An L-match antenna coupler with no variable capacitor
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- Опубликовано: 11 окт 2020
- Variable capacitors can sometimes be hard to find. Especially during this time of lockdown with all hamfests cancelled. Described is a 1.8 to 18 MHz L-match antenna coupler that uses double sided fibreglass printed circuit board as a substitute. It's described in Sprat 185 (Winter 2020/21).
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Glad to see this! About 25 years ago I told a friend he could build his own capacitor and he used copper and glass. Worked great. Again about 10 years I helped another friend build one just like you did. He needed a large variable for 160 meters and we built one and put small variable in parallel with it. Worked great! I don’t know why you don’t see more simple L networks in use.
Really creative, that's the ham way!! All should note: This network is low-pass, so it helps filter out any spurious harmonic content.
Love the raw simplicity of what you do! Inspiring!
Ive made a variable capacity from some pieces of rg8 coax that slide inside pieces of copper water pipe. These are used in my ground tuning unit also inspired by you!
Thankyou.
I've occasionally made temporary caps out of PCB material. It's nice and high voltage insulating as long as the copper is filed away from the edges of the board, and it's convenient to get a precise capacitance just by using a file, saw, or Exacto, or even a flat-blade screwdriver tip. But I found that over time and humidity changes the capacitance will drift a bit and leakage will go up as the board absorbs moisture. But this is a handy emergency antenna tuner, and dirt cheap, too.
👍😀 Thanks Peter. As always, simple but clever solutions that work.
Peter, I love what you do. This is grass roots amateur radio and I like it! This is what it is all about, experimenting. I find what you do inspiring, keep it up.👍
Peter, you should really vacuum all that nasty sand out of your FT817. Sand and radios don't mix well. I don't fancy radio on the beach right now (Scotland... a cold dark wet place!).
Great design and thinking Peter as always 👍👏👏
When I do L-matches, the coil taps are at 1/2/4/8 and so on turns. Binary increments. UFB matcher though for the SOTA and QRP guys.
Genius. Keep it simple. Much though I love Arduinos, a simple L-match needs no shit like that!
Thats clever! Same binary sequence as used in attenuators and yout QRP tuners.
Hi Peter, great stuff! Exactly the spirit of ham radio DIY. BTW, I couldn’t see you, but it sounded like you were talking through a mask. Crazy times we live in.
Thank you Peter. Great idea. Best wishes from ZL3ABX
Great job! 73s From the USA!
Good Job brother.
Great stuff Peter. Very informative and keeping it cheap! Nice.
73
Nick M1DDD
Very cool
Congratulations ! - I like that ! - Clever, Simple, Solid state : the variable capacitor, cannot be broken :-) best regards - 73 - Marian - YO7MR
good job Peter dont use it on high power :) done that with a friend, we tested a pc board cap at different power levels, all ok in the qrp levels, but lots of heat in the high power ranges, remeber ol man Alez (zs1L) burnt his fingers, we had a laugh.. or two, it did work though. We even stuck the cap (bords) in olive oil , it did help with hte heat :) the smell was awfull though :).
johan zs2cx
This makes me wish there was a way to hack a truckstop swr meter, to auto calibrate. Can you really calibrate to a dummy load, and as long as you stay within a few khz, trust it being calibrated? I really screwed up and bought a fixed output, no swr or poor match detecting lil hf rig. It is a big deal to have an antenna to trust to keep the tx wattage out of the heat sink, but it takes a high-feature radio (not 3.6 GM engine) or lots of scopes and meters, and the old school light bulb circuit proves resonance, but you can still be far off on impedence match.
Dear
vk3ye, LZ2GNA from Bulgaria writes to you! I have been watching your materials on RUclips for a long time. I see that you are a good radio amateur, but I was interested in what you do, what is your profession?
. Interesting.
Wouldn't sliding the PC boards in such a way that the overlap determines the capacitance accomplish the same thing and be simpler to use?
I've seen you do it with your mag loop antenna.
Doing it this way is different but not better.
Regardless, I enjoy your channel very much and eagerly watch everyone of your new videos.
I built one of these in the 70s..
Peter, good job,only you could come up with that Tuner ! 72, 73 Jerry K9UT
Nice!!! And cheap!
Wonderful design
Quite Cheaper than Expensive Variable Capacitors , though it may handle more Power ..
Perhaps you may glue 4 to 6 Neodymium Magnet beneath the Board Edges , These Magnets (Look's like a Coin or Watches Batteries) ..
Then you may stick the "Capacitor Board" on the CAR Roof , Hood or Back Side , next to your mobile whip antenna as Mobile Tuner ..
Endless ideas with such design ..
By the way , Nothing special about "Neodymium Magnet" other than it has more power relevant to "Lower Profile" footprint
... (roughly 8 Normal Magnets = 6 Neodymium)
Normal and "Neodymium Magnets" both are fine and readily available at ACE HardWare , Mr.Diy or any HardWare store particularly that HardWare stores inside Malls ..
Don't forget to buy a "Super Glue" , Good Luck
I wonder what the capacitance of 2 plates sliding with a thin sheet of plastic would make. Similar to the trombone capacitor bit flat.
Anyway, nice demonstration of capacitance. Hopefully someone would get an idea from this and go build one.
Easy way to find out. Just make one.
@@allancopland1768 Yeah. But do not have the measuring devices to find out though.
I did consider that but it is very pressure dependent (like a compression trimmer) so there may be variation.
I seem to recall seeing a project where someone had moving copper clad boards to make a variable capacitor. BTW, William, if you have an HF receiver and an inductor of known value, that's all you need to fairly accurately measure capacitance (I think Peter did an earlier video on this?). However, the exact values are not critical, you don't need to measure them - if you make a capacitor using Peter's approximate dimensions and 50% rule, this will probably work.
This is pretty good idea if connected with some relays and Arduino. Could make a pretty good ATU. Or even a manual tuner where the relays would be controlled by an encoder.
Noooooo. Much though I love Arduinos...this is a KISS project.
@@allancopland1768 I simply do not find this practical. It is like with the antenna, if the antenna is too complicated and has too many parts you will use it only once. Yes, if it happens that I survive the 3rd world war and then I will have to build an antenna tuner having 20 jumper wires may not be an issue. Anyway, this thing can be easily rented out to the producers of Mad Max.
@@radioastronomy2001 You don't find shifting a few taps around 'practical'.... lol! I can think of better ways to implement this design but the idea is sound. It could be made more compact than a 'normal' matcher using a flat inductor so what the beef really? I'll be building a 'flatter' version for SOTA use.
@@allancopland1768 No I do not find it practical. For SOTA and other outdoor adventures I use KX2 with a built in tuner and battery. Quick to setup and easy to teardown after. I am not saying that the idea of using the PCB as a capacitor is bad. It is actually very sound. However, I do not see myself walking or hiking with a cutting board and all the wires. Can you imagine using this thing on a mountain top in a foggy weather with high dew point and water on everything. Playing around with the stiff cracking wires in even -5C. Where is a will there is a way... Clearly I am lacking this will :-)
Yup, you lack the will. I also have a KX2, with the internal matcher but it's completely useless as a trail radio. Too many holes to let water and dirt in . It has never been used outdoors. For outdoors, I have an FT817 and the soft case. It's just so much more practical. I'll definitely build *my* version of this matcher as a 'flatpack' using a flatwound inductor. GL.
Haha, this was very creative. There a lot of content in youtube. But this belongs to top 5% :) TNX de OH6KXL
Love it! KG5OBD