Don,
I agree with your 40 dB isolation number, and would expect that to be fairly
conservative, since that would result in a +10 dBm level at the
non-operating receiver. The ARRL Lab tests all product review receivers for
IMD response at up to +10 dBm input and there have never (to my knowledge)
been any failures.
But this question comes up frequently in many contexts and the stumbling
block is that there are no "max safe rcv levels" published by manufacturers
(only exception I'm aware of is the Collins 75A4, which has a sticker by the
receive antenna terminal "Do not exceed 50 V," which translates to 50 W at
50 ohms, or +47 dBm -- more than most solid state gear can handle, I would
expect!).
So my question is has (or can) Elecraft actually come up with a "max safe
rcv level" spec for their receivers? This would be great, not only for those
wanting to use a multi-radio switch, but also for those setting up Field Day
or other multiradio environments, or especially for those who use a receive
only antenna.
Two other comments about the original question:
The switch isolation figure assumes that all shields are solidly connected.
Loose connector backshells, or bad shield solder connections, can result in
signals propagating around the switch that can be higher than the switch
crosstalk.
Another potential limitation is that the switch crosstalk spec likely
assumes that all ports are terminated in 50 ohms. If the non-operating
receiver is turned off, or is on another band, the input Z can be very
different and result in higher voltage than the spec would predict.
Regards, Joel Hallas, W1ZR
Message: 10
Date: Fri, 30 Dec 2016 18:44:58 -0500
From: Don Wilhelm <donw...@embarqmail.com>
To: stan levandowski <sjl...@optonline.net>, Elecraft@mailman.qth.net
Subject: Re: [Elecraft] {OT} - Variation on use of a coaxial switch
Message-ID: <805217a9-a8a2-7b82-ff34-db2765bea...@embarqmail.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Stan,
If your maximum power is 100 watts and the isolation of the switch is
40dB or more then I don't think you have any problem.
73,
Don W3FPR
On 12/30/2016 5:49 PM, stan levandowski wrote:
> I would like to use a coaxial switch for an unintended use and I'm not
> sure if it's a good idea in terms of RF isolation and potential
> equipment damage.
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