In January, at the Schertz TX hamfest, I picked up a little oddity: an MFJ-1026 Deluxe Noise Canceling Signal Enhancer, for $25 cash.
This magical box takes the input from the main antenna and mixes it with the input from an auxiliary antenna and allows you to shift and invert the relative phase until a specific QRM signal vanishes. The seller told me it was fine and worked great and that he didn’t need it anymore because he moved his station to a quieter QTH. Whatever. Flea market noise. A search showed it retailed for $240, so if it worked, it was a steal.
It didn’t work.
However, it was repairable. MFJ, in their infinite wisdom, engineered this with a soldered rice-grain lightbulb as a fuse for the auxiliary antenna. If a strong signal from the transmit antenna got into the auxiliary, the bulb would blow and save the preamp. Well, this particular bulb was blown, rendering the unit unusable, so the seller got rid of it on my dime and I profited. I picked up a box of rice-grain bulbs for cheap and soldered one on the board. And it worked, kinda.
Thing is, you have to use an auxiliary antenna that has similar polarity and resonance to your main antenna and is some distance away, or it just won’t work. I found successful configuration to be difficult, so I mothballed the unit.
Every Sunday, the Austin Amateur Radio Club holds a 10-meter net at 3pm CT and, for at least the past half year, there’s been some nearby noise source that spews birdies and wideband noise every 30MHz. One those wideband noise patches lands exactly on top of the net frequency of 28.410MHz.
Every. Damned. Sunday.
So even with my radio’s best noise filtering, attenuation, and DSP processing, it’s still a struggle to hear my Austin neighbors on the net. So I’d had enough. After the debacle of this weekend’s Field Day exercise, where I experienced this QRM for a lot of my failed 10m contacts, I decided to at least give the box another try. This time, instead of using an antenna outside near my main 10m antenna, I opted to use a small, semi-directional magnetic loop inside my apartment.
That was the best decision of the whole Field Day weekend. It worked. It fucking WORKED.
By tuning the mag loop so it was resonant at 28.410MHz, and then rotating the loop and tweaking the amplitude, phase, filter, and inversion controls of the MFJ-1026, I was able to effectively cancel most of the two noise sources near my apartment and knock my noise level from the usual S8 down to S3. That’s a significant improvement, and I was able to join the net and enjoy operating radio as I heard most of my Austin-area contacts.
I don’t care if it’s a hack, but that little box contains some kind of magic. Who fucking knew, eh? I’m not sure if it’s the “right way” to solve the problem, but if I can hear what someone’s got to say, then my job is done. Pragmatism over Idealism, that’s what I say.
I just wish I would’ve done so at the beginning of Field Day and used it as a tool in my box of tricks for hearing contacts. But now I know.
Now. I. Know.