Feb - Surrey Radio Contact Club
Contents
1. AFS CW Contest 10 January This was supported by Alun G4WGE John G3BFP John G38MCx and Steve G4FYF John G3BFP wrote The four man team claimed a total score of 3730 points not an award winner but we wont be bottom Operating John G3BFP as usual kindly forwarded some log extracts This month the amount of DX has been reduced somewhat but John still managed JT1CO Mongolia on 40m ZL2AGY on 30m and HSOZCY 4 Thailand on 17m Anybody else doing any DXing HF or VHF Next A Meeting We are pleased to have John GBMNY back to give us a talk on Packet Radio As most people will be aware there has been a reduction in packet activity over recent years from its peak However it continues to endure and develop with APRS just being one application that has come along It is certain to be a very interesting evening and hopefully will be a spur to get re connected on packet lf any member does want to get going again I m sure there will be help advice and encouragement from John at the following B meeting Looking forward to seeing you all next Monday 1 February THE CALENDAR SECTION SRCC and Local Club Meeting Dates Sutton amp Cheam RS Natter Night Vice Presidents Lounge Sutton United Football Club Gander Green Lane Sutton 8pm Sec John GOBW V 020 8644 9945 www scrs org uk Crystal Palace AGM All Saints Church Parish Rooms Beulah Hill from 7 30pm Bob G3OOU 01737 552170 Meet norm2. magic and ripped some turns off the coils to tweak the response of the BPF This has led to a lot of band mush disappearing and signals becoming much more intelligible Also confirmed the DBM was doing what it should do so onward to the PA Steve Jones G4FYF Jan 2010 Issue 2 27 Jan 2010 Page 8 of 9 E amp OE Programmable Frequency Counter G4FYF This is my latest homebrew bit of test gear for the shack It s a frequency counter based on IKSOIL PIC16F84 design and can be programmed with the following offsets VFO IF IF VFO VFO IF and prescaler ratios Br A E 4 au Programmable Frequency Meter G4FYF Programmable Frequency Meter also used this to try my hand at using SMDs for the first time Wasn t as difficult as imagined and it functioned first time y g FOL zz Siel aia This was also a first for producing a photo etched PCB The low tech approach from an idea by Eamon Skelton using a 500W halogen lamp for the exposure It worked remarkably well after a bit of experimentation with exposure times the small pads for the SMDs and fine tracks were all well defined after etching All in all a very worthwhile little project The PDF for this is http www ik3oil it _ private Frequenzimetro_eng_2003 pdf I obviously didn t use his PCD design I also have the PIC code if anybody is interested IK3OIL has a nice website that is worth a view http www i
3. the aerial connection point but after a 4 pole low pass filter that is common both to the TX and RX This introduces a loss of around 1 to 1 5db on received signals so if out of band rejection is less of a priority than sensitivity then rearranging the antenna feed and switching can provide a useful improvement This entails removing the diode switching coupling and decoupling circuitry from the back end of the filter to the front end This is not a task for a beginner as it requires both good de soldering technique to remove the required components without damage to them or the printed circuit board The modified arrangement is shown below Issue 2 27 Jan 2010 Page 5 of 9 E amp OE D13 Lon 1N4148 aaa R116 150 C146 In ANTENNA a 0 ANTENNA FILTER SKT 33 C137 L28 1p8 tal L26 L27 i L31 L32 L33 L34 141 Di6 F144 R117 14 135 100K X y C151 C156 C148 C153 L29 x rake 132 C138 aC 140 C14 C149 C152 C154 C157 139 mutes O14 3 X X x 017 142 PUM9401 tn This is achieved by e Removing C141 D16 and C144 e Making a small PCB to hold C141 D16 and C144 that has connections for miniature coax RG174 in and out and ground and for a wire connection to allow D16 to be biased As there is insufficient space within the shielded RF compartments this is best mounted above the shield plate cover and fixed to the side of the radio s chassis The shield plate cover needs to be drilled with 3 small
