Saturday 3rd October on 144.325 MHz USB from 1400 local time. Then 28.320MHz USB from 1500-1530 local time. Please see the Calendar entry and Forum for further information.
Having endured some sixteen or so weeks of the lock-down the gradual return to normality started from the 6th of July was very welcome news. Radio amateurs have been fortunate to be able to continue with their hobby, keeping in contact with their fellows over the air waves aided by the connectivity of the internet for those without access to space for aerials.
Southdown A.R.S. are incredibly fortunate to have a radio site at Beachy Head where we can pursue our radio interests away from the radio noise and interference caused by Broadband and electrical equipment. And on a hill at an altitude of 480 feet near open fields with some great views!
Wishing to enjoy these facilities as soon as possible a small group of members planned a radio camp at the site. With numbers being strictly limited to six attendees outside family groups. The event was posted on our Forum and Calendar awaiting responses on first come first served basis.
Initially there were responses from three members wishing to attend both Friday and Saturday, with apologies from some who were already attending other functions. We were planning to continue our members cumulative contest from 1630-1830 Friday with the added bonus of the IARU HF contest running over the weekend. This gave plenty of opportunity for radio operating on HF for those wishing to participate.
Andy 2E0GNE and Tim M0THM were first to arrive at the site with Barry G8DXU slightly delayed collecting provisions and diesel for the site generator, which was running very low.
We pitched our tents, with the usual difficulty securing even substantial, tent pegs in the hard ground and beach substrate. The aerial to be used in the contest was a 20m Dipole, deployed from the main Tennamast. We also ran a 100 foot long wire for the Station Radio C12 to the 8m mast on G8DXUs Land Rover Defender FFR. The Larkspur Station Radio C12 was brought along just in case there might be members who wanted a contact on Top Band, but this did not happen during this event. However it did reveal a couple of faults, such as dirty ATU relay contacts and intermittent lamp connections. Plus a loose ground connection on the Plessey MkIV plug of the control harness, making the PTT intermittent. These problems have all now been rectified in readiness for VMARS Dynamotor Day on the 29th of August.
Our members contest started at 1630 local time on 14.055MHz when it was hoped that we may be able to make contact with Dick SV0RPE in Crete. However after a couple of CQ calls, no members were heard using CW so we switched to USB
Our first contact with a club member was actually on the 15 metre band with Steve G8NFZ
Our next major event would be the 2 metre and 70cm Low Power contest running over the weekend of 1st 2nd August respectively. This is a 25 Watt maximum power event and on this occasion must be for single operators only.
There was the added bonus that during the same weekend the European HF contest is also running. We made an entry in this event in order to keep a couple of members occupied whilst G8DXU operated in the main VHF event.
Overall the weekend of 10-11th July was very enjoyable, with the few members attending making the most of the opportunity to get out into the open air and do some radio operating.
It is with regret that the society has learnt that Flemming who was an early member of SARS become a silent key some weeks ago..
Flemming G4MJC had great enthusiasm for VHF and particularly 6m where he was often heard during contests. He will be sadly missed by his fellow amateurs. Our condolences go out to his family.
Several SARS members made contact with Ian whilst he was in Holland at West Kapelle on Top band (160m) using 1976kHz USB. Contact was also established from Beachy Head on (60m) 5363kHz USB by G8DXU and G1KAR/P with Andy 2E0GNE operating.
Anthony G4UPY was also on net, together with Chris G3XFE in Heathfield. Thanks go out to all stations for their co-operation and especially to Ian for making the effort to include SARS members in these interesting inter-European propagation experiments.
Previously a long standing member of SARS, Barry Chuter G8CVV became a Silent Key on Sunday 26th of July. Barry had moved from Eastbourne to Minehead about two years ago to be closer to his family.
He had a special interest in VHF and was renown for his knowledge and expertise in High Voltage generation and research into lightening. The title page on this site shows one of Barry’s demonstrations of a small Tesla coil discharge!
