www.bvwm.org.uk for a virtual tour of the museum and comprehensive background information.
Peter G4FYY
There is nothing unusual on the outside of the house to hint at extraordinary treasures that lay within. Gerry’s house is one in a large Victorian terrace and the outside appears like any other in the street. The first clue that things might be somewhat different inside came when Gerry opened the front door wearing a white lab coat and we glimpsed for the first time row upon row of wooden wireless cabinets occupying every visible surface in the hall and disappearing into shadows up the stairs. Gerry welcomed us into a large front room where we were surrounded by yet more wireless and early televisions (including the very first television) for a preliminary cup of tea and a chat. This was an opportunity to get to know a little about Gerry’s life-long passion for wireless that began when he was just 4 years old. We learned how Gerry started collecting and repairing old wirelesses that he could not bear to see consigned to the scrap heap. We also learned about Gerry’s commercial success in manufacturing valve audio amplifiers and in vintage wireless restoration. In the latter case, [quote] ”it was like shooting fish in a barrel”.
Throughout this discussion, my attention was drawn to the most enormous audio horn behind Gerry’s chair that, from where I was sitting, appeared to be growing out of the back of Gerry’s head. Seeing our interest, Gerry moved his chair to reveal a very large wind-up gramophone on which he put a ’78. The volume and fidelity surprised us all.
Gerry was born in this house that is now the museum and has lived here all his life. These days his bedroom is on the ground floor for reasons that became apparent when he led us up stairs past more mahogany cabinets on more shelves to more rooms where beds no longer had any fitting place. Shelves upon shelves of wireless lined every wall. The landings also carried their share. Surely, here must be at least one of every type of British wireless ever made. And being the passionate restorer that Gerry is, most if not all were in working condition.
The visit to the workshops in the garden revealed yet another plethora of wireless history. There were rooms of glass cabinets containing hundreds of valves and components. Another room was lined with cabinets of drawers bursting with every spare part imaginable. Some rooms were punctuated with wireless and TV chassis. Yet another room was given over entirely to mains transformers. At one time, Gerry manufactured his own ‘R’ valves in these workshops. Today, one of the larger work areas is a classroom equipped with test benches where invited school children are encouraged to discover the magic of wireless for themselves.
We eventually returned to the house for a final cuppa (courtesy of Trisha who seemed to be able to find her way around any kitchen) and a wind-up discussion on the bygone era of wireless. Thank you Gerry for making the day such an interesting one.
Special thanks to John, G3VLH for organising the day, (and who, in the event, wasn’t able to make the visit) and to Richard G4ANN for transporting us all in his people carrier.
See the Museum’s web site at http://www.bvwm.org.uk for a virtual tour of the museum and comprehensive background information.
Peter G4FYY
Wednesday, December 9, 2009
HF Antennas, ATU’s and other Homebrew Projects
(What every amateur needs to know on these important subjects) by Bob Burns G3OOU
On 28th October we were delighted to welcome the return of Bob Burns G3OOU. In addition to being an active designer and builder of HF and VHF radio equipment Bob is a retired professional engineer with wide experience in antenna and equipment design, and is an excellent speaker. Bob describes his interest as “Amateur Radio - HF CW Operation, Aerial developments, Heathkit equipment restoration and upgrades. Giving talks on RF Communications topics”. Which brings us neatly to this evening’s event……..
HF Multi-Band Dipole Antenna
Bob started his presentation with a description of his stub-loaded HF band dipole antenna. Experiments had originally started some years back with a classic G5RV and a 10W transmitter, and had rapidly moved on to open wire feeders instead of coaxial cable, with instant improvements in contact rates and signal reports. To address 1.8 MHz matching, loading coils and extra end sections were initially tried with some improvements over the basic G5RV. The original idea for the aerial shown below was found in articles in QEX & CQ magazines and has been further developed for the current location. The length of the top started at 132 feet and has been adjusted to obtain a resonance on 1.84MHz with the stubs in place, and will change with aerial height and location - it is now 125 feet overall. The stubs exhibit an extremely high Q, have little or no effect on bands where they are resonant in odd multiples of a quarter wavelength, and increase the overall electrical length of the aerial on all other bands. A Z-Match or other balanced output ATU is required.
