Hi there, I use a minicircuit PSC-2-1 combiner, something like a 20$ device or less, to use both a vertical antenna and an horizontal at the same time from LF to UHF. Antennas in principle should be far away each other. However somehow mine are very close, the vertical being on top of the horizontal. Often when a signal drops on one antenna it gets stronger on the other. Indeed fading is reduced, the signal is often increased by more the 3db, sometimes 2S units. The drawback is that constantly you get the loudest noise floor of the noisiest antenna added by up 3db. This solution works best when the noise floor of both antennas are the same. Signal to Noise ratio is likely to be increased and fading reduced. But it works quite badly if you have e.g. S8 noise floor on the vertical and S5 on the vertical, i.e. when the noise "spread" between the two antennas is large. In this case you would had rather better off using the horizontal because of the higher noise.
73 Franco iz2oos 2011/8/8 K9sqg <[email protected]>: > There is a slight addendum that I believe should be added to the traditional > belief that antennas need to be physically separated in order to use them > for diversity reception. While I agree with the statement for identical > antennas, it does not necessarily hold for dissimilar antennas. Why? If > the two antennas are identical, then they will be equal in all attributes > and unless they are physically separated, then the signal could be expected > to be identical with either antenna, fading included. But what about > dissimilar antennas? If you have two antennas in close proximity, but they > are different, they can be used to counter the results of some types of > fading. For example, if the two antennas have different radiation/reception > patterns, they might exhibit different characteristics if the fading is > along the lines of the signal arriving from different elevation angles. > I've never seen an article address this phenomenon but based upon empirical > data, it does work. > My installation uses two horizontal loop antennas approximately concentric > with each other, that I use on the 40 m band for the Drake Nets and HF swap > nets. The 40 m loop is about 12' high and the 80 m loop is about 25' high. > Models of these antennas show that the radiation/reception patterns are > different as one would expect; a horizontal loop antenna used on frequencies > higher than the fundamental will exhibit more low angle lobes as the > frequency is increased. It is interesting to observe how signals from > different directions and distances are received when using both antennas, > one connected to my TR-7A and one connected to my R-7A. Sometimes one > antenna is better than the other, and sometimes they are the same. What is > most interesting is that sometimes a signal that is Q5 copy on one antenna > can't be heard at all on the other. This results in coverage that would > otherwise be impossible had these two, close proximity antennas not been > used. > While many diversity systems use two receivers with various schemes for > connecting the AVC lines etc., you can achieve the same thing functionally > by using the perceptual and cognitive abilities of the human operator. Feed > the signal from one antenna/receiver to one side of your headphones, and > feed the signal from the other antenna/receiver to the other side of your > headphones. While this system isn't supposed to work, I haven't told my > antennas that yet so they just keep on working... > > > > -----Original Message----- > From: Dennis Monticelli <[email protected]> > To: Nigel A. Gunn, W8IFF/G8IFF <[email protected]> > Cc: Drakelist <[email protected]> > Sent: Sun, Aug 7, 2011 8:29 pm > Subject: Re: [Drakelist] Fading > > Yes. Diversity reception is a well known technique, but you need a radio > so-configured or a separate box to process the inputs from the two > antennas. The antennas must be physically separated from each other > sufficiently that a fade on one would not necessarily occur in the other at > the same time. The good news is that the technique really does work. > > Dennis AE6C > > On Sun, Aug 7, 2011 at 4:27 PM, Nigel A. Gunn, W8IFF/G8IFF <[email protected]> > wrote: >> >> Look up "diversity reception" >> >> >> On 08/07/2011 11:22 PM, Neil M Califano wrote: >>> >>> This is a bit off topic, but how can two receiving antennas be used to >>> reduce fading? >>> >>> _______________________________________________ >>> Drakelist mailing list >>> [email protected] >>> http://mailman.zerobeat.net/mailman/listinfo/drakelist >>> >> >> >> _______________________________________________ >> Drakelist mailing list >> [email protected] >> http://mailman.zerobeat.net/mailman/listinfo/drakelist > > _______________________________________________ > Drakelist mailing list > [email protected] > http://mailman.zerobeat.net/mailman/listinfo/drakelist > > _______________________________________________ > Drakelist mailing list > [email protected] > http://mailman.zerobeat.net/mailman/listinfo/drakelist > > _______________________________________________ Drakelist mailing list [email protected] http://mailman.zerobeat.net/mailman/listinfo/drakelist
