[Elecraft] {OT} - Variation on use of a coaxial switch (stan levandowski)
Harry Yingst
hlyingst at yahoo.com
Sun Jan 1 18:18:08 EST 2017
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 <sjl219 at optonline.net>
To: elecraft at 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-bounces at mailman.qth.net] On Behalf Of
> John
> Sent: Sunday, January 1, 2017 1:41 PM
> To: jim at audiosystemsgroup.com; elecraft at 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-bounces at mailman.qth.net] On Behalf Of
> Jim
> Brown
> Sent: 01 January 2017 19:32
> To: elecraft at 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-bounces at mailman.qth.net] On Behalf Of
>> Dale Martin
>> Sent: 01 January 2017 17:31
>> To: elecraft at 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 To: Elecraft at mailman.qth.net
>>> Subject: [Elecraft] {OT} - Variation on use of a coaxial switch
>>> Message-ID: <1d09982f.1e408.15951ec5b8d.Webtop.41 at 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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>
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