Meet the RSGB - Saturday 22nd Oct

An Invitation to:

Meet the RSGB

at

Normandy Centre, Denne Road, Horsham

at

1200 until 1700 hrs on 22^nd October 2011

In co-operation with

SCARF

(Southern Counties Amateur Radio Forum)

arranged by Mike Senior, G4EFO

RSGB DRM for Sussex.

Programme:

12.00 - 2.00pm meet have a drink and ploughmans lunch ( food by pre order only ) , visit other clubs represented.

2.00 - 3.00pm President of the RSGB: Talk and Q&A

3.00 - 3.15 comfort break

4.00 - 4.15 Mark Allgar from HQ: Talk and Q&A session

4.15 perhaps any final socialising

Hall to be clear by 5.00pm.

Cloth Cable

The following clever method of creating a retro look was posted to the QRP-L list and is reproduced with the permission of the author, Chris K4FH.

I've always liked the look of cloth cable over plastic insulated cable. I bought a pair of head phones that had a retro look and it used a cloth cable.

I've formulated a way I can simulate the look using paracord.

1) Cut a length of paracord

2) Using the butt end of a drill bit, insert the bit into the cord and use a lighter to singe the cord.  This keeps it from unraveling.  I use the bit to keep the cord from closing up.

3)  Run as many strands of #22 stranded inside the cord as you need.  

4)  Solder those to the connector

5)  Use the strain relief in the connector to hold onto the paracord.

After you get one end done allow the cord to relax and then do the other end.  This keeps it from being bunched up.

It is not a perfect replication of look and feel.  You can hold it and tell there is wire inside and room for more wire.  In 550 there is not much room for more than 3 wires.  If you want to make something bigger
try the larger dacron used as antenna rope.

I chose the silver ends with the springs because I wanted a nice look. I also made a cable for my J-38.  Since one end uses terminals I used heat shrink to bind the lead wires (with terminals) to the cord and make it look nice.  

In the audio cable in the pic I used a single pair of spare wire I pulled out of some CAT-5.

With this method you can make any length you want with any number of wires you need.

73,
Chris k4fh

Military Matters

As some of you may know,  V.M.A.R.S,  Vintage and Military Amateur Radio Society are a group of like minded people who have an interest in preserving and refurbishing military and civil radios.  Many of their members have fully fitted vehicles with all their radio equipment mounted within.  These vehicles can often be seen at Fairs and Shows throughout the country and their owners are only too glad to answer any questions you may have about their kit.

On the 10^th September they held an operating day near Gatwick Airport in the grounds of a house called Hunters Moon.  The owner of which is also a member and a licensed operator.  As I had the time I visited the site to see what was going on as my knowledge of Military Radios is limited.  I must add that I only located the site after ringing the organiser.

I was welcomed by the site owner who explained what the attendees were doing and where to park.  A few show vehicles and tea tent were located by the entrance which made the site more inviting.  Further up the field was a line of wire dipole antennas and another radio equipped vehicle.  At the end was a large tent for sleeping and cooking for some of the ‘crew’.  To the right was a wonderful display of military radios past and present all set out on various tables and in two vehicles.  Perhaps sets with names like No9, No18, Larkspur and Clansman amongst many others would have brought back memories for some of you.

A few of the display vehicles on show, all fully kitted out.  Yes, even a 6 pound anti-tank gun.

The wonderful display of radios on the tables, the army tent used for sleeping in, the Landrover overloaded with radio kit and finally an Austin Champ with a full Larkspur set up.  Note the Loop Antenna!

During my time there I asked many questions regarding the use of the radios and discovered that most of them will operate on the amateur bands easily.  Some of the radios are not as easy to operate as ours but will perform very well.  The quality of build is probably better in many respects as they have to endure harsher conditions than ours.  They could be operating in the Artic or a steamy jungle and are expected to perform with the same efficiency.

A few other members arrived and started to set up their antennas and rig layouts.  In the four hours I was there only one other ‘outsider’ looked in at the event, pity, because I felt that a bit more support from outsiders would help them along.

I enjoyed increasing my knowledge and made to feel very welcome by the members.

Give it a try next year.

