Jul 04

Modular 2 Meter Ground Plane by KC4NYK

After researching 2 Meter Ground Plane antennas for my new ICOM IC-V82 Handheld I built one “hardwired” as we say in the software industry, meaning that it was soldered together permanently. The design was for approx. 146.00 MHz, i.e. the middle of the tuning range for the unit as I understand it.

Of course immediately after completing it I realized that it would be better to make it packable and to have several sets of elements so that it could be fine tuned at the upper or lower edge of that tuning range and even 6M and UHF frequencies as well. So I set to work by first examining each part and the connector options at each stage.  I concluded that by utilizing a plate with the corners bent to the customary 45 deg. angle I could attach the various elements to that very conveniently. I also saw that the hex standoffs proliferatiing in my junk box would be very convenient attachment points.

This way the elements can be soldered into the socket end and the threaded stud could then be threaded into the plate or affixed with a nut on the other side. Regular solder can be used for steel, copper and brass or, better yet, for weatherability,  silver solder can be used for all of those as well as stainless steel. Silver solder can be applied using a propane torch and is available at welding supply and some mega hardware stores now.

Note that the vertical element needs a hex connector to attach to which should be  soldered to the center pin of the SO-239. The plate is attached to the SO-239 with four 1/8″ Pop Rivets and then the elements are attached to the plate.

Using Rhino, my design tool of choice, I produced the accompanying drawings. The critical part - the plate - is dimensioned but the tolerances are guidlines and are not as important as the bend angle of the radials, determined by the angle of the corners are bent to (45 deg.). The measurements for the elements can be found on multiple (and sometimes conflicting) web sites so I will leave the messy details of that to the wizards that know much more about tuning antennas than I do at the time. I merely offer a construction method that may have some value for a portable and collapsible antenna that can be broken down and put in a briefcase or other luggage suitable for travel, backpacking and, of course my favorite mode of transportation - sailing!!

Exploded Diagram

front

Side

Top

Underbelly

Dimensions::

Dims

Here are the dimensions for the MGPA antenna element lengths  for the 146 MHz segment of the 2 meter band :

Vertical element -  19.3125″

Radials (4)           -  20.1875″

Be sure to trim the elements AFTER they have been soldered into their respective sockets MINUS the threaded portion.

Bon Apetite!

Rob Thomas, KC4NYK

Apr 06

Members of the Old Guard

I know this is a real imposition on your time but I plan to commence documenting things that seem to baffle us newbies and post them somewhere that others can benefit. So it is not just for yours truly that I beg of your time.

I want to get more serious about my antenna situation and although the “Yo-Yo-Vee’ is probably great for backpacking, etc. I really want to make sure my base station has adequate robustness so that it’s not adding a liability to my lack of wattage firepower. To that end I would like to get your feedback on what kind of coax I should use. I’ve done enough research on the internet to thoroughly baffle myself. Is it RG-8, 58 213? I’m going about 24 feet out to the dipole and up 16 feet for a total run of 40 feet. Add to that a 12′ connector that passes through the exterior wall of the domicile with a PL259 on either end, that can be disconnected in inclement weather. In fact it’s only connected when I want to Tx or Rx.
Also, currently I have a #12 gauge wire connected to an existing ground pipe that was evidently used to ground the aluminum siding on the house at some point although it has never been connected during the time that I have had the house nor have I read anywhere that it should be. Any thoughts on that would be much appreciated. My observation is that when I connect this “ground” wire to any of the QRP radios that I have (running of an ac power supply to produce the 12v - 13v needed) it causes a terrific hum and so I normally don’t hook it up. It does not seem to have that affect on my NC300 however and it is hooked up to that. One note is that my tests with the aforesaid QRP rigs has been by tatking it off the connector on the back of the NC300. Would that induce any hum? Would that be nay different than running both off of a ground plane consisting of a couple of large 1/4″ copper bars as put forth in the ARRL antenna book?

Hopefully this will culminate in my being able to join you on the 15M ” Thursday Night Ragchew” .

Thanks and 73,

Robert Bruce Thomas, KC4NYK
Public Information Officer