[Elecraft] Coaxial Transfer Switches

Mon Jan 2 15:51:20 EST 2017

Just did some shopping on the Internet and found transfer switches by Teledyne starting at about $275.  Did not find any Birds, used or otherwise, and the Transcos I found were in the $800 range.  I confess this was a very quick search.

Interesting that many if not most of them require 28 VDC.  Anyone know why?  Is that a marine application?  These seem too heavy for aviation.  

The subject is of interest because I have two MFJ SPDT switches, neither of which I particularly like.  One of them works fine if the switch knob is toggled back and forth a few times.  And that’s the one that’s been indoors all its life.  Anyone found something DPDT, store-bought and acceptable, in a moderate price range?

Ted, KN1CBR

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    Message: 22
    Date: Mon, 2 Jan 2017 17:17:46 +0000
    From: Richard Fjeld <rpfjeld at outlook.com>
    To: "elecraft at mailman.qth.net" <elecraft at mailman.qth.net>
    Subject: Re: [Elecraft] {OT} - Variation on use of a coaxial switch
    	(stan levandowski)
    Message-ID:
    	<CO2PR16MB0121FBC4083B15A3BD853CC1BF6F0 at CO2PR16MB0121.namprd16.prod.outlook.com>

    Content-Type: text/plain; charset="Windows-1252"

    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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    Message: 23
    Date: Mon, 2 Jan 2017 12:32:49 -0500
    From: Don Wilhelm <donwilh at embarqmail.com>
    To: rsoifer1 at aol.com
    Cc: elecraft at mailman.qth.net
    Subject: Re: [Elecraft] KXPA100 with PX3
    Message-ID: <202d1e55-1ae8-03b1-c271-f99c1bfb23c5 at embarqmail.com>
    Content-Type: text/plain; charset=utf-8; format=flowed

    Ray,

    Have you tried running the TX Gain Calibration on the KX3?
    It may be that the KX3 wattmeter is not well calibrated.

    If you do the TX Gain Calibration manually, it must be done on each band.
    The KX3 Utility automates the process.

    73,
    Don W3FPR

    On 1/2/2017 11:55 AM, rsoifer1 at aol.com wrote:
    > Don and others,
    >
    > The good news is that you were right: the RJ-45 connectors in the 
    > control cable were not making good contact.  I fixed that and PA ON 
    > operation of the KXPA100 is now working.
    >
    > The bad news, however, is that in Basic operation with PA OFF, the 
    > KX3/KXPA100 puts out full power, but the most I can get out of it with 
    > PA ON is 50-60 watts.  The attenuator is set for OUT/AUTO and there is 
    > no more than 1 or 2 watts reflected power.
    >
    >

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    Message: 24
    Date: Mon, 2 Jan 2017 12:42:49 -0500
    From: rsoifer1 at aol.com
    To: donwilh at embarqmail.com
    Cc: elecraft at mailman.qth.net
    Subject: Re: [Elecraft] KXPA100 with PX3
    Message-ID: <1596046c9bd-5f8-281ef at webprd-m06.mail.aol.com>
    Content-Type: text/plain; charset=utf-8

    Hi Don,

    I tried that but an external wattmeter confirmed the KXPA100 forward and reflected power readings.  Something in the KX3 is holding down the power output when PA is ON, but not when PA is off.

    73 Ray W2RS

    -----Original Message-----
    From: Don Wilhelm <donwilh at embarqmail.com>
    To: rsoifer1 <rsoifer1 at aol.com>
    Cc: elecraft <elecraft at mailman.qth.net>
    Sent: Mon, Jan 2, 2017 10:33 am
    Subject: Re: [Elecraft] KXPA100 with PX3

    Ray,

    Have you tried running the TX Gain Calibration on the KX3?
    It may be that the KX3 wattmeter is not well calibrated.

    If you do the TX Gain Calibration manually, it must be done on each band.
    The KX3 Utility automates the process.

    73,
    Don W3FPR

    On 1/2/2017 11:55 AM, rsoifer1 at aol.com wrote:
    > Don and others,
    >
    > The good news is that you were right: the RJ-45 connectors in the 
    > control cable were not making good contact.  I fixed that and PA ON 
    > operation of the KXPA100 is now working.
    >
    > The bad news, however, is that in Basic operation with PA OFF, the 
    > KX3/KXPA100 puts out full power, but the most I can get out of it with 
    > PA ON is 50-60 watts.  The attenuator is set for OUT/AUTO and there is 
    > no more than 1 or 2 watts reflected power.
    >
    >

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    Message: 25
    Date: Mon, 2 Jan 2017 10:45:00 -0700 (MST)
    From: Bob N3MNT <bob at hogbytes.com>
    To: elecraft at mailman.qth.net
    Subject: Re: [Elecraft] KXPA100 with PX3
    Message-ID: <1483379100689-7625370.post at n2.nabble.com>
    Content-Type: text/plain; charset=us-ascii

    What band are you seeing this reduced power out on.  It will most likely be
    different for each band.

    --
    View this message in context: http://elecraft.365791.n2.nabble.com/KXPA100-with-PX3-tp7625187p7625370.html
    Sent from the Elecraft mailing list archive at Nabble.com.

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