BrianG

2E0MZB

CARC Programme 2011

Issue:         October 2011 Meetings:  Every Wednesday Evening commencing 8.00 pm Every Sunday Morning from 10.30 a.m. Main Meetings: 4th Wednesday in the month starting at 7.45 for 8.00pm (unless otherwise advised.) MONTH DATE TOPIC BY September Wed 28th FFT’s and the PC in your Shack. An overview of the new wave of mainly low cost computer-based test instruments, including Vector Network Analysers, oscilloscopes and spectrum analysers. October Wed 12th Wed 19th GB3MH A presentation on our newest and technically most advanced local repeater. This covers the site acquisition history, hardware and installation, with an explanation in simple terms of the network architecture and the way to access/operate through EchoLink/IRLP. Excalibur, SDR-IQ, broadband loop, and novel applications.  Malcolm G3NZP, David 2E0DDG & Richard G4ANN Mike Underhill G3LHZ November Wed 23rd Wed 30th Technical Systems in Air Traffic Control in the UK HARC/CARC Challenge.  This promises to be another fiendishly plotted but fun contest by our friends from Horsham ARC.  Do come along to take part in this fun evening. Alan O’Donovan G8NKM December Fri 2nd Wed 7th CARC Annual Fish and Chip Supper – put it in your diary! Introduction to Microwaves Part 2 by Derek G3GRO.  A follow-on to Derek’s excellent talk earlier in the year. January Wed 25th Annual General Meeting Another date for your diary!

CRAWLEY ROUNDTABLE

The 2011 Crawley Roundtable is on Sunday September 11.
As usual we will be running the UK Microwave Group annual construction contest for the G3VVB trophy. Please do bring along your constructed equipment and enter the contest. Entries do not necessarily need to have been constructed during the last year.
Do come along and support the construction contest and hear the talks.
Below is the finalised timetable:

Microwave Round Table - Sunday 11th September 2011

          Crawley Amateur Radio Club

10:00AM   Venue opens

12:00     Construction contest judging commences

13:00     Lunch (rolls, sandwiches, tea/coffee available)

13:30     Opening address by Derek G3GRO

          and the results of the construction contest

14:00     'An Experimental Transverter for 3.4 GHz' or "Fun with filters"

           - by Mike Scott G3LYP

14:45     'An Examination of Local Oscillator Noise'

           - by Chris Bartram GW4GDU

15:25     Break (tea & coffee available)

15:45     'A simple Diode RF Power Meter usable from HF to 6.0GHz'

           - by Peter Head G4FYY and Derek G3GRO

16:30     End of meeting

If you need further information, contact Derek Atter G3GRO or Chris Whitmarsh G0FDZ 

 





Access to Site:



The access road into Tilgate Recreational Centre

and the CARC Clubhouse (Hut18) is via the sliproad at the new traffic lights on

the southbound carriageway of the A23 (Brighton Road), just south of Crawley

heading towards Brighton, and about 200m from the Broadfield Football Stadium

roundabout which is well signposted.
The Clubhouse is accessed via a fairly narrow track for about

200m. Watch out for anti-traveller caravan chicanes then turn right at the 3rd

sleeping policeman!

· 

More Directions:   CARC Directions
· 

Roundtables:   General Info
Click here if

you do not see the main microwavers.org menu bar on the left

  

GB3MH

The GB3MH 2m analogue and Echolink/IRLP Repeater at Turners Hill was commissioned on 26th August at 18:00. This is working well as a local repeater but we are having some technical problems with the DTMF Echolink/IRLP signalling and the audio pass through from local RF to Echolink/IRLP. Work is underway to debug the problem and we will post an update when these issues are resolved.



The Technical details are:

CALLSIGN	GB3MH
BAND	2M
CHANNEL	RV50
OUTPUT	145.6250 MHz
RX1	145.0250 MHz
MODE	ANALOGUE
QTHR	IO91WC
LOCATION	W SUSSEX
NGR (view)	TQ337354
REGION	SOUTH-EAST
CTCSS	88.5 Hz
KEEPER	G3NZP
IRLP NODE	5877

The projected coverage is shown below.







Reports are appreciated and may be added as comments to this blog entry.



Stewart/G3YSX

NEW MEMBERS EVENING

CARC Meeting 27th July 2011



At the July Committee Meeting it was suggested by our training instructor Malcolm Harman G3NZP that we should run a "show and tell" evening at which all recent Intermediate students bring along their radio related project and spend 10 minutes or so explaining reasons for choice and how it works. The committee agreed that this was a good idea and it was left that Malcolm should liaise with the members concerned.



Part of the RFC /RSBG Intermediate Exam involves a whole series of practical assessments of which the Radio Related Project is just one. Nevertheless it's the most interesting because it's down to the student to agree with the Instructor a sufficiently challenging construction task to be assessed as part of the course work.



This would accomplish two things. Most importantly it would offer an opportunity for others to get to know our new members better and personally welcome them into the club. Secondly it will provide a very interesting evening of mini-talks.



We had at least three Intermediates confirmed and two possibles, dependent on work commitments, each kindly agreeing to make a short presentation on a project they have built.



On the evening we had three new members, Ian Coulson, David Davies and Barry Denyer-Green. Two other members who had hoped to be available and to give presentations, Biton Walstra and Graham Parsons, had work commitments and sent their apologies. Hopefully they will have other opportunities in the coming weeks.







