Simple Rules of Coax Fed Antennas
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- Опубліковано 10 гру 2022
- Years ago, I attended a presentation that Nigel (SK) G4NRR gave. He explained that dipoles resonate on every other harmonic and full wave loops were resonant on every harmonic. These extremely basic rules are the fundamental build blocks of almost every antenna I build. See what you think. Callum, M0MCX.
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It is amazing when the theory works like it should. BUT, more amazing is that the theory is always more complicated and practical application is just a bit different. When I first heard of your antenna I, like lots of others, thought that it was rather pricey and that I could make one much cheaper, maybe a third of the cost.
Then I saw videos of those that actually tried it. They were 50% to 60% or more and then spent hours of trial and error to get their antennas to perform well. Now, that is fine if you enjoy doing that. If that is your hobby, God love you and have at it. But, I like to put something up and have it work, if not the first time, in short order. And, I put a value on my time.
So, Cal, you make an antenna for people like me. I also applaud you for being so open with your information for those who want to have a stab at making their own I hope you continue to do well for many years.
Hey! Yes, I love folks making them.. Often they have told me that after thay had made THEIR contraption, they come and buy mine :)
In all honesty, i watch these Antenna builds all the time and hardly anybody talks about how to connect the wires. They just discuss lengths, layouts, propagation, etc., etc. But not the electrical connections. Beginners need to know that stuff! :)
Yep!!
One summer afternoon my Dad had me doing something in the backyard at the picnic table, I don't even remember what it was, while he put together the new barbeque grill. After about 30 minutes I heard him laugh at something. About 5 minutes later he was finished with the grill and came over to help me finish up. I asked him what he was laughing at. He pulled a small slip of paper out of his pocket and handed it to me. It read "When all else fails...read the instructions!" He then said "If I had done that to start with I'd have saved myself about 20 minutes!" Perhaps you should include a similar slip of paper loose in the box with all the other bits and bobs as you guys like to call them. 😁
Brilliant!
2 cycles ago in 1990 I spoke all over on 5w except to the East, as I was in a steel framed tower block at 120ft agl, 200asl. The front to back was superb. I once wired up the metal window frames up as a 2 window dipole with a tuner and made many US contacts on 10m! The good old days.
Brilliant!!
I enjoy listening to you stories you paint a good picture....I got lost while listening and could imagine myself in your shoes especially when you would add those pictures in time to time...nice work on the story telling. Thanks for sharing a part of you life with us.
Wow, thank you
Good video. I have done a lot with Beverages and Beverages on the ground. On the low bands the signal is there but the noise is the problem. Most receive antennas have negative gain. The absolute most important thing is directivity. By that I mean one or more nulls in the direction of the noise. Direction being both azimuth and elevation. I use my K3 like you noted for my 160 meter contesting. Europe BOG on main RX in one ear and the other two BOG/Beverages on the sub receiver. I have worked many 160 contests with all receiving ( 6 or 7 hundred QSOs) done with wires laying on the ground! One guy in Europe sent me a note that he was running 5 watts when he called me on 160 and he was surprised I heard him!
Good points!
Always love to hear the Commander.
I'm on a losing battle.. Lol! Harkens to the days of actually listening to a signal vs looking at a screen. Love it!
Ha! I know :)
Thanks for your consistently positive and good humored approach!
I appreciate that!
Cheers, Callum! I'm an a American with a "stupid question", but a little background first.
After been a CB enthusiast back in the 70's (I had a Penetrator 500 on the roof of my house for my RadioShack 23-channel radio). Recently, I "inherited" a 23-channel Cobra 138 that I want to get operational. I have a magnet-mount for my vehicle,, but I need a "base" antenna.
I'm
Hmm.. My question got cut short... I'm building a "base" antenna. First thought of a dipole (because its easy), but thought I'd make it vertical for the "omni" radiation pattern. But then thought to change the bottom (negative) radiator to ground plane radials. Here's the question: If there are only 2 radials 180 degrees opposing, how does that affect the radiation pattern? Does it make the it directional (like a horizontal dipole)? I know more radials is better, but I have to consider space and orientation of the antenna. Thanks!
OK.. if its high enough then place the radials at 45 degrees.. A slant. Angle doesn't. After too much. High enough is about half a wavelength..
