How easy is it to get good DX performance and good efficiency across 40 metres through 10 metres with a single wire vertical? Connect with my channel by subscribing and commenting.
Interesting discussion Tim. I've never been keen on the whole 9:1 idea, primarily due to the amount of loss in the coax due to the high SWR. If going for a multiband a vertical antenna, I would say either go the DX Commander route with multiple vertical elements or (as you suggested) put a tuner at the base. You are absolutely correct that there will be some loss in the tuner but it will be insignificant compared to the losses in the feedline due to the mismatch if using a 9:1 & tuning it in the shack. I'm led to believe that these tuners are fairly efficient, even with a big mismatch. Obviously this doesn't solve the issue of the RF going skyward on the higher frequencies due to the antenna being too long. Realistically a choice has to be made based on your main operating bands. A 10m vertical will act as a 1/4 wave on 40m & a 1/2 wave on 20m. It will probably also do ok on 30m. I would consider this a fair compromise for those bands but trying to use it on other bands will probably be very disappointing. Same is true with a 5m vertical for 20m & 10m. Again it will probably also do ok on 12m, 15m & 17m, so I would consider it a fair compromise if targeting those bands. However I can't imagine that it will do to well on 30m or below.
At QRP levels length becomes critical as any inefficiency spoils DX opportunities. I do not use ground radials (the antenna is elevated about 9' off the ground) but do ground the un-un which seems to help on a 31' length and i get about 6-7 watts at the antenna from 10 watts at the rig. This video has given me a couple of extra ideas to try. cheers Tim and 73 . M7BLC
A very informative vid there Tim. I use a 9:1 with a 7.6m wire. It works quite well on 40 thru 10, with SWR spikes managed by the tuner. I do find it doesbhave low SWR on some parts and I do not have to tune it. It has been effective on DX QSO's, with US, Caribbean, Brazil, India to name a few. I do have about 250m of radials too.
good explanation, and this is why, with 5w qrp here, resonant verticals are the only way to go really, and as 40m and 20m are the only bands ever open down this way, No need to worry about multiband ants. But I have worked the high bands once when there were open, using a 40m vertical and extremely high swr, but still got qso,s. Because when the high bands are open, there really open, and its easy to get dx over 10k.
Thanks for the video. I’ve build a 9/1 vertical, I think I used 29ft length of wire. It was terrible although it tuned fine. I tried the same antenna with ground radials and seemed loads better. Could be worth modelling it with radials Tim and comparing the results.
Very interesting study. Great presentation. What transformer and wire length could one use for 160 and 80 meters with limited space? I and lucky by having a 25-28 meter tree.
Hi Tim, thanks for this excellent explanation. In you next videos, I suggest to add some of the graphs or radiation patterns given by your simulation tool. EDIT : Silly me, you did show the radiation pattern ! Definitely, I am a subscriber. 73 F1SOC
Thank you for this explanation Tim, especially where you discussed the compromise nature of a vertical fed by an unun. I have been wanting to design such a vertical antenna, with a max height of 10 meters, that can give credible performance (adequate angle of rad. and low loss) within 14 to 30 Mhz. I wanted to include 20, 17, 15, 12 and 10 meter bands only. What would you say the best antenna height be ? Thank you 9H5LX
Hi Vincent, the 7.6m long vertical would do nicely on those bands and still give you an OK version for 40. If you wish to focus exclusively on 20-10 then a 7m long radiator would do very well as a 5/8 wave on 12 in particular. 73
yes, great way to gain a better understanding of the physics and workings of this antenna. What about using the 31 ft length and a 49:1 transformer? I think we would see a better match and, the angle of take off would stay lower on the upper bands like 10. I like your what if scenarios.. and then back it up by real world tests. keep up the great videos. --K1QS.
Yep done and shown that quite a few times. I agree it’s a very good set up. Of course you still get the high lobes on 10 as it’s a full wave on that band 73
I use a 35.5 foot wire sloping L that generally outperforms my OCF 134 ft. Dipole on 40 meters and 20. I have a remote relay to switch between them to A/B the two antennas. (I send switched DC down the coax from my home brew tuner). I feed them both with their own 1:4 transformers. I can operate 40 with the tuner "out" and low SWR on 40 and 20 meters. I have a little question of why people use less than a quarter wave on 40 meters when a few more feet will significantly raise its radiation resistance and greatly reduce ground losses. I previously used a 53 foot random wire that would put me in S. AMERICA and B.C. on 160 milliwatts. (Also fed with homebrew 1:4 wrapped on a transistor radio ferrite antenna core.
Hello Tim, use an old toroid from an old Tv, 9:1, with 4,40 meters of wire, result in Vertical End Feed JS20 Portable/Fixed, work very well without any tuner from 20 meters to 10 meters. 7351.
