Author Archives: Administrator

Transmission Lines

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Steven Ring M0SVR delivered a technical talk on the theory and practical uses of radio transmission lines. This was followed by a practical session where simple home-made test equipment was used to measure the characteristic impedance (Zo) of several readily available types of cables. The cable test set-up used is illustrated in the picture. This exploits the use of a quarter-wave length of cable to transform the impedance at the right hand end down to 50 Ohms at the left hand end of the cable under test shown in the picture. A 50 Ohm impedance measurement bridge was used to measure the quality of the 50 Ohm match at the left hand end of the cable under test, whilst a 1k-Ohm variable resistive load (R-load) fitted to the right hand end of the cable is adjusted to achieve a good 50 Ohm match as measured on the bridge. The characteristic impedance (Zo) of the cable under test can then be calculated from the formula: Zo = Square-root(50 x R-load).

Graham
G0MGC

Reading July 2016

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A a very pleasent day spent meandering around Reading Rally. In my humble opinion a better rally this year than Newbury. The first picture below (although not brilliant) tried to show a new tri-band mini beam on test can’t remember who from but claims to be totally portable and with a fantastically light head load.  To be honest I was at the other end of the show so by the time I got to the arena the demonstration was over. I also couldn’t hear the audio from the PA system well either so apologies on that.  In the foreground of the picture there was a model army vechical display which was interesting and I did manage to see some of that. In terms of spend!!! dare I say it I did buy wisely this time and not with either my eyes or heart but head. Some millspec 214 (ex test lab) feeder approx 50m made off neatly with N type £10, ideal for my portable stuff. Galvanised coated base for my antenna mast (perfect inside diameter 65mm) to allow full rotation once slotted together – spot on and some N type connectors and adopters (as you do).  Nearly talked into a NOS IC7000 but resisted.  Very good day indeed. Same time next year  ????

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Have you seen these characters????

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Following on from Andrew’s post I couldn’t help but add the picture took by Thornbury Carnival staff. Struck me as a cross between the blues brothers (only more of us) and a bunch of people you probably wouldn’t buy a car from… :).  We had fun so who cares!! Great day and looking forward to more of the same.

Mark M6KMJ

 

 

Service outage

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Members may have noticed a problem with the website tonight…..

I applied an update which seemed to work ok but which destroyed the formatting of text on our web pages.  After about 1.5hrs of trying to resolve the problem I’ve restored the backup from last night.  Thus any posts/updates people have made since 02:30hrs this morning will be missing and will need recreating.

The update still needs to be installed and I will try again when I have a little more time to investigate the cause of the problem.  Hopefully its something that is effecting other websites, so may get fixed quickly.

The webmaster

 

 

Training Room Activity

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Good to see the training room being used last evening. Our latest trainee to go through his practical with John M0HFH. Chance set of photo’s taken whilst I was operating the HF set sat next to them. Good luck to Ron on the rest of his practical and exam when he is ready.

Looking forward to many QSO’s when he is licensed.

Mark M6KMJ

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Field Event Planning 2016

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As those who were at the programme planning session last week know I rather haphazardly stepped into the planning for this years event!! Know I was really happy to honestly LOL.

On a serious note I will be asking for volunteers who may want to enlist their help and support on the event which we are considering is 2 instead of  3 days as was last year. Current dates set are 30th April – 2nd May and over the weekend we will  be hoping to run a club equipment test day and still to be decided perhaps a personal equipment day?

We have new members amongst us since last years event. I am particularly keen to enlist them if I may and perhaps we can discuss your thoughts and what you feel you would like to be experimenting with.

For now then if can ask anyone interested in helping on the day, staying over the weekend and/or coming to specific theme if it were to run to post their thoughts to this page and more importantly their project request/s that they feel we should explore over the weekend. I am keen to make this a clear themed event this year e.g. frequency, band/s, antenna type, radio type, home brew etc etc.

We have some On Air Nights coming up so I intend to enlist a few people to help so be prepared to be volunteered!

See you all on Weds.

Mark M6KMJ

 

 

Propagation forecast tools

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Many thanks to Peter (and his able assistants) for the informative presentation on ‘Propagation Forecasts’ this past Wednesday, I found it fascinating and very useful.

On a related note I happened to stumble across the following news on the RSGB website:

The RSGB Propagation Studies Committee has begun work on a new web HF propagation prediction service. It will feature both area coverage predictions as well as point-to-point on-demand predictions. Presently, only area coverage has been completed and this can be seen at www.predtest.uk. This will soon be followed by the P2P predictions. It is planned that following these trials the RSGB website will host the predictions. Comments and suggestions are invited by Gwyn Williams, G4FKH via email to g4fkh@sky.com.

The site itself (screenshot at the top of this post) also mentions that the Python source code behind the new tool is open source and available on GitHub.

Please share your own propagation tools with us in the comments below 🙂