NOVEMBER 3 VICTOR ECHO MIKE
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NOVEMBER 3 VICTOR ECHO MIKE

ham radio Projects and musings from a (Relatively) new operator

Loving the standards

11/27/2016

4 Comments

 
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     No, I'm not referring to the Jazz standards by Duke Ellington or John Coltrane - I'm referring to the "standards" that exist in ham radio and electronics.  While the standards aren't always followed, it is nice to be able to rely on certain things, like the fact that red wires are generally positive and black wires are generally negative.  It's also great that powerpoles are generally assembled with "Red on the Right."  Another "standard" that we use in Ham Radio is the 50 ohm antenna/feedline system standard.  Then there's the pneumonic that my dad taught me as a kid to remember the legs of a transistor - his name and his two buddies - Ed, Barry, & Charlie (Emitter, Base, Collector.)  None of these however, are the standard that I'm geeking out about today.
     Today, I'm excited about the 3/8-24 thread standard that we use for antenna's.  I have no idea how this standard came about, or even if it's really the ideal thread and bolt size for our service's application, but I'm still pumped about it.  Why is that?  Because it makes playing around easier when parts made by different manufacturers fit together!  In my case, I'm thankful for it, because it let me play around, and use parts from my Buddipole Antenna in my mobile mount while I activated Hopewell Furnace for National Parks on the Air.

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     For this arrangement I put 2 of the 11 inch arms together, screwed them into the mount on my trunk, followed by the coil, and then one of the telescoping whips to top it off.  Because I was shooting for the 20 meter band, and I wanted as much efficiency as possible, I basically started with the telescoping part fully extended, and the tap on the coil set to jump over pretty much the entire coil - this made the antenna resonant a frequency higher than 20 meters, meaning the antenna was electrically to short.  To "lengthen" the antenna I just adjusted the coil by moving the tap down (physically) a couple windings at a time, until I found the point where one tap made the antenna just a little to short, and the next tap made it just a little too long.
     Since I started with the telescoping whip fully extended, I chose the tap that made the antenna just slightly too long, and then I adjusted the telescoping whip to make shorter, to fine tune the antenna where I needed it.  It worked great!
     Now, without an actual antenna range, and all kinds of fancy measurement tools, I can't actually make any performance claims, but it "felt" like this worked better than my 20 meter hamstick normally does.  My logic is this:
  • It ended up being a slightly longer antenna than the hamstick.  More antenna element and less coil generally makes for a more efficient antenna, all else being equal.
  • The coil for the Buddipole has a much larger diameter and more spacing between windings than the tiny wire tightly wound around the fiberglass rod inside the hamstick.  A Bigger coil, bigger wire, more space between windings also generally makes for a more efficient antenna.
  • The diameter of the antenna element is larger, so in theory this should also be more broad-banded than the hamstick.
     Now, for 20 meters, I'd probably be even better off with something that can be full size, with no coil, like this little number from MFJ (17' telescoping whip), but since I don't have one of these, I'll just make what I have work.  At some point I plan on grabbing a couple of these at it would definitely help give me more flexibility with my portable antenna stuff.  Once I do, I'll be sure to share what I find as I play around with it.

     Playing around with this arrangement also made me realize that I have a couple other options that should work better than my hamsticks too (when I'm parked anyway - I'm not about to use this while going 70mph down the highway, I have no idea what wind loads the Buddipole parts where designed to handle!)  The first and most obvious would be to use the same arrangement, but with the tap on different spots of the coil to use it for 6, 10, 12, 15, 17, 30, and 40 meters.  I also realized that it "might" work to put both coils in a row, one after the other, to use it on 80 meters - I'll let you know how that works out when I have time to try it.
    With all that being said, I'll wrap up with a salute to the 3/8-24 standard, and say "thank you" to all the manufacturers that so kindly make stuff according to the standards!
4 Comments
Dan Farrell. AA3LY
11/27/2016 14:48:47

Interesting stuff, thanks.
What are you going to delve into after NPOTA?

Reply
Vance - N3VEM
11/27/2016 17:06:53

Thanks Dan! I have a couple things up my sleeve for when NPOTA ends. As far as on the air stuff, aside from just rag-chewing and general operating, I'll be participating in KFF (check out parksontheair.com) which is an international program similar to SOTA and IOTA that has been apparently going on for a few years. I'll probably do a post soon about that, as I've already started submitting some logs to that program.
I've also had an ongoing "secret" project that I've hinted at in a couple of my blog posts, which I'll continue to work on, and once it's all wrapped up I'll put it up as a series of posts detailing the project.
Finally, I also still have the ongoing construction of my new shack in the basement that will get a bunch of my time and money thrown at it as I get chunks of both available :-)

Reply
marc
12/11/2016 21:22:41

What mount did you use(I have a hatchback), I was just thinking today as I ordered a 3 magnet 3/8x24 mount that I could use my buddipole parts to make this into some type of vertical.

Reply
N3VEM - Vance
12/12/2016 08:29:43

The mount I have in my vehicle is a ball mount made by Jerry Breedlove (He makes some very heavy duty stuff - great for mounting large and heavy antenna's.) However, you could replicate what I did here with any mount that accepts a standard 3/8 x 24 threaded antenna - the tri-mag mounts, regular mag mounts, and many lip and fender mounts all use that thread, so you can probably do the same with the mount you ordered.

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    - N3VEM -

         Welcome to my Ham Radio Blog!  This blog was started primarily to share my two concurrent shack builds - my mobile station and my home station.  Over time, this has grown to include sharing about my operations, and general radio-related thoughts that I have as a newer operator.  
         
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