Gosh, everybody, I didn't mean to create any controversy. FYI, I
already have a high quality (??) Alpha Delta switch where "...unused
terminals are grounded" and that's what I'm going to use. I'll just
have to be careful.
I use my KX2/KXPA100 most of the time and that's the position the switch
will be routinely be in. The other switch position will be connected to
50' of un-terminated coax. Every once in awhile I feel like operating
my little KX1 a) while lying in bed, b) by a roaring fire in my
fireplace while it's snowing, c) on my front porch on a summer night
with a glass of iced tea and d) on the back deck while doing BBQ.
The switch and the 50' of coax allow me to connect my KX1 to my SGC-231
and (amazingly!) there's enough RF to kick the coupler into action.
It's nice to get out of the shack and operate simply once-in-awhile and
a good doublet beats a piece of wire by a country mile.
Thanks to all and Happy New Year.
On Sun, Jan 01, 2017 at 04:49 PM, Bill Johnson wrote:
John,
That MFJ switch is also a good example of some poor construction which
some
of the MFJ equipment has/had. I have some MFJ-998 equipment which had
some
excellent construction.
73,
Bill
K9YEQ
-----Original Message-----
From: Elecraft [mailto:[email protected]] On Behalf Of
John
Sent: Sunday, January 1, 2017 1:41 PM
To: [email protected]; [email protected]
Subject: Re: [Elecraft] {OT} - Variation on use of a coaxial switch
(stan
levandowski)
Jim,
Indeed, and an observation I too had made (you'll note I didn't say
it's 'in
service', merely 'given to me').
I was just trying to provide an illustration of what was being
described by
Dale.
John (XLX)
-----Original Message-----
From: Elecraft [mailto:[email protected]] On Behalf Of
Jim
Brown
Sent: 01 January 2017 19:32
To: [email protected]
Subject: Re: [Elecraft] {OT} - Variation on use of a coaxial switch
(stan
levandowski)
The isolation provided by this switch will be really poor. In addition
to
the capacitive coupling of the switch itself, note that only the
center
conductor is carried between inputs and outputs, so that the chassis
carries
return current. This adds a lot of inductance to the path, and causes
crosstalk between circuits.
The RIGHT way to do this is to provide a coaxial path, so that return
current is confined to the coax shields. If you look inside the Alpha
Delta
switches you see that they are built that way. There's not coax cable
between in and outs, but the physical construction is such that the
body of
the switch forms the return path. Not perfect, but FAR better.
73, Jim K9YC
On Sun,1/1/2017 10:37 AM, John wrote:
What Dale describes below is a very similar configuration to the MFJ
switch I was given a year or so ago - an MFJ-1703.
I just popped the lid off and took a photo of the insides for you:
https://www.dropbox.com/s/h28jny6vrkj7rdj/2017-01-01%2018.28.00.jpg?dl
=0
The only difference being that it's basically a DPDT slide switch,
rather than a rotary. Works just as well.
At least, I think that's pretty much what he was describing anyway.
Stick a dummy load on one output and your antenna on the other, and
your two rigs on the two inputs.
73, and a firm left handshake,
John (XLX)
-----Original Message-----
From: Elecraft [mailto:[email protected]] On Behalf Of
Dale Martin
Sent: 01 January 2017 17:31
To: [email protected]
Subject: Re: [Elecraft] {OT} - Variation on use of a coaxial switch
(stan
levandowski)
Stan,
I haven't taken the time to read all the other responses, but have
you considered building your own coax switch.
Parts: 1 aluminum box, 4 SO-239's, 1 two-pole, multi-position rotary
switch (you only need 2 positions, but more is okay), 100w dummy load
Mount the SO-239's (J1-J4) and rotary switch
Wire up the switch thusly:
Pole 1 to J1 (KX2)
Contact 1 to J3 (antenna feedline)
Contact 2 to J4 (dummy load)
Pole 2 to J2 (KX1)
Contact 1 to J4 (dummy load)
Contact 2 to J3 (Antenna feedline)
When you switch one radio the antenna, the other radio is then put on
the dummy load.
73,
Dale, kg5u
------------------------------
Message: 3
Date: Fri, 30 Dec 2016 17:49:21 -0500 (EST)
From: stan levandowski To: [email protected]
Subject: [Elecraft] {OT} - Variation on use of a coaxial switch
Message-ID: <[email protected]>
Content-Type: text/plain; charset=UTF-8; format=flowed
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.
I'm no expert in this area but I know this list is a wealth of
expert
opinion, so
here's my question:
I want to buy a two position coaxial switch. ?I want to connect ONE
antenna to it and switch this antenna between a KX2/KXPA100 (100
watts) and a KX1 (about 3 watts). ?The coax cable coming from this
switch to the KX2 is a short piece of RG8X and the coax cable going
from this switch to the KX1 is 25' of RG-174 (yes, I already
computed the dB loss and I can live with).?
Am I likely to cause any damage to to either piece of equipment?
Thanks,
Stan WB2LQF
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