Wideband regenerative (ferrite rod) loop antenna

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Re: Wideband regenerative (ferrite rod) loop antenna

Post by Admin on Fri Oct 27, 2017 5:36 pm

Hi Glenn,
That sounds like a very worthwhile project.
At the moment I am rather busy in Spain (no radio this time) and when I return to Sweden time will be short.
I am presently building an oscilloscope and boxing the 0-30MHz DDS signal generator.

After that it could be an idea to make something similar to your suggestion.
In the 60's I did a lot with Q-Multipliers (first with 6C4, then with AF114). Worked a treat, but a little positive feedback can increase sensitivity, and if the components are chosen correctly possibly a TX/RX antenna, with regeneration.
Let me think about that for a while.

Anybody else intrerested in taking up this challenge?

BR Harry

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Wideband regenerative (ferrite rod) loop antenna

Post by Glenndk on Tue Oct 24, 2017 10:06 pm

Hi Harry

I have a "challenge"...

It is possible to built a regenerative wideband ferrite antenna - maybe up to 30MHz? (with e.g. magnetic material 61; page 17-18 ( http://web.archive.org/web/20170806130801/http://www.g8jnj.net/Balun%20construction.pdf ) or (2)). Please note that the ferrite rod can be removed - and then you have a wideband regenerative loop antenna.

There are schematics and good description of a regenerative wideband ferrite antenna in the following patent (1). E.g. use op-amp LMH6647MF (-3dB at 55MHz).

Do you or others want to try to built it?

-

(1) Patent:

Patent seems to be close to be expired; 23 years: 1994: Wideband ferrite full shortwave-antenna:
The positive feedback provided by the feedback current lowers the antenna impedance which, in turn, increases the effective area of the antenna:
https://patentimages.storage.googleapis.com/pdfs/US5296866.pdf
Quote: "...
The outstanding stability of this active antenna
...
The reason why an antenna with regeneration has greater sensitivity than one without regeneration may be understood in terms of the concept of antenna “effective area.”
...
It is yet another object of this invention to provide an improved broadband active antenna system.
..."

(2) Possible ferrite rod:
https://web.archive.org/web/20170212031426/http://www.schubert-gehaeuse.de/prod01.htm
Quote: "Ferritstab bis 30Mhz verwendbar".

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