The open wire feeders and the two stubs are made of 16SWG (1/16 inch or 1.6mm diameter) enamelled copper wires spaced 0.90 inch apart with insulators approximately 7 inches apart. The insulators should be UV resistant for maximum length of use in high sunlight locations. The aerial can also be loaded up on 50, 70 and 144MHz with an appropriate ATU (a VHF Z-Match is fairly easy to construct) although more of the radiation occurs from each end than from broadside. All in all, a good multiband aerial.
The original polythene insulators lasted some 5-7 years before becoming brittle from UV exposure. They are being replaced with 8mm diameter acrylic insulators which should last rather longer.
A half size version would work well down to 3.5MHz with an overall length top of 66 feet and stubs of 16 feet 6 inches in length.
Bob then went on to describe the construction of his open wire feeders. These are detailed more fully on his website http://www.qsl.net/g3oou/. The use of such an antenna led naturally on to antenna matching units and here Bob had some interesting ideas, based on the classic Z-Match design. First was to extend the low frequency coverage from 3.5MHz down to 1.8 MHz by switching in an additional inductor below the 80m – 40m coil. The second was the housing of the unit.
Antenna Matching Unit
G3OOU has built a dual Z-Match covering 1.8 - 146MHz in a Heath SB series cabinet with the appropriate metering and switching for multiple transmitters and aerials. Two SWR bridges are used, one for the HF bands and one for VHF. The meter and small knobs are from a Heath SWR Bridge and the front panel has been painted and labeled to match other Heath units.
The VHF section uses a very similar circuit to that of the HF unit although the component values are significantly less, C1 is a single section variable capacitor and HF switch sections S1a and S1b and coils L5 and L6 are not required although S1c and S1d are required. C2 is 35 + 35pF. Note that the minimum value of C1 on VHF should be a few pF so some form of selection may be required and the wiring should be a short as possible. L1 = 2t 1.2inches ID spaced 0.75 inches in total, L2 = 3t 1.0 inch ID spaced 1.0 inch overall. L1 positioned concentrically over L2. L4 = 2t 1.2inches ID spaced 0.75 inches in total, L3 = 3t 1.0 inch ID spaced 1.0 inch overall. L4 positioned concentrically over L3. All coils wound with 16swg enamelled copper wire. The layout of the VHF section is much more critical than the HF section so some adjustments may be required for each constructors own version.
SB-101 and SB-301 Rebuilds and Upgrades
Bob on his website describes one of his passions as “Collecting, updating and rebuilding Heathkit radio communications equipment”. He has several ongoing projects to improve the Heathkit SB-101 transceiver and SB-301 receiver designs to add extra modes and take more account of modern band conditions whilst retaining much of the original architecture. The obvious areas to address included dynamic range, spurious responses, WARC bands, Frequency and Amplitude Modulation, RF and IF selectivity, CW break-in and RIT.
Having used the 7360 beam deflection mixer in an SB-301 rebuild he decided to use those venerable but still very high performance valves as mixers in both the transmit and receive paths and one as a transmit balanced modulator. Bob had brought examples of these projects, which created a lot of interest from the members.
Practical
An interesting feature of most of the equipment Bob brought down was the use (or re-use) of Heathkit cabinets, and Bob doesn’t seem to let an opportunity of acquiring one at junk sales and the like. Newly acquired second hand units have their cabinets washed in the bath to get them clean. Sometimes it being necessary to use a kitchen lemon cleaner and a soft nail brush to remove stubborn grime. Certainly the ones we saw looked new.
Front panel paints are usually Revell or Humbrol - their nearest to "Heathkit green" being No 48. A good primer is required on aluminium. Rub down painted panel with wet and dry paper and flat wooden block.
Front panels of the finished equipment are lettered with dry transfers to give that professional finish. Letraset has restarted the manufacture of dry transfer lettering in white and black. This type of product is also available from Decadry, a Belgian company with UK outlets. Bob not liking gloss finishes on front panels, uses an acrylic clear matt or silk protective spray on top of the lettering.
