The insertion loss and the isolation between ports on splitters are
interesting points indeed. Yes, the data is correct IF the source and the
loads are what is required by the splitters. Thus if one uses a plain old
TV 75 ohm splitter the data is correct in terms of isolation and insertion
loss if the source is 75 ohms and the load is 75 ohms on each port.
Since most receivers are not devices which provide a 50 ohm load via their
inputs, then all bets are off. Looking into the receiver with an analyzer I
find that most wander between 30 ohms and upwards of nearly 150 ohms,
depending on frequency. Yes, I know we'd like to think the receiver input
is 50 ohms but most are not.
I say save your money, take the easy way out and use a plain old cheap 75
ohm TV splitter. After all the mismatch would produce a SWR of only 1.5:1
You'll have about 1/2 S unit loss (3 to 4 dB) and some 15 to 25 dB
isolation depending on frequency. I just did a sweep using a 50 ohm source
and 50 ohm loads from 1.0 MHz to 50 MHz on a $3.00 RS unit that was in my
junk box.
73
Bob, K4TAX
----- Original Message -----
From: "Eric F Richards" <efricha@dimensional.com>
To: <tentec@contesting.com>
Sent: Wednesday, August 06, 2003 2:24 PM
Subject: Re: [TenTec] Antenna Splitter
> At 01:52 PM 8/6/2003 -0500, you wrote:
> >What you need is a switch, so that the impedance of each radio is not
> >disturbed by the connection to the antenna and another radio.
> >
> >A splitter would decrease the signal level to each radio and cause the
need
> >for a correction factor on minimal detectable signal.
>
> Both the mini-circuits and stridsberg splitters (which are made with
> mini-circuits component splitters) provide over 20dB isolation between
> the radios and just over 3dB loss of signal.
>
> I know from where I speak -- I use stridsberg splitters, mini-circuits
> splitter boxes and mini-circuits component splitters. The breakdown is
> as follows:
>
> 1 mini-circuits microwave splitter
> 1 stridsberg 4-way V/UHF splitter
> 2 stridsberg 2-way V/UHF splitters
> 2 stridsberg 4-way HF splitters
> 2 stridsberg 2-way HF splitters
> 1 mini-circuits HF splitter transformer in a phasing box I built.
>
>
>
> >Since band fading follows a 20 minute pattern on average, you should be
able
> >to do short term switching by hand and compare signals received
> >independently on an antenna.
> >-Stuart
> >K5KVH
> >
> >
> >_______________________________________________
> >TenTec mailing list
> >TenTec@contesting.com
> >http://lists.contesting.com/mailman/listinfo/tentec
>
> --
> Eric F. Richards
> efricha@dimensional.com
> "The weird part is that I can feel productive even when I'm doomed."
>
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>
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