Ham Radio / Off-grid communication
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🔎 Please read my article, How to Dox Anyone: A Liz Fong-Jones Story. (Xitter), (Substack).
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- Dołączono
- 30 Cze 2023
A 20m dipole would work best around 40m wavelength. Assuming you're not doing something exotic, it would be half-wave—two quarter-wave conductors arranged in a straight line.
To be clear: I mean the total length between the tip of each pole (i.e. 10m + 10m = 20m).
Results around 20m wavelength would understandably be dogshit in comparison.
- Dołączono
- 22 Wrz 2021
An antenna tuner can help with that, I believe. I have this dipole myself: https://en.wikipedia.org/wiki/G5RV_antenna
888Flux
kiwifarms.net
- Dołączono
- 6 Lip 2021
Awesome. The bulletin will transmit twice, once at 16:00 UTC and again at 23:00 UTC. The 23:00 UTC window should have better reach into Europe, but both should work. The bulletin should only take about 8 minutes total. I'll add a counter at the very top that you can go in and just edit the line so we can keep track of re-transmissions
Dumb question but do you mean a 20 meter half wave dipole where both elements are 10 meters? Or a 20 meter dipole?
Ostatnio edytowane:
- Dołączono
- 29 Sie 2019
Anytime you run across someone who has a long expired ticket and they start fumbling around about waiting on the FCC 10/10 times its because they are a diddler. "Pending" might as well be ham for groomer. In my experience some hero up at the FCC will just leave the diddlers in "Pending" forever. I know this because there are 2 local diddlers we have kept our eyes on for years. I actually joined a few local clubs just so i can keep an eye out for new club applications. One vanished as soon as his name was in the papers, the other tired to stick around for awhile but everyone from our repeater club kept reminding him his license was expired and asking him if he needed help with the FCC website etc etc until he finally fucked off.
GodGivenAirwaves
kiwifarms.net
- Dołączono
- 29 Cze 2026
As far as antennas go, I can vouch for Hexbeam antennas, if you want directionality + multiple bands, there are plenty of plans to go with, pretty much all of them can be built DIY.
- Dołączono
- 30 Cze 2023
When you're working in metres, the calculations are pretty easy. The speed of light is close enough to 300,000,000 m/s that you can use the fraction 300 / Freq to get corresponding wavelengths in the MHz range. Then just divide by 2 or 4, depending on pole count.
- Dołączono
- 15 Gru 2022
This is what I have, 20m total, 2 10m elements. SWR is consistently under 1.2 without tuning. What confuses me is that it does so well at 40m but not higher bands.
888Flux
kiwifarms.net
- Dołączono
- 6 Lip 2021
A linear full wave dipole for the frequency you want to operate on will have an extremely high impedance at the feedpoint in somewhere around the kiloohms. Not to mention an extremely inefficient radiation pattern. Without a matching network like an antenna tuner, it's not even possible to tune up.
A half wave dipole has it's current maximum at the center, and gets us closer to matching our 50 ohm load. A theoretical half wave dpiole in free space sits somewhere around 73 ohms. The mathbabble is 73 +j 42.5 where the real part represents the radiation resistance and the imaginary is the leftover inductive reactance
Remember what the purpose of an antenna is. We want to match our transmitters 50 ohm output as close as possible. This is why for antennas we use a half wave dipole and not a full wave.
across the 20 meter band? It's most definitely your feedline radiating, or some other problem in the shack. And if it's flat across the board there is some other issue going on. A 40 meter half wave dipole (20 meter total in length) will be resonant on 15 meters though. What are you using for coax?
Been working on a WASM version of the JS8call-improved decoder that you can run directly in your browser. Don't know if it will be ready before the Kiwi Bulletin but if it is, I'll drop a link and the source repo for anyone who wants to give it a spin.