@@DXCommanderHQ Right. I forgot to mention that I was planning that. Well, actually that was an option to help adjust SWRs. But I saw that doing that helps the radiation pattern.
Thanks for the reply and all the videos. I've learned a lot, even if you ARE "beating a dead horse"! LOL!
OBTW... And now for something completely different...
I couldn't help but notice your drums and PA system, not to mention (why do we say that when we do anyway?) that you have sound-control panels on the wall. Obviously you play in a band. Do you have a UA-cam channel dedicated to the band?
...and the guitars...
Thank you for sharing you experience packed old man brain with us all Callum.
I'll be saving this video as my OM brain tends to forget stuff.😆🍻👍
Glad you enjoyed it
Great presentation! You explain things so exquisitely that it actually makes sense!
It's because I love simple things!
Thanks to you I made a 40 meter loop and it's phenomenal. Loving EFHW antennas also
Nice work!
Your piano analogy was a perfect explanation. It made it really click for me. Thank you so much!
You're very welcome!
Great presentation Cal! I must have seen everything you have published about the DX Commander by now, and yet I always learn something new! This time I picked up on the element "order", I had heard it before, but it did not sink in, time methinks to rewatch some of the earlier videos. Keep up the great work, your journey of RF discovery is not only instructive but fascinating, like putting a 10m antenna 18mtrs up a pole! Thanks for all your hard work and the effort you put into making these videos so much fun. 73 Jim M7BXT
Yes, it's a strange discovery!
Jewels of knowledge and experience as always DX Commder Rocks !
Thanks again!
Great stuff. Many thanks!
Thanks for the explanation. I had a couple of good laughs. Adore your sense of humor Callum
Glad you enjoyed it!
Terrific presentation, Callum! I watched one of your original videos on Rudy's shortened radials a few years ago, use shortened radials them, and they work great. Thank you also for plugging the loop on the ground antenna. Your narrative about how you came up with the DX Commander is totally awesome. 73 de Jeff, KF5KWO
Yes Herr.. I have discovered where the 120 x 1/4 wave radials myth comes from now.. It was Dr Brown from RCA in the 1930s. BUT the difference was analysing short 1/8th wave (or less) Medium Wave broadcast antennas.. Then, you would need more radials fot better efficiency. But Rudy's science was excellent.
Great you came up with the RST “Problem”. In that perspective I’m old school as well .
For reducing noise, I built me a half square antenna and was surprised how good it reduces noise and gives you pretty good gain in 2 directions.
Keep up your work, thanks de HB3XBL 👍🇨🇭
Great tip!
I've been watching you for some time. I just got my technician license here in the US. You make all these concepts understandable. I am happy to buy your antenna once I get more HF privileges and look forward to speaking with you someday from Massachusetts.
Fantastic! ANd good luck!
Awesome info Callum!!
Thanks!
I'm a rare American Cal, I read the manual..I have ruined way too much expensive gear in my days by not doing so..I agree that a signal strength report is relative to each individual...To me as a guitar player it's like which Tubes sound better in my amp EL34's vs 6L6's, 10 people will probably have at least 5 different opinions..Anyway cool video!!
All good comments. And agreed. I well written fast user guide can sometimes be a joy to glance over.
Good evening Callum, what a wonderful video and the beginnings of DX commander. That’s a fantastic journey that you’ve taken keep up the good work and take care of yourself. Thank you for your videos.
WD5ENH
Steve
Ah-ha thanks Steve!
I’m a new(ish) ham - recently got my General - had a novice 25 years ago. Love your programming. Thanks for your content. I’m starting with a 10 meter mobile (Stryker SR-995HP) and a 4 element Yagi in the US - SW New Hampshire at the top of a 1200 foot hill. Not all set up yet and saw your piece on coax last night. Super helpful. Looking at Icom 7300 but investigating the Yaesu FT-710 and some older all bands.
Wow. Welcome aboard friend!
If you have an HF rig with dead finals, but receive is good, you could use it for a receive radio at low cost!
That receive idea seems like a good option for folks who are into shortwave listening.
great stuff Callum!
Awe thanks!!
One of the funny parts of resonance and SWR is it's only a measure of the antenna and radio. The results is what's important and that's what gets out.
Nice job
Tnx
so basically its "RTFM" (read the ------- manual) well said, nobody seems to "have time" these days to look at how a manufacturer designed their product to work. one exception when its in chinglish, that can be problematic . thanks for another very informative vid.
Now I know what you use for RX haha. I am noticing exactly the same thing with a 130ft EFLW at 10 feet with Chameleon Hybrid mini transformer on lower bands. The noise almost entirely goes away on it. Upper bands, the vertical is usually better.
Due to trying to get a net about 1000km away, I am actually going to raise it in a couple of steps (18 feet, then 46 feet) and evaluate any differences.
As discussed in email, I may go to a full wave loop for 80m (and 40 likely) with the guying style the power utility uses for their poles.
Cool!!!!
A little improvement could be a colour coded sticker on the base plate (or coloured dots). I would like to know what would be a good first antenna for DXing. I have just bought a RTL-SDR dongle and I love it although i now realise the antenna is crappy for shortwave listening. (so far my fave. thing is knowing what the boats near me are up-to and knowing what plane is flying overhead.
I don't quite have a TS-990S, I've got the little brother, the TS-890S. But I have an old Yaesu FT-101ZD Mk0 from 1979 passed to me from my dad from his brother. I use it as a backup, but a fun radio to operate. But the 890 is just as difficult, I often go to youtube to figure it out. I sadly must admit, I just recently took my DX Commander down to keep it out of the weather from lack of use.
Oh!
Great Info as a new ham I now understand something! Scott KF0HRF Iowa usa
Glad it was helpful!
one of your best Callum - really enjoyed this - great advice...G0KPZ
Ah. Tnx!!
Hi Callum Great video! I been thinking about a Wire Yagi for people to make cheap at home. 3 or 4 element. The driven and parasitics in an inverted v formation. hanging from a rope horizontal between 2 trees/poles... Not sure if you talked on that on other videos great videos! thought I'd throw it out there for ideas cheers !
Yes, folks do this sometime on say 80m.. But ideally needs to be high(ish)
@@DXCommanderHQ Thanks! Great videos! how you come up with such cool ideas! You can do a lot with 100 watts and a piece of wire! Haha 73s
You give me hope... you are about a year older than me and I have some business ideas I want to launch on.
Do it!
I want to make a loop for shortwave. I keep forgetting to plan one. I need coax to even try it I guess. Never tried it. I recently strung out a simple 100 feet of insulated hookup wire from the end of my camper opposite the electric meter away from power lines to a tree. The interference in my camper was terrible so no radio. Then in my main living area I ran a wire out the window and connected it to a bolt on the frame of my metal camper roof that is anchored to the ground. No shielded lead in wire but it`s working great for shortwave and medium wave using a Tecsun PL-330. I`m gonna connect another 100 ft spool of wire to the end of it and try that next. I may turn left and make a partial L shape to see if I get more signals from other directions or just use two more spools to go both directions.
OK.. So for shortwave.. Depending on the connection you have on your radio, you can make a closed loop.. So out of one side and straight back to the other.. Or maybe have a look at something called Loop On Ground.. Folks sell them for $20 or so. But you will need coax for that and it literally lays on the ground.
Do you recommend to always use a 1:1 current choke balun (or simply wrap turns of coax on pvc pipe) on unbalanced antennas like verticals to keep current mode rf off the coax back to radio ?
I don't recommend one way or the other. I don't use one for a ground vertical BUT I know that apparently I probably should!
LMAO "What the hell is this word manual mean" Just did the Wikipedia search on sig report. Thanks Cal love your videos
Yes, but you will be on a losing battle :)
I believe the vertically polarized QRM theory dates back to when most QRM was created by arcing and sparking of appliances, etc. These days with SMPS, etc. it's open slather.
Good point
Always educational and fun. Another great video!! Jack K5FIT
Thanks again!
Hi Calum hope you’re well … it does say on your site that the 7m pole is out of stock ? … I have your 7m pole already ! Would you
have the plates and spreaders in stock I could purchase ? Thanks 2e1paw
Paul.. The POLES are in stock (I will check why website says different) and we are waiting on the alloy plates to make up the kits. SHould be this week (I hope!).
could your vertical be somewhat directional if you un hook half the ground radials on one side the half you left hooked up would receive and transmit better in that direction ????
