[Moon-net] 2 receivers with the same antenna

[Marko Cebokli]

Hello,

I still think the resistive divider (just make a triangle of 50 ohm resistors 
or a star of 50/3=16.6 ohm resistors...) is the best choice:

1. after the LNA low loss is not so important. Actually in measurement, loss 
can be beneficial (reduced ripple etc...).

2. with halfway sensibly designed receivers, the isolation is not really 
important - of course, if one of your RXes is a direct conversion type, it 
would be - but in that case, even the fanciest of hybrid couplers will not 
give you enough isolation :-)

73, Marko S57UUU

(in TV, the band is wider than the IF, so one TV's LO can easily fall onto the 
others input frequency, making it a different story...)




On Saturday 17 November 2007 20:45, Sergio wrote:
> Gabriel,
>
> as other have you suggested, you can practically use a resistive power
> splitter to accomplish your job.   Theoretically that 'shall' not be the
> cleanest and best way, though.  In a truly perfect scenario the
> receivers shall not 'see' each other and that cannot be accomplished
> simply by a resistive splitter.
>
> It seems strange but receivers might be leaking RF coming from the
> oscillator chain or other sources through the antenna.  In this case the
> other receiver might not be 'too happy'.  It is clear that a very
> detailed investigation shall be carried out to evaluate the frequencies
> and magnitude of the possible interfering signals. In some cases it
> might not be a problem, maybe just like in your case.
>
> Anyhow it does happen, I've seen it a number of times in some cheap home
> TV installations where strange lines were appearing on the screen after
> some two or more TV sets were connected with resistive or even inductive
> splitters on the same antenna.  Ok AM TV tuners are all but
> technological devices but they are a proof of that being a possibility.
> Imagine that during WW2 the receivers LO leakage was even used to detect
> the proximity of the enemies sometimes, no radars needed!
>
> Go ahead and use your splitter now. Hi.
>
> Ciao
>
> Sergio IK2MMB
>
> Gabriel - EA6VQ ha scritto:
> > Hi,
> >
> > Might be this is a silly question, but I can't find very much information
> > about this subject using Google.
> >
> > What is the right (lowless) way to connect two 144 MHz receivers to a
> > single antenna?
> >
> > I want to make some tests comparing the reception of my usual receiver
> > against an SDR-IQ receiver. What kind of splitter should I use?
> >
> > 73. Gabriel - EA6VQ
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