For new metalwork the chassis aluminium is known as NS4 half hard which cannot be bent as it is too brittle but extremely strong. The G3OOU local supplier is Outlook Stockholders Ltd, Woodcote Grove Farm, Meadow Hill, Coulsdon, CR5 2QQ. Tel: 020 8668 9656. Web URL: http://www.outlookmetalstock.com/ .They can supply a bending grade as well.
Space constrains dictate that this is only a very brief summary of Bob’s presentation and you are urged to visit Bob’s technical site: http://www.qsl.net/g3oou/ for very full details of most of the projects briefly outlined here, circuits of the ATU’s and much, much more besides.
John Longhurst G3VLH
On 28th October we were delighted to welcome the return of Bob Burns G3OOU. In addition to being an active designer and builder of HF and VHF radio equipment Bob is a retired professional engineer with wide experience in antenna and equipment design, and is an excellent speaker. Bob describes his interest as “Amateur Radio - HF CW Operation, Aerial developments, Heathkit equipment restoration and upgrades. Giving talks on RF Communications topics”. Which brings us neatly to this evening’s event……..
HF Multi-Band Dipole Antenna
Bob started his presentation with a description of his stub-loaded HF band dipole antenna. Experiments had originally started some years back with a classic G5RV and a 10W transmitter, and had rapidly moved on to open wire feeders instead of coaxial cable, with instant improvements in contact rates and signal reports. To address 1.8 MHz matching, loading coils and extra end sections were initially tried with some improvements over the basic G5RV. The original idea for the aerial shown below was found in articles in QEX & CQ magazines and has been further developed for the current location. The length of the top started at 132 feet and has been adjusted to obtain a resonance on 1.84MHz with the stubs in place, and will change with aerial height and location - it is now 125 feet overall. The stubs exhibit an extremely high Q, have little or no effect on bands where they are resonant in odd multiples of a quarter wavelength, and increase the overall electrical length of the aerial on all other bands. A Z-Match or other balanced output ATU is required.
The open wire feeders and the two stubs are made of 16SWG (1/16 inch or 1.6mm diameter) enamelled copper wires spaced 0.90 inch apart with insulators approximately 7 inches apart. The insulators should be UV resistant for maximum length of use in high sunlight locations. The aerial can also be loaded up on 50, 70 and 144MHz with an appropriate ATU (a VHF Z-Match is fairly easy to construct) although more of the radiation occurs from each end than from broadside. All in all, a good multiband aerial.
The original polythene insulators lasted some 5-7 years before becoming brittle from UV exposure. They are being replaced with 8mm diameter acrylic insulators which should last rather longer.
A half size version would work well down to 3.5MHz with an overall length top of 66 feet and stubs of 16 feet 6 inches in length.
Bob then went on to describe the construction of his open wire feeders. These are detailed more fully on his website http://www.qsl.net/g3oou/. The use of such an antenna led naturally on to antenna matching units and here Bob had some interesting ideas, based on the classic Z-Match design. First was to extend the low frequency coverage from 3.5MHz down to 1.8 MHz by switching in an additional inductor below the 80m – 40m coil. The second was the housing of the unit.
Antenna Matching Unit
G3OOU has built a dual Z-Match covering 1.8 - 146MHz in a Heath SB series cabinet with the appropriate metering and switching for multiple transmitters and aerials. Two SWR bridges are used, one for the HF bands and one for VHF. The meter and small knobs are from a Heath SWR Bridge and the front panel has been painted and labeled to match other Heath units.
The VHF section uses a very similar circuit to that of the HF unit although the component values are significantly less, C1 is a single section variable capacitor and HF switch sections S1a and S1b and coils L5 and L6 are not required although S1c and S1d are required. C2 is 35 + 35pF. Note that the minimum value of C1 on VHF should be a few pF so some form of selection may be required and the wiring should be a short as possible. L1 = 2t 1.2inches ID spaced 0.75 inches in total, L2 = 3t 1.0 inch ID spaced 1.0 inch overall. L1 positioned concentrically over L2. L4 = 2t 1.2inches ID spaced 0.75 inches in total, L3 = 3t 1.0 inch ID spaced 1.0 inch overall. L4 positioned concentrically over L3. All coils wound with 16swg enamelled copper wire. The layout of the VHF section is much more critical than the HF section so some adjustments may be required for each constructors own version.
