I always asked myself which was the Twin Talker 3600's original spring antenna gain.
The physical features of the spring antenna, if we want so call it, are: a spring of 20.5 coils, diametre 5 millimetres and 29 millimetres long, the wire's diametre is 0.7 millimetres.
I tried to input data into the 4nec2 simulator, to see, in outline, how it behaves: after measuring the radio's printed board and simulating it like a ground plane, the spring, of course, as an aerial.
To make resonate the spring, I had to reduce a lot the wire diametre, else the spring resonated 22 MHz upper, if who projected the antenna, took care of this and that... I correctly input the data into 4nec2.
Here is the final result:
Without surprise, we can see that this antenna has a negative gain but, for the local use, it's good enough. With this antenna I connected T-rex, 181 km far away.
To end, here is the .nec file of this spring antenna simulation with 4nec2 program just analized.