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RE: LF: RE: Ferrite broadband (LF-MF) antenna?

To: <[email protected]>
Subject: RE: LF: RE: Ferrite broadband (LF-MF) antenna?
From: <[email protected]>
Date: Fri, 22 Jun 2012 17:01:27 +0200
Importance: Normal
In-reply-to: <[email protected]>
Reply-to: [email protected]
Sender: [email protected]
Hello Daniele,once I used the 12au7 as mixerstage in an old tube broadcastreceiver with very good results,much more sensitive and less IM than the usual ECH81.I never tried it but  my guess it 's very good for a hi-Z pre-amp
 
73
 
Victor
PS.no semiconductor is a match for a warm glowing glass tube.
-----Oorspronkelijk bericht-----
Van: [email protected] [mailto:[email protected]]Namens Daniele Tincani
Verzonden: vrijdag 22 juni 2012 16:36
Aan: [email protected]
Onderwerp: Re: LF: RE: Ferrite broadband (LF-MF) antenna?

Hello Victor, thanks for your reply. In fact, now I think I will use the 12AU7 for a hi-Z pre-amp for a whip or a tuned loop (this again is just for playing with that old glassy lady :-)). As for the BD139, I didn't even suspect it could be used in a RF preamp, I tought of it as good for power stages...
73
Daniele IZ5WWB
 

Da: "[email protected]" <[email protected]>
A: [email protected]
Inviato: Venerdì 22 Giugno 2012 16:19
Oggetto: LF: RE: Ferrite broadband (LF-MF) antenna?

Hello Daniele,
 
some months ago I made a broadbanded ferriterod to cope with heavy qrm on the 80 and 160m band.The ferite comes from a submarine and is specified 10KHz to 4 MHZ with a symmetrical feedingcable to a ELK675 or other receiver without a preamp.Since I don't have such a receiver I made a balanced two stage amp with 4x BD139 grounded base.The antenna copes good with the QRM on 80 and 160,it also performs very well on the MW broadcastband.In the range 200-500KHz it is sometimes better than the E-probe,below 200KHz the E-probe wins.IM is no problem but maby the noise of the amp is to high below 200KHz.
The ferriterod is about750X100mm!
I don't think the 12AU7 is a good choice for a low inputimpedance amp...Zinput 2X BD139 is about 3 Ohm.
 
73
GL
Victor
PA3FNY
 
-----Oorspronkelijk bericht-----
Van: [email protected] [mailto:[email protected]]Namens Daniele Tincani
Verzonden: vrijdag 22 juni 2012 9:42
Aan: [email protected]
Onderwerp: LF: Ferrite broadband (LF-MF) antenna?

Hello LF,
 
I apologize to you all for resuming a topic that was already largely debated here. I have seven of those quite known russian surplus ferrite rods (20cm x 1cm) and - just for my fun - I'm planning to spend some time in building an LF-MF antenna with them. I would like to obtain a broadband (untuned) antenna, ideally VLF-LF and/or LF-MF, suitable for outdoor installation, so what I would appreciate some suggestions about is the required low-impedance amplifier, similar to those used in air-core broadband loops, if it does make sense of course. Any ideas? I found an unused 12AU7 in my drawer, could it be effectively chosen as the active device (low voltage) for such amplifier?
Thank you for any feedback
73
Daniele IZ5WWB
 


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