[TowerTalk] Two signals on the same frequency?

[Gene Smar]

TT:

     For a commercial implementation of the subject configuration, Google 
"MIMO."


73 de
Gene Smar  AD3F


----- Original Message ----- 
From: "Gary Schafer" <garyschafer at comcast.net>
To: "'K8RI on TT'" <k8ri-on-towertalk at tm.net>; <towertalk at contesting.com>
Sent: Sunday, August 14, 2011 7:09 PM
Subject: Re: [TowerTalk] Two signals on the same frequency?


>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 at contesting.com [mailto:towertalk-
>> bounces at contesting.com] On Behalf Of K8RI on TT
>> Sent: Sunday, August 14, 2011 6:05 PM
>> To: towertalk at 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
>> > _______________________________________________
>> >
>> >
>> >
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>>
>>
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