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

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Dale Martin, KG5U

Re: {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 <[hidden email]>
> To: [hidden email]
> Subject: [Elecraft] {OT} - Variation on use of a coaxial switch
> Message-ID: <[hidden email]>
> 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

John-6

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

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:[hidden email]] On Behalf Of Dale
Martin
Sent: 01 January 2017 17:31
To: [hidden email]
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

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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Jim Brown-10

Re: {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:[hidden email]] On Behalf Of Dale
> Martin
> Sent: 01 January 2017 17:31
> To: [hidden email]
> 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 <[hidden email]>
>> To: [hidden email]
>> Subject: [Elecraft] {OT} - Variation on use of a coaxial switch
>> Message-ID: <[hidden email]>
>> 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:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html Message
> delivered to [hidden email]
>
> ______________________________________________________________
> Elecraft mailing list
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> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
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> Message delivered to [hidden email]
>

John-6

Re: {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:[hidden email]] On Behalf Of Jim
Brown
Sent: 01 January 2017 19:32
To: [hidden email]
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:[hidden email]] On Behalf Of
> Dale Martin
> Sent: 01 January 2017 17:31
> To: [hidden email]
> 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 <[hidden email]>
>> To: [hidden email]
>> Subject: [Elecraft] {OT} - Variation on use of a coaxial switch
>> Message-ID: <[hidden email]>
>> 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:[hidden email]
>
> This list hosted by: http://www.qsl.net Please help support this email
> list: http://www.qsl.net/donate.html Message delivered to
> [hidden email]
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net Please help support this email
> list: http://www.qsl.net/donate.html Message delivered to
> [hidden email]
>

Bill K9YEQ

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

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:[hidden email]] On Behalf Of John
Sent: Sunday, January 1, 2017 1:41 PM
To: [hidden email]; [hidden email]
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:[hidden email]] On Behalf Of Jim
Brown
Sent: 01 January 2017 19:32
To: [hidden email]
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:

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stan levandowski

Re: {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:[hidden email]] On Behalf Of
> John
> Sent: Sunday, January 1, 2017 1:41 PM
> To: [hidden email]; [hidden email]
> 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:[hidden email]] On Behalf Of
> Jim
> Brown
> Sent: 01 January 2017 19:32
> To: [hidden email]
> 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:[hidden email]] On Behalf Of
>> Dale Martin
>> Sent: 01 January 2017 17:31
>> To: [hidden email]
>> 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: [hidden email]
>>> Subject: [Elecraft] {OT} - Variation on use of a coaxial switch
>>> Message-ID: <[hidden email]>
>>> 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:[hidden email]
>>
>> This list hosted by: http://www.qsl.net Please help support this
>> email
>> list: http://www.qsl.net/donate.html Message delivered to
>> [hidden email]
>>
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net Please help support this
>> email
>> list: http://www.qsl.net/donate.html Message delivered to
>> [hidden email]
>>
>
> ______________________________________________________________
> Elecraft mailing list
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> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message
> delivered to [hidden email]
>
> ______________________________________________________________
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> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
> ______________________________________________________________
> Elecraft mailing list
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> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
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> Message delivered to [hidden email]
>

Bill K9YEQ

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

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

73,
Bill
K9YEQ

-----Original Message-----
From: Elecraft [mailto:[hidden email]] On Behalf Of stan levandowski
Sent: Sunday, January 1, 2017 5:01 PM
To: [hidden email]
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:

Elecraft mailing list

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

In reply to this post by stan levandowski

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 <[hidden email]>
To: [hidden email]
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:[hidden email]] On Behalf Of
> John
> Sent: Sunday, January 1, 2017 1:41 PM
> To: [hidden email]; [hidden email]
> 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:[hidden email]] On Behalf Of
> Jim
> Brown
> Sent: 01 January 2017 19:32
> To: [hidden email]
> 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:[hidden email]] On Behalf Of
>> Dale Martin
>> Sent: 01 January 2017 17:31
>> To: [hidden email]
>> 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: [hidden email]
>>> Subject: [Elecraft] {OT} - Variation on use of a coaxial switch
>>> Message-ID: <[hidden email]>
>>> 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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>>
>> This list hosted by: http://www.qsl.net Please help support this
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>> [hidden email]
>>
>> ______________________________________________________________
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>>
>> This list hosted by: http://www.qsl.net Please help support this
>> email
>> list: http://www.qsl.net/donate.html Message delivered to
>> [hidden email]
>>
>
> ______________________________________________________________
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> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message
> delivered to [hidden email]
>
> ______________________________________________________________
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> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
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>
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>

Richard Fjeld-2

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

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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Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

IK4EWX

R: {OT} - Variation on use of a coaxial switch (stan levandowski)

Sorry, but why not buy a used Bird Coaxwitch with his isolation higher than 80 dB?I use them and like them very much.
Ian IK4EWX

Invio eseguito dallo smartphone BlackBerry 10.
Messaggio originale
Da: Richard Fjeld
Inviato: lunedì 2 gennaio 2017 07:13
A: [hidden email]
Oggetto: Re: [Elecraft] {OT} - Variation on use of a coaxial switch (stan levandowski)

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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Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

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Deni F5VJC

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

I'm using an LDG DTS-4 to connect 3 rigs (one spare port for test
equipment) to one antenna feed.

73 F5VJC

On 2 January 2017 at 07:19, <[hidden email]> wrote:

> Sorry, but why not buy a used Bird Coaxwitch with his isolation higher
> than 80 dB?I use them and like them very much.
> Ian IK4EWX
>
> Invio eseguito dallo smartphone BlackBerry 10.
> Messaggio originale
> Da: Richard Fjeld
> Inviato: lunedì 2 gennaio 2017 07:13
> A: [hidden email]
> Oggetto: Re: [Elecraft] {OT} - Variation on use of a coaxial switch (stan
> levandowski)
>
> 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.
> >
> >
> >
> >
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>

Charlie T, K3ICH

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

In reply to this post by Richard Fjeld-2

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

-----Original Message-----
From: Elecraft [mailto:[hidden email]] On Behalf Of
Richard Fjeld
Sent: Monday, January 02, 2017 1:13 AM
To: [hidden email]
Subject: Re: [Elecraft] {OT} - Variation on use of a coaxial switch (stan
levandowski)

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

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

Richard Fjeld-2

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

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
>
>