4. 0 Page 2 of 9 E amp OE Philips Commercial External LED Light LumiPlus LED Pool Lighting Last B Meeting Because of a mix up over the meeting dates given to the Trinity Bursar the meeting was held in the Rehearsal Room instead of the usual Sanderson Room The meeting was the usual mix of chin wag and fix it with as usual John G8MNY bringing along a wide range of test gear Committee We are pleased to welcome back Gareth G4XAT who has agreed to be co opted Also the last meeting had Steve G4FYF in attendance as an observer who was most welcome myself missed the meeting which was chaired by Roger G4WAY because of a flue like symptoms which luckily had cleared up within 48 hours 2M FM Net An initial test for coverage was undertaken on Sunday 24 January at 1015 on 145 35MHz FM with myself and the following members taking part G4FKK G8MNY G4XAT G4DDY G6JXA G8TB and G3ENG Everyone heard everyone else OK except Bernard G8TB and Gareth G4XAT As an experiment a net will be held on Friday evenings at 8pm on 145 35MHz or minus if busy or QRM for the next few weeks to see if there is enough interest and momentum to keep it going In particular we are trying to encourage participation from M3 M6 licensees from Trinity school and other club members who for whatever reason are unable to get on Top Band The club used to hold a net on this frequency and time in the 1970 s so this is in a way a revival of
5. 3 100 C R2 1n 100K If all connections have been made correctly double check it is time to test Connect power to the MX294 and switch on Then connect a signal source and check the receiver is working OK and then re adjust L1 for best S N on a weak signal Though I did have an MX294 at one time with the BQF51 front end I did not get around to modifying it though I did write up the steps in my notebook I will make this a subject of a future article in the club newsletter 20 meter QRP transceiver G4FYF I have been fancying building a QRP HF transceiver so set to work on a BITX design based on the Ashhar Farhan VUB3ICQ concept I designed etched separate boards used ferrite cores instead of tap washers and IC voltage regulators instead of Zeners and a Hartley VFO Wired the boards together last night and with a bit of tweaking it sprang into life It seems to be hearing pretty much as my trusty FT101ZD is but audio a bit tinny possibly inadequate speaker I was impressed with myself BPF Input output mixer xtal filter VFO BFO bal mod Mic AF amps Now to get the TX FET PA up and running I think I will need the G3MNY magic to peak everything for best performance Then find a box to put it in Intended phase 2 a VFO stabiliser and digital frequency display la IK8O0IL this being a SMD project boy I m really getting carried away now Having now taken this to the last B meeting John G8MNY worked his
6. SURREY RADIO CONTACT CLUB FEBRUARY 2010 no 809 CLUB NET 1 905 MHz Sunday 9 30am Hon Sec Ray Howells G4FFY 16 Handel Walk TONBRIDGE Kent TN10 4DG 01 32 357474 CLUB Internet WEB Site htto www gs8src org uk E Mail secretary g3src org uk MONTHLY MEETINGS 1 AND 3 MONDAYS 7 30 FOR 7 45pm Meetings at Trinity School Shirley Park Croydon CR9 7AT A MEETING 1 Feb 2010 Packet Radio with John G8MNY B MEETING 15 Feb 2010 FIX IT ADVICE CHIN WAG CLUB STATION MOVE IT ON VHF Co ordinator G8IYS John Simkins 020 8657 0454 G3MCX John Kennedy 020 8688 3322 Committee Member Co Opted Technical G4XAT Gareth Evans 020 8462 2837 Recycling Dear Members amp Friends Hello and welcome to the February 2010 Newsletter which is being edited Ray G4FFY I m afraid my time in January has been spent on the dreaded tax return which hopefully by the time you receive this Newsletter will be done and dusted That should then give me time to start finally clearing the garage of the storage boxes and shifting what is not wanted It is also Radio Fairs time again and we start preparing for the next Kempton Rally on Sunday 18 April 2010 We are also preparing the Motor Caravan for the new season and plan to finalise the aerial installation any thoughts on a good HF mobile system would be appreciated 73 Ray G4FFY This month s meetings For the A meeting on Monday 1 February 2010 we are pleased to welco