The Valient 3 - Ian, David and Barry



Ian bravely started the ball rolling with a small FM receiver/tuner kit that he had built. This covers 1.5 to 100 MHz and after a few initial problems and “a prod with a sharp stick” burst into life. Ian explained that amongst the difficulties that he experienced were that the kit was now obsolete and the amount of backup from the supplier was pretty limited. However he has spent more than half a century using a soldering iron and the practical aspect held no real fears for him.



Next up was David Davies. He described a low-ish cost alternative to the Kinetics SBS-1 radar receivers that currently retails for around £400. David works at Redhill Aerodrome and there was a need for three such receivers in order to receive the ADB-S (Automatic Dependent Surveillance Broadcast) signals from approaching light aircraft and to triangulate their bearings. He found a kit designed and marketed by a German amateur which sold for some 50 Euros and decided to give this a try. The result was a very neat and cost-effective little unit, which plugs into the USB port of his MacBook. Operating on the appropriate 1090MHz channel frequency, and running the appropriate software which includes PlanePlotter, (a program for Windows that provides a radar-like display of aircraft derived from ADS-B position reports), and with a makeshift antenna David was able to give a live demonstration of the receiver with the screen rapidly filling up with aircraft ID signals. Fascinating.







David's radar receiver









David with the read out from his radar receiver



Barry, last but by no means least, had two projects for us. Starting with his PP3 - powered solid-state regenerative receiver this was a very neat 3-band radio covering 80, 40 and 20 metres, and will have brought back happy memories to many of us who similarly cut their teeth on these simple but effective designs. Barry spends quite a lot of his working life staying in hotels and this little receiver with a length of wire strung out of a window keeps him in touch with the world.







Barry's receiver and signal generator



Barry’s second piece of home brew was an RF signal generator with switched bands and housed in a small Eddystone-type aluminium enclosure. Very useful for aligning and fault-finding on other receiver projects.







Barry with his signal generator



This is only a very brief write up of the various projects and in no way does justice to the amount of work that these brave chaps put into building and de-bugging their projects.



Thank you, Ian, David and Barry for your excellent presentations, which made for a most enjoyable evening.



John G3VLH

Electronic tutorials

Adrian, G3VJM, draws our attention to an excellent site on basic electrical and electronics theory. This site looks like it will be useful to those studying for their Advanced License.



Based in Northern Texas, OpAmp Electronics delivers a series of free, comprehensive, and detailed tutorials of the basic fundamentals of electricity and electronics authored by Tony Kuphaldt. Among the 59+ chapters on DC, AC, Semiconductor, and Digital theory to guide you through your studies or electronic projects, please feel free to navigate the different segments of our site for additional electronics assistance.



The electronic tutorials found on this site were written by Tony Kuphaldt, and can be found at http://www.opamp-electronics.com/tutorials/index.htm

Another Active Antenna

Ron, G4GXO recently drew the attention of the QRP community to an engineering report released by the US government describing a Voltage Probe Antenna (VPA) Design 5 kHz to 500 MHz. The design dates back to April 1973 and was produced by GTE.



The objective of the overall development of the Voltage Probe Antenna (VPA) was to produce a miniature, mast mounted, omni-directional antenna that would operate over the band from 5 kHz to 500 MHz for communications reception. In addition, it was desired to optimize the antenna at 150 MHz and 400 MHz.



The report of the report can be found at:



http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=ADA030178



The report itself is at: http://handle.dtic.mil/100.2/ADA030178



As Ron reports, "The images but they are all "washed out" by the copying process. However, there are some illustrations of the test range which suggest a short pole (about a couple of feet high) onto which the antenna is mounted. At the base of the pole is a ground pane to simulate salt water - presumably this aerial was for covert use when the submarine was at snorkel/periscope depth. The aerial element appears to be small, probably around 30cm high by 15cm diameter. There is also mention of the "probe" being a bi-cone, a wideband VHF/UHF antenna - note that one of the design objectives was to provide LF to UHF coverage optimized at 150MHz and 400MHz; VHF aviation/marine and UHF aviation bands?"







The circuit is quite interesting since at first glance it looks like a conventional FET input active antenna similar to the PA0RDT design that we are all familiar with, with the modification that an MMIC is used in place of a transistor in the second stage. However on a second look (an reading the text) I see that there is an interesting subtly to quote from the report:



"The amplifier consists of two active stages; the first stage consists of a low-

noise field-effect transistor used for active impedance matching, and the second stage consists of a low-noise microwave integrated circuit that provides actual voltage gain.



"The field-effect transistor is operated in a cource-follower(sic) configuration with an additional gate~to-source capacitor C2 added to alter the input impedance characteristics and to improve high-frequency performance. At low frequencies where the gate and source of the transistor have an in-phase voltage of nearly equal magnitude, capacitor C2 essentially disappears from the circuit as very little voltage appears across it. This provides a very high impedance at lcw frequencies that approaches 1.5 megohms shunted by 4 pF.



