Tunable Slot Antenna: Build, Test, and Optimization for 2m, 70cm, and Beyond
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- Опубліковано 15 жов 2024
- Email List: eepurl.com/iGP0Ck
Johns Book: amzn.to/4deLWes
Patreon: / hamradiorookie
Past slot box antenna video: • DIY VHF 2 meter Ham Ra...
I revisit the box slot antenna design and show some improvements that can be made. This compact and portable antenna is ideal for POTA, SOTA, or even setting up on your deck for 2-meter, 1.25-meter, and 70-centimeter bands. Inspired by John Portune's ‘The Slot Antenna for Ham Radio,’ I explore how shorting blocks can tune SWR and frequency for better performance across multiple bands.
Join me as I build, tune, and test this high-Q antenna, perfect for those wanting to optimize their setup for specific frequencies or gain versatility. I also talk about how to improve bandwidth, troubleshoot designs, and how this antenna can be stacked for extra gain.
Let me know if you’d prefer a high-Q, band-specific antenna or one that covers a broader spectrum with less tuning. Plans for this build are available through my Patreon. Stay tuned for more antenna projects and designs!
In awe again Ben. First off, prototyping in cardboard - much underrated construction material; second, the friction-fit jumpers - simple but so effective. The black build variants rock. This seems like a natural for an expedition flat pack. Also, dare I say ... box kite? Fine engineering and superb explanation.
Definitely on the agenda in the future
OUTSTANDING work! Very glad to see someone not just building, but designing new concepts and really pushing the envelope. You've got this! 73 OM
Thank you very much! I’m not sure I’m coming up with new concepts as much as mashing a bunch of ideas together and standing on the shoulders of giants
Super Cool Ben! Always enjoy seeing your process!
way to go! amazing how well the tape antennas work - John P also has his barberpole helical design that would be fun to use too
Thank you
Hi again. Read the book e-cover to e-cover. It seems I have owned a slot antenna in the 90s. I bought a couple of them from a retired radio repairman (along with a pair of 6M FM mobile tubs rigs with service manual) The antenna was a cubic inch in size, SO-230, a mounting tab, a wire, and some hardware. It was a "hidden" mobile CB/10 antenna. The wire was about 3 feet long. Not a slot and not a 10M antenna.
Well. You attach the mounting ear under a trim screw into metal on the front or rear window (top). The wire was run down the window to the bottom. There were several means of attaching the wire to the edge of window. The included adjustment tool was used to get best SWR. It worked just as good as my quarter wave with less directionality. The second on was taken apart (that is why you get two). It was a simple compression cap matching network. I wish I knew where they are or even the name of the thing.
THANKS!!
I’m going to have to research this!
I'm building a phased horizontal slot array to cover 2m and 70cm bands using aluminium 1.8mm sheets it's absolutely fascinating how compact and how well they work. Great content.
There are times when I want an extremely high-Q antenna on 2 meters. APRS is a perfect example as all transmission and reception is done on 144.390 MHz in the USA. DE WA1KLI
What bandwidth would you want? I can squeeze more Q out of these.
@@VE6SFX_HamRadioRookie 10KHertz would be plenty, although I don't think it would be feasible to make an antenna with that high Q.
Thats awesome love the different builds you do im interested in a 2m one for sure
Thank you
Thanks!
!!!!! Thank you
@@VE6SFX_HamRadioRookie you are very welcome!
I can see a use for both a set frequency and multi-band antennas. Its all dependant on what the task is at hand.
Ie: I have 2 mobile radios used as my home base stations. One is set solely for use as my Echolink station, so I leave it set on a single frequency. The other is for crossband, and making various repeater contacts. So I use it all over the 2M / 440 scale!
Thanks! This helps
Love the video! Audio is exclusively coming out of the left channel for me. Something to fix for next time.
If memory serves, SLOT antennas have opposite polarization to conventional. I assume, although both planes horizontal, the actual polarization is vertical??? Have you checked or modeled the radiation pattern? If so, is it basically omnidirectional?
Yes slots are vertically polarized and this is for the most part omni directional but there will be lobes created by the jumper shorts
Hey, glad to hear you are back and playing with antennas. Any updates on selling the bnc connectors on the pcb boards? I know I could use a couple to play building antennas
Yes I really need to do that.
@@VE6SFX_HamRadioRookie Thank for the reply. I get it, too many projects, not enough time :) 73
This is clever as hell. I would have Never expected that the radiation would come from the edge of the element.
Thank you. It was after thinking about it that I realized all measurements were based on the edge. Then I figured it was worth a try.
