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Re: [Smartuners] SGC-231 with Inverted L

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  • DALE
    A dummy load is not resonant. It is a pure resistive load. Has no capacitive or inductive properties. I have a multiband vertical on my roof that is supposed
    Message 1 of 22 , Oct 31, 2011
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      A dummy load is not resonant. It is a pure resistive load. Has no capacitive or inductive properties.
      I have a multiband vertical on my roof that is supposed to be resonant on most bands. My tuner has trouble tuning it on most bands. Works almost as well bypassing the tuner.
      Works better on my non resonant antenna's.
      dale





      From: "JC Daehler" <hb9ibz@...>
      To: Smartuners@yahoogroups.com
      Sent: Friday, October 28, 2011 3:23:13 PM
      Subject: Re: [Smartuners] SGC-231 with Inverted L

       

      Rudy,
      I do not disagree with your explanation regarding couplers not liking a resonant antenna and apply this rule whenever I can.
      I own and have owned a variety of coupler, SGC230,231,237, Icom Ah2 and now Ah4, as well as Motorola 2265 and Harris RF382. 
      Occasionally, in order to test the system, I hooked up a 50 ohms dummy load (can't be more resonant than this) to the output.....the coupler tuned, and no smoke seem to be generated.  Do you have an explanation for this?
      Tks
      73
      JC
      VE7OI


      From: "k8swd@..." <k8swd@...>
      To: Smartuners@yahoogroups.com
      Sent: Friday, October 28, 2011 11:41:16 AM
      Subject: Re: [Smartuners] SGC-231 with Inverted L

       
      Jerry: the numbers are for non-resonant lengths of wire for use in an end-fed application. The first two numbers are min max length in feet for a "non-resonant "window". The third number is the center of the window in feet and the last number is the center in meters.

      Physics still rule regardless how you hook up an antenna to your rig. An antenna is "resonant" in a particular area of the bands and when one wanders away from that area, the antenna is no longer "matched" and is physically too long or too short. The coupler tries to provide the missing length by inserting capacitance and/or inductance as needed. The lower in frequency and shorter the antenna is, the more demand is placed on the coupler to compensate. This creates loss in components inside the coupler and that can be dissipated as heat. If there is too much heat, it has to go somewhere. Usually the heat turns into smoke and the magic ceases. I have had a fire inside of a SGC-235 coupler and have seen the magic smoke leak out.
      Back to matching and why the above is important. If non-resonant window lengths of wire are used for the antenna, the coupler does not have to work as hard to achieve a match because not much has to be added by way of capacitance and/or inductance for the radio to see a 50 ohm load. But don't forget about physics and performance. 23' minimum antenna length is NOT accidental. It is the minimum length of antenna wire of the first "practical" non-resonant window that the coupler's components can adequately provide the missing inductance and/or capacitance for, and still radiate an "OK" signal (provided the other half of the antenna is adequate).

      By using antenna lengths that fall into a non-resonant window, high current and voltages are kept away from the coupler and that keeps the components inside cool and happy. If a resonant length of antenna wire is used off the designed frequency, high current or voltage could appear at the coupler and you will soon incur repair bills. That's why you don't hook up a half wave length of wire to a coupler and try to match it. Will a coupler match a half wave dipole on other frequency bands? Yes. But consider a 40 meter dipole (1/4 wave each side of center) is a 1/2 wave each side of center. If you mount the coupler in the center--guess where the high current will be on 20m--at the coupler! Not good! But shorten the wires a couple feet and now the high current moves away from the coupler out on the wire someplace, on all bands you try to operate on within coupler specs.
      If you have room for a 40m dipole and want to put your coupler at the center of the antenna, then use 28-30' on each side rather than 33'. 39', 58' or 76' would be even better. I have used all these lengths and with a AH-4, SGC-230 or SGC-235 coupler, I like 58 and 76 the best and so do my couplers (I have all 3 I listed).

