Stefan There will be strong competition from January for DX contacts so you will need to get your Rx problems solved to keep up. One way TX is not an option. QSO CW mode is the preferred option on MF
The emitter follower transistor have a very low output impedance, no problems for receiving purpose but... if you use a long coaxial cable you connect a capacitance of about 100 pF/meter between outp
Thanks Claudio. I just installed a newer power supply for the probe, which runs at 15V instead of 12V. This should rise the clipping points a bit. Samlls steps... There are some occasional QRM traces
Hello Stefan, Did you try feeding with battery ? Also, an isolating-transformer between the power-feeder and RX ? I experienced 1-2dB drop of noise level with the battery, and small improvement with
Am 09.10.2012 17:51, schrieb mal hamilton: [...] Even a modest sized loaded vertical gives enough signal capture, has hi-Q on the frequncy of interest when resonated followed by a good well designed
Hi Roelof, In the moment it's just in my mind, not on the paper. I thought it is no good idea to publish anything as long as the problems are not solved. Of course all the problems are not only comin
LF, Another question just comes up here: Actually a coax cable must be terminated with its impedance at the ends, i.e. 50 Ohm for a RG58 cable. Otherwise there are standing waves or travelling waves
Thanks Johan for the confirmation. Well, the latest tests and mearurements show that there are strong IM when using no 50 Ohm termination on the RX end. The appear and disappear, just visible all the
Hi Stefan, in many cases it is perfectly OK to have a singly terminated transmission line. If your RG58 coax is terminated with 50+j0 ohms at the end, your active antenna output stage will see 50+j0
Thank you Claudio, I will consider that when the probe is down from the roof next. There are a few dB in reserve, i'm still far away from the RX noise. But now it looks much better! Still some IM but
Hi Roelof, So, this is the drawing (fasten your seat belt): https://dl.dropbox.com/u/19882028/LF/DK7FC%20LFMF%20RX%20and%20RXantenna.png (2.2 MB) You see, there are 2 receivers connected to the cable
Hello Hideho, Thank you for your ideas. Yes, i'm using isolation transformers where ever i can. The problem is nearly solved, at least i can now receive reasonably on MF and LF to the same time. Howe
Stefan I am not convinced that these type of Active probe antennas are suitable in an environment where there is a strong noise source or other strong adjacent signals present on the same band. A bet
case 1, Oscillation: you are right case 2, instability: appear as overshoting or ringing response at step or pulse. See the attached image. Sometime instability became self-oscillation if load impeda
Hello Stefan, Thank you for the circuit diagram. You might try to add a 10 - 100 uF electrolytic capacitor in parrallel to the 1 uF capacitor in the "Fernspeiseweiche". This sometimes helps to stop u