7. able 30 year later although now obsolete The next time I needed a flasher to do the same thing I had to use a PIC Progress what progress During the 80 s red ultra bright LEDs became available and I even went as far as building a touch controlled torch with a provisional patent application on it to establish prior art is I believe the term Unfortunately for my bank balance and future career neither Duracell who were basking in the glory of how successful their clever Dura beam torch was which had 30 of the market at that time nor Eveready could be tempted by the offering Ironically it s taken 20 years and the might of Chinese manufacturing to flood the market with decent LED torches LED lighting has come of age and is here to stay mainly driven by the need for less energy consumption and longer service life Plus I prefer the light and I like experimenting To that end you could wastes several hours browsing the site http www instructables com search for LED lights and be amazed Page 1 of 9 E amp OE Power LEDs as such started to appear in the mid noughties and Elektor Electronics published a comprehensive review of the offerings and performance in 2004 how things have changed in 5 years My son Joshua had need of a decent off road bike light and after trying a 20 watt halogen we needed something better Elektor came to the rescue again with a timely published circuit using a SMPSU chip from Linear T
8. al note was on wall warts plug top PSUs and how I d replaced some of my fleet with some nice units I found on eBay for a mere 2 each rated at 12 volts and 2 amps With the two I replaced on our cable modem and router we are saving some 30 watts 24 7 356 which amounts to at least 20 a year When you start to look it s amazing how much is being wasted What we need now is for the unit cost to come down to make it a financially worthwhile exercise Only this time I hope it does not take the 20 years that CFL s have taken to become reasonable aarm Blog February 2010 hope everyone has survived the recent extended period of snow without mishap nothing though compared to 1963 or 1947 I m told Last A Meeting This was a well _ attended presentation and talk on LED iania by Gareth G4XAT As most people will know Gareth is a keen experimenter and constructor and nearly everything he brought along was a good example of his ingenuity Gareth will have an article on LED lighting either in this issue or a later one Jim Gale G4WYJ also brought along some examples of LED lighting for swimming pools The pictures below were taken on the evening by John G8MNY John Bike Handlebar LED Light has also contributed some design ideas on circuits to power and re charge batteries for LED lighting which will probably appear as part of Gareth s article and is also available as a packet bulletin Issue 2 27 Jan 201
9. ally monthly on 1 Friday http www g3oou co uk CATS How to Lose your SMD Virginity with Terry Giles G4CDY Meetings normally held St Swithun s Church Hall Grovelands Rd Purley 8pm 2 4 Monday s Contact Andy Jackson G8JAC on 020 8651 2727 g8jac btinternet com W amp DARS On Air and Construction Martin Way Methodist Church Buckleigh Avenue MERTON PARK SW20 9JZ 7 30 for 8pm 2 amp last Friday s Details Jim MOCON on 020 8874 7456 http www gx3wim org uk 15 Feb Fix It Advice Chin Wag Move It On Bromley amp District Meeting Programme Planning Meetings normally on 3rd Tuesday s Victory Social Club Kechill Gardens Hayes 7 30 for 8 Paul M3PGW bdars greenwand net or www bdars org uk Reigate Amateur Transmitting Society Main meeting 3 Thursday s at RNIB Redhill College Philanthropic Road Redhill 7 30pm www qsl net rats or rats qsl net Sutton amp Cheam RS introduction to Military Communications with Mike O Beirne G8BMOB Vice Presidents Lounge Sutton United Football Club Gander Green Lane Sutton 7 30 for 8pm Sec John GOBWV 020 8644 9945 www scrs org uk Dorking amp District Radio Society Weak Sinal Propagation Reporter WSPR Walter Blanchard G3JKV Meetings normally Friends Meeting House Butterhill South Street Dorking opp Spotted Dog Details David Smith MOSXD on 07808 579501 http www ddrs org uk or ddrs secretary yahoo co uk W a