SB-101 and SB-301 Rebuilds and Upgrades
Bob on his website describes one of his passions as “Collecting, updating and rebuilding Heathkit radio communications equipment”. He has several ongoing projects to improve the Heathkit SB-101 transceiver and SB-301 receiver designs to add extra modes and take more account of modern band conditions whilst retaining much of the original architecture. The obvious areas to address included dynamic range, spurious responses, WARC bands, Frequency and Amplitude Modulation, RF and IF selectivity, CW break-in and RIT.
Having used the 7360 beam deflection mixer in an SB-301 rebuild he decided to use those venerable but still very high performance valves as mixers in both the transmit and receive paths and one as a transmit balanced modulator. Bob had brought examples of these projects, which created a lot of interest from the members.
Practical
An interesting feature of most of the equipment Bob brought down was the use (or re-use) of Heathkit cabinets, and Bob doesn’t seem to let an opportunity of acquiring one at junk sales and the like. Newly acquired second hand units have their cabinets washed in the bath to get them clean. Sometimes it being necessary to use a kitchen lemon cleaner and a soft nail brush to remove stubborn grime. Certainly the ones we saw looked new.
Front panel paints are usually Revell or Humbrol - their nearest to "Heathkit green" being No 48. A good primer is required on aluminium. Rub down painted panel with wet and dry paper and flat wooden block.
Front panels of the finished equipment are lettered with dry transfers to give that professional finish. Letraset has restarted the manufacture of dry transfer lettering in white and black. This type of product is also available from Decadry, a Belgian company with UK outlets. Bob not liking gloss finishes on front panels, uses an acrylic clear matt or silk protective spray on top of the lettering.
For new metalwork the chassis aluminium is known as NS4 half hard which cannot be bent as it is too brittle but extremely strong. The G3OOU local supplier is Outlook Stockholders Ltd, Woodcote Grove Farm, Meadow Hill, Coulsdon, CR5 2QQ. Tel: 020 8668 9656. Web URL: http://www.outlookmetalstock.com/ .They can supply a bending grade as well.
Space constrains dictate that this is only a very brief summary of Bob’s presentation and you are urged to visit Bob’s technical site: http://www.qsl.net/g3oou/ for very full details of most of the projects briefly outlined here, circuits of the ATU’s and much, much more besides.
John Longhurst G3VLH
Plans For VHF NFD 2010
Still flushed with the success in VHF 2009 coming first overall in the open section and band leader on 23cm, we must however no rest on our luarels and start planning now for 2010!!
To that end I have produced an outline design for the proposed 23cm antenna which I am cofident will not be beyond the capability of our very talented and resourceful team to construct on site. I attach a photograph therefore of what I had in mind. Go to it Chaps !!
73, de Derek Atter, G3GRO Hon Chairperson.
To that end I have produced an outline design for the proposed 23cm antenna which I am cofident will not be beyond the capability of our very talented and resourceful team to construct on site. I attach a photograph therefore of what I had in mind. Go to it Chaps !!
73, de Derek Atter, G3GRO Hon Chairperson.
HOW TOMATO KETCHUP (ALMOST) HELPED RAISE THE Q
During a visit to the Mc Michael Rally in the summer (12th July), my attention was caught by an old and very encrusted tuning capacitor. My cursory interest immediately triggered the words “that’s a pound, mate”, an offer I felt I couldn’t refuse. Then, after the deal was done, “I dunno what you’re going to do with it”. I replied with some quip about keeping a door open, but my impulse buy was inspired by a vision of restoring this fine piece of tank engineering to its former glory and putting it to good use in (yet another) magnetic loop antenna. The weight of the thing suggested it was made from something other than aluminium and since it showed no interest in a magnet, I deduced the construction was brass with some kind of alloy cast end plates.
First attempts.
Carrying this beast around the rally for the rest of the day made my arm ache but became a conversation piece with several sellers. One suggested that the vanes might even be silver-plated. Another suggested that a solution of baking powder might do the trick. However, when I arrived home later that evening, I decided to try Cillit Bang as a first line of attack. The dirt began to lift after about 20 minutes and the letters CYLDON CES.TR.25 became visible on the back plate. Then I tried the hot baking soda bath idea. Not a good move. This left the capacitor coated in a white powdery residue that seemed to seal in the remaining dirt and crud. My gut feel was that this needed something acidic.
