I was wondering if there are any anti tracking benefits to randomly modulating a 100W TX between say.... 15 and 85Watts smoothly and randomly... both in terms of when and for how long
the power output is changed.

It does not stop initial triangulation of course as long as the signal is detectable but would it make it
much more difficult to locate when mobile trying to assess signal strengths on the go.... if it was 40Watts one second, 20 the next and then 2 mins at 60Watts
and then 2 mins at 70Watts and then 30 seconds at 15Watts and.... well you catch my drift.

Of course it has a few problems especially at fringe reception areas but it just popped in me head.

The more I think about it the more it probably would not make any difference. The point source that a DF array would be triangulating, even mobile... would
still be in the same place.

Just a thought, a not very good thought.

If they can detect within couple of hundred meters they come look for your dipole anyway.

Maybe it would be better for AM and SW ? I heard they are harder to DF ?

maybe a transmission could be heard by noone and be on a band were it couldn’t be heard by anyone,

I have to admit to not understanding this above, sorry.

The area of greatest radiation on any given TX antenna is known to be where the current flow is highest. TX antennas have alternating current and voltages and they exist at different points on the antenna.

For a 1/4 wave, let's say a GPA.. the highest current is at the feed point.

The same for a dipole, maximum current is in the middle. You can see this current and voltage oscillation on this GIF :

You can see in the centre of the 2 poles the voltage (pink) remains at zero, no movement, which means current is at maximum. (and vice versa there is very little current at the ends of the poles) E is the electric field from which we determine the polarization, in this case horizontal.



Whilst the feedpoint can change as in for example a half wave that is fed at the end the current centre remains the same the centre of the antenna.

As I understand many antenna for MW are either 1/4 waves or coil loaded shortened 1/4 waves. This means the highest current is at the feedpoint.

This explains why if you fed a 1/4 wave from the top of a tower block it would perform very well as the current centre is up high. However if you have a ground mounted vertical
1/4 wave (full size or coil loaded) your maximum current radiation is at the bass of the antenna close to or on the ground. This has a few problems associated with it.

1) Max radiation probably coincide with max obstacles that can attenuate the signal, houses and other buildings are the obvious ones.

2) As your current centre is near or on the ground you will have significant ground losses, this basically means the earth below your antenna is part of your antenna system and the earth is very lossy, and some of your RF turns into minuscule amounts of heat in the ground itself warming up the earthworms.

As such any 1/4 wave antenna is a serious compromise without something like an ideal of 40 x 45m long radials on or just below the ground.

The rule is put as many and as long ground radials as possible, and if you cannot put long ones put more short ones.

In any event it will be a compromise. A tower block would be great but of course, there are vast numbers of people who might want to mess around with MW
who won't be going anywhere near a tower block with all the practical and probably legal problem it can create.

You can load a vertical antenna higher up than the base, this increases current flow higher up the antenna but is a bit more complex to calculate and has practical tuning
issues as you coil is maybe at 9m high instead of within hands reach. You can also add for example a cross shape at the top of the antenna and connect that directly to the radiating element
(soldered) this influences the current distribution and increases current flow toward the top of the antenna where there are less obstacles and further from lossy earth.

Zozo bloke used some kind of really short antenna but avoided some problems by having the current centre above local obstructions and therefore got good performance from it. I think it was called a Sandpaper antenna but seemed to be some kind of modified commerical ham radio design, I might be wrong on the zozo details though but I think that's about right..