"At high frequencies where the voltage on the source of the transistor begins

dropping and the phase shift becomes important, signal voltage begins to develop

across capacitor C2. This provides a signal path around the first-stage transistor Q1. As the frequency goes progressively higher, the impedance of capacitor C2 drops quite low until the input impedance of the amplifier approaches that of the second-stage amplifier A1. At high frequencies (above 100 MHz), the first-stage amplifier Q1 adds very little to the performance of the circuit.



"Diodes CR1 and CR4 provide burnout protection for the input of the amplifiers. Resistor R3 is provided to suppress transients on the output cables so the voltage limitations of the output capacitor are not exceeded."



The amplifier performance specifications, measured in a 50-ohm test system,

are given in the report are shown below:



Frequency Range 5 kHz to 500 MHz

Gain 11 dB +/- 1dB

Noise Figure 8dB at 150 MHZ and 400 MHZ

Output Power

(1 dB Compression) 6 dBm

Intercept Point

(Third order) 17 dBm

DC Power 45 mA_at +12 Vdc

15 mA at -12 Vdc

Physical size 1x1x0.5 inches



It would be interesting to redesign the antenna using more modern components for use as a wideband scanning antenna.



Stewart/G3YSX

Sine wave Oscillators

Steve G0XAR recently posted a pointer to a very interesting Texas Instruments tutorial on the threory of sine wave oscillators on a course materials page at University College of Santa Barbra.



The paper can be found at:

http://www.ece.ucsb.edu/courses/ECE137/137B_S11Theo/oscillators.pdf

CARC Training Courses

Malcolm, G3NZP reports that currently he has two. possibly three, interested candidates for the proposed Foundation Course now set for weekend 15th/16th October, commencing 09.30 at Hut 18, Tilagate Recreational Park, Crawley. Closing date for entry Friday 23rd September. Please put any other candidates in touch with Malcolm.

Malcolm also proposes to run an Advanced Examination on Monday 5th December at 19.00 which will be preceded by four of five weekly seminars to help bring students up to speed. Application for the exam to Malcolm by 7th November.



Malcolm G3NZP is QTHR and can be reached on 01342 713573.

Stewart/G3YSX

FUNcube Dongle as a Radio Telescope

A number of club members have a FUNcube dongle SDR receiver and so I thought that I was draw attention to an interesting post by M0TFO on funcube@yahoogroups.com.



M0TFO draws attention to a Radio Astronomy paper describes the use of the AMSAT-UK FUNcube Dongle Software Defined Radio as part of a Radio Telescope. In the paper Dr David Morgan of the British Astronomical Association Radio Astronomy Group (BAA-RAG) describes how he used the FUNcube Dongle as the heart of a Radio Telescope operating on 1420 MHz.



He concludes that "A newly available SDR component has been shown to be very capable of acting as the heart of a simple and inexpensive three component radio telescope.".



You can download the paper `Experiments with a Software Defined Radio Telescope' by Dr David Morgan at http://www.britastro.org/radio/projects/An_SDR_Radio_Telescope.pdf



Some interesting, but more general radio astronomy projects can be found at http://www.britastro.org/radio/projects/otherproj.html



I have yet to explore the group, but BAA-RAG Yahoo Group http://groups.yahoo.com/group/baa-rag/ looks as if it might be worth joining.



Stewart/G3YSX

Military Maritime Communications

CARC MEETING 29th June 2011

By Dr Andrew Gillespie Technical Director Thales Communications





Reliable networked communications to maritime platforms represents a significant technical challenge. Dr Gillespie’s presentation focused on the problems faced in providing Web Services over low bandwidth, intermittent bearers such as HF and V/UHF radio.









Andrew began by outlining the background to HF communications and its present needs in military and professional applications. Historically HF communications has been widely used by military, commercial, government, aid and relief organisations. However, the end of HF as a usable technology has been forecast for many years. The advent and growing usage of satellites at one time seemed to further hasten the demise of high frequency communications. To misquote Oscar Wilde “news of its death is greatly exaggerated”.



For all its long distance capability HF is susceptible to noise, interference, ionospheric variabilities and disturbances and other limiting issues that are not present in satellite communication. However, the major drawback of satellite for military comms is cost. Satellite time and bandwidth are expensive, and alternatives are needed to provide a common platform for member states, in NATO, for instance.



For some years there have been other alternative HF networking protocols in use. Some of these rely upon Automatic Link Establishment (ALE ) using the FED-1045 or MIL-STD 188-141B standard protocols. ALE uses anti-collision methods, multiple channels, and channel occupancy checking to avoid interference in multi-user HF spectrum. If one channel is busy, it moves to another one until it finds a good one.



