Skip to main content

Rockmite Log 22/11/29 : Antennas, broken keyers, and SWR meters

 Based on comments from the RSGB dipole antenna notes, I'm back to thinking I should try the 'radio in the middle' dipole configuration for the Rockmite. The page mentions that the coax leading to a dipole can pick up a noticeable amount of noise without a balun. I have a Rockmite board already wired up this way. The issues with the radio in the middle mode of operation are:

  • Biggest of all in this climate: moisture! I currently house the radio bare between the antenna wires. It's very, very foggy here on occasion. That, I suspect may also kill propagation though, so in its own way may not be an issue.
  • Obtaining the necessary length of CAT-5 wire to carry power, audio, and keyer signals
  • Tension relief for the antenna leads that hook directly into the board. (Especially important since the tree suspension system uses tree branches in conjunction with twine to support the antenna as close to horizontal as possible using increasing amounts of tension.
On a pragmatic note. The keyer—at the moment, it looks like it's the button itself—broke last night. So, I've got to setup a small soldering station this morning to make the whole thing better. A bit of a chore. It's that far left button (for dits) shown in the picture below.



OK! The key's fixed! 




I setup a small soldering station in the house (we got a deal from Radio Shack during hte pandemic)


The bad button's on the left. I moved it to the unused right-hand button with under the board wiring this time.



The underboard wiring seems to have fixed the issue I had with the headphones 'singing' when they were near the keyer.

Before I move too much farther along with this, I need data on how well the current antenna operates. For example, do I need insulators between the antenna and the twine supporting it? One way to answer that question would be to look at the standing wave ratio of the antenna, (SWR), and for that I'll need a low-power SWR meter like this one from lloydm.net.


Operations:
Moving to the other side of the hill, (away from SF and towards the Southeast Bay), worked! No QSOs, but the RBN did pick up the station! Also! The higher antenna seemed to haved helped with signal strength into Canada. Note the 5 dB increase in signal to noise ratio!
The noise that was present when looking at town from the other tree setup is gone in this location.




Comments

Popular posts from this blog

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 concept very sim

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

More Cowbell! Record Production using Google Forms and Charts

First, the what : This article shows how to embed a new Google Form into any web page. To demonstrate ths, a chart and form that allow blog readers to control the recording levels of each instrument in Blue Oyster Cult's "(Don't Fear) The Reaper" is used. HTML code from the Google version of the form included on this page is shown and the parts that need to be modified are highlighted. Next, the why : Google recently released an e-mail form feature that allows users of Google Documents to create an e-mail a form that automatically places each user's input into an associated spreadsheet. As it turns out, with a little bit of work, the forms that are created by Google Docs can be embedded into any web page. Now, The Goods: Click on the instrument you want turned up, click the submit button and then refresh the page. Through the magic of Google Forms as soon as you click on submit and refresh this web page, the data chart will update immediately. Turn up the: