OPEN UNIVERSITY AMATEUR RADIO CLUB
NEWS LETTER no:46
G0OUR Affiliated to the OU Club and the Radio Society of Great Britain
Please make a note of our forthcoming 2019 AGM which is on Thursday 24th of January at 12.30pm. As last year, we’ll be in Central Meeting Room 06, on the ground floor. This is accessed from outside via the Central Meeting Rooms entrance, near the shop. An email reminder will be sent nearer the time, and local members are urged to attend if they can. Subscriptions are due in January and remain at £5. Please send to the OUARC Treasurer, Paul Maher, IT, Berrill Building, O.U., Walton Hall, MK7 6AA. Email paul.maher@open.ac.uk.
We’ve made good progress on the antenna front since the doom and gloom of the last newsletter. To cut a long story short, Estates arranged for contractors to replace the broken section of the old P60. In fact they ended up replacing all three mast sections, which was an easier and better solution. Unfortunately during the process the crossbeam got completely mangled, along with the VHF colinear. Our main concern though was the Hexbeam, especially due to the trees and buildings around that made the job very awkward. Thanks to the skill of the contractors that survived unscathed and was refitted to the new mast. We have fitted a new crossbeam and repaired and replaced the 40m dipole. It would be possible to repair the colinear at some stage. The crossbeam also carries a halyard and now holds up an 80m inverted L with two elevated radials. This involved some fiddling to get it working right. The radials were resonated first as a low dipole, then the top section and a shunt coil across the feedpoint were adjusted (with some interaction) to get the antenna resonant and matched. Without the shunt coil the SWR was near 3:1. So we can finally use all bands (except for topband) again, 80m to 6m.
Surprisingly the safety flapper on the new mast did not (could not) work as designed and fitted, but Adrian M0ANS came up with a solution – using a loop rather than a single rope now enables it to be engaged and disengaged. The other odd thing is that the fitted top wire rope is the wrong length (too long), so it’s not possible to fully extend the mast. We’re probably stuck with that until the cable is replaced as part of routine maintenance. The luffing cable on the HD P60 has finally been replaced.
We’re still awaiting clarification regarding the report on the big M100 mast. If we get the go ahead we may put that up again, depending on manpower available. The topband antenna would need repairing first. The current LF antennas aren’t in the same league as those we had on the big mast, and a topband antenna isn’t really practical.
Equipment wise, all is pretty much ok touch wood. The intermittent amplifier tripping has mysteriously fixed itself, so fingers crossed it will stay fixed. The LED power meter bargraph has an intermittent fault, but this is not too much of a problem in practice. We had an RFI problem which caused the Winkeyer to crash, but only on 15m. This has been fixed by re-arranging cables and adding some ferrites.
The other good news is that the local interference problem has finally been resolved. The cause was a VFD (Variable Frequency Drive) motor system used for a fume extractor fan on a nearby building. The harmonics from this wiped out everything from Long Wave through to the HF bands. Estates and the electrical contractors Kent were very helpful in resolving this. Fitting a sinewave filter to the driver output seemed the obvious answer, but was not recommended by the manufacturers. However eventually with good grounding and screening of the cable and motor the problem was solved. In general the ever increasing noise levels are having a big negative impact on the hobby, and there’s so sign of that improving, it seems set to get worse.
A big thank you to Paul M0OOM and Anne who manned our pitch at the DDRC boot sale at Stockwell Park, Luton back in May, raising £70.90 for club funds. We did not bid for OU Club funding this year, however the mast repair / replacement was funded by Estates and we are very grateful for that. (The OU Club has been part of Estates for some years now).
Many thanks to our Secretary Adrian M0ANS for representing us at the OU Club Fair in October. Thanks also to the RSGB for supplying posters, leaflets and badges for this event. Adrian prepared some A4 prints for the display boards and said it went really well. He spent most of the time chatting to people about the hobby, and a lot of interest was shown.
Some time back we were approached by Adrian Poulton (a fellow radio amateur) of the T312 course team regarding making a video in the OUARC shack. This finally came about in early December and will be used as supporting material for Block 3 of the course, which among other things looks at the design features of the Elecraft K3 and KX3 radios. We are very grateful to Adrain M0ANS for his effort and hard work on this project. As well as the radios, details of our triband Yagi antenna were discussed along with HF propagation, and different operating modes.
Again we urge members to make use of the G0OUR station, and in particular to put in an appearance at club meetings in the shack on Thursday lunchtimes, from 12.30ish. New active members are also very welcome.
That’s about it for now; hope to see some of you at the AGM on the Thursday 24th January. Meanwhile have a great Christmas and New Year.
Contact: Adrian Rawlings adrianrawlings@googlemail.com