Within the military environment any alternative system must be capable of interoperability across the organisation(s), and this requires agreement of technical standards. Within NATO STANAG is the NATO abbreviation for standardization agreement, which sets up processes, procedures, terms, and conditions for common military or technical procedures or equipment between the member countries of the alliance.



Each NATO state ratifies a STANAG and implements it within their own military. This provides common operational and administrative procedures and logistics, so one member nation's military may use the facilities - stores and support for instance - of another member's military. STANAGs also form the basis for technical interoperability between a wide variety of communication and information (CIS) systems essential for NATO and Allied operations.



The NATO standard STANAG 5066 is used extensively for HF military, government and commercial data communications. STANAG 5066 is a NATO specification for running data applications over HF Radio. Operating over an HF modem STANAG 5066 provides an interface for data applications to use and share an HF modem. It provides core data link services to enable applications to operate efficiently over HF radio, and specifies a protocol that enables a clean separation between applications and modem/radio level.



Over time the expectations of immediate results have already been realised by the Internet and mobile phone technology, where the press of a button brings instant information and communication without any need for operator intervention, knowledge or experience. HF radio has traditionally relied on the knowledge, experience and skills of operators to select optimum frequency, data rate and other parameters to optimise link performance. Any viable modern HF system must de-skill the operation: thus operation to the user seems fast and automatic.



This was a most interesting update on modern data comms from a military/defence perspective and, given its many complexities, was presented in an easy to understand way.





John Longhurst G3VLH

CARC MEETING March 2011

An Introduction to Microwaves Part 1 by Derek Atter G3GRO

For various reasons, it was necessary to have a change of programme for the March meeting. Without a speaker we had to find a replacement at relatively short notice. As valiant as ever, Derek G3GRO stepped up to the plate. His presentation, originally scheduled for the May meeting was titled “An Introduction to Microwaves - Part 1.”

Now as many of us know, in addition to his amateur radio activities, Derek in his working life was a professional microwave engineer and he has a wealth of knowledge and experience at his fingertips built up over many years to pass on in this specialised area of communications.

The microwave spectrum is usually defined as the frequency range from 1.0 to 300 GHz, with most common applications being within the 1 to 30GHz range. The microwave spectrum is divided up into a series of sub-bands as shown in Table 1. below.

L band 1 to 2 GHz
S band 2 to 4 GHz
C band 4 to 8 GHz
X band 8 to 12 GHz
Ku band 12 to 18 GHz
K band 18 to 26.5 GHz
Ka band 26.5 to 40 GHz
Q band 30 to 50 GHz
U band 40 to 60 GHz
V band 50 to 75 GHz
E band 60 to 90 GHz
W band 75 to 110 GHz
F band 90 to 140 GHz
D band 110 to 170 GHz

Table 1. Microwave Spectrum sub-bands

As a conversion guide, a 30-centimetre wavelength is equivalent to 1 GHz (to convert from frequency to wavelength, divide the speed of light 300,000,000 meters per second by the frequency in cycles per second to get metres of wavelength).

Starting with the basic means of getting a microwave signal from A to B Derek introduced us to coaxial lines in various forms, suspended strip line (or tri-plate line), printed circuit micro-strip, waveguide and the Goubau Line. Waveguides included rectangular and circular, size adapters and coax to waveguide transitions.

Derek suggested three typical routes for the newcomer to start on microwaves -
• Wideband Gunn Oscillator/DRO
• G4WDG Modules
• Mix and Match surplus units

Klystrons are used as amplifiers at microwave frequencies to produce both low-power reference signals for superhet radar receivers and to generate high-power carrier waves for communications. The klystron is capable of amplifying or generating microwaves with greater control and precision than is available from the magnetron.

Reflex Klystron Oscillator

Early amateur 10GHz Microwave Power source. Used as Local Osc.and FM TX - approximately 10mW RF output. Originally developed in WW2 as Radar LO.


Magnetron
The “secret weapon” of WW2 this high powered vacuum tube enabled the Allies to develop high power microwave Radar and can produce up to 5 MegaWatts of Pulsed RF. In addition to radar and communications use the magnetron is used in domestic microwave ovens.

Travelling Wave Tube (TWT)
The TWT is employed to amplify radio
frequency signals to high power, usually in an electronic assembly known as a travelling-wave tube amplifier (TWTA). A common use of TWTAs is as an amplifier in satellite transponders where the input signal is very weak and the output needs to be high power.

Travelling Wave Tube (TWT)

Input RF at (2) continuously interacts with, and velocity modulates travelling electron beam, to produce much-increased RF at output (6). - Capable of very high gain up to 50dB +. (4) is attenuator to suppress backward wave. Basis of BWO oscillator

The TWT was a very popular device on Amateur microwave bands before availability of transistor PA’s. G3GRO used TWT at Masthead on 10Ghz fed with 2.4kV helix voltage.


