Re: LF: RV: EA in LF

[DK7FC <selberdenken@posteo.de>]

Hi Luis,

Am 11.10.2017 12:42, schrieb VIGILANT Luis Fernández:

https://www.dropbox.com/s/tqzu5wxu3tfvnsv/MF%20and%20LF%20coils.jpg?dl=0

That looks very nice! You seem to have a playing field on the roof, just like i do :-)
The area on the roof seems to be quite high. At once it comes to my mind that you could install a 15m or 20m vertical antenna, the felxible ones that are offered for the 160m band. You could mount them isolated, for a few 10 kV. There is enough space to fix it with say 2x 3 isolating cords. Then you will have a much higher radiation resistance and need less L for MF/LF/VLF.

I do not recommend class-E PAs. They may be fascinating and very efficient but the SWR is very critical and you need more time and care to precisely adjust the components to reach that high efficiency. Better use a simple current-mode class D PA. It can be done quickly, a 100W version is almost trivial to build.

For the frequency generation i actually recommend to use the NEO-7 module. For QRSS/CW/OP32/EbNaut it is the perfect solution.
The PSK can be done with simple XOR gates, like CD4070. You need to build the PSK stage after the /2 divider. With a CD4093 (for example) you can build a PTT function, so the VFO can run continuously.

73, Stefan

 

I’m using an Ultimate3 with DDS (The old version) running at 2 x frequency to feed the D-Class PA

 

EbNaut in LF is also in project. But I’m puzzled at how to modulate the carrier at LF. I’m not sure if the D-Class PA

would work for phase modulation. The driver is not a typical one, but a PWM controller SG3525A. It is a modified

“Ropex the First” which was designed as Xtal CW TX. So it will ruin any try to transmit with coherent signal, I’m afraid L

 

Working also in a  Class-E PA. Whcih will be much easier to  drive with coherent signals

 

73 de Luis

EA5DOM

 

De: owner-rsgb_lf_group@blacksheep.org [mailto:owner-rsgb_lf_group@blacksheep.org] En nombre de DK7FC
Enviado el: miércoles, 11 de octubre de 2017 11:05
Para: rsgb_lf_group@blacksheep.org
Asunto: Re: LF: RV: EA in LF

 

Hello Luis,

Very well! Not a bad result for 30W :-)
Which L does your loading coil have?

2017-10-11 08:48:19 EA5DOM  1398km 137457.954Hz 163mHz -36.8dBOp  88% 20.7dB

2017-10-11 07:48:19 EA5DOM  1398km 137457.960Hz 106mHz -38.3dBOp  65% 17.5dB

2017-10-10 04:48:19 EA5DOM  1398km 137488.938Hz 177mHz -38.2dBOp  65% 19.0dB

2017-10-09 15:48:19 EA5DOM  1398km 137509.949Hz 174mHz -38.7dBOp  88% 20.6dB

Unfortunately my LF RX is overloaded by the local VLF transmissions (20m diatance between the antennas) but we can see that i can receive you beginning in the late afternoon until the morning :-)

How do you generate your frequency? Is it a coherent signal? Looks like the bandwidth is relatively high...

You could use one of the recent discussed NEO-7 GPS modules to generate the frequency directly. This would give you an ultra stable and precise carrier...
It would even work for EbNaut which is BTW a very good idea to try anyway :-)

73, Stefan




Am 11.10.2017 10:09, schrieb VIGILANT Luis Fernández:

Hi LF

 

I keep running Tx Op32 every hour at 30W to antenna