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{OT} - Variation on use of a coaxial switch

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stan levandowski

{OT} - Variation on use of a coaxial switch

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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Don Wilhelm

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

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
>
>
>
> ______________________________________________________________
> Elecraft mailing list
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Bob Nielsen-4

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

In reply to this post by stan levandowski

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
>
>
>
> ______________________________________________________________
> 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 Rowlett

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

Been using two old B&W 5 position switches to switch between rigs and antennas. No problems, though I run 10 watts or less.

73 Bill KC4ATU

On Dec 30, 2016, at 6:47 PM, Bob Nielsen <[hidden email]<mailto:[hidden email]>> wrote:

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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stan levandowski

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

In reply to this post by Don Wilhelm

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
>>
>>
>>
>> ______________________________________________________________
>> 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]
>

Don Wilhelm

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

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

On 12/30/2016 7:29 PM, Ron D'Eau Claire wrote:

> The difference between a hobbyist (Amateur) and a "pro" is that the pro gets paid to find out what he doesn't know.
>
> 73, Ron AC7AC
>
> -----Original Message-----
> From: Elecraft [mailto:[hidden email]] On Behalf Of stan levandowski
> Sent: Friday, December 30, 2016 3:53 PM
> To: [hidden email]
> Cc: [hidden email]
> Subject: Re: [Elecraft] {OT} - Variation on use of a coaxial switch
>
> 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
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
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> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>

k6dgw

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

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

Nr4c

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

In reply to this post by stan levandowski

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 <[hidden email]> 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
>
>
>
> ______________________________________________________________
> 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]

stan levandowski

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

Why not a good idea?? The unselected radio is "off" so wouldn't a
grounded antenna connection on the unselected radio actually be a good
idea? Stan.

On Fri, Dec 30, 2016 at 08:53 PM, Nr4c wrote:

> 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
>>
>>
>>
>> ______________________________________________________________
>> 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]
>
>

Jim Brown-10

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

In reply to this post by Don Wilhelm

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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Joel R. Hallas

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

In reply to this post by stan levandowski

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

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

In reply to this post by stan levandowski

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:
[hidden email]

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