I don’t use uhf/vhf in a way that I am scanning around AND transmitting across the band. I am either talking on a specific repeater or setting up for winlink. The only thing I do across the band is scan and receive listening with the occasional transmit nothing like hinting Pota on hf, but that is just me. I think you could have indexed locations to move the jumpers that are labeled such that you know where to put it depending on where in the bands you want to be
I like the indexing idea thanks!
Love the concept. But i need something for my attic, so i would need a low Q/broadband variant, one for 2 m and one for 70 cm with duplexer.
Awesome‼ Thanks 👍
Thank you too for watching!
Stacking a bunch of these with a phasing harness could make for a really interesting looking EME array?
Agreed
Very interested. Would love to see it 3d printable. Also curious if copper tape makes a difference.
Copper tape and Aluminum tape can be used but they are not a durable as the faraday tape. But it does warrant a test in the future for sure!
Foil tape is why I came here. Much more readily available than Faraday cloth. Since the flat conductor is attached to a semirigid flat surface and not foldable fabric tape, durability should be less of and issue. John Portune made many prototype and finished antennas with Al and Cu tape. My guess is the velocity factor will be different so Al and Cu version would have different dimensions that a Faraday cloth version.
How about an automated antenna tuner? Not sure how cost effective it may be? But you might be able to throw in a linear actuator, a scissor lift or multi leg worm gear design to adjust the gap between the two plates. But you could adjust the width / gap at the flick of a switch.
(If I understand that changing the gap retunes the antenna?)
Essentially yes the gap is what tunes and then the matching section needs to move that will affect the tuning… so it’s a iterative process
Interesting. Here in Europe the 2 metre band is 144 to 146, and only the 145.0 to 145.8 is used for FM repeaters and simplex, so the high Q may not be too much of an issue.
Did not think about it that way. You have a good point
You have lasted a lot longer on antennas that I thought. And I see you have found a work around for that pesky hot melt lead based glue. Just a quick question - is that dBi or dBd? Off to check out the book.
Wellll it can be both The difference between dBi and dBd is how antenna gain is measured.
dBi (decibels relative to an isotropic radiator) refers to the gain of an antenna compared to a theoretical isotropic antenna, which radiates equally in all directions.
dBd (decibels relative to a dipole) compares the gain to a standard half-wave dipole antenna, which is a real-world reference.
Generally, a dipole antenna has a gain of about 2.15 dBi. So, to convert between the two:
Gain in dBi = Gain in dBd + 2.15
At least that’s my understanding
Your experiment makes me wonder how close the planes could be constructed? Could one of these be made where the bandwidth is so narrow it'd make an effective repeater antenna that didn't need filters?
That’s kind of what I am thinking. In Johns book he has one slot antenna where it is just a jigsaw blade width and it’s ultra narrow bandwidth
@@VE6SFX_HamRadioRookie Indeed. I'm going to have to get this book. I also have some crazy ideas whose questions may be answered there. 73
More gain is interesting, and high Q might reduce overload if you are close to a transmitter, as I was a few weekends ago.
Yikes! Did you overload a HT?
@@VE6SFX_HamRadioRookie Yes, I was on the highest peak in VT with LOS to all of my usual chasers. I could barely hear the strongest station, just managed to wring 4 contacts out of the noise. Ordered a spectrum analyzer, which showed my HT was receiving fine, so I concluded my front end was overloaded by the broadcast transmitters less than a mile away. Probably going to get one of the Sotabeam filters. I need an Elmer to tell me whether a high Q antenna would work the same way.
Interesting. I’m not convinced this would help much. Tuning is for the most part transmit. Not necessarily for the recieve
A high q antenna would be great for APRS
Agreed
This thing screams 3D printing. Are you going to sell step or stl files?
I can do that when I get there
The more I think about this I really think you might be on to something here. I can make compliant mechanisms to spring load connections and print in a BNC bulkhead hole… THANK YOU! I’ll be adapting my design because of this comment. I love all the feedback I get that sparks new ideas.
I was thinking having SendCutSend cut STLs out of plastic would be super cool.
Great idea!
No audio on the right channel
Sorry I will do better next time
imagine there are shops in China who stick copper to a very strong carrier material made out of glass and some weird glue. imagine those shops make any design...ANY....design for almost zero dollars. and they even sponsor your most often viewed video's when you are a nerd as I am. Imagine you let them make your designs so you can sell them...73's ON4NDO
Yup PCB Way sponsors me from time to time
@@VE6SFX_HamRadioRookie 😂😂👍
In awe again Ben. First off, prototyping in cardboard - much underrated construction material; second, the friction-fit jumpers - simple but so effective. The black build variants rock. This seems like a natural for an expedition flat pack. Also, dare I say ... box kite? Fine engineering and superb explanation.
Box kites have been considered and one day when I have time I plan on this. Thank you for watching