80m Vertical – High voltage elevated radials

RF Weld - Click to zoom

RF Weld – Click to zoom

The M0XXT Double Xray Firm had one of our outings again last weekend with myself, Tim (M0URX) and James (YOMsoft author). We built our biggest vertical yet, a loaded quarter-wave for 80 meters. Click the picture to compare Tim and I against its size. Awesome! 21 foot (6 meter) scaffold pole with 40 feet (12 meters) of SpiderBeam pole above. We’re getting an 18 meter version of this which should be great fun.

For speed of assembly on the day, we used 4 very thin strands of insulated copper wire out of a three-pair (6 way) telephone reel for the elevated radials. They’re very thin but would do the job of allowing us to raise this baby up in the air 6 meters.

The radials ended up at ground level, wrapped around galvanised tent pegs. Without realising it, we were trusting the insulation coating of the wire itself to keep the radials from being grounded. Actually, we never really thought about the consequences! Anyway, a 100w squirt proved most efficient and we achieved a 2:1 SWR curve from 3.625 to 3.750. We needed to shorten it a few more inches, however before we took it down again, I thought it prudent to fire 400w up it to make sure nothing broke down. Thump; I stuck a good carrier from the ACOM 2000 down the pipe and “pop”. The SWR pinged up to over 3:1. What had happened?

The insulation on every single tent peg had broken down in an instant and melted through to convert our careful elevated radial system into a grounded system in a flash.

NATO stock number 5985997014493 – Reel and Ant Wire Assy

Nato Antenna Part 5985997014493I recently purchased an interesting reel of antenna cable made up of various different lengths of antenna wire and connectors in a contemporary design made of modern materials. The handle and bearing appears to be aluminium but the reel is of a high-impact plastic. This would have been fabulous if made in aluminium. There’s quite a few different lengths of this stuff and since I’ve yet to pull it all out in the garden, I can’t fathom it all out while its trailing around a room.

I need to work out exactly what it is. If you happen to know, can you email me please? I’d like to know the history and technicals.

Google is showing no documents for part number 5985997014493 so if you came here from that search, chances are this page was unique.

Callum.

“Floating Shack” progress

Narrowboat drawingProgress on the narrowboat continues (USA visitors, you’ll have to google narrowboat) with the steel being cut this week. Shell should be finished by end of Feb for fit-out during March, April and May 2008. Some of my boating chums enjoy hearing about the design so I’ve uploaded the latest drawing.

Click the picture.

Find me in the narrowboat forum on Yahoo here: http://groups.yahoo.com/group/Narrowboats/

Under-voltage fixed

Voltage GraphicI’ve been running on less than 200V AC most evenings for the last 18 months. Weird stuff was happening to my linear amplifier and I was getting higher output during the day to the evening. To cut a long story short, Central Networks have just completed a complete re-engineering job at the end of our cul-de-sac with a new transformer and new feeder. Amazing what you can get done if you are polite (not a strong point of mine).

Have you checked your AC at peak times? You may be surprised.