Gunn Oscillators 

 The “Solfan” Gunn diode oscillator & Mixer assembly ex- Doppler intruder alarm is readily convertible to 10Ghz ham band and popular for wideband FM or ATV use. Around 10milliwats RF output

Transmission Lines are the coupling devices used for transferring a microwave signal from one part of the transmitter, amplifier or other equipment to another part of the circuit. Transmission lines come in number of forms from coaxial cable through to waveguide, depending on the application.
This was an extremely interesting presentation, and an invaluable introduction to this highly specialised area of communications. We look forward with anticipation to Part 2 of Derek’s talk later in the year.

John Longhurst G3VLH

Another 2m Contest from CARC Hut 18

Following the recent success of Brain and Howard taking part in a 2m QRP contest from the CARC clubhouse, I was inspired to try my hand.

I had intended to spend the majority of the evening of Tuesday 5 July sorting out the equipment returned from Kent after the RSGB VHF NFD contest of the previous weekend. However it occurred to me that I had everything to hand to make a good stab at that evening's RSGB 2m UKAC contest. These run every Tuesday evening of the year with the first Tuesday of the month being 2m, the second 70cm, the third 23 and 13cms, the fourth Tuesday for 6m and when there is a fifth Tuesday in the month this is used for 4m.

You can find the calender here http://www.rsgbcc.org/vhf/

The rules are fairly simple with the normal 1pt per kilometer worked multiplied by the number of unique locator squares of UK contacts i.e. IO91, IO92, JO03 etc. You can of course work European stations and these do count for points (the number of km) but their locator squares are not counted towards the multiplier. This is deliberately designed to encourage UK stations to work each other and increase activity, at the same time giving stations all over the UK a fair chance at doing well.

So instead of tidying the clubhouse (don't worry I did that on Wednesday 6th), I dug out my old IC275H and the 400W 2m PA, hooked it all up to the club 17element beam and tested it out. All seemed to work OK despite not having the masthead preamp which has been repaired but is awaiting fitting to the tower. I didn't bother with a CQ caller as the contest is only 2.5 hours long, starting at 1900Z and finishing at 2130Z. This proved to be the right decision.

Unfortunately neither did I have my adapter lead with microphone preamp to allow the normal Heil HC4 headset to be used with the IC275. Most Icom radios supply 8V on the microphone pin which at a minimum need a capacitor in line to prevent damage to the Heil mic insert. This 8V is present to power a mic preamp built into Icom microphones. This means that the level of other non Icom microphones is too low and needs an additional microphone preamp.

I ended up just using the Icom fist mic that comes with the radio.

As I had little idea how well or badly the club site would work for a 2m contest I wasn't sure how many QSOs were likely. I opted to use the Minos logging software written specifically for RSGB VHF contests by Mike Goodey, G0GJV. This excellent piece of software has all the contests preloaded ensuring that they are scored correctly. Simply enter the station information such as your call, your locator etc and the software does the rest. A good tip is to ensure that your PC clock is correct. Minos uses this clock to log the QSOs.

You can find documentation and downloads here http://minos.berlios.de/

Operating as G6RC, the contest itself proved to be very enjoyable. At times it was more like HF than VHF with 3 or 4 stations replying to a QRZ call. In total I worked 131 QSOs in 2.5 hours with ODX being MM1DDD/P at 598km. Also worked were GI, EI, GW, F, DK ON and PA. I deliberately didn't spend much time with the antenna pointing at Europe but in hindsight it might have been worth a short period bagging the big stations at 700+km for extra points.

The claimed scores for the contest can be found here

http://www.rsgbcc.org/cgi-bin/claim.pl?Contest=144MHz%20UKAC&year=2011

At the time of writing, with the execpition of Bryn, G4DEZ and Dave GI4SNA both of whom have excellent VHF QTHs, equally good equipment and are seasoned operators, the other stations above G6RC are all portable, a huge advantage in a VHF contest.

So lessons learned.

The CARC clubhouse is a great site for UK VHF/UHF/SHF contests.

The IC275H is a great receiver. I barely suffered from QRM despite many other big stations on the band. It is certainly my radio of choice.

I need to be better at working pileups. Picking the full call, first time from the melee will certainly speed up the QSOs leaving time for even more.

Get the headset working properly. Bring the right lead.

Move the computer screen down making it easier to operate the logging. The radio doesn't need much tweaking and can easily sit off to the right of the computer screen.

So the next 2m UKAC contest is on Tuesday 2nd August. I hope to be at the club to give that a go. I will have had knee surgery the week before so it might not be possible. If anyone else is interested in this or other Tuesday evening events, let us know.

Alternatively if you fancy a portable entry that too can be great fun. Remember to claim the score both individually and for the Crawley ARC.

