Antennas By N6LF

A large ID clamp-on RF current transformer

Earlier this year I posted a description of a simple clamp-on RF current transformer.  Since that time I have updated the design with a much larger ID and the core held in a spring-clamp that allows easy on/off in the field.  The following is an update of the earlier post: Download Current transformer 2 .  File size = 460 kB.

Back to NK7U for more tests

Earlier I posted a report on the work done last October on the 80m 4-square at NK7U.  After that work there were still many unanswered questions so I and W2VJN went back to NK7U at the end of May to run more tests.  The following is report on that trip.Download Report on 29-30 May 09 measurements .  size = 175 kB.

This series of tests also generate more questions than answers but I think it may be interesting to those who might have an array near a tower.

An example of the effect of tower coupling on an array

It's well known that a nearby tower can affect the performance of a vertical array but I haven't seen any articles which give an actual example.  Last fall I made such measurements on an 80m 4-square which clearly show just how bad the interaction can be.  Attached is a summary of those measurements: Download NK7U array tests 7 Oct 08 .  This file is about 73 kB.

Vertical-tower interactions

Interaction between a vertical and a nearby tower can be a very real concern.  I have done a short NEC modeling study on the subject which sheds some light on the subject. It's far from complete and I will no doubt expand it in the future but I have received a number of questions on the subject so here is the study in its present form.  Download Tower coupling study  The file is approximately 250 kB.

Tower resonance measurements

I mentioned on the towertalk reflector that I had been trying to make accurate measurements of resonance in grounded towers with large antennas systems on them.  A number of people asked for the details.  So here they are: Download Some notes on measuring tower resonances .  These are only preliminary notes which give the general idea of what I'm about.  In due course they will be updated.

73, Rudy N6LF