RE: LF: remote antenna tuning

[Rik Strobbe <Rik.Strobbe@fys.kuleuven.be>]

Hi Stefan,

 

thanks for the info.

In one of the previous mails you asked me about the PA: it is a push-pull class D PA. I am using that type of PA for many years on 136 kHz and 500 kHz (now 475 kHz) to my satisfaction.

Using a couple of cheap IRFP450's it produces up to 500 W RF power at 85% effeciency. And it is very forgiving to mismatch.

 

73, Rik  ON7YD - OR7T

 

---

Van: owner-rsgb_lf_group@blacksheep.org [owner-rsgb_lf_group@blacksheep.org] namens Stefan Schäfer [Stefan.Schaefer@iup.uni-heidelberg.de]
Verzonden: zondag 10 november 2013 16:22
Aan: rsgb_lf_group@blacksheep.org
Onderwerp: Re: LF: remote antenna tuning

Hello Rik,

Am 08.11.2013 22:43, schrieb Rik Strobbe:

Hello Gary, Graham, Dave,

 

thanks for the info. I will build the MBMU tuning meter.

 

73, Rik  ON7YD - OR7T

BTW, i'm using this circuit in addition to the M0BMU phase meter to automatically steer the motor that rotates the variometer coil: https://dl.dropboxusercontent.com/u/19882028/LF/DK7FC%20Automatic_variometer_tuner%20.jpg Minor alignment of the circuit may be necessary in order to prevent mechanical self oscillations of the system. It works very well since 2 years now. And it looks as i'm using the same motor as G4WGT :-) On LF i have to re-tune the resonance peak when doing QSY by 10 Hz(!) so it would work on MF without a problem.

Actually a good idea to build it here for MF too. One could use a simple CAT5 cable to bring the DC voltage coming from the phase meter to the shack and to bring the motor supply voltage back to the coil. If i would be a mircocontroller programmer, it would be easy to realise a power meter, impedance meter, antenna current meter, phase meter (digital displayed). Such a LF/MF station seems never to become complete :-)

73, Stefan/DK7FC