Wednesday, November 4, 2015

Another approach to coil stability.

The brake on the wire spool hub is set to hand tight plus three quarters of a complete turn. This yields a very high wire tension on the coil feed wire. The results are a uniform wind and no shift of wire on the form.


It doesn't get better than this. The whole 10 foot tube shows this consistency !
Here is another lathe shot:


This is a picture of the wire spool stand and the tube, at the half way point in construction.


 
And here is the finished antenna;

I fired this coil up on the low end of forty meters and was pleasantly surprised. I found three resonance points on the tuning capacitor on my MFJ antenna turner, and each time I changed frequency slightly on my transceiver, I had to reset the MFJ unit.
The next step will be a twenty footer !!! Must wait for the return of warmer weather.
A quick note to the coil builder. Stay with the Cantex conduit. I had occasion to try to use brand x PVC electrical conduit for a test trial and ran into serious problems;
1. Check for rigidity. The "x" 10 foot section took a bend on the way home in the back of my car. Not good.
2. Try drilling holes for tap positions. I drilled six holes; two were difficult and four went through the material like butter. Not good.
3. Here's the show stopper. The bell end was not sized correctly. It seized on my sheave mandrel and was an absolute nightmare to remove. Really not good.
In fairness to the conduit industry, I must point out that their product(s) are not designed for my applications.

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