73
Mike
G0KAD

Summer Social Event Saturday-23rd July 2011

FOLLOWING recent the Successful Club Dinner Held in May,

The Hon. President and the CARC Committee Extend an

Invitation to Members, XYLs/Yls and Family Members

to join them in a new Venture :

“The President’s Lunchtime Garden Party”

To be Held at the QTH of the Hon. President, Derek Atter, G3GRO at No.1 Little Crabtree, West Green, (Off Ifield Avenue ) 12-00 for 12-30 until approx 4-00 pm

A Substantial, Mainly Cold Buffet Lunch will be served including
with it a Glass of Wine and Soft Drinks etc. plus afternoon tea later.

Proposed Menu :

Assorted Sandwiches :
Brown & White Bread With the following fillings :
Cheese & Home-made Chutney, Ham & Tomato,
Egg & Cress Mayonaise, Coronation Chicken.

Crudités :
Batons of Carrots, Cucumber, Celery, Peppers,Spring Onion,
Cherry Tomatoes, Tiny Pickled Onions.
Bread Sticks, Assorted Crispsands Savoury Biscuits

Dips :
1000 Island, Mild Curry chilli & Philadelphia Cheese
4-Cheese dip, Honey & Mustard

Hot Items :
Sausage Rolls, Barbecued Chicken Legs, Cocktail Sausages on Sticks
Mini Meatballs on sticks, Chicken, Bacon & Mushroom Vol-au-Vents

Deserts:
Old Fashioned Sherry Trifle; Chocolate, Strawberry & Cream Gateau

Cost per Head : £8-00
Bring a bottle if you fancy more than one glass of wine (If you are not driving !!)

It is planned that the event should take place in the garden but if we happen to
be unlucky with the weather, we plan to transfer inside to the conservatory and
sitting room etc. - even, God forbid, to the shack !!!
( Note, Parking on Little Crabtree is restricted until 5-00pm on Saturdays but some parking
spaces will be available. - Collect a resident parking permit immediately on arrival at
No.1Little Crabtree and place on the dashboard. Alternatively free parking is available
directly across on the opposite side of Ifield Aveue 100 yards away in the car park by the
Horticulture Club and Labour Party Club )

To reserve places for the lunch, please contact Richard, G4ANN, the Hon. Treasurer
ASAP at the Club or telephone on 01342 715333 or via e-mail : G4ANN,
g4ann@copthorne.org.uk so we can quickly establish numbers.

Our First 2m Contest

Recently we were made aware of the Practical Wireless 2 Metre QRP Contest taking place on the 12th June. Power is limited to 3 watts and you can operate /P or from a home/club station. It started at 0900hrs to 1600hrs UTC. Two of us, Howard G4PFW and myself decided to have a go. We tested my FT290 but it was not performing too well with the Clubs antenna system but the FT817 was fine, it performed all day without a hitch. A borrowed power supply (thanks Ted) and a few of my adaptors and we were ready to go on time.

We started, using the callsign G6RC and sweeping the frequencies to see who we could hear then tried to make contact to build up the score, later we sat on a frequency and tried many CQ calls without much success. At the time the weather in the South of England was terrible with a low pressure system and heavy rain coming up from France, I am certain this suppressed the signals and made hearing other stations elsewhere difficult. We had most of the early contacts with stations in our own grid square apart from one in France (JO00UV) and one in Belgium (JO10UV). (Where did they come from?) Later we started to get one or two out of our area then it all went quiet as lunchtime approached. As the contest was not a high pressure one we decided to take a break but still listen where we could.

As it was a Sunday our normal club meeting took place and many members were very supportive of our efforts. (You know who you are)

Howard at the helm

The afternoon continued much as before with sporadic contacts being made. We were surprised when others were giving numbers like 072 when we were still in the lower 20’s. How were they doing it, maybe they were outside the weather depression or on higher ground and were reaching parts that others could not. Not to be put off we continued and were rewarded when I made a contact in the Belfast area. The last hour or so we worked harder and although we could hear a few more, we were unable to pull them out of the hash.

Our total for the day was 25 contacts spread over 9 locator squares, not a lot considering the work done. Conditions were very difficult. A steep learning curve to us newcomers to 2 metre contests. This would be an ideal starting point for those newcomers to the hobby. We now have to wait for the results to be published.

Our thanks go to all the members that supported our efforts and to the club for the use of the shack on the day.

BrianG
2E0MZB

G3NZP - SOS Champion

The following announcment has just appeared in the latest RNLI 2011 SOS Radio Week Newsletter:

"Icom individual award

The individual that raised the most money (over £240) for the Royal National Lifeboat Institution (RNLI) during SOS Radio Week 2011 was Malcolm Harman (G3NZP) and for his massive contribution he receives an Icom IC-E80D D-star dual band hand-held transceiver".

Malcolm would like to thank all those members who sponsored him and made a donation. It seems a very nice little radio (and most appropriate considering Malcolm's contribution to GB7MH) and he says that without CARC help he would not have won. Club members that still have a copy of March 2011 RadCom can be reminded about the event.

