Re: [Elecraft] {OT} - Variation on use of a coaxial switch

[Edward R Cole]

I use a Dow Key 412-2301 Transfer Relay to select my 6m kilowatt amp 
or bypass it to the antenna.  It is powered with 26vdc and has 
N-connectors.  Don't recall isolation figures but think they were in 
60-dB range.  One could use this relay for TR with a kW amp, or to 
connect to two radios to two antennas or loads.  Its wired like a 
DPDT with internal crossover.  It cost me $40 used.


BTW if you have some of these surplus 24-28vdc relays, I sell a 
regulated 5A power supply that is adjustable to 28v:

http://www.kl7uw.com/fs.htm

73, Ed - KL7UW
  http://www.kl7uw.com
Dubus-NA Business mail:
  dubus...@gmail.com 


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Re: [Elecraft] {OT} - Variation on use of a coaxial switch (stan levandowski)

[Richard Fjeld]

This sounds the same, and I made it to protect the front end of each 
radio by switching the radio not being tested to my dummy load in case 
one of the radios should transmit. I intended my switch for receive 
comparisons.  I am surprised the commercial switches can handle a 
kilowatt and provide adequate isolation.  I wouldn't want to use that 
kind of power with the switch I made.

I didn't know about the switches you mention.  I thought there should be 
a need for them, so I called MFJ.  I like to protect my equipment. I 
know guys who don't think this way. Maybe MFJ didn't sell any and 
discontinued them. At the time, I thought they described them rather 
vaguely, missing the whole purpose.  Maybe I haven't found them on their 
website now.

Dick, n0ce


On 1/2/2017 7:06 AM, Charlie T, K3ICH wrote:
> Several companies (Bird, Transco) make what you describe.  It is a four
> terminal coax relay called a "Transfer Switch" that for example, connects
> any two antennas to any two radios, but never at the same time.  In other
> words, radio A connects to antenna 1, and at the same time, radio B connects
> to antenna 2.  Activating the switch ( either mechanical or electrically
> activated) changes the condition for A to 2 and B to 1.  Most are good for a
> kilowatt well up into the UHF ranges.   For HF, I made one using a heavy
> DPDT relay.
>
> 73 Charlie k3ICH
>
>
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Re: [Elecraft] {OT} - Variation on use of a coaxial switch (stan levandowski)

[Richard Fjeld]

Years ago, I built such a switch to prevent accidents should one radio 
transmit when comparing two radios. It is basically an a/b switch such 
that a radio became the active radio by switching the antenna to it, and 
simultaneously switching the dummy load to the inactive radio. Neither 
radio is without a load regardless of the switch position.

My switch is just a prototype using an aluminum project box.  I called 
MFJ and suggested they build one. A couple guys got on the call with me, 
and not long afterward, I saw a product advertised that seemed to be 
it.  It had decent specs for isolation. I can't find it on their site 
now.  The only thing that comes close to it might be the MFJ-1705, but 
they are describing it differently and there is no schematic.

If this isn't the correct switch, It could easily be converted. The 
important hardware is there.  I think I used a DPDT switch (I could 
check mine).
It should have the small coax wired between the connections. I Don't 
remember the nomenclature for that.

Dick, n0ce


On 1/1/2017 5:18 PM, Harry Yingst via Elecraft wrote:
> I've also have thought about running a switch so I can switch between a 
> couple of radios here (and a way to idiot proof it).
>
> I have considered building up something using relays (or a manual switch) 
> that would switch each radio into either a dummy load or into the antenna 
> path.
>
>
>
>
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Re: [Elecraft] {OT} - Variation on use of a coaxial switch (stan levandowski)

[Harry Yingst via Elecraft]

I've also have thought about running a switch so I can switch between a couple 
of radios here (and a way to idiot proof it).

I have considered building up something using relays (or a manual switch) that 
would switch each radio into either a dummy load or into the antenna path.




