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## Re: [TowerTalk] Two signals on the same frequency?

 To: "'K8RI on TT'" , Re: [TowerTalk] Two signals on the same frequency? "Gary Schafer" garyschafer@comcast.net Sun, 14 Aug 2011 19:09:31 -0400 mailto:towertalk@contesting.com>
 ```A ham that I knew some years ago (an avid Do's) claimed that he and his buddy across town would sometimes get on the same frequency and one would zero beat the other by holding the telephone up to the speaker at one station and to the mike at the other station as they were both keyed up. Then one would talk into the mike and phone at the same time. He claimed that in a pileup that neither could break by themselves, got done easily with the two stations. If you think about a stacked array with the ability to feed in phase or out of phase, sometimes one is better than the other. It all depends on how the two or more signals are arriving at the other end when there is diversity involved. When the array looks more like a point source then absolute phase is more important. But I suspect that when there is significant separation in antennas then arrival phase at the other end is not as predictable. 73 Gary K4FMX > -----Original Message----- > From: towertalk-bounces@contesting.com [mailto:towertalk- > bounces@contesting.com] On Behalf Of K8RI on TT > Sent: Sunday, August 14, 2011 6:05 PM > To: towertalk@contesting.com > Subject: Re: [TowerTalk] Two signals on the same frequency? > > On 8/14/2011 5:47 PM, Jim Brown wrote: > > On 8/14/2011 2:23 PM, Jim Brown wrote: > >> The short answer is that the > >> signals from multiple antennas will ADD algebraically, > > One VERY important point is that for the signals to ADD, they must be > > SYCHRONOUS -- that is, on precisely the same frequency, coming from > the > > same oscillator. In practical terms, this means a signal generated by > a > > single transmitter, then fed to two power amps that feed different > > antennas. Or a single transmitter (with or without a single power > amp), > > split between multiple antennas. > > > > If the two signals were not synchronous (that is, from two independent > > transmitters) their phase relationships will be random, and addition > and > > subtraction will be quite unstable and unpredictable. > > Even then the signals remain synchronous only if they travel equal > distances to the antennas. IOW same electrical length of coax between > transmitter, splitter, and amps assuming no phase difference in the > power divider. Then the same electrical distance of feed line to the > antennas from the amps with no intervening hardware such as tuners. > Maintaining true phase over distance even in split systems is, or can be > a real PITA. <:-)) Fortunately, except in phased arrays (which are a > bit forgiving), or selectable stacked arrays. This type of problem is > rarely encountered in ham radio. > > 73 > > Roger (K8RI) > > > > > 73, Jim K9YC > > _______________________________________________ > > > > > > > > _______________________________________________ > > TowerTalk mailing list > > TowerTalk@contesting.com > > http://lists.contesting.com/mailman/listinfo/towertalk > > > > > _______________________________________________ > > > > _______________________________________________ > TowerTalk mailing list > TowerTalk@contesting.com > http://lists.contesting.com/mailman/listinfo/towertalk _______________________________________________ _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk ```
 Current Thread Re: [TowerTalk] TB3 Bolts, (continued) Re: [TowerTalk] TB3 Bolts, john [TowerTalk] Two signals on the same frequency?, Jari Jussila Re: [TowerTalk] Two signals on the same frequency?, K1TTT Re: [TowerTalk] Two signals on the same frequency?, Andy Re: [TowerTalk] Two signals on the same frequency?, Chet Re: [TowerTalk] Two signals on the same frequency?, Andy Re: [TowerTalk] Two signals on the same frequency?, Jim Brown Re: [TowerTalk] Two signals on the same frequency?, Jim Brown Re: [TowerTalk] Two signals on the same frequency?, K1TTT Re: [TowerTalk] Two signals on the same frequency?, K8RI on TT Re: [TowerTalk] Two signals on the same frequency?, Gary Schafer <= Re: [TowerTalk] Two signals on the same frequency?, Gene Smar Re: [TowerTalk] Two signals on the same frequency?, Jim Brown Re: [TowerTalk] Two signals on the same frequency?, Jim Lux Re: [TowerTalk] Two signals on the same frequency?, K8RI on TT