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T-15 Antenna Tuning Coil Rewind
In an attempt to fix a bad T/R relay for my HQ-180, I accidently transmitted into the receiver and fried the 40 meter antenna tuning coil T-15. After numerous attempts at trying to find a replacement through emails, ads, etc., I had no luck. I had seen numerous You Tube videos done by Pete K7PP aligning Hammarlund receivers. In one of his videos he had a need for the 80 meter coil and he had indicated that his brother had wound one for him since he was in the coil winding business. So, I contacted Pete and asked if his brother would wind one for me. He decided that it wouldn't be cost effective to just wind one coil. So, Pete mentioned that maybe I should just try to wind it myself. At first I didn't like the idea but after much thought I decided why not. It didn't work anyway so how could I make it any worse. So, the quest in figuring out what and how to do it began. I had lots of help and ideas from numerous parties on the Hammarlund Reflector.
Here is the fried antenna tuning coil for the 4-7.8 mhz band. You can see the burned windings and it also burned right through one of the wires making it useless now.
Here is the top view and location of the T-15 can.
Here is the view and location of the T-15 can under the chassis which encloses the coil. Not the easiest to get to but not the hardest either.
After a lot of emails and discussions about what to use for wire to rewind this coil, I ended up finding an inductor that I took wire from to rewind my coil. The original wire was "Litz" wire which is a multistrand wire. I was finding it difficult to get the correct gauge and strand number. This is where a lot of discussion took place on the Hammarlund Reflector. While looking for the correct Litz wire, I came upon this inductor which looked to be wound with a wire that was very close, if not right on the same size as the fried coil.
Here is the start of the rewind. I disconnected the primary windings to make it easier to rewind the coil. I labeled the terminals in order to be sure I had them hooked up properly when I finished winding the coil. Before I removed the old wiring I had to take high resolution pictures in order to count the windings. It is very difficult to see how many windings were there since this wire was so small and I wanted to be sure I had the correct number or it might have caused some issues in tuning. The pictures made it quite easy to count the number of turns. I held the windings in place with rubber cement. Someone else had mentioned using fingernail polish which probably would have worked quite well also.
Here is the finished product. It turned out great. I put it back in the radio and fired it up and it now had good volume and it worked quite well. I followed up with a complete alignment on the radio to be sure everything was tuned according to specs. Now, 40 meters is once again alive and well.