Malcolm says that Icom wish to present this prize at a suitable venue (rally, club meeting, etc.) and have photographs taken to issue in press release. We look forward to seeing this.

Congratulations to Malcolm, and on behalf of Malcolm and the RNLI, thanks to all who sponsored him

Stewart/G3YSX

A Double Whammy for Biton and an Intermediate Call for Graham

Last week CARC members Graham Parsons (2E0XDZ) and Biton Walstra (2E0WAO) both obtained their Intermediate Licences. Each had self studied for some time before taking the examination on the same Saturday afternoon. However in Biton’s case he had to pass the Foundation first, so success at two levels within a few hours. Congratulations to both candidates and once again thanks to Dick Lupton for invigilating.




Of course all necessary practical assessments had to be undertaken prior to sitting their exams and this was accomplished some weeks earlier during an all day session in Hut 18. I think both students enjoyed the day and learnt a lot, especially while calibrating an analogue VFO, one of the more interesting required elements, particularly in these days of synthesised radios. None of this would have been possible without the able assistance of fellow trainer Ted MacDonald.




Malcolm Harman (G3NZP)
Training Secretary

T&K Brackets

Over the last couple of weeks there has been an interesting discussion on rsgbtech@yahoogroups.com (http://groups.yahoo.com/group/rsgbtech/) on the subject of T&K brackets. The simple question that started the thread was which way round to the two brackets go?

Although one normally sees T&K brackets mounted with K at the bottom, I pointed out that there was some useful information here: http://www.aerialsandtv.com/polesandbrackets.html#PictureOf12&24T&Ks , which says :
There are two opposing views as to which should go at the top. The K is obviously the more robust bracket and the received wisdom is that this should go at the bottom because, being further down, the wall is stronger there. However the top bracket is probably under the most stress (certainly if the wind is blowing the pole away from the wall) and so some think the K should go there instead ! Basically one has to work out the relative importance of the two factors for the particular install being undertaken. For an install at the peak of a gable I would put the K at the bottom, whereas on a strong flat top wall I`d put the K at the top. Basically it`s six of one, and half a dozen of the other, but,if in doubt put the K at the bottom

More information can also be found at http://www.wrightsaerials.tv/

Sound reasoning for the K at the bottom model was provided by Graham G8EWT who said:

The reasoning was that, as has already been stated in this thread, it is the stronger of the two and is better able to carry the vertical load. Hence the U bolt needs to be tightened really well. A tightened bolt reduces the chances of the pole rotating or sliding down but risks deforming the circular shape of the pole and therefore reduces its ability to withstand sideways forces without buckling. As the K is carrying the vertical load the function of the T is simply to provide resistance to lateral forces. It only needs to be moderately tightened and thus the risk of deformation is eliminated.

At this point in the debate I remembered a note on the subject written in March 1984 by Pat Hawker drawing attention to BS6330: Code of practice for reception of sound and television broadcast, which has some useful information on the subject. However I had long since lost track of my copy of the text.

Ian GM3SEK noted:

It would be worth tracking down, because that guide was written for Band 1, 2 and 3 aerials which were very similar to yagis for the VHF and UHF amateur bands. That isn't so true of modern broadcast aerials. One tip that you won't see in a British Standard is to insert a length of wood where the tube passes through the top bracket, which is the point of highest bending stress. The wooden filler prevents the thin-walled tube from collapsing, and spreads the bending stress away from the U-bolt. For the typical 50mm/2in tube, use a 600mm/2ft length of 37mm/1.5in square timber with the corners shaved off to make a rough octagon shape. Almost any kind of straight-grained timber will add a lot of strength. Do not aim for a tight fit - make it just firm enough to hold in place when you install the mast, and after a few days outdoors it will swell to a tight fit. (The octagon shape is actually better than a turned cylinder because it leaves room for the wood to adjust as it swells - and very importantly, it leaves gaps for water to drain past.)

Unfortunately BS6330 is no longer available, searched my study and tracked down my copy of BS6330 in box of papers, unopened since we moved house 8 years ago. I found quite a few other "treasures" on the way.

It does not have quite as much information as I remembered, but does give some information on types of loading (in terms of antenna type) mast length and dia, spacing of fixing etc. There is a lot of information on distribution systems which is not relevant to the subject in hand.

As to TK, although it always shows T over K in the drawings, all it simply says "where double brackets are used for all mounting one should be a tripod in order to provide proper support
against vertical thrust. The brackets should be spaced at least 450mm apart.

Since most of the text in BS6330 is not applicable to our interests. The key part, which contains valuable information relavent to the type of small to medium sized VHF and UHF amateur radio antennas has been posted here: http://carc.org.uk/carc_ftp/Extract%20from%20BS6330.pdf.

- Stewart/G3YSX