Blood Everywhere
At the back of my mind was an idea to try a weak solution of hydrochloric acid (sold as ‘Brick and Patio Cleaner’), but how weak should the solution be? Previous experience showed that a 25% solution of HCl will etch a copper PCB in a matter of seconds. Something less potent was required. Then I remembered that vinegar is good for cleaning lime scale on taps etc. and I reasoned that a clinging vinegar based goo would be even better. There was a very old bottle of tomato ketchup the larder and I eagerly set to work shaking the stuff all over the capacitor, working it well between the vanes with a paint brush. The result resembled a bloody massacre and was very satisfying. I left the great red glob in a plastic bucket with a plastic lid to ferment overnight.
Stage 3 – Cleaning off the bloody mess
I looked into the bucket the following morning with less enthusiasm than the night before and realised that some serious cleaning was going to be required to clean off the abomination of blood clots. So I boiled up a water/vinegar solution in an electric kettle. This is a well-known method for de-scaling kettles and turned out to be a good guise to conceal my real motives from the domestic director. It also gained me a few house work brownie points. The downside was that boiling vinegar made the whole house smell like a chip shop and it was fortunate that I did this while the governor was distracted with other duties. I used 1 litre of Sainsbury’s Basics Vinegar (13p per 500mil bottle!) to 500mils of water and left the capacitor to soak in the hot solution for an hour.
It turns out that tomato ketchup is sticky stuff and great globs of it lodged stubbornly between the vanes in the most inaccessible places in accordance with the laws of Murphy. It took a cloth wrapped around a knife to dislodge the more persistent clumps. I began to feel that perhaps the tomato ketchup idea was not such a good idea after all.
Defeated to Disassembly
Having failed dismally in my attempts to short cut the cleaning process, I finally resorted to disassembling the capacitor down to the last nut and bolt and cleaning each part individually with brass/silver polish. This proved to be laborious task but revealed that the capacitor vanes were indeed silver-plated and that the end plates were probably cast from bronze. The final result of my labours is shown in Figure 2.
Was it a worthwhile exercise? Yes, I think so. The result is a fine, battle worthy split stator variable capacitor that should withstand well over 10kV when tuning a magnetic loop antenna. However, next time I’ll definitely pass on the tomato ketchup.
Peter G4FYY
First attempts.
Carrying this beast around the rally for the rest of the day made my arm ache but became a conversation piece with several sellers. One suggested that the vanes might even be silver-plated. Another suggested that a solution of baking powder might do the trick. However, when I arrived home later that evening, I decided to try Cillit Bang as a first line of attack. The dirt began to lift after about 20 minutes and the letters CYLDON CES.TR.25 became visible on the back plate. Then I tried the hot baking soda bath idea. Not a good move. This left the capacitor coated in a white powdery residue that seemed to seal in the remaining dirt and crud. My gut feel was that this needed something acidic.
Blood Everywhere
At the back of my mind was an idea to try a weak solution of hydrochloric acid (sold as ‘Brick and Patio Cleaner’), but how weak should the solution be? Previous experience showed that a 25% solution of HCl will etch a copper PCB in a matter of seconds. Something less potent was required. Then I remembered that vinegar is good for cleaning lime scale on taps etc. and I reasoned that a clinging vinegar based goo would be even better. There was a very old bottle of tomato ketchup the larder and I eagerly set to work shaking the stuff all over the capacitor, working it well between the vanes with a paint brush. The result resembled a bloody massacre and was very satisfying. I left the great red glob in a plastic bucket with a plastic lid to ferment overnight.
Stage 3 – Cleaning off the bloody mess
I looked into the bucket the following morning with less enthusiasm than the night before and realised that some serious cleaning was going to be required to clean off the abomination of blood clots. So I boiled up a water/vinegar solution in an electric kettle. This is a well-known method for de-scaling kettles and turned out to be a good guise to conceal my real motives from the domestic director. It also gained me a few house work brownie points. The downside was that boiling vinegar made the whole house smell like a chip shop and it was fortunate that I did this while the governor was distracted with other duties. I used 1 litre of Sainsbury’s Basics Vinegar (13p per 500mil bottle!) to 500mils of water and left the capacitor to soak in the hot solution for an hour.