      Rudy, K8SWD


      Sent from my BlackBerry® smartphone with Nextel Direct Connect

      From: "Jerome Sodus" <jsodus@...>
      Sender: Smartuners@yahoogroups.com
      Date: Fri, 28 Oct 2011 11:11:58 -0400
      To: <Smartuners@yahoogroups.com>
      ReplyTo: Smartuners@yahoogroups.com
      Subject: RE: [Smartuners] SGC-231 with Inverted L

       
      Hey, hey, Rudy,
      What happened to you?
      I was looking forward to the answers. :)
      73 Jerry-km3k
       

      From: Jerome Sodus [mailto: jsodus@... ]
      Sent: Wednesday, October 26, 2011 12:45 AM
      To: ' Smartuners@yahoogroups.com '
      Subject: RE: [Smartuners] SGC-231 with Inverted L
       
      Hi Rudy,
      I still have issues, such as:
      “…it does not match physics.”???
      What are all the numbers about like 23-32-27.5-8.5? Is that the length of one leg of a dipole or the total-length?
      “….the heat has to go somewhere…..”; what heat?
      BTW, as I see it, to bring up performance/radiation gets us off topic, which is matching.
      73 Jerry-km3k

      From: Smartuners@yahoogroups.com [mailto: Smartuners@yahoogroups.com ] On Behalf Of k8swd@...
      Sent: Tuesday, October 25, 2011 11:28 PM
      To: Smartuners@yahoogroups.com
      Subject: Re: [Smartuners] SGC-231 with Inverted L
       
       
      A "match" does not equal "performance" and effective radiation. Even though a 231 will match--it does not match physics.
      min-max-center

      Feet/Meters (center)

      For example---(23' feet is minimum; 32' is maximum; 27.5 (or 8.5 meters) is the center of the "window"


      23-32-27.5-8.5

      35-44-39.5-12

      52-64-58.5-17.7

      70-82-76-23.2

      92-98-95-29.1

      105-113-109-33.2

      140

      A 40m dipole does not fall into a non-resonant "window" as it is 33' on a side. It will work great on 40, and OK on higher bands, and will "match" on lower bands, but if fed with coax, the heat has to go somewhere and that's inside the coupler and/or the coax. Ladder line feed would be better.

      33' is an 1/8th wave on 80m and only a 1/16th wave on 160m. Not very efficient at all. Will and SGC "match" it? Sure? Can one make contacts with it? Sure. If you can't use anything else, go for it!

      For inverted V use on 160-6, I would opt for at least 3/8ths wave on each side of center for 160, but would expect weird lobes on 20 and up.

      The SGC manual recommends a minimum of 23' of wire to "match", but that does equate to "effective" performance--only an adequate match the coupler can handle--provided the ground is appropriate for the "system".

      Just like a bullet--there is no replacement for displacement. Bigger is usually better!

      Rudy, K8SWD
      Sent from my BlackBerry® smartphone with Nextel Direct Connect

      From: "Jerome Sodus" < jsodus@... >
      Sender: Smartuners@yahoogroups.com
      Date: Tue, 25 Oct 2011 22:11:08 -0400
      To: < Smartuners@yahoogroups.com >
      ReplyTo: Smartuners@yahoogroups.com
      Subject: RE: [Smartuners] SGC-231 with Inverted L
       
       
      Well, where to start in reply….
       
      1. I have a dipole sized for 40-meters that has a SGC-237 at the dipole’s center and fed with coax.
      This arrangement came from an ARRL book by W1AB and this arrangement is his first choice.
      My antenna-coupler matches on all bands from 160 to 6 meters.
       
      2. This arrangement of putting the coupler at the dipole’s center is also seen in the SGC-237 manual for an Inverted-V antenna.
       
      3. I’ve struggled to understand the posting below from k8swd but regretfully I have to write that I cannot make sense out of it.
      As examples….“This puts the high current away from the coupler and makes it work less harder to achieve a match.”
      I cannot follow the listing of numbers and Feet/Meters (center), etc.
       