10. echnology who have been very helpful over the years with free samples for school It worked producing light levels well beyond commercial units costing 100 s Things move on though and after several of the chips had died due to open circuit operation I investigated driving them directly from AA NiMH cells Although right at their upper limit of 1 amp forward current I have over a 100 hours running on my unit and it shows no signs of deteriorating The key is to keep them cool Things never stay still for long in technology and whilst browsing the internet I found a neat little driver IC that was clearly designed with power LEDs in mind 8 32 volts in 0 1 2 amps out via a current sensing resistor dimmable including total shutdown at less than 90UA drain what more could you want www dealextreme com supplied a set of 10 for a mere 2 38 each free delivery and experiments began again The circuit is so small surface mount that it s a bit fiddly to hack but hack it I did and it s robustness and flexibility will see it doing duty in a whole new range of lights Like any SMPSU it likes to broadcast its behaviour and some users report that it wipes out their FM car radio when used as an internal courtesy light replacement Better RF design capacitors at least should clean them up enough to solve most problems There was more padding in my talk but I d be happy to expand on anything you want to know more about My fin
11. holes for the two miniature coaxial cables and the bias wire e Cutting the PCB track between L28 and junction of D16 C141 e Cutting the PCB track between the junction of C139 L29 and D16 C144 e Cutting the PCB track between the junction of L34 C156 C157 R117 and the antenna socket e Adding an insulated wire link from L27 to L31 e Adding a small PCB containing C141 D16 C144 and connections for input output and ground e Connecting an insulated wire link between the junction of D16 C144 on the new PCB and C139 and L29 e Connecting miniature coax inner RG174 between junction of L34 C156 C157 R117 and C141 e Connecting miniature coax shield RG174 to ground adjacent to L34 e Connecting miniature coax inner RG174 between C144 and antenna socket connection e Connecting miniature coax shield RG174 to antenna socket ground If all connections have been made correctly double check it is time to test that the new antenna changeover arrangement has been made correctly Connect power to the MX294 and switch on Then connect a signal source and check the receiver is working OK If so then re adjust L1 for best S N on a weak signal Then check the transmitter side and connect a dummy load and power meter and check that normal power out is achieved An alternative to re using the existing diode switching would be to use a miniature encapsulated changeover relay 9V to 12V and this could be similarly fixed to the side of the radio chassis as per
12. k3oil it menu_eng htm click on projects to find some useful stuff Steve Jones G4FYF Jan 2010 SIGNING OFF That s it for this month apologies if I have missed anything while compiling this newsletter For our main meeting on Monday 1 February we welcome back fellow club member John G8MNY for his talk on Packet Radio The B meeting is on Monday 15 February Don t forget we now start at 7 45pm at Trinity School Many thanks for the Newsletter contributions from Pat G4FDN and Steve G4FYF more always welcomed Row G4FFY 73 and 88 Posted 27 Jan 2010 Issue 2 27 Jan 2010 Page 9 of 9 E amp OE
13. me back at short notice John G8MNY who will be presenting a talk on Packet Radio with the regular Fix It and Move It On Meeting on Monday 15 February 2010 NEXT A MEETING Monday 1 Feb 2010 Packet Radio John G8MNY 7 30pm for 7 45pm We are pleased to have John G8MNY back to give us a talk on Packet Radio As most people will be aware there has been a reduction in packet activity over recent years from its peak However it continues to endure and develop with APRS just being one application that has come along It is certain to be a very interesting evening and hopefully will be a spur to get re connected on packet If any member does want to get going again lm sure there will be help advice and encouragement from John at the following B meeting Pat G4FDN Issue 2 27 Jan 2010 G4DDY Maurice Fagg 020 8669 1480 LAST A MEETING Monday 4 Jan 2010 High Power LED s amp Sustainable Designs G4XAT Gareth has kindly sent me a summary of his talk as follows Where did it all start In 1975 with a 50pence LED that lasted all of 1 2 a second an illuminating talk by Gareth G4XAT I can even remember who I bought it from Trampus Electronics where are they now I wonder This costly investigation was followed by purchasing a LM3909 LED flasher which I built into a key fob case and used for a few years As an indication sorry of how popular the chip would prove they were still avail
