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- เผยแพร่เมื่อ 8 ส.ค. 2022
- In the third video of my series looking at how to improve the efficiency of ground mounted verticals, I examine the importance or otherwise of ground radials. Do you need many? What determines how many (or few) you need? When is not worth adding any more?
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Finally someone who knows what he is talking about
Another gem Tim. I have probably 1000m of radials in bunches 🤣. Another way of checking how many you need is to do this. Put down 4 radials and check where the antenna is resonant. Add another 4 radials and see if this changes. It should lower. Keep adding radials until the resonant frequency stops lowering. At this point your ground isn't sucking all your your radiated RF away 👍
In fact I did a video on this in my early days th-cam.com/video/hE0RMzJjwKQ/w-d-xo.html
Great points Colin!
Grand slam Tim! The radial field is often overlooked because people only "see" the vertical tower. Obviously that's only 1/2 of the antenna, but the non-engineering types don't see it until you explain it. You've done a SUPERB job. Keep up the great work M8.
Thank you!!! 73
Superb. Now I see why they called you a ham hero. Great work digesting that with tables and charts.
That’s very kind of you, thank you! 73
Hi Tim. Not sure how I missed this one - but it is a really excellent summary of the subject. It is now available in perpetuity for anyone who asks the Q "how many radials should I use". Great job mate.
That’s very kind Tom, diolch!
Just found this now Tim, excellent look at the problem...I have been fighting with this with varied results for 30 odd years now...
Very good info Tim .... Thanks for putting all the data together in one video, Cannot wait for the next video. 73.
Thank you Darren that’s very kind 73
This is so useful for a newby like me. Thank you Tim.
My pleasure Chris.
Great information, nice video.
Thank you!
Great explanation Tim..
Thanks for simplifying the maths! 😊
You’re welcome and thanks! 73
Very interesting Tim, like the new “learning type” method and goes well with your other practical videos. Thanks for taking the time and effort to share it with us all and look forward to learning more as we go. 73’s M0ONM
My pleasure Eamonn 73
Great video, diolch Tim 👍
Diolch!
Excellent video Tim, thanks! So I have a DX Commander 1/4 wave vertical (up to 40m). Using the instructions and also watching the Cal video (re Rudy et al), in the end I have 160m of wire in the ground. This is made up of about 50 radials in total - each one connected to the ground plate and slightly pushed into the ground. The hot weather of late has lead to ground shrinkage and some of the radials have reappeared. I am sure moisture content will play a part, but that is for another day. So with this multi band antenna I can get SWR to be 1:1 on the portion of the band I need. For 40m I can get SWR 1.2 over whole band. So far so good. That said, early on when setting the antenna up I grounded only through the Coax by mistake. It performed amazing, and then I realised the mistake and connected back the radials. I do not like to share / admit this, as it was back breaking work to get the 160m of wire into the ground. So I like to think that "every little bit helps !". But it does go to show perhaps the difference between the the data and real world communication. Mark, 2E0MSR.
Interesting Mark. Of course in your case the quality of the ground abs above everything the propagation for that time would’ve helped. Take care 73
lesson from that graph is use a 1/2 wave radiator 😁😁 using stub matching, I bet 1/2 wave vertical is most efficient antenna, though it probably would be difficult to get 1/2 wavelength for lower frequencies, not sure most hams can put up a fully erected 1/2 for 40 meter band.
You can do a loaded one for 40m with a 34uH coil 10m from the transformer and around 1.7m of wire further on from the coil.
Hi Tim,
Great information. Callum has done quite a bit of experimenting on the radial field for the DX Commander antennas, and has come up with an easy to use formula. Put down (at a minimum) at least two wavelengths of radials at the lowest wavelength to be used and up to four wavelengths for best results. Stay safe. 73 WJ3U
Yes almost at my figures there Don. 73 take care
Thanks for the video. I have few questions to which I don't find answers in any videos. 1.) Does radials need to be insulated? Why not bare copper wire? 2.) Why 32 individual radials? What if you just weave a massive copper net on the ground around your antenna? Or a spiderweb of interconnected radials on the ground around your antenna with all wires connected at each junction point?
1 and 2: don’t have to be insulated but this does prevent long term corrosion. The alternative ground system would work. It’s elaborate but provides you used a good conductor it would work
Very informative, thanks Tim. If that many radials are needed I wonder about the efficiency of a single raised counterpoise, often used with field portable stations. I'd be interested in your thoughts. John VA3KOT
Raised radials .. a pair at 180 degrees from each other would be the equal of dozens on the ground. A single raised one MAY be a little directional
My rule of thumb is that if the ground isnt covered in evenly layed out radials and the XYL isnt complaing, then you dont have enough down.
Best indicator of all!!
Hi Tim, thanks for looking at this, but I wonder whether the theory includes the false premise about antenna efficiency, I.e. that feeding at a high impedance point greatly improves radiator efficiency.
So envious of people that can lay down some radials. I can only get very short radials in a 12 degree fan at the antenna base. It dose not work. Very Interesting video many thanks.
Ah well you can only do what you can. Thank you for stopping by and commenting 73
Hi Tim, Another great video. I think this one proves that a 1/2 wave vertical is a good choice. The question I have is if I put a 1/2 wire up vertical for say the 10-meter band, how do I match that to my radio?
With a tuned LC circuit at the base or with an 49:1 impedance transformer
Yes - with a 49:1 or 64:1 transformer OR tuned LC circuit 73
Agree
THANK YOU SO MUCH Tim G5TM FOR YOUR HELP
the mystery revealed 24 radios per band Wonder fantastic 24 radios 40 meters, 24 radios 20 meters, 24 radios 11 meters 80,10 MTS roe 1,1 spectacular TX/ RX SPECTACULAR I was investigated for 3 years, .... EC5APA ..... always 24 RADIALS PER BAND💖💖💖
Thanks!
