Originally Posted by 7designs
You wouldn't happen to have a schematic would you? All I am finding is commercial units and designs for ham.
You're right, it is hard to find a good article.
You'll need two antennas. Two wires, or a wire and a loop.
For two wires, build a parallel tuned circuit that will resonate in the medium wave band and put that in series with your wire antenna. (confusing, eh?)
Use what parts you have on hand, but if you pull the variable cap and loop stick antenna out of some portable AM radios, then you're good to go.
(eliminate C4 and the radio gets hooked up at the bottom)
Make one circuit for both antennas and put them on a switch, or use clip leads so you can choose antenna A, B, and BOTH.
The phasing is very frequency specific in this circuit, so tune into the station that you want to make GONE. Let's say 720khz WGN. Peak the circuit on antenna A for max S meter reading. Switch to antenna B and do the same for WGN. For best results the S meter reading should be the same on both antennas. Many times it is not, so a 50k ohm variable resistor (potentiometer) in series with each of your antenna leads allows to you make them the same. Next, flip your switch to BOTH (or attach both antennas to your receiver at the same time with clip leads) and -carefully- adjust your variable caps until you null WGN. If WGN is S9 on each antenna, you should be able to drop it down to S3 or even make it dissapear (!) leaving weaker stations underneith in the clear.
If you have a wire and a tunable loop, do the same thing. Adjust both your wire and loop for max signal strength, connect them both together, and adjust the tuning to null your 'pest'.
When you change frequencies, you'll have to re-tune your circuits, but this method works VERY well and I've used it to log many Mexican and South American stations when they normally would be covered up by stateside stations. I've done it during the daytime on my local stations and have heard stuff at sunset that I could never hear otherwise. The loop/wire combo is very potent and I've also had good results phasing a wire vs a vertical. Go out to a park, lay out some wires on the ground (BOG antenna) and phase those together. The limits are only in your imagination.
Super cheap DX!
There are other ways to phase antennas (broadband), but this is the simplest way, and very effective.
I've had a couple MFJ-1026s and they work very well. The problem at my QTH is that the surface mount components get overloaded by my local stations and I get slop across the whole band. When I use BIG antennas, it gets even worse, so I have better luck using my home brew phasers.
I use big variable caps and big coils, but use what you can get your hands on.
(if you're into FM DXing also, you can phase FM yagis with a slightly different circuit for the same effect. Getting sneaky to log the rare ones!)