Tag Archives: NooElec Balun 1:9 v2

Grayhat’s NCPL (Noise-Cancelling Passive Loop) antenna “tweak”

My NCPL antenna

Many thanks to SWLing Post contributor, Grayhat, who shares the following modification he made to a Noise-Cancelling Passive Loop antenna last year. He’s kindly allowed me to share his notes here, but apologized that at the time, he didn’t take photos of the project along the way and recycled many of the components into yet another antenna experiment.

Grayhat writes:

Here’s a simple tweak to the NCPL, made easy for anyone. Let’s start with the commercial NooElec 9:1 balun version 1 (not 2) … made in USA.

Look at the schematic of the balun:

Cut the R1 (0 Ohm resistor – jumper) so that the center tap of the transformer won’t be connected to ground, then solder a short piece of wire to the tap.

The first pic (top) shows the balun seen from top side, the arrow indicates the small hole going to the transformer tap.

This pic shows the bottom of the board with the trace to cut and the spot for soldering the tap wire (needs cleaning with a bit of sandpaper to remove the cover paint). The solder is as easy as 1-2-3 once the trace is cut and the spot cleaned just insert a wire from the top of the board and solder it to the bottom and there you go!

Build the NCPL using “fat” coax (RG8 will do) with the top cross connection.

NCPL modification schematic

Side note: the top “cross connection” is the weak point, so it would be a good idea putting a short piece of (say) PVC pipe over that point, the piece will also help suspending the loop or sticking its top to the support pole, as for the feedpoint, a small electrical junction box will fit and protect the tiny balun from bad weather

Now the difference: connect the two center conductors of the NCPL to the balun input and the braid to the wire going to the center tap (as above).

Such a configuration will give some advantages over the “standard” NCPL one. The loop will now be galvanically isolated from the feedline/receiver so it will have much less “static noise.” Due to the tap, the typical 8 pattern of the loop will be preserved, this means that the loop will now have much deeper nulls.

By the way, the balun could just be wound w/o buying it. I suggested the nooelec since that way anyone with little soldering ability will be able to put it together. Oh and by the way it’s then possible adding a small preamp at the balun output if one really wants, any preamp accepting a coax input will work. 🙂

Again, if you can/want, give it a try !

Many thanks for sharing this, Grayhat! We always welcome your inexpensive, innovative urban antenna projects!

Post readers: If you have question, feel free to comment and I’m sure Grayhat can help. 

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The NooElec Balun 1:9 v2

Many thanks to SWLing Post contributor, Grayhat, who writes:

Hi Thomas, was about to write you about some infos related to the NooElec balun when found that they now offer a v2 model:


The new balun has the same schematic as the previous one:

But it is slightly bigger, has a better connector for the antenna wires and (according to NooElec) uses a transformer which allows the tiny balun to work more efficiently from 0 to around 70 MHz (check out the charts found in the downloads section of this link).

The transformer used, judging from the pics, is a CoilCraft WB9-1, whose data can be found here:


As I wrote the reason for this was the fact that a friend of mine reported that he used the (v1) balun with a Loop On Ground (LoG) Antenna !

If you look at the schematic (above) you’ll notice that there’s a “jumper” labeled R1 (zero Ohm resistor). That tiny detail is important, see, leaving the balun as is, it will work fine with a longwire, one just connects contact #1 to the antenna and #2 to a counterpoise or ground system and there he goes, BUT there’s another way to use the balun, that is, CUT the “jumper” (ok, resistor) labeled “R1”. If you cut it, the balun will become a 9:1 isolation transformer and with such a modification will work just fine with the KK5JY “LoG”
antenna: http://www.kk5jy.net/LoG/

According to what my friend reported, the balun works just fine, and although probably the ferrite core used in the V1 isn’t up to par with the original one used by KK5JY, the difference isn’t so huge.

Oh, and I also suspect that the modified balun may work fine with the KK5JY simpler passive loop http://www.kk5jy.net/rx-loop/ which may be a nice antenna for restricted spaces!

I think it may be of interest to people not knowing/willing to wind their own baluns, at that point one may just need an enclosure to protect the balun and putting up a receive antenna will be as easy as 1-2-3.

Thank you for sharing this! Readers: Grayhat has been encouraging me to deploy a LoG antenna at my home and I do plan to do so in the coming months. Please comment if you use a LoG similar to the KK5JY model and what your results have been.

Thank you again for the tip, Grayhat!

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