Meteor Scatter Of VHF Signals 3

We have looked at meteor scatter in quite a bit of depth already in the last two instalments posted to this blog.

If you want to read them, they are posted on Friday so just look back for the last two Fridays. Today, however, we will continue the series by looking at how to get the signal to the receiver.

Antennas
I always start a post on antennas by saying the same thing: the antenna is the most important part of your setup, it doesn't matter how fantastic your receiver, if the antenna doesn't deliver the signal then you won't hear the station!

So, if it all comes down to money (as so often it does) then you get more signal for your money by spending it on the antenna not the receiver.

Bear this in mind as we look at antennas by frequency.

50MHz
I began meteor scatter using TV frequencies around 50MHz which is (in Europe) Band 1. In particular, I listen on channel R1, which is the old Russian channel, and channel E2.

Again, I must stress that analogue TV is disappearing fast so make sure that the station you choose is still broadcasting before you attempt to listen to it!

I began using a random length of wire and then acquired an old adjustable dipole which I could set to the exact frequency and put this up in the attic of the house.

What a difference! Signals were not just a little stronger but considerably stronger and that convinced me to always try to use the best antenna I could.

So, for these frequencies a metal dipole is perfect while a wire antenna cut to the frequency in use is almost as good. Antennas made of metal tubing have a wider frequency range rather than wire which is one reason why they are preferred for antennas at these and higher frequencies.

However, if all you have is wire, cut a dipole for the centre of the range you want to hear and it will be almost as good (and a lot cheaper).

The formula is 468 divided by the frequency and this gives the total length of the wire in feet. If you search for '6m dipole antenna formula' you will get various construction projects as well that will help.

Simply adjust the length to suit the range you use and cut the length of wire in half to make two identical sections. Connect one (it doesn't matter which) to the inside wire of a length of coax and the other to the screen wire. Now connect to the receiver and you are set to go.

If you mount the antenna outside (and this is preferred) always make sure that the join between the coax and the wire is well waterproofed with self-amalgamating tape. If water finds a way into the join you will lose a lot of the signal because it will then get into the coax.

Finally, know the direction that the signal will arrive from and position the antenna so it is pointing towards that direction.

2m 70cm
For the 2m and 70cm amateur bands, a purpose built yagi antenna works well but requires a rotator. However a simple dipole or collinear will catch the signals almost as well.

On these bands, meteor scatter signals are less strong so some extra help from the antenna is a good idea.

You can construct 2 metre antennas quite easily from stiff wire and PVC tube. Do this if you want to try the band first but a purpose built amateur radio antenna is not that expensive and probably a good deal better. That said, I had a lot of fun making 2 metre antennas out of wire and PVC piping!

Again, the higher the better for this band so that the antenna is clear of obstructions.

That concludes this post on antennas. Next week we will look at something that I found completely fascinating and which took my enjoyment of meteor scatter to a whole new level.