The placement of a coil on an element affects the third harmonic. If you can work out exactly where to put this coil, we can then force a harmonic on almost any band you like. In this example we have made a compact 40m antenna of only 6.5m long and then made 20m to work on the third harmonic with very little loss. See what you think. Callum.
https://youtu.be/uNqA6dy6cbY – Last Video Discussing this Concept
https://youtu.be/L9HX7352ukw – End Effect Discussion
https://youtu.be/V8Qq4-0_TjQ – The Custom Hybrid SkyLab
https://youtube.com/live/x-za2pjmNjE – Live Stream where I Switched Between
We destroyed an 80 feet tower in 5 seconds. But the 60 foot version worked GREAT! Full parts list for my home-brew 60 feet tower made from scaffolding poles, connectors and poly rope detailed in this video – and also below. TAKE CARE because if anything goes wrong, you are into an extremely serious accident.
You will need:
– 4 x alloy poles (optionally one in steel)
– About 1,000 feet (330m) poly rope (lorry rope)
– Some sort of tilt-hinge (I have made a couple of these on this channel)
– 3 x straight scaffolding connectors
– 1 cross joiner (for just above the tilt mechanism)
– 2 hinged connectors (if you wanted to make the crossbar)
– At least 4 large guy points (you can home brew from angle iron)
– Selection of 6mm / 1/4 inch bolts to tap the poles for guy points
– at least 3 x 4-way guy points for the scaffolding poles
– Steel carabiners with a decent high rating
– Hard hat (seriously!)
– Know how to tie knots!
More Videos:
▶️ https://youtube.com/playlist?list=PLcC64tNkZB7zFt6NV9fnnde2lP11fUTQ8 Antenna Modelling
▶️ https://youtube.com/playlist?list=PLcC64tNkZB7xtKohJRipVLQ6rxYzRP8eq Tips and Tricks
▶️ https://youtube.com/playlist?list=PLcC64tNkZB7xwhA0Msm_bNT4CQ_Bj5D4c Antennas
▶️ https://youtube.com/playlist?list=PLcC64tNkZB7wc6svNLY7IDthw1YCFNq9W Live Streams
▶️ https://youtube.com/playlist?list=PLcC64tNkZB7w9dp9Eqg_UhamrY5Ck3dyX My Stuff
▶️ https://youtube.com/playlist?list=PLcC64tNkZB7xvc3rHlpqqCkiBdAzYe8cf Ham Radio Training
This is my regular ham radio Friday session, live from Warwickshire. Today I fancy switching between an experimental antenna and the Signature 12.4. Join in the live chat, see if you can hear me or just listen in. Callum.
This is the 40m / 20m special design I’m testing out. It’s 6.5m lonf (only) and has a 35uH coil at around 5.5m. Resonates on 20m and 40m. Let’s try it out! Callum.
Are you wondering why your antenna is shorter than it should be? In this video, we’ll explore the concepts of end effect, velocity factor, and height above ground and how these affect the electrical length of an antenna.
First, we’ll explain how end-effect shortens the electrical length of your antenna and how it can be compensated by adjusting the length of the radiator. We’ll also discuss how velocity factor affects the propagation speed of electromagnetic waves and how it can vary depending on the type of coating or material.
Then, we’ll dive into why height above ground affects the tune of an antenna.
Whether you’re a beginner or an experienced ham radio operator, this video will provide valuable insights why adjustiung your antenna can be slightlly "weird" sometimes! Stay tuned and let’s dive into the world of antennas!
Callum.
More Videos:
▶️ https://youtube.com/playlist?list=PLcC64tNkZB7zFt6NV9fnnde2lP11fUTQ8 Antenna Modelling
▶️ https://youtube.com/playlist?list=PLcC64tNkZB7xtKohJRipVLQ6rxYzRP8eq Tips and Tricks
▶️ https://youtube.com/playlist?list=PLcC64tNkZB7xwhA0Msm_bNT4CQ_Bj5D4c Antennas
▶️ https://youtube.com/playlist?list=PLcC64tNkZB7wc6svNLY7IDthw1YCFNq9W Live Streams
▶️ https://youtube.com/playlist?list=PLcC64tNkZB7w9dp9Eqg_UhamrY5Ck3dyX My Stuff
▶️ https://youtube.com/playlist?list=PLcC64tNkZB7xvc3rHlpqqCkiBdAzYe8cf Ham Radio Training
Is it true that coax needs to be 18 feet – or multiples of 18 feet for your CB Radio? I’m going to address the myth about specific lengths of coax that some CB operators believe will magically match their antenna to their radio. We’ll explain why the impedance along the coax varies with frequency and length, and how a mismatch can cause losses and affect the SWR of your system. We’ll also give practical advice on how to properly match your antenna to your radio and minimize losses.
Loft / Attic Home-Brew CB antennas. Three Rules: Needs to be compact, easy on the wallet (cheap!) and easy to construct and understand. I have built loft / attic antennas, both verticals and dipoles for 11m (10m actually) with varing success. Other ideas are Delta Loops, horizontal loops and also remember commercial mobile antennas can ideal for lofts and attics – you will need a bit of a ground plane though. Chicken wire or just regular wire can assist. Beware that loft antennas can sometimes sound noisy because they will be directly above all the electrics in the house. However, they are still cheap and fun to make. Good luck, Callum.
If you want me to build this. Let me know. However, in this video I explain the principles behind antenna design using Maxwell’s equations and the moment method starting with a simple vertical antenna, I demonstrates how we can predict resonant frequencies and also how we can make the antenna shorter while still maintaining its resonant frequency.
Then, let’s look at adding a coil to a vertical antenna, and how this affects the resonant frequency of the antenna’s harmonic – for instance how 7MHz is also resonant on 21MHz. Using a combination of the moment method (software simulation) and spreadsheet calculations, I’ll demonstrate how the position and value of the coil can change the antenna’s harmonic frequencies.
This video is a great resource for ham radio enthusiasts who are interested in understanding the technical aspects of antenna design and how to optimize their antennas for specific frequencies. Whether you’re a beginner or an experienced radio operator, you’ll find valuable insights and practical tips in this informative and engaging video.
In a nutshell, this isn’t an end-fed but a Dipole or a Vertical. I am VERY excited about this research. Can it be right? Using a loading coil to pull the 3rd harmonic for 21MHz down to 14.2MHz. Let me know what you think – then we can head out to the field and see if this works.
