KC3LUM

Oh fun! Wish I had more free time to lend a hand. Clocks are very interesting devices.

I watched this interesting video on measuring the harmonics that are generated in Baofeng radios. I understand why it is important to keep the harmonics within regulated specifications, but as I watched how the measurements were taken I cant help but feel like the antenna is an important part of the equation. If your antenna is not resonate at the frequencies the energy is not radiated (or at least radiated significantly lower). It would be much more convincing to me if the testing took into account the voltage standing wave ratio (VSWR) measurement on the antenna and then did the math to estimate the actual radiated energy from the radio. If you look at the whole system at the end of the day, the antenna is also a filter...

VSWR [pronounced by many as 'viz-rar'] is the Voltage Standing Wave Ratio in an RF system. I have commonly seen this measurement called S-W-R in the HAM community, which is not "wrong" but it is like saying dB instead of dBm when talking about RF power measurements. When you say SWR you could be talking about the ratio of standing waves in a kiddy pool or even the ocean. Luckely no one actually pays attention to the waves in the pool, and all HAMs know what you mean by SWR. I want to take a moment to talk about VSWR and its significance to the community. First we need to start with Impedance. Impedance is the opposition to current flow in a system and is measured in Ohms. If you have wondered why co-ax cable is spec'ed at 50ohms, it is to maintain the same network impedance. Your transceiver is expecting a 50ohm network. 50ohm is set as the standard.. except for 75ohm networks like your cable tv and most satellite equipment. When your network is all balanced you achieve a near perfect energy transfer. In the real world this is never achieved mostly due to antennas, but we will get to that in a minute. If you have ever tried to connect your radio to an antenna using RG-11 (cable tv coax) from home depot you would have noticed desegregated transmissions, this is because RG-11 is build for a 75ohm network. You can imagine your coax as a network of inductors in series and capacitors in parallel to ground. The inductance changes with the length of the cable and the capacitance changes with the space between the center conductor and the shield. If the coax is installed properly, and the connectors have the proper impedance characteristics as well, then the transmission line will be very close to 50ohms. Antennas are where the impedance mostly gets fooled with. You will see that antennas are marketed for certain frequency bands, this is because they have an impedance of close to 50ohms at those bands. I have little idea how the wizards that do antenna design are able to make that magic, but there is definitely an art to it. You may be able to receive a wide range of frequencies from a given antenna, but if you transmit with a frequency that is outside of the band the antenna was designed for then the impedance would be to high and you could blow up the amplifier on your transceiver. What do the numbers mean? In a perfect world you would have a VSWR of 1:1, meaning the network is perfect and all the energy you transmit to the antenna would be radiated from the antenna. Unfortunately we live in the real world and you will see values more along the lines of 1.4:1 to 2:1 meaning that you are missing out on 2.8% to 11% getting to your antenna. Here is a video of standing waves in a pool of water here is a video of standing waves on a plate and here is a video on RF standing waves

As a new HAM with only my Tech license (so far), I have been very interested in what repeater setups look like in the real world. Do clubs set up systems with two transceivers and a diplexer or is it all in one transceiver? Is it just an expensive transceiver and a "heap" of parts donated by club members? What is the deal with "System Fusion" and "D-star"? Please post your clubs setup so we can discuss and learn about the different aspects of the set ups. Pictures would be great too!

Last weekend I made my first HF contacts on the #CherryTreeNet @ 3.920Mhz I had so much fun! Thank you to @K3MRI for letting me operate on his mobile deploy rig, and thank you so much to @K4RT and @wb4kfo for sending my these nice post cards! It looks like I am going to need to order my own custom cards to send back. I realize this is a normal custom for HAMs to send these cards, but being a new HAM I somehow never expected to be lucky enough to get one! My Lovely wife, "Babe, you got fan mail from your radio people!"