Yes, that was an interesting experiment; why disagree on the conclusion - it all makes sense. When it comes to the "long wire" type of antenna, the second wire end could be connected to the ground/minus, to avoid overloading (a capacitor might be needed to connect the other end to the built-in antenna). There should be a HF pre-amp transistor in the DR-920C receiver, which can be potentially removed, and then the long wire antenna can be connected directly... but without the pre-amp there will be other issues like inconsistent volume level, depending on each signal strength, fading in and out. If I had the DR-920C, I'd do the following: using a passive loop/frame antenna, connected through a HF transformer to both antenna and the ground. Long wire... probably no. 👍🏻
Yes, that was an interesting experiment; why disagree on the conclusion - it all makes sense. When it comes to the "long wire" type of antenna, the second wire end could be connected to the ground/minus, to avoid overloading (a capacitor might be needed to connect the other end to the built-in antenna). There should be a HF pre-amp transistor in the DR-920C receiver, which can be potentially removed, and then the long wire antenna can be connected directly... but without the pre-amp there will be other issues like inconsistent volume level, depending on each signal strength, fading in and out. If I had the DR-920C, I'd do the following: using a passive loop/frame antenna, connected through a HF transformer to both antenna and the ground. Long wire... probably no. 👍🏻