  From: stan levandowski <sjl...@optonline.net>
 To: elecraft@mailman.qth.net 
 Sent: Sunday, January 1, 2017 6:01 PM
 Subject: Re: [Elecraft] {OT} - Variation on use of a coaxial switch (stan 
levandowski)
   
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:elecraft-boun...@mailman.qth.net] On Behalf Of 
> John
> Sent: Sunday, January 1, 2017 1:41 PM
> To: j...@audiosystemsgroup.com; elecraft@mailman.qth.net
> 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:elecraft-boun...@mailman.qth.net] On Behalf Of 
> Jim
> Brown
> Sent: 01 January 2017 19:32
> To: elecraft@mailman.qth.net
> 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:elecraft-boun...@mailman.qth.net] On Behalf Of 
>> Dale Martin
>> Sent: 01 January 2017 17:31
>> To: elecraft@mailman.qth.net
>> 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
>&g

Re: [Elecraft] {OT} - Variation on use of a coaxial switch (stan levandowski)

[Bill Johnson]

Stan, please forgive my post.  Not meant to criticize you.

73,
Bill
K9YEQ

-Original Message-
From: Elecraft [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of stan 
levandowski
Sent: Sunday, January 1, 2017 5:01 PM
To: elecraft@mailman.qth.net
Subject: Re: [Elecraft] {OT} - Variation on use of a coaxial switch (stan 
levandowski)

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:elecraft-boun...@mailman.qth.net] On Behalf Of 
> John
> Sent: Sunday, January 1, 2017 1:41 PM
> To: j...@audiosystemsgroup.com; elecraft@mailman.qth.net
> 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:elecraft-boun...@mailman.qth.net] On Behalf Of 
> Jim
> Brown
> Sent: 01 January 2017 19:32
> To: elecraft@mailman.qth.net
> 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:elecraft-boun...@mailman.qth.net] On Behalf Of 
>> Dale Martin
>> Sent: 01 January 2017 17:31
>> To: elecraft@mailman.qth.net
>> 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 

Re: [Elecraft] {OT} - Variation on use of a coaxial switch (stan levandowski)

[Bill Johnson]

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:elecraft-boun...@mailman.qth.net] On Behalf Of John
Sent: Sunday, January 1, 2017 1:41 PM
To: j...@audiosystemsgroup.com; elecraft@mailman.qth.net
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:elecraft-boun...@mailman.qth.net] On Behalf Of Jim
Brown
Sent: 01 January 2017 19:32
To: elecraft@mailman.qth.net
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:elecraft-boun...@mailman.qth.net] On Behalf Of 
> Dale Martin
> Sent: 01 January 2017 17:31
> To: elecraft@mailman.qth.net
> 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 <sjl...@optonline.net>
>> To: Elecraft@mailman.qth.net
>> Subject: [Elecraft] {OT} - Variation on use of a coaxial switch
>> Message-ID: <1d09982f.1e408.15951ec5b8d.webtop...@optonline.net>
>> 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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> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailma

Re: [Elecraft] {OT} - Variation on use of a coaxial switch (stan levandowski)

[John]

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:elecraft-boun...@mailman.qth.net] On Behalf Of Jim
Brown
Sent: 01 January 2017 19:32
To: elecraft@mailman.qth.net
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:elecraft-boun...@mailman.qth.net] On Behalf Of 
> Dale Martin
> Sent: 01 January 2017 17:31
> To: elecraft@mailman.qth.net
> 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 <sjl...@optonline.net>
>> To: Elecraft@mailman.qth.net
>> Subject: [Elecraft] {OT} - Variation on use of a coaxial switch
>> Message-ID: <1d09982f.1e408.15951ec5b8d.webtop...@optonline.net>
>> 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
> *
>
> __
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft@mailman.qth.net
>
> This list hosted by: http://www.qsl.net Please help support this email 
> list: http://www.qsl.net/donate.html Message delivered to 
> j...@eeek.org.uk
>
> __
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> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft@mailman.qth.net
>

Re: [Elecraft] {OT} - Variation on use of a coaxial switch (stan levandowski)

[Jim Brown]