14. mp DARS Amateur TV by John Stockley GBMNY Martin Way Methodist Church Buckleigh Avenue MERTON PARK SW20 9JZ 7 30 for 8pm 2 amp last Friday s Details Jim MOCON on 020 8874 7456 http www gx3wim org uk Issue 2 27 Jan 2010 Packet Radio with John G3MNY Spring Surplus Equipment Sale 10 May Project Constructing Project Evening Construction Contest SRCC Meetings indicated in BOLD at venue of Trinity School Rally Calendar etc 25th Canvey Radio amp Electronics Rally The Paddocks Long Road Canvey Island SS8 OJA Open 10 30 Parking Catering Disabled Facilities Trade Stands Contact Dave G4UVJ 01268 697978 evenings www southessex ars btinternet co uk Harwell Radio and Electronics Rally Didcot Leisure Centre Adjoining St Birinus School Mereland Road Didcot OX11 8AY Oxfordshire Contact Ann Stevens 01235 816379 www g3pia org uk e mail rally g3pia org uk Rainham Radio Rally Rainham School For Girls Derwent Way Gillingham Kent ME8 OBX Contact Trevor GGBLYW 0771 7678 795 Cambridge and District ARC Rally Wood Green Animal Shelter King s Bush Farm A1198 London Road Godmanchester Cambs PE29 2NH Contact David MOGUM 01954 203080 www cdarc co uk e mail rally2010 cdarc co uk Spring West London Radio amp Electronics Show at Kempton Park www radiofairs co uk Lecture stream Opens 10am 4 Rally List http www rsgb org eve
15. nts index php Web Site of the Month From Charles MOBIN this month take a look at Dick Cappels Project Pages http cappels org dproj Home htm G3ASG WW2 Memories of a Voluntary Interceptor http www bbc co uk dna h2g2 brunel u1 600338 Radio Constructors Circuit Archive Valve TRF http www vintageradio me uk radconnav valvetrt Haminfo toolbar for your browser http www haminfobar co uk New club for Morse code http www essexcw org uk Web Hosting amp Domain Name Registrations http billing qth com index php G3XBM QRP projects on U tube http www youtube com profile gl GB amp user G3XBM G3XBM QRP web site http www g3xbm co uk G4TPH Magnetic Loop Antennas http www g4tph com Regen RX http groups yahoo com group regenrx More Web SDR s http websdr ewi utwente nl 8901 Updated GQRP Club web site http www garp com tech htm JAB Electronic Components http www jabdog com index htm Page 4 of 9 E amp OE Pye MX294 Receiver Sensitivity Improvements by Pat McGuinness G4FDN These notes not previously published came about after discussions with Gareth G4XAT on a recent club Sunday net Gareth mentioned that he planned to get mobiling again on 2M FM with a MX294 but he was concerned about its apparent lack of sensitivity I have experimented with MX294 s in the past so I share my findings and Suggested mods from my notebook now so others can try them out I no longer have the highband MxX294
16. s I modded so the photographs included here are from a lowband one I still have The component layout is the same for both lowband and highband though obviously component values vary The MX294 has two main variants one with a bipolar NPN front end transistor in the RF amplifier stage board marked AT28790 and one with a dual gate MOSFET RF amplifier board marked AT28873 In my opinion the RF amplifiers in the MX294 are not insensitive per se they are just encumbered by lots of RF filtering which in itself is not a bad thing as it gives a wider margin of protection from out of band signal overload But if your priority is sensitivity then the following modifications can give a worthwhile improvement In carrying out the mods described here it is assumed that the reader has access to the MX294 circuit diagrams and description or service manual or The PMR Conversion Handbook by Chris Lorek and published by the RSGB but I have included the essential parts of the circuit diagram in this article 9 IN4 amp 148 R116 150 C146 ANTENNA SKT In ce ANTENNA FILTER y 33 L28 dt X L26 L27 C141 Di C 1 amp 4 L31 L32 L33 L 4 202 UM94019 2n x 14 135 C156 C151 x C148 C153 L29 a rake C132 ebm Sar See ee C147 C149 C152 C154 C1571 R11 5 5 x L100 D17 tn It can be seen from the circuit diagram above for both MX294 variants that antenna changeover done by diode Switching is not done at