It turns out that tomato ketchup is sticky stuff and great globs of it lodged stubbornly between the vanes in the most inaccessible places in accordance with the laws of Murphy. It took a cloth wrapped around a knife to dislodge the more persistent clumps. I began to feel that perhaps the tomato ketchup idea was not such a good idea after all.
Defeated to Disassembly
Having failed dismally in my attempts to short cut the cleaning process, I finally resorted to disassembling the capacitor down to the last nut and bolt and cleaning each part individually with brass/silver polish. This proved to be laborious task but revealed that the capacitor vanes were indeed silver-plated and that the end plates were probably cast from bronze. The final result of my labours is shown in Figure 2.
Was it a worthwhile exercise? Yes, I think so. The result is a fine, battle worthy split stator variable capacitor that should withstand well over 10kV when tuning a magnetic loop antenna. However, next time I’ll definitely pass on the tomato ketchup.
Peter G4FYY
Tuesday, December 8, 2009
Report on December 2009 Foundation Liciense Course
I pleased to report that the weekend's Foundation Course went extremely well, but only due to the invaluable support from fellow instructors Brian Gutteridge (2E0MBZ) and Ted MacDonald (G4TTY). Also with nine candidates taking the exam, the job of Invigilator and marking was only made possible with the help of Dick Lupton (M0RXZ).
Thanks also go to Derek (G3GRO) for coming on 20 metres to assist with the HF practical assessments and to Stewart (G3YSX) for helping out with some 2-metre QSOs
Eight students passed, and we welcome Ben Murray as a new member of CARC.
From left to right in the attached photo, names of the successful candidates are as follows:
James Stewart, Anthony Craven, Paul Raine, Nick Vaughan, Ben Murray, Daniel Richman, Steve Pantony and Maureen Comber
73 Malcolm
(G3NZP)
Thanks also go to Derek (G3GRO) for coming on 20 metres to assist with the HF practical assessments and to Stewart (G3YSX) for helping out with some 2-metre QSOs
Eight students passed, and we welcome Ben Murray as a new member of CARC.
From left to right in the attached photo, names of the successful candidates are as follows:
James Stewart, Anthony Craven, Paul Raine, Nick Vaughan, Ben Murray, Daniel Richman, Steve Pantony and Maureen Comber
73 Malcolm
(G3NZP)
CARC Fish and Chip Supper 2009
On Friday 4th December, CARC again celebrated the forthcoming Christmas with its annual fish and chip supper.
As you can see from the photographs taken by Adrian (G3VJM) a great time was had by all.
Especial thanks go to Richard (G4ANN) and XYL Trish for the repast and to Dick (M0RXZ), Ted (G4TTY) and Malcolm (G3NZP) for getting the club house into a state fit to receive our guests.
73, a happy Christmas and a healthy and wealthy New Year
Stewart/G3YSX
As you can see from the photographs taken by Adrian (G3VJM) a great time was had by all.
Especial thanks go to Richard (G4ANN) and XYL Trish for the repast and to Dick (M0RXZ), Ted (G4TTY) and Malcolm (G3NZP) for getting the club house into a state fit to receive our guests.
73, a happy Christmas and a healthy and wealthy New Year
Stewart/G3YSX
VK9XX QSO At Last!
Having chased the German VK9XX expedition on Chrismas Island way down in the Indian Ocean several times earlier this week on 40 metres CW with no success using my relatively low windom antenna at the home QTH, I was finally successful last night (25th Nov.) at the CARC Club station at my first opportunity of using the potent set-up with the new StepIR antenna with its 40m folded dipole on the Versatower working the DX station through the pile-up after only the third call. It is always difficult to decide where to park your call within the chasing pack which covers several khz. This time I was lucky and got a reply almost immediately despite not being able to turn the antenna for optimum signal due to a problem with the clamping of the beam to the stub mast thus leaving the antenna pointing approximately eastwards!
73, de Derek G3GRO
73, de Derek G3GRO
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