4 Aug 2011

VLF beacon transmitter schematic

G3XBM's VLF 5W Earth Mode Beacon
This is the schematic of my TDA2003 5W ULF/VLF beacon transmitter used in recent earth mode tests. The frequency is derived from a 4.48MHz crystal that is divided down to either 8.760 or 1.095kHz using a 4060 IC. This is keyed in either 10wpm CW, QRSS3 or QRSS30 with a K1EL beacon keyer IC. The output of the TDA2003 is matched to the resistance presented by two earth electrodes using a tapped toroid transformer. Best DX is now 6km across the fenland near me.
at 19:32
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7 comments:

Anonymous said...

Hello Roger

Haver you any plans for the high power amplifier.
I have some TDA2030 IC's , do you know what the maximum output power is for that device.

Tony

Thu Aug 04, 08:01:00 pm GMT+1
Anonymous said...

Roger

Have you got the winding details for the output matching transformer.

Tony

Thu Aug 04, 08:06:00 pm GMT+1
Roger G3XBM said...

Tony

The toroid used in mine was an ex-PMR one (used in the Pye M206 audio I think) but a 3C90 toroid should be suitable. Mine has about 10 turns on the primary and around 50 turns on the secondary tapped around every 10 turns. The toroid is about 50mm diameter. I will replace the ex-PMR one with a 3C90 when I next rebuild the unit.

Thu Aug 04, 09:26:00 pm GMT+1
Anonymous said...

Thanks for the info Roger

Tony

Thu Aug 04, 09:47:00 pm GMT+1
Anonymous said...

Roger

The TDA2030 is rated for 14 Watts output.
I will try and print the data sheet tomorrow.

Tony

Thu Aug 04, 10:16:00 pm GMT+1
Anonymous said...

to Roger G3XBM
i have made the VLF Beacon and I just receive from Amidon T200-3 ferrite for VLF , I just wanted to know what is the diameter of the wire of 10 primary and 50 secondary you used.
thanks in advange
Panos sv2mch

Mon Mar 26, 06:52:00 pm GMT+1
Roger G3XBM said...

Panos, I would use reasonably thick wire (1mm or more) if possible, although at QRP levels it is not too important.

Mon Mar 26, 07:49:00 pm GMT+1

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