THE FIVE MEG EXPERIMENT
I applied for my NOV (notice of variation) in July last year, so I was one of the first to get on the band early in August. Like the other NOV holders, I was keen to experiment with aerials. Ending up with a dipole at sixteen feet, I was achieving good coverage of the UK. Between 80 and 40 metres, the five spot frequencies occupy an interesting part of the spectrum. But what's happened to the expected congestion of five megs? I must admit to having been quiet on 5mHz of late.
Before we were allowed on 5mHz, I heard a chap talking about it on 40 metres. He said that he'd applied for his NOV and intended to "coordinate five meg activity". I believe that too many people have tried to do this, resulting in so many big brother issues that people have been frightened off.
We are being monitored, you must use the SINPO method of reporting signals, you must send in your log sheets, you mustn't do this, you must do that, you have to carry out aerial experiments... It's no wonder that people have run away. I'm now back on 5 megs with an 88 foot doublet at 25 feet above ground fed with 300 ohm twin. And it works very well. So, what is the five megs experiment all about? Read on...
NVIS stands for, Near Vertical Incidence Skywave. Basically, this means firing your radio signal straight up to the ionosphere where it is reflected and comes more or less straight back down. What's the point? The idea is that, in jungle or mountainous terrain, you can get your signal over obstacles to the receiving station. Straight up, and straight back down the other side of the mountain. See the diagram below.
The MUF, maximum usable frequency, is the highest radio frequency which can be successfully reflected off of the ionosphere at a given time. Obviously, it is important to know the MUF when using NVIS.
When working across town on 40 metres, there are two factors to consider. Is your ground wave reaching the other station? Is your Near Vertical Incidence Skywave reaching the other station? In reality, the station on the other side of town is probably receiving a combination of both.
When testing your new 40 metre dipole, don't try contacting your mate a few miles away. The chances are that he won't hear you. Or, at the very least, your signal will be weak with him. On 80 metres, the chances are that your ground wave will travel further and your skywave will come straight back down from the ionosphere. QSB and strange phasing effects can be troublesome when working stations a few miles away.
I often monitor RAF Volmet on 5450kHz. This makes a good beacon station as they're on twenty-four hours a day. The computer generated female voice can get somewhat boring at times, but it's a good indication as to conditions on five megs. Actually, I have heard that the female is in fact a blow-up doll. ???###!!!
The combined cadet force
THE SINPO CODE
Click HERE for a PDF printable version of the SINPO table