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”

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 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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4 thoughts on “The NooElec Balun 1:9 v2

  1. RonF

    Something doesn’t make sense about the pics, schematic, & description.

    From the pic above & on the nooelec site, it’s clearly a WB9-1 transformer – except that, according to Coilcraft’s datasheet (and the through-hole WB9-1L i’ve got here & just tested), neither side is centre-tapped. Coilcraft in fact don’t list a centre-tapped 9:1 in the WB series; the closest would be the 8:1 WB8-1TL or TSL.

    Maybe it’s a custom transformer – though Coilcraft usually mark those differently. Wonder if Nooelec originally designed their board for something like a Minicircuits ADT9-1T+ – which is centre-tapped on the high-impedance side – then changed transformers without checking?

    Grayhat &/or his friend might like to check whether the CT pin connects to either side of that winding. It’ll be interesting to see if it does.

    1. RonF

      And … re-reading now, I see that the description & circuit refers to the older v1 balun, which /does/ use what looks like a Minicircuits TC-series centre-tapped balun. Should’ve read more carefully!

      1. Andrew

        If you check the back side of the v2 board (image on nooelec website) you’ll see that the center tap is grounded through a resistor marked as R1 and given that both the v1 and v2 share the same schematic, my guess is that the board in the pic may be some pre-production unit


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