- Dołączono
- 7 Lip 2016
coax or some other component is sinking a lot of heat then, the feedpoint impedance should be extremely high for a centre fed full wave dipole. It would need feeding with twinfeed to work properly.
- Dołączono
- 7 Lip 2016
Something is burning up. High SWR on its own cannot make coax radiate, on a balanced antenna.
The only time I had something similar, coax had been damaged, arced over and carbonised some of the dielectric making an impromptu dummy load.
- Dołączono
- 15 Gru 2022
Thanks for helping me with this! I don't have much equipment, but I can say that SWR goes way up on 120m, 60m, 30m, 15m, of the ones I tested, SWR consistently low on 80m, 40m, 20m, 10m. THough at 10 I'm getting an SWR of 1.7
I'm using 50 ft of RG8x feedline, so it has some losses, but I get great propagation with just 5W from the transmitter so I can't imagine my losses are too bad.
I should admit I purchased a purpose-made balun for the dipole, so that might effect how you think of it.
I'm using 50 ft of RG8x feedline, so it has some losses, but I get great propagation with just 5W from the transmitter so I can't imagine my losses are too bad.
I should admit I purchased a purpose-made balun for the dipole, so that might effect how you think of it.
NortelNutworks
kiwifarms.net
- Dołączono
- 28 Cze 2024
Nothing with a software suicide pact involving built-in pinned certificates deserves to be called "pretty solid", ever.
- Dołączono
- 15 Gru 2022
I re-read this and actually unstad what you said. Thanks for explaining why it isn't radiating well at 20 meters!
Again, I'm using RG8x feedline, it's a portable rig with my G90.
Is there any way I can test the feedline and balun for faults with a multimeter? Nothing seems visually wrong with them.
GodGivenAirwaves
kiwifarms.net
- Dołączono
- 29 Cze 2026
If you have the space for it, a fan dipole is a great way to get multiple bands from one antenna. Alpha Delta makes a series of fan/linked dipoles, Personal experience with the DX-CC Model, as long as you get the two sides separated the swr is flat in the non WARC bands 40-10, with 80m elements including loading coils which while compromises the antennas Q on 80 gives you less of a hassle on length.
WARC Bands can be tuned with most built in tuners also. DX-CC Can be tuned using a wider range external tuner to 160m easily!
Dipole wire antennas are like the easiest to construct DIY, fan dipoles for multiple bands.
Xeigu G90 has one of the best internal antenna tuners, there are videos of people tuning up metal sculptures, bleachers, shopping carts, and guard rails. The only downside of the g90 is the lack of AM Broadcast band filtering which leads to over-driving the front end, you might find yourself hearing your local AM Station on the ham bands. You can buy external AM Filters pre-made from amazon that match the g90's max output power.
WARC Bands can be tuned with most built in tuners also. DX-CC Can be tuned using a wider range external tuner to 160m easily!
Dipole wire antennas are like the easiest to construct DIY, fan dipoles for multiple bands.
Xeigu G90 has one of the best internal antenna tuners, there are videos of people tuning up metal sculptures, bleachers, shopping carts, and guard rails. The only downside of the g90 is the lack of AM Broadcast band filtering which leads to over-driving the front end, you might find yourself hearing your local AM Station on the ham bands. You can buy external AM Filters pre-made from amazon that match the g90's max output power.
- Dołączono
- 15 Gru 2022
It's amazing, I can tune up to anything with this thing, it's incredible. My only concern is radiating efficiently. I remember hearing that you can put a metal spike into a tree and use the tree as a radiator.
GodGivenAirwaves
kiwifarms.net
- Dołączono
- 29 Cze 2026
yea, that will do it....
Looks like the wire elements are corroding too, speaker wire only lasts so long in the sun.
14 AWG THHN Stranded from your local hardware store will do the trick, make sure to heat-shrink the ends to stop corrosion.
You can also bounce signals off of the Aurora, 6 meters works great for that. You will know when it's Auroral propagation when the signals sound "ghostly".