20161121 70cm / 2m white stick antenna

I have a 2.2m dual band (70cm/2m) antenna on the chimney – a generic one thats a bit like the Diamond antenna white stick – called an X200

For some strange reason the 70cm repeater that’s just up the road from me was really weak S2 (and up and down like a mobile signal) and I thought something had gone wrong with the antenna – the coax (RG58, and yeah I know its lossy for V/UHF, beginners cock up!!) was new and only been there for a couple of months, same as the antenna, so its not the coax right! SWR was OK too, no issues there…

The antenna is not easy to get up or down… 2m was OK so that was enough for now… until a nice sunny November day when I did get it down…. opened it up and in there is a 7pF cap.. so the only thing it can be is the cap, the rest is just brass / copper wire… 

I tried for a while to find a 7pF 1kV cap small enough for the antenna… it’s really really really small and thin especially for a 1kV – a few people said its impossible to be 1kV but it was clearly marked (not that you can see very well from this pic, sorry)!!

Anyway, I couldn’t find one.. then one bright spark @KandaSales – http://www.kanga-products.co.uk/ – (G6YBC), Thanks Dennis, reminded me of what I had just learnt – 2x 15pF caps in series would equal 7.5pF DOH!!!! of course it bloody does… (beats head against wall for being a dumb a**e!) – He very kindly found me a link to some ‘small’ blue ones – above is a picture of one of them next to the original – these blue ones are 6kV so would easily do the job but they are a little fatter… So in true ham style I had to improvise – I had to melt the plastic behind where the caps would go so that they would sit low enough to fit… looked ok in the end I think… 

EDIT: I stand corrected – I was writing this post January 7th 2017 and trying to remember everything but Dennis, (G6YBC, Kanga Sales) pointed out that it was a typical HAM/twitter joint effort – so in addition to Dennis finding the caps I would also like to thank, in no particular order…, Jenny (G7CKF) @Jenny_Alto – Pete @Mi0VAX  – Rob @G7IGB – Ian @GM0URD and last but no means least Ian @MW0IAN – and if I’ve missed you, sorry, its not intentional 🙂

I thought that was it, put it all back together, tested it outside on the ground and tried accessing the repeater… NOPE!! still the same problem… I was so disappointed and thought it was going to have to be a new antenna… I connected up again however this time with a patch lead as I had pulled the original coax out to replace it anyway (I shouldn’t have used the RG58 in first place eh), and everything was fine, the repeater was as strong as I would have expected it to be… doh AGAIN, its the coax eh!!! I should have tried that first – Grrr, I’m so cross with myself… I just didn’t think it would be that because it was new and well sealed at both ends – there was no water in the cable, and no damage along its length so it must be a manufacturing issue in the coax… anyway, I replaced the RG58 with RG213 and the incoming signals on both 2 and 70 are now so much better, as are my outgoing..

Lesson learned – antenna issue? ALWAYS START WITH THE COAX, it’s the weakest link!