Barry was a Staff Sargent in the local TA in which he served from the 1970s until retirement. Barry developed the “Chuter Box” to facilitate voice communications over the MODs Triffid / Ptarmigan radio system. He was also a Technical Officer working in the local Eastbourne “C” Submarine Repeater station.
He will be sadly missed by members of the society, together with his friends in the TA and British Telecom.
Over the course of two lectures in February 2020, club member Steve Sims G8NFZ presented a series on operating the IC-7300 HF transceiver for the benefit of club members. He has now compiled these slides into a video series, which can be found embedded below. Our thanks to Steve for his extensive work on this series and for taking the time to edit & record these videos so that all can benefit. The YouTube playlist can be found here.
Results have been posted in the updated September 2020 AirTime.
After careful consideration and in light of the fact that a significant proportion of our membership is particularly vulnerable to COVID-19, the Committee has taken the decision to indefinitely postpone all future monthly meetings as well as meetings at the Cafe Continental on Wednesdays, until further notice. Meetings at the club shacks will continue with attendance at the discretion of members.
We hope to be able to reinstate future meeting dates as soon as possible, but in the meantime a special club net is planned, with the following details:
Every Wednesday 14:00 hrs, 70cm GB3ZX (Butts Brow) repeater
Output: 430.825 Mhz
Input: 438.425 MHz (+7.6 MHz)
Input tone: 88.5 Hz
Please see our calendar for details of scaled-down events, camps and activities, these are generally limited to six members. On-Air meetings and contests are still open to all members.
Part 7 in the series “From Larkspur to Clansman” by G8DXU
Having acquired a large quantity of non working IBMUs the following outlines the author’s experiences in carrying out basic repairs on these units. The excellent article in VMARS signal by Collin Guy describes the general operation and physical construction of this equipment. For those that are not VMARS members some operational details will be provided here.
With most equipment that may have unknown faults it is always good practice to connect the unit under test to a laboratory bench power supply with current limiting. For testing purposes the supply voltage should be set at 24V with an initial current limit of about 600mA. When switched on, correctly functioning units will draw an initial surge current whilst capacitors charge and then settle to a quiescent current of around 46mA.
The first IBMU examined was switched on and the top line of the LED display showed VLO. This indicates a low voltage input or failure of one or more of the internal power rails.
Dismantling the unit for service.
Disconnect the 2-pin power input connector and cable linking between output and battery tray.
To access the internal boards remove the front panel Hex screws. Carefully hinge the front panel away from the main case, taking care not to damage the flexible printed connector on the left hand side. Unclip the 40-way ribbon cable connecting the front panel to the Logic Module. Now remove the three hex bolts holding the plate that retains the cards in position. Remove this plate and store with the bolts for later refitting.
The 40-way ribbon cable can now be reconnected whilst some voltage checks are performed.
Connect the power input to the current limited supply and switch the IBMU on. Using a voltmeter with reference to chassis ground, check the voltages at the pins on the front of the Analogue module.
Voltages on the test-points appearing on the front of the Analogue module.
Looking at the front of the card the various test points are as shown.
- + 15V
- A GND (Voltmeter Negative connection)
- – 15V
- + 5V
- + 5V
- – 5V
Voltages on fully working units should be close to those indicated but on faulty units one or more will be found to be low or nil. When incorrect, low or high voltages are found, the first place to look for faults is on the Power Supply Unit Card. This requires the power card to be withdrawn from the frame for further investigations.
All individual cards are provided with a cord at the front, which should be used to withdraw the card from the card frame. To reduce the possibility of damage to the semiconductors by Electro Static Discharge (ESD), precautions should be taken.
This normally entails the wearing of a proprietary conductive wristband and cord together with the use of conductive matting on the workbench. Cards that are withdrawn awaiting repair should be handled and stored in conductive plastic bags.
