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Jan 21

BITX40: L-Match Tuner Update

In a previous post (BITX40: L-Match Tuner for an End Fed Antenna)I built an L-Match tuner using advice from Peter Parker, VK3YE. I also followed his “Tune for Maximum Brightness” RF current indicator. I had indicated that the current indicator worked fine, and I thought I did, but I was not seeing the results I wanted. After re-watching the aforementioned video, I realize that I’d wound something like 6 turns on the toroid instead of the recommended 3! I even knocked it down to 2 to try to get a little more sensitivity. The result was that I can now see how much capacitance I need to add to get a good tune.

An Upgrade or Two

I was not satisfied with the tuner I’d built though, and certainly not with the capacitor I’d previously used. I bought an inexpensive air variable capacitor on Ebay, but it was obviously far too large for an altoids tin. The PSU enclosure I was saving for the BITX40 case was not being used, and so I decided to use it for the tuner instead.

One side of the enclosure has a grid for airflow, and I was able to use that to mount everything. The LED shroud is simply a soda cap with some tape on it, hot glued to the case. I also made the coil longer and mounted it with hot glue. Screw terminals with wingnuts are for connecting the antenna and counterpoise. You can see in the pictures, I used standard 1/4″ bolts and nylon insulators for the antenna connection. The same thing, sans the nylon insulators, is for the counterpoise connection.

I ordered a 12 position switch to replace the alligator clip arrangement. Once I have it in hand, I’ll install it and also install the lid to the case. Then I’ll  cover the other side of the case with something to seal it off.

Up Next, we’ll review the QRP Labs VFO/Signal Generator kit. Stay tuned!

 

1 ping

  1. BITX40 Builds: AB1OP and the PC PSU Case - Misc dot Geek

    […] still plenty possible. I also thought about using a PC PSU enclosure, but ended up using it for my L-Match tuner […]

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