27-09-2018, 07:29 AM
(This post was last modified: 27-09-2018, 07:31 AM by Murphyv310.)
Hi Mike.
The directional nulls should be very sharp, even a few degrees of rotation should bring back a fair increase in signal level.
Here I can receive Radio Caroline on 648KHz quite easily but the adjacent frequency can cause a lot of problems. Now I have two ways of removing side-band splatter.
1 is to carefully rotate the loop to null the Spanish station, this works well with only a small drop in the wanted signal.
2 is to use the SdrPlay receiver and trim off the offending side-band from the Spanish station.
The whole idea with a magnetic loop is the use of the balanced amp, without it being balanced there would be no way of rejecting local noise and the nulls would go or are least be much reduced.
It is important to use close tolerance components in the build, a neat layout and if possible transistors that are as closely matched as possible. Toroid transformers must also be carefully wound with matching turns and gaps, its not hard but attention to detail really can improve performance.
I firstly fitted my two transistor amp about 10 years ago and improved it around three years ago with a better sealed box and intermodulation protection.
The directional nulls should be very sharp, even a few degrees of rotation should bring back a fair increase in signal level.
Here I can receive Radio Caroline on 648KHz quite easily but the adjacent frequency can cause a lot of problems. Now I have two ways of removing side-band splatter.
1 is to carefully rotate the loop to null the Spanish station, this works well with only a small drop in the wanted signal.
2 is to use the SdrPlay receiver and trim off the offending side-band from the Spanish station.
The whole idea with a magnetic loop is the use of the balanced amp, without it being balanced there would be no way of rejecting local noise and the nulls would go or are least be much reduced.
It is important to use close tolerance components in the build, a neat layout and if possible transistors that are as closely matched as possible. Toroid transformers must also be carefully wound with matching turns and gaps, its not hard but attention to detail really can improve performance.
I firstly fitted my two transistor amp about 10 years ago and improved it around three years ago with a better sealed box and intermodulation protection.
