Antenna Specs


#1

I have a very simple set up which gives me an interesting aircraft monitoring system around 12 miles from Heathrow.

Reading up I see it is often recommended to snip the top off a supplied aerial if it is too long, thinking this to be a simple idea I unscrewed the aerial from its base. With no effective aerial now connected to the device it was still picking up 8 aircraft on Skyview.

At this point I wondered if there was any value in snipping a few mm off the top of my present antenna, left it for now.

Appreciate outdoor aerials must be ideal but wondering about indoor aerials when mine still worked without the whip screwed in.

Geoff


#2

It’s a question of being happy with the way it’s currently working, and/or trying to make it work better. Based on your location, the proverbial ‘wet noodle’ will likely ‘work’.

There is also the cost/benefit ratio of improvements. In this case, the cost is practically zero. Just make sure to follow that old saying: measure twice, cut once.

If the antenna you are using is the mag mount type, it’ll also help to add a ground plane. Find a metal lid with around 70 mm in diameter, and it should work.

The fact the antenna is indoors is mostly irrelevant in this case. Being indoors the signals will be weaker/attenuated, but the impedance matching is still important. The frequency is not attenuated and/or changed by the fact the antenna is indoors.


#3

You are inside you can even get away with jamming a wire down the threads.

Thus you can use the old whip if you don’t like it.

Probably just bend some copper at one end so it’s wide enough to jam in there. Then cut to length.

A simple food can cut to length is a good idea for the magmount aerial.
Or you can just use a large ground plane like a metal plate.

With the can plus magmount you might want to lead the cable through the can. But all that is basically just trial and error it’s hard to predict how such a frankenstein antenna behaves.

Still most standard whip antennas are not meant for ADS-B but DVB-T and therefore are quite a bit too long.


#4

#5


#6

Two questions;

  1. Is the wire 68mm :sunglasses:
  2. Were the cookies (biscuits for us Brits) tasty.

Geoff


#7

.

No, the wire is 53 mm. The screw of base is itself 15 mm, and coax is soldered at bittom of the screw. The total length becomes 53+15 = 68 mm.

He ate all the biscuits. Ask him. jpg