Rockmite 20: Dipoles Really are Bi-Directional

I was back up on Sourdough Trail with the Rockmite 20 on Wednesday. The weather was gorgeous and as long as the sun was out it was warm enough to shed a few layers. I ran into a few dove as I hiked up out to the end of the ridge, but the resident moose must have been hiding out.

I hung the dipole between two trees at the point of a ridge line that points off to the East at an altitude of 10,200 feet. The antenna was oriented just a little bit to the northeast due to the positioning and availability of suitable trees for antenna supports.

View Larger Map
KD0FNR station location and antenna orientation

Antenna support

After CQing for awhile, I was rewarded with a callback from KB8AP in Central Point, OR who provided me with an RST report of 439 while I could read him at 239, RST reports being rather subjective things with the Rockmite since it has no S meter. After we chatted for a bit, I CQ'ed again and immediately heard back from KC8ITC in the opposite direction, Saline, Michigan with a report of 559! Sure enough, just like the very nice write-up on on dipole antennas at Wikipedia predicted, I had a nice bi-directional radiation pattern. This little radio is a constant source of entertainment. It's a great excuse to go wandering around in the forest, and it consistently provides greater than 1000 mile per watt QSOs!

View Larger Map

These great contacts on the dipole got me to wondering what could be accomplished with a Yagi antenna. The Yagi provides directionality and gain by pushing more RF energy in a single direction. Next week I'll try it out. The guys at the Rockmite Yahoo Group have been helping me with antenna design tips. They have already provided one good pointer in suggesting that I not let the dipole actually come into contact with the trees I'm using for supports. The higher the dipole and the more isolated it is, the better its radiation pattern should be. They're providing lots of good ideas for tuning Yagis to the 50 ohm Rockmite as well. They pointed out the BLT QRP antenna tuner[pdf] and that led to the N7VE LED SWR bridge[pdf]. I'll keep you posted if I try them out.

Have fun!
73 de KD0FNR

Comments

Cool Math Tricks: Deriving the Divergence, (Del or Nabla) into New (Cylindrical) Coordinate Systems

Now available as a Kindle ebook for 99 cents ! Get a spiffy ebook, and fund more physics The following is a pretty lengthy procedure, but converting the divergence, (nabla, del) operator between coordinate systems comes up pretty often. While there are tables for converting between common coordinate systems , there seem to be fewer explanations of the procedure for deriving the conversion, so here goes! What do we actually want? To convert the Cartesian nabla to the nabla for another coordinate system, say… cylindrical coordinates. What we’ll need: 1. The Cartesian Nabla: 2. A set of equations relating the Cartesian coordinates to cylindrical coordinates: 3. A set of equations relating the Cartesian basis vectors to the basis vectors of the new coordinate system: How to do it: Use the chain rule for differentiation to convert the derivatives with respect to the Cartesian variables to derivatives with respect to the cylindrical variables. The chain ...

The Alcubierre Warp Drive Tophat Function and Open Science with Sage

I transferred yesterday's Mathematica file with the Alcubierre warp drive[2] line element and space curvature calculations to the +Sage Mathematical Software System today, (the files been added to the public repository [3]). If you haven't used Sage before, it's a Python based software package that's similar in functionality to Mathematica. Oh, and it' free. I also worked a little more on understanding the theory, but frankly, I made far more progress with the software than the theory. What follows will be a little more of the Alcubierre theory, plus, a cool Sage interactive demo of one of the Alcubierre functions[1], as well as a bit about my first experience with using Sage. Theory The theory is fun, but it's moving slowly. Here's the chalk board from this morning's discussion Alcubierre setup the derivation using something called the 3+1 formalism which means we consider space to be flat, (in this case), slices that are labelled ...

The Valentine's Day Magnetic Monopole

There's an assymetry to the form of the two Maxwell's equations shown in picture 1. While the divergence of the electric field is proportional to the electric charge density at a given point, the divergence of the magnetic field is equal to zero. This is typically explained in the following way. While we know that electrons, the fundamental electric charge carriers exist, evidence seems to indicate that magnetic monopoles, the particles that would carry magnetic 'charge', either don't exist, or, the energies required to create them are so high that they are exceedingly rare. That doesn't stop us from looking for them though! Keeping with the theme of Fairbank[1] and his academic progeny over the semester break, today's post is about the discovery of a magnetic monopole candidate event by one of the Fairbank's graduate students, Blas Cabrera[2]. Cabrera was utilizing a loop type of magnetic monopole detector. Its operation is in...

Copasetic Flow

Search This Blog