[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

*Subject*: [Linrad] Re: Phase relationship V to H in Linrad RX*From*: Leif Asbrink <sm5bsz.com; leif@xxxxxxxxxxxxxxxx>*Date*: Mon, 16 Mar 2009 18:41:55 +0100

Hi John, > Is there a degridation of Linrad (or MAP65) if the H and V signals are > out of phase. NO. But you would loose information about what polarisation you actually receive so the computation of the optimum transmit polarisation would become incorrect. What Linrad does is the following: 1) Compute the correlation between H and V (a complex number averaged over a long time) 2) Find out what combination of H and V that would minimize the correlation. 3) Compute the signal B using the data of step 2. The B signal will contain noise only. 4) Compute the A signal with the combination of H and V that makes the correlation zero between A and B. The combination of H and V uses one real and one complex number. The phase of the complex number is the phase shift between H and V for the spectral peak selected for the computation. A and B are the results of an orthonormal transformation of H and V. Having a minimum in B means that all the signal energy is available in A. This is fine for weak signals in a background of white noise. If one wants to use the algorithm for suppressing a strong interference, one would click on the interference signal and listen at an offset frequency in the B channel. The desired signal would not be at maximum, but in such cases having the interference kept at minimum would be the optimum. Linrad does not have the code for selecting polarisation based on another spectral peak than the one that is selected for the output because nobody seems to ever have this kind of problem. It seems the number of WSE HFA units on the HF bands is rather low.... > I am thinking of HF rx for wisper, My H and V may have > several wave lengths difference in feed line. Is this a problem? No. On HF you might as well use two V or two H antennas that are well separated or pointing in different directions. > I'm still thinking of this as diversity reception, perhaps a bad model > but the only mental picture I have. I hope it is different now:-) 73 Leif / SM5BSZ --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Linrad" group. To post to this group, send email to linrad@xxxxxxxxxxxxxxxx To unsubscribe from this group, send email to linrad+unsubscribe@xxxxxxxxxxxxxxxx For more options, visit this group at http://groups.google.com/group/linrad?hl=en -~----------~----~----~----~------~----~------~--~---LINRADDARNIL