17. st newsletter Two proposals have been tabled so far The first is a 25 30W outboard PA for an FM handheld based on the Mitsubishi RF power modules obtained by Maurice or possibly 50 60W PA based on two modules see design by G8MNY in the last newsletter The second suggestion comes from Gareth G4XAT concerning a high power LED table inspection lamp If you have a preference for one or the other we will be taking a show of hands at the next meeting to gauge before the committee makes a decision 75 Anniversary Lunch Just a reminder that this will be held on the afternoon of Sunday October 10 2010 10 10 10 an easy date to remember at the Holiday Inn Hotel Sutton between the Civic and Secombe Centres and a short walk from Sutton railway station fe ee as Cae Ae a i g r og ie a ot i CELI LT The hotel also has free designated disabled parking for those attending The time of the event and its location has been chosen to facilitate participation by country members John G3MCxX is in the process of contacting members to gain their commitment to support this important event in the club s history It would be helpful if members could confirm their attendance as soon as possible Can ask that any member who would like to attend but anticipates travel difficulties could they discuss them with John G3MCX and the committee what can be organised in terms of lifts or mini buses Page 3 of 9 E amp OE 80m
18. that It should be noted that the Sunday Top Band net continues as normal Issue 2 27 Jan 2010 Top Band Net this continues to be enthusiastically supported on Sunday s on 1 905 MHz LSB at 0930am On the net last Sunday Martin G4FKK reported completion of a PW Poppet 0 5W AM transmitter for Top Band and after the net this was aired on 1 942MHz to good effect after the club net had finished Myself Maurice G4DDY and John GS3ENG also came up on AM Martin s TX sounded very good and was 59 with all participants G8MNY Technical Bulletins those on packet will be well aware of the large number of technical articles covering the full spectrum of amateur activity that John has written Less well known is that these are available on the internet Some are listed at http skywaves demon co uk tech_articles htm but the index hasn t been updated for a while Access to all of them including some by other authors in HTML directory format can be had via http skywaves demon co uk technical We will have to see whether we can get them mirrored on the SRCC website to make them more accessible For those of you wanting to get going on the 2m FM club net then John s Full Wave Dipole design is recommended Comparison tests have shown it to be superior to the Slim Jim The article for this is located at http skywaves demon co uk technical Aerials 2M_ Fullwave Dipole paf Project for Construction Evening this was mentioned in the la
19. the diode switching PCB and Similar connections made for the miniature coax and wire for powering the relay on for TX This circuit arrangement is shown below Relay A has a single pole C O contact Issue 2 27 Jan 2010 Page 6 of 9 E amp OE AN TEMA A SET ANTENNA FILTER As can be seen from the diagram above all the diode switching components have been removed On transmit Relay A is energised and contact A1 changes over the antenna socket connection from the TX to RX A further 1 to 1 5dB of loss reduction in the RX path can be achieved by modifying the tuned circuits at the input to the RF amplifier The details for this are different for the BFQ51 and BF981 variants Here is the unmodified circuit diagram for the BF981 variant R6 100 od og 1n 100K je C14 C16 C18 C19 C21 22 C3 i i imi imi ai rrr Fe afl ul eo fl lbe uf lb Pep lac 3 1 TA ie ae ae ae The modification involves removing one of the coupled tuned circuits on the input and re arranging the connection point of g1 on TR1 BF981 This reduces the loss from the antenna to TR1 by 1 to 1 5db The modification is as follows e Remove C3 C4 and C6 e Remove Ri e Remove L2 strictly speaking it can be left in situ but no longer is used e Connect an insulated wire link from the junction of C2 amp L1 to the former junction of C4 C6 R1 and g1 on TR1 BF981 Issue 2 27 Jan 2010 Page 7 of 9 E amp OE R C12 41
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