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:elecraft-boun...@mailman.qth.net] On Behalf Of Dale
Martin
Sent: 01 January 2017 17:31
To: elecraft@mailman.qth.net
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 <sjl...@optonline.net>
To: Elecraft@mailman.qth.net
Subject: [Elecraft] {OT} - Variation on use of a coaxial switch
Message-ID: <1d09982f.1e408.15951ec5b8d.webtop...@optonline.net>
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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Re: [Elecraft] {OT} - Variation on use of a coaxial switch (stan levandowski)

[John]

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:elecraft-boun...@mailman.qth.net] On Behalf Of Dale
Martin
Sent: 01 January 2017 17:31
To: elecraft@mailman.qth.net
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 <sjl...@optonline.net>
> To: Elecraft@mailman.qth.net
> Subject: [Elecraft] {OT} - Variation on use of a coaxial switch
> Message-ID: <1d09982f.1e408.15951ec5b8d.webtop...@optonline.net>
> 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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Re: [Elecraft] {OT} - Variation on use of a coaxial switch (stan levandowski)

[Dale Martin]

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: Elecraft@mailman.qth.net
> Subject: [Elecraft] {OT} - Variation on use of a coaxial switch
> Message-ID: <1d09982f.1e408.15951ec5b8d.webtop...@optonline.net>
> 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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Re: [Elecraft] {OT} - Variation on use of a coaxial switch

[Joel Hallas]

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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Re: [Elecraft] {OT} - Variation on use of a coaxial switch

[Jim Brown]

That may be one difference. But having been a pro who got paid for 
giving advice about things that matter to a client, what being a pro has 
always meant to was to make sure that I was


1) Never giving advice you were not certain of; and
2) Always ready to say "I don't know, but I'll find out;" and
3) Always ready to say "Not within my expertise, let's ask xxx:" and
4) Always ready to hire xxx to get the right answer if I was contracted 
to do it, or if the client was willing to pay for it.


73, Jim K9YC

On Fri,12/30/2016 4:59 PM, Don Wilhelm wrote:
I would differ from that a little bit.  The difference between the 
amateur and the pro is that the pro knows how to conceal his mistakes.
Take it from a former woodworking pro. 



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Re: [Elecraft] {OT} - Variation on use of a coaxial switch

[Nr4c]

Note that many antenna switches short the in-used antenna to ground so you 
would be shorting the output of the in-selected radio to ground.  NOT a good 
idea. 

MFJ makes a switch that connects 2 radios to 3 antennas. Flip the switch and 
the antennas are switched to the other radio. Put a dummy load on unused 
antenna and you are set. I'm not sure of the model number but it's in their 
catalog. 

Sent from my iPhone
...nr4c. bill


> On Dec 30, 2016, at 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.
> 
> 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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Re: [Elecraft] {OT} - Variation on use of a coaxial switch

[Fred Jensen]

T-shirt the other day:

MECHANIC

Curious enough to take it apart

Professional enough to put it back together

Smart enough to hide the extra parts

73,

Fred K6DGW
Sparks NV USA
Washoe County DM09dn

On 12/30/2016 4:59 PM, Don Wilhelm wrote:

Ron and all,

I would differ from that a little bit.  The difference between the
amateur and the pro is that the pro knows how to conceal his mistakes.
Take it from a former woodworking pro.

I don't know how that transfers to electronics, a dead semiconductor
device is difficult to to conceal.

73,
Don W3FPR


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Re: [Elecraft] {OT} - Variation on use of a coaxial switch

[stan levandowski]

Thank you, Don. An Alpha Delta has that isolation. I thought it would be 
OK but as a hobbyist and not a pro, I don't know what I don't know. 
 Happy New Year.

Stan WB2LQF


On Fri, Dec 30, 2016 at 06:44 PM, Don Wilhelm wrote:


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.

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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Re: [Elecraft] {OT} - Variation on use of a coaxial switch

[Bob Nielsen]

As long as there is sufficient isolation in the switch there should be 
no problem.  I have done exactly as you describe with my KX2 and IC-7100 
using a MFJ-1702C switch, which is rated for better than 60 dB of 
isolation to 300 MHz.


Bob, N7XY

On 12/30/16 2:49 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.


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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Re: [Elecraft] {OT} - Variation on use of a coaxial switch

[Don Wilhelm]

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.

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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