Card Module Numbering
For testing purposes and Built In Test Equipment (BITE) reports, Cards or Modules are numbered from Right to Left looking at the front of the IBMU. Thus the Power Card is MODULE 5. Faults are reported on the LED display using these numbers.
Power Supply Card – Module 5
Fortunately the power supply is largely an independent unit that can be tested as a separate entity. Once the card has been placed on the bench and taking the usual electrostatic precautions as above, the heat-sink needs to be removed. Unscrew the bolts holding the power transistor tabs and remove the screws retaining the PCB to the heat-sink. Ensure that the mica and silicone insulators for the transistors are safely kept for correct reassembly.
Once the heat-sink has been removed carefully examine the components for any obvious signs of damage or overheating. The main cause of failure in these units is usually due to faulty Tantalum capacitors, these often fail short circuit.
The photograph shows one such capacitor (C40, Pink, EuroTant) approximately bottom centre. This has actually burnt out and is typical of such catastrophic failure in power applications. All Tantalum capacitors in the IBMU should be treated as suspect! And it is therefore suggested that these are changed for new items. The following is a complete list of Tantalum capacitors in the PSU Card: –
|C11, C16, C20, C38||22uF 40V|
|C14, C26||22uF 16V|
|C40, C54||33uF 25V|
If desired only the faulty capacitors need to be replaced. It is however strongly recommended that all of the above capacitors are changed for new Tantalum items. The ESR of Tantalum capacitors is lower than electrolytic types, however 22uF 40V Tantalums are quite expensive (approx £13 each). Given the only slight degradation in performance and for amateur use, it is probably expedient to replace these with electrolytic types.
The following list of part numbers from Farnell Electronic Components gives suitable replacements.
CAPACITOR 10uF 50V 881-2594
CAPACITOR 22uF 63V 881-2640
CAPACITOR 33uF 25V 110-0482
CAPACITOR TANT 22uF 110-0470
The above components are suggestions only and not an endorsement of any particular manufacturer or supplier.
The PSU printed board has plated through hole connections and components should only be removed by the use of a good vacuum de-soldering station. Hand solder pumps are unlikely to have sufficient suction to remove parts without damage to the delicate lands and tracks.
Capacitors should be tested with a capacitance meter or component analyser. Such as the Tinsley Prism Databridge
Short circuit items are more easily located by using a Tone Ohm made by Polar Instruments or similar circuit resistance tracer. For those not familiar with the Tone Ohm, these identify resistance deviations by change in tone from a voltage-controlled oscillator. There is also a digital display indicating resistance, voltage or current at the point of test. These units are brilliant for locating faults with shorts or disconnections on printed boards.
With a Capacitance meter, check the capacitance of C40 & C54 in circuit. This should read approximately 290uF due to 220uF + 33uF + 33uF in parallel and should not be substantially lower than 286uF -10%
LED Display codes
CAP = CAPACITY
DCHG = DISCHARGING
CALC = CALCULATING
VLO = VOLTAGE LOW (DC Input Low <21V or internal fault)
VHI = VOLTAGE HIGH (DC Input >32V)
TEMP = Power Interface failure (Temperature on Heat-sink >90C)
MOD1 = MODULE 1 Fail (Logic Module)
MOD2 = MODULE 2 Fail (Analogue Module)
MOD3 = MODULE 3 Fail (Driver 1 Module, battery charge channels 1-4)
MOD4 = MODULE 4 Fail (Driver 2 Module, battery charge channels 5-8)
MOD5 = MODULE 5 Fail (PSU Module)
MOD6 = MODULE 6 Fail (Control & Display Module) Front Panel/Switch)
SW181 Iss 1.31 U2 Date 11.03.94
SW220 Iss 1.06 U2 Date 16.02.98
IBMU manufactured by Widney Aish, Poole, Dorset.
Later units marked, Charge Electronic Design, Poole. Dorset.