Automatic Mobile Resonator

<body topmargin=0 leftmargin=0 marginheight=0 marginwidth=0> <table cellpadding=0 cellspacing=0 border=0><tr> <td valign="top" height=90 BGCOLOR="#006699" TEXT="#080000" background="1fcfd5a3.jpg"> <div> <FONT SIZE="5" COLOR="#000000" FACE="Arial" ><B>BIT Company</B></FONT><B>    </B><B> |     </B><A HREF="index.htm" TARGET="_top" TITLE="BIT Company"><U><B>home</B></U></A></div> <bR> <div> </div> </td> </tr><tr> <td valign="top" height=390 BGCOLOR="#FFFFFF" TEXT="#080000"> <div> <I>Automatic Mobile Resonator</I></div> <bR> <div> <B>A major limitation of mobile, marine mobile, or portable radio operation is achieving a efficient, wide bandwidth, compact antenna system. Practical limitations for mobile operation limit a total antenna + mount height of less than 12 feet. Many years ago I tested my 14 1/2 foot 75 meter Newtronics Hustler against the flourescent bulbs in my local gas station. Took quite a while to clean up the mess!</B></div> <bR> <div> <B>Even with the total antenna length of approximately 12 feet, the useful bandwidth of this type of antenna is less than 20 kHz. With the impedance/coupling shifts due to to terrain (yep, very true) or weather (again, true) the available frequencies can change markedly. If you run HF mobile and have a dynamic SWR meter that you can see without dying in a car crash, go look!</B></div> <bR> <bR> <bR> <div> <B>  <IMG SRC="31d6e2c0.jpg" border=0 width="110" height="300" ALIGN="BOTTOM" HSPACE="0" VSPACE="0">    <IMG SRC="31e642c0.jpg" border=0 width="100" height="300" ALIGN="BOTTOM" HSPACE="0" VSPACE="0">    <IMG SRC="320772c0.jpg" border=0 width="375" height="300" ALIGN="BOTTOM" HSPACE="0" VSPACE="0">  </B></div> <bR> <div> <B>Hence. the Mobile Resonator. This device, using a screw driven "slinky" type coil, when inserted between the ball mount and a center loaded 40 meter fiberglass commercial whip with the resonator tip shortened to 9 inches, measured SWR was close to unity over the entire 40 and 20 meter ham allocations. Tuning time was less than one second at extreme ends (bottom of 40 to top of 20). Power required for the vector/impedance curcuitry and the motor drive is 10 mA idle and 60 mA when active. The prototype inductor was made by stretching to straighten, then winding tempered 12 gauge copper wire, repeated dips in polyurethane (thrice), then end forming and mounting. </B></div> <bR> <div> <B>Below is the first version built with a old Command set (WW 2) roller inductor which worked fine with a C. B. whip:</B></div> <bR> <div> <B><IMG SRC="32158a90.jpg" border=0 width="600" height="169" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></B></div> <bR> <div> <B>Those roller inductors are kinda hard to come by these days.</B></div> <bR> <div> <B>There was a fixed station version built that was a pi network and somewhat more complex. </B></div> <bR> <div> <B><IMG SRC="322582d0.jpg" border=0 width="600" height="301" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></B></div> <div> <B>It was happy taking a kilowatt of SSB and tending my ~75 meter dipole all the way through to 10 meters. Nice doo-dad.  Somebody oughta sell this gadget!</B></div> <bR> <div> <B>The schematics of the mobile unit are below. Unfortunately, I seem to have lost the circuit board layout, probably went the way of several pick-up truck loads of wet stuff after the 1998 el Nino flooding. The original is still here and with interest, I might just spend the time to re-do it. </B></div> <bR> <div> <B><IMG SRC="32390e20.jpg" border=0 width="400" height="226" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></B></div> <bR> <div> <B>This was the test set-up with the roller inductor version. Specs were the same.</B></div> <bR> <div> <B><IMG SRC="32458a60.jpg" border=0 width="600" height="422" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></B></div> <bR> <div> <B><IMG SRC="32658e80.jpg" border=0 width="600" height="232" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></B></div> <bR> <div> <B>And, as usual, the component values are not given. You want them, ask me. EVERY DAMN TIME I publish a full, free design, the buzzards get all happy selling the stuff.  </B></div> <bR> <div> <B> </B></div> <bR> <bR> <bR> </td> </tr></table></body>