Good morning, sorry if I didn't answer all the appreciated replies but yesterday I sat there to do some tests and I have to say that maybe the apparent poor sensitivity on the low ranges of the LN amplifier can also be attributed to the positioning of the loop? In fact I moved the test loop (1 mt) inside the laboratory connected to the T-Bias with another shorter test cable (even if the longer external cable is fine) and things seem to be going better. It is true that maybe positioning the loop on a branch of a tree (about two meters high) with a metal net less than three meters away plus one of those mobile shelters for cars probably also made of metal structure, with a sheet metal shed on the side also less than three meters away... maybe it's not the best condition for this reception band, while on others with other types of propagation it goes decidedly better. I tried with the sample made both with the two types of jfet (2SK932 and original 2SK715) and with the normal two transistors amplifier with the BFU590 (qx) and the results are more or less similar, so... I don't think there are problems of construction or electronic components. Having said that, I answer individually to those who answered me:
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Dave Martin: What do you mean? The coupling capacitors are those in the diagram, already used similarly in other amplifiers.
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Tom VE3PSZ: Ferrite material is always 73. BN 73-302 ferrite core.
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Steve Ratzlaff: Yes, I have had a NanoVNA from some time and in fact I really needed to understand how to do some bench tests of the amplifiers with that instrument. I made a diagram that I put together with the photos of the two boards, to understand if I understood well how to make the connections you suggested, if you can take a look at it... /g/loopantennas/photo/299839/3872714?p=Created%2C%2C%2C20%2C2%2C0%2C0
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Martin Southwest UK: Windings are correct, I have always taken into account the construction diagrams that appeared on the Wellgood Loop page which are always valid. However, for the test I tried to invert or rather "rectify" the connection of the secondary of the first transformer and obviously the amplifier DOES NOT WORK AT ALL...
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Everett N4CY: In the meantime, thanks for the private replies, that's why I asked you if you sell an unpopulated board of your version to see what differences there may be... mine is already double-sided, since SMD elements need to be mounted. I also did some tests with the insulation of the copper wires from the ferrite body using 3D printed insulators and although I can confirm that the 73 material conducts (we are about 25-30 Kohm) at least audibly I don't see/hear differences, which surely there will be instrumentally...
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On the side of the discussion, yesterday I also tried to build the "Everett N4CY" version of the LZ1AQ amplifier using 4 BFU590GX transistors (the ones in the bigger case) and I have to say that the first tests are really impressive, at least inside my lab it receives better than the LNs and even better than the original LZ1AQ that I also placed outside hanging from a tree and powered via CAT7 network cable!! I was really amazed...ok thanks to everyone, Francesco Caizzi IU4TSV
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