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

[Daniele Tincani <danieletincani@yahoo.com>]

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: "victor13@online.nl" <victor13@online.nl>
A: rsgb_lf_group@blacksheep.org
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: owner-rsgb_lf_group@blacksheep.org [mailto:owner-rsgb_lf_group@blacksheep.org]Namens Daniele Tincani
Verzonden: vrijdag 22 juni 2012 9:42
Aan: rsgb_lf_group@blacksheep.org
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