[Icom] Coax Switches Revisited

Mon, 19 May 2003 11:07:23 -0400

Try the calculation the other way around:

What S meter reading would 1mw of r.f. applied to the antenna port produce?

73
DR
----- Original Message ----- 
From: "Lefczik, Larry D" <[email protected]>
To: <[email protected]>
Sent: Monday, May 19, 2003 10:53 AM
Subject: RE: [Icom] Coax Switches Revisited

> 100Watts - 50 dB = 0.001Watts  1mW into the front end of a receiver.
Scary?
>
>
> + Frank, I have run those test on the Diawa cavity switches in
> + the past.  If
> + memory serves, they provide about 50db of isolation per port
> + to about 300
> + mhz and about 40db above that.  Dave
> +
> +
> + > >
> + > >Hi Folks,
> + > >
> + > >Well on Thursday I decided to start doing some tests on my
> + XXX brand coax
> + > >switches as to the amount of isolation between the
> + selected rig and the
> + > >other 5 "grounded" positions.  I do have external grounds
> + run to the case
> + > >of the switches.
> + > >
> + > >I used some very small wire and a little pickup coil run
> + to the outside
> + the
> + > >box to a small 12 volt light bulb. When running 100 watts
> + to the dummy
> + > >load, the bulb would light at about 50 to 60 % of it's
> + normal output,
> + > >interesting.
> + > >
> + > >Next I unhooked the other 5 rigs from the switch and
> + hooked the bulb to
> + one
> + > >of the unused coax connectors and fired up a rig at 100
> + watts in RTTY to
> + > >the dummy. Guess what? the bulb blew.., Burned out, toast etc.
> + > >
> + > >So, I have to wonder what is this doing to the other 5
> + rigs hooked to the
> + > >switch even though the rigs were off?  I think I know now
> + why my Icom PCR
> + > >1000 had the front end fried on it.
> + > >
> + > >So, major changes took place based on these tests.
> + > >
> + > >I removed the switches and went back to my old method of
> + isolation and
> + rig
> + > >switching by using feed thru bulkhead coax connectors
> + mounted on a panel
> + > >with the various rigs hooked to the back side and then the antenna
> + > >selection just hooks to whatever rig I wish to use at the
> + time. Simple
> + but
> + > >I feel it is whole lot better and safer. I will update the
> + pictures on my
> + > >web page later tonight.
> + > >
> + > >This was my test run under controlled conditions and your
> + mileage may
> + > >differ.
> + > >
> + > >73
> +
> ----
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