Aw: AW: LF: Variometer es Loading coils, from DK 8 ND

["Hans-Albrecht Haffa" <dk8nd@web.de>]

Dear Lowfers, Medfers,

for suitabel matching  I use a transformer (See Jerry Sevicks Balun Book, "Transmission line transformers", ARRL Publications) and a loading coil with variometer, for 1,8 MHz, 136 kHz and 472 kHz. Between HF and LF I use two Vac-Relais, (Normally open contact, abt. 30 kV/10 A from Jennings), 136 k and 472k I switch with banana plugs manually.  Running to and fro for alignment of the variometers, I am using a Antenna Analyser in the shack (VA3 , Kit from Funkamateur.de) . Input resistance for 136k is about 300 Ohm, for 472 kHz abt. 60 Ohm.

Parallel to the metal marconi vertical antenna are two Fiberglas rods, 10 m and 12 m, tuned for 7 MHz and 3,5 MHz as short helix Antennas.

I do not know, if the present solution (used in three different qths) has disadsvantages for LF, that I did not realize till now.

My proposal:

- Resonant circuit in the stile of VK2AOU as base loading coil

- Or using two Helix-Antennas tuned for 472k and 136k parallel in HB9ASB-Style. How mutch the two rods must be spaced, that the electric fields are not partially shorted? Think of the influence of trees near to the antenna at 136k.

Anyway I recomend using two loading coils or two variometers with separate drives.

A not extremely cheap possibility is an electric cylinder as drive for the variometer.

http://produkt.conrad.de/45973183/elektrozylinder.htm

55, Hans-Albrecht

DK 8 ND

Gesendet: Sonntag, 13. Januar 2013 um 19:44 Uhr
Von: "Joe DF2JP" <df2jp@gmx.de>
An: rsgb_lf_group@blacksheep.org
Betreff: AW: LF: Variometer es Loading coils

Hi Stefan, LF

 

I´ve just fixed my antennaswitch today.

It´s a ceramic switch 4” diameter, fit well into on of these gray HT-Tube.

But it is switched manually.

Will check if it works with my 17,5 kV on LF next days.

 

https://www.dropbox.com/s/t6pyjfhsecykg9n/antswitch1.jpg

 

https://www.dropbox.com/s/pyll4voh7ieavwe/antswitch3.jpg

 

73 Joe

 

---

Von: owner-rsgb_lf_group@blacksheep.org [mailto:owner-rsgb_lf_group@blacksheep.org] Im Auftrag von Stefan Schäfer
Gesendet: Sonntag, 13. Januar 2013 17:39
An: rsgb_lf_group@blacksheep.org
Betreff: Re: LF: Variometer es Loading coils

 

Sri, typos:

Am 13.01.2013 17:29, schrieb Stefan Schäfer:

But then the switch has to withstand the HV when TXing on MF.

...on LF.

  and a high inductance of the transformer then the 50 Ohm side is...

when