Hi Tim excellent video, as usual 😉. Only a question: is available a chart that compare loss vs radials number and lenght with fixed radiator lenght (for instance 1/4 wavelenght)? Thanks and 73 de Franco, iw2hus
Hi Franco! Which length did you wish to check?
@@timg5tm941 Hi Tim! Thanks for the answer. My goal is a good compromise ground plane for an inv L 80m band and 40m 1/4 wl. with a lot of radials 3,4, or 5 m. TU and 73 de Franco, iw2hus
Oh Tim what a controversial subject hi. Hope your well mate.
Here my 40m vertical has 100 10m radials and swr is ok, and the ant works great. Recently did a wee video about my 20m vertical which is connected to the same 100 10m radials which works great, but testing another 20m vertical stuck in a tree with only 4, 5m radials worked the same dx with better propagation, so to those who struggle for space, a small amount of radials can still get you a qso, so don't always rely on calculator info completely, put a vertical up with what you're got and give it a go.
Well presented video Tim, best wishes and let's see you out and about on the air, we love your mobile qsos. 73 zl3xdj
Hey Brian I’m good and thank you for your information. I’m hopefully our next week early morning so hopefully we’ll bump into each other
Interesting as always, I am fortunate to have conductive ground here in Norfolk (though probably not at the moment). I stripped down a lot of scrap CAT5/ 6 cable for my radials, So I have 112 8m radials, though not all fanned out properly yet. I do like to challenge accepted wisdom, I am not convinced that the conductivity of the soil has the predicted effects on the number of radials required.
Take a hypothetical case of a deep non conductive "ground" where radials laid on it effectively operate as elevated radials. Just a few quarterwave radials will yield high efficiency with a quarterwave vertical. (Very non-intuitive). The table at 3:20 looks dodgy to me, over a 10:1 improvement in ground loss resistance going from 60-120 radials does not follow the trend of the remainder of the table. Some data suggests that 1/4 wavelength is far from optimal for ground mounted radials and can lead to increased losses. (Rudy Severns in QEX). Definitely an interesting video, well done.
Thank you! It’s a fascinating subject for sure! Appreciate your input here 73
@@timg5tm941 yes it is fascinating and the more you know the more you want to know!
Your videos are enjoyable to watch and thought provoking. 73
Great video, one question..for 40m you need 240m of radial. If I can’t have them 1/4 wave length long then put as many shorter radials to equal the 240 meters worth of radial?? Is that correct?
Yes absolutely
Is there a device or procedure to measure your local ground properties?
And what if you used a thin but solid metal disk of quarter wavelength radius under the antenna? Isn't that an infinite number of radials?
Does it work better in winter when the ground is wet from rain?
Maybe someone else could chip in with data here?
@@timg5tm941
"Determination of Soil Characteristics Using a Low Dipole" by
Rudy Severns N6LF
:)
Actually I want to build a nvis antenna and this document gives great info. However I can not tell if the vertical gain outweighs the loss being so close to the ground. Ie you might be better off with a normal Dipole higher in the air.
From my own experience, the 1/2 wavelength vertical works better both receive and transmit than a 1/4 wavelength vertical antenna.
KD8EFQ/73
Yes I’ve had better luck with 1/2 waves too 73
@@timg5tm941 I was intending "experience" and "results", upon switching out between a 1/4 wave and a half wave antenna, and a local operator on the 10-meter band telling that the 1/2 wave antenna gave him 1/2 a db stronger signal than the 1/4 wave antenna with just 100 watts!
I have made a 3 band vertical (like the dx commander) i have 18 radials 3m long i tuned the antenna with them laying on the ground. Now that i have buried them 2cm undergound the swr curve shifted and i was wondering if i just have to retune the antenna or is something else wrong.
You’ve altered the ground and the impedance. I wonder out of curiosity if the swr sweet spot has seen the antenna become electrically longer or shorter?
@@timg5tm941 It has made it longer so now I have to retune it.
I have watched several videos now regarding ground radials. I am a little confused. Just about everyone says the number of radials is more important than the length of each radial BUT they also keep referring to 1/4 wave lengths of the radials. So, which is it? 32 radials for 80 meter band is one heck of a lot of wire.
Isn't it a forth size downsized scale of the main meter size? Quarter. Wave of whatever meter band....yes you just chop it measure it to a 1/4the size.
I am using 2.7 wavelengths on 40 meters and 18 wavelengths on 6 meters (108 meters of radials)
It’s a decent amount 👍
How many? Oh, about a million or two would do nicely..
all of them. you need all of them. in fact, replace the ground radials with a giant parabolic ground mounted copper dish.
Ideally!
Your figures are somewhat at odds with the AARL Handbook chart (Figure 3.25). Given that the esteemed Rudy Sevens is one of your sources, I'm thinking that the AARL chart may be off.
More than a few have questioned the ARRL figures on this one
About 8% of men are colorblind. I'm one of them. Color-coded maps and line graphics have always been a challenge. Hint, hint.
As an amateur video maker having the time to cater for all requirements is an issue. I’m sure you can find the data elsewhere using other formats. I’m sure no hints are required for you to do so.
Come on folks...smash that Like Button!!! 1340 views and only 115 Likes! Great video Tim...Thanks! KA2PBO
Thanks Rick!
𝓹𝓻𝓸𝓶𝓸𝓼𝓶 🏃
Ok