No.. WHat would happen only is that you would transmit worse at the back.
Enspiring story and how you got started. There appears to be a market for an auto RX / TX switch to provide an RX input for rigs with only one RF connector. DX Engineering has one but its expensive to source here in the UK. Maybe a new product idea for you?
Yes.. Good idea 💡
I've been using a £50 QRM Eliminator with my 7300 to do the same job as a fancy £200 switch. Wire from radio's Send auto-switches Rx/Tx. LoG to the Aux port, DXC to Ant. In clear conditions I have the gain on both turned up but when it's noisy, I turn the DXC gain down a bit to receive mostly on the LoG.
@@gm1sxwraymond882 Could you send a link and type (model) of your QRM eliminator as this sounds a good solution?
Tried multiple times to reply with a link but they are getting removed.
Look on auction site. Mine has the separate power and PTT line sockets on the back. 58 - 62 pounds.
With enough radials, it is not so much the tuned length of the radial as it is that you are coupling to the actual earth. The earth then carries on being the ground plane. Consider, if you put a two-meter antenna on the trunk of your car. Depending on which direction you go, the length of the ground plane will vary. But from a practical point of view that doesn't matter.
Indeed.. And lengths don't change the tune either.
100% on the RS report comments and the 120 radials myth! Pat Hawker G3VA SK believed that radials were largely pointless at higher frequencies and one good elevated counterpoise was far more effective.
OK, so Pat was wrong.. However at HEIGHT (on high frequencies) he's almost right.. But you need two.
Man oh man. I got my 12.4 Signature up and wondered why it measured awful, then realized I had laid out the radials, but hadn't connected them. 5 minutes later, all was mostly tickety boo.
Haha.. We've all done it :)
What would happen if you fitted a 1:1 balun at the feed point of a DX Commander?
Nothing really. I've never done it. But nothing stops you doing it either. Or a choke if you must..
@@DXCommanderHQ Hi Cal I hope you are well mate. The reason I ask as I think it may help with RX common mode noise. I would be most interested to see if adding a 1:1 balun made any difference.
Hi Callum - Is the paper by Dr George Brown on radials on the Internet?? Tony VK2IC
Erm.. Now, it's on the Discord server.. Tom found it and posted it there.. discord.io/dxcommander (and Nathan also bought a copy for me - which was kind of him)
@@DXCommanderHQ - Thanks Callum much appreciated - Been a ham since 1966 - Joined the Royal NZ Navy as an R/O in 67 - Was in UK for about 9 months from October 71 to to 1 June 72 - Have been interested in ham radio and AM Radio antennas since I first become a ham - but there is always something you learn
I've been paranoid of my transmit overloading the RX preamp and blowing it on a secondary receiver- is this a real issue or am I imagining it?
Secondary receiver..? Erm depends if you are on the same freq on 2nd radio.. If you are on a harmonic, probably OK.. There is a cheap product called a "front end saver" - I'm sorry I don't have a link..
My first hf radio was a 101zd mk 3 great radio. I find if all else fails "RTFI"
HAHA Yes!!
I despair when I hear such stories about people who have (allegedly) passed a radio license exam.
Hello sir ,
Am planning to use Rg6/U 30meters connected to dual polarity feed by signalsky . It will be compatible
Sounds good.
@@DXCommanderHQ the rg6/U 75ohms and 50ohms dual polarity feed do you think am getting a problem with it ?
Working on a 40m loop, 4:1 balum, using temp electric fence posts. Seeing what that would Bo on both TX and RX!
Done that. Works just fine.
@@DXCommanderHQ Thx. 73.
The 40m loop on temp electric fence posts works!
Callum you gotta know that it's Unamerican to read the directions.
Good point!
There's that 80/20 rule again lol
Always!
Have trouble understanding what your saying. Too much British accent..
Switch on subtitles or watch more TV!
Not sure that's Callum's problem but thanks for sharing.
Rudy N6LF lives on Oregon. He must be getting on in years now. Callum you really should try to interview him for the channel.
Also, ZS6BKW (now G0GSF) who's in West Kirby, UK
Haha yes!
I've added them both to the list. Thanks!!