      73 Jerry-km3k

      From: Smartuners@yahoogroups.com [mailto: Smartuners@yahoogroups.com ] On Behalf Of k8swd@...
      Sent: Tuesday, October 25, 2011 8:00 PM
      To: Smartuners@yahoogroups.com
      Subject: Re: [Smartuners] SGC-231 with Inverted L
      The problem stems from where you want the high current to be--definitely NOT at the coupler!
      When using the coupler (SGC-Icom-Alonco-Yaesu) and an end fed wire system over radials (on ground or elevated) or against a good ground (big metal area) the wire should NOT be resonant in ANY ham band. This puts the high current away from the coupler and makes it work less harder to achieve a match.
      I'm am not going into the math--just do this! It works! Be sure your ground side is RF bigger than the radiating side--physically and electrically.
      OTOH if you are trying to load (can't tune!) A resonant dipole, you will end up having freqs with high voltage at the coupler--not good. Make a dipole with non-res lengths and feed with ladder line, but only use on the band or higher freqs than it is cut for.
      Older ARRL antenna handbooks had a chart for this. I have no idea why ARRL has omitted the chart in later editions
      Check this out from my notes!
      min-max-center
      Feet/Meters (center)
      23-32-27.5-8.5
      35-44-39.5-12
      52-64-58.5-17.7
      70-82-76-23.2
      92-98-95-29.1
      105-113-109-33.2
      140-149-145-44.2
      Additional length chart
      ""Random""-length-in-feet…
      "REVISED: 29 35.5 41 58 71 84 107 119 148 203 347 407 423"
      Sent from my BlackBerry® smartphone with Nextel Direct Connect

      From: N1KHB@...
      Sender: Smartuners@yahoogroups.com
      Date: Tue, 25 Oct 2011 18:08:37 -0400 (EDT)
      To: < Smartuners@yahoogroups.com >
      ReplyTo: Smartuners@yahoogroups.com
      Subject: Re: [Smartuners] SGC-231 with Inverted L
      Jerry,
        The problem is that many HF ham bands are arranged in wavelength multiples. So, the first band that you've cut the wire for will be fine. However, some of the successively higher frequency bands can and often do present a high (reactive) Z because they are even multiples due to being a half wave, or 1.5 wave, etc. Those lengths become harder for the tuner to handle because the higher Z's may be near or beyond the Z limit that the design range of the tuner can handle.
         Zat clearer?
      Best,
      Joe N1KHB
       
      In a message dated 10/25/2011 5:56:58 P.M. Eastern Daylight Time, jsodus@... writes:
      Rudy-k8swd writes, “You should never use a resonant length of antenna wire on any band on the output side of an SGC coupler.”
      I find that to be a particularly interesting statement, which I have trouble accepting.
      To me, a resonant antenna would have a pure resistance (meaning no reactive component) at some frequency and, as long as that resistance is low enough for the SGC-coupler to match, everything should be ok.
      So I’m wondering what k8swd has in mind here.
      73 Jerry-km3k


    • Paul@N4LCD.com
      ... A friend of mine put his SGC 230 near the ground for convenience, then connected a 160 meter quarter wave inverted L wire to it, and laid out several
      Message 2 of 22 , Nov 1, 2011
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        >One other thing Jerry­SGC recommends that the
        >“ground” side of the antenna be physically
        >larger than the “positive” side of the
        >antenna. I have heard 5% to 10% larger. I have
        >never been a fan of mounting the coupler at any
        >appreciable height and using it in a dipole
        >configuration simply because it is hassle to
        >take it down. I more often than not use my
        >couplers mobile or portable. It might be a good
        >idea if using a coupler at the center of a
        >dipole to have the hot side about 26.5’ long and
        >the cold side about 30’ long. Both lengths are
        >still in a non-resonant window, yet the ground
        >side is larger than the radiating
        >side. Somewhere I read that in this
        >configuration, a dipole leg should be between
        >7-25m or 23’ to 80’ long. Again, the minimum
        >and maximum are non-resonant lengths.

        A friend of mine put his SGC 230 near the ground
        for convenience, then connected a 160 meter
        quarter wave inverted L wire to it, and laid out
        several ground wires, on the ground, each 5%
        longer than the inverted L wire. It worked very
        well on multiple bands. It was probably 80 feet from his shack.

        I've got a 230 and am thinking about putting up
        an 80 meter full wave loop in the backyard, with
        the 230 at the feed point, which would be under the soffit near the shack.

        Paul N4LCD
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