I played with 9:1 unun verticals, I ended up running to verticals. 1 for 40m -17m which was 29.5 feet and one that was 24.5 feet that worked well for 15-10. They are compromises so you have to make compromises with them.
how fo you add the 9:1 in MMANA? I am trying to make a wire version of the cha250b antenna but need to work out what unun I will need (tried making the cha250b unun but it is to dificult), the cha250b is 23 foot 5 inches. I know in MMANA you add loading but I have no clue what you type into the boxes for each unun. Reason I want to make one is that I cant justyfy spending nearly £400 on an antenna if it wont work in my situation so want to build a wire version to test first.
Tim...what is your feeling about the 31' version to cover 40/20/17 and 15 only? Do you feel better about it's DX chances eliminating 12/10 then? Thanks, looking now to do a new project
Hello Tim I am a new subscriber and new Ham. In need of advice from your excellent knowledge. I've just put up an 9:1 Unun with 20 metres length of wire for 80 through to 10 metres. Thankfully I have a 100 foot garden with a tall willow tree. The antenna is mounted horizontally one end at 12 metres sloping up to 22 metres height. I've an old Icom ic 728 with the external icom 160 atu, grounded to an earth rod. Feed is 20m of RG8 mini coax. There is a slight sag of approx a metre from the highest end. Is this ok? Would the unun benefit being grounded to an independent earth rod? Maybe a counterpoise and what recomended length? I think I should of gone with a 49:1 Much appreciated if I could please have advise from some one experienced...
Thank you for your kind words. Wow you have a nice height on that antenna. Are you able to fit around 132 feet of wire into your garden? Even if you run it as an inverted L? I think a 49:1 efhw of that length will get you an excellent match 80-10 and you only need to have a choke about 5m or so from the transformer (or further) and maybe another one just before the coax enters the shack. With that height you’ll do very well indeed. No need to earth anything with a 49:1. Especially running around 100 watts or less. Hope this helps? 73
@@timg5tm941 Ahh thank you for replying. Yes the height is quite amusing, looks as if I defied gravity. I've six fence panels across so I guess thats over 36ft width and a conifer tree even higher in the corner I can drop a draw string over it with the drone, i think 132ft would squeeze in. Only just doing the foundation level with the 10 watt limit I probably won't go up to the intermidiate until next year. Would the choke be one of those "ugly balun" things? Again thank you I very much appreciate your advice. 73
You could do .. be interesting to see how that turns out. The impedance of a quarter wave will be somewhere between 36-50 ohms. So a 9:1 might well reduce this to a small figure which some tuners may find harder to match. A 4:1 might be more forgiving maybe
Regarding antenna modelling: Decades ago, for quite a few years, I used to frequent the 'rec.radio.amateur.antenna' newsgroup (remember those?) where the true, well-known names, subject matter experts (and an occasional lunatic) used to hang out, endlessly discussing the nitty-gritty of antenna modelling and how it relates to the real world. Back then, it was reported that there was a 'mysterious' discrepancy between the (modelled) far-field signal strength of a quarter-wave vertical over an infinite ground-plane, as compared to a modelled vertical dipole. The discrepancy was variously reported as being +3dB or +6dB in favour of the quarter-wave vertical over an infinite ground plane. That seemed very odd, that less antenna would work better than more antenna. Conceptually, in a perfect model, they should be identical (the old ground-plane 'mirror' concept of a quarter-wave vertical). To be clear, none of this is referring to just the peak at some take-off angle; but the entire pattern over the entire hemisphere (think 'average'). It was kinda a big deal. If I recall correctly, some of the discrepancy was eventually attributed to carelessness (by some, not everyone, thus the variable reports: +3dB and +6dB). The dumb error was feeding the virtual feed points with a constant voltage source (which is common in some modeling SW at the time, still today ?), thus (for the same voltage) causing double the current (thus 2x power) into the lower impedance 37-ohm ground plane as compared to the 73-ohm vertical dipole. They forgot to normalize the applied RF power; a bit duh-obvious in hindsight. Easily corrected. Once that silly error was sorted out, there still remained a significant discrepancy (perhaps 3dB if memory serves), in favour of the quarter-wave vertical for the signal strength in the far field. My suggestion to this dilemma was quite simple, but I never heard anyone confirm or refute it (although some dismissed it out of hand). In the computer, the 'universe' (the model space, perhaps a 3d matrix) is obviously not infinitely large. So if you cut-off one-half the 'universe' with your infinite ground plane, then there's zero energy going into the lower half, and thus perhaps the resultant field strength in the upper half of the virtual universe would naturally double. Common sense? In other words, perhaps this reported discrepancy is merely an artifact of the computer model, and one that is perhaps not easy to overcome. If the people writing antenna modelling SW have sorted this out, I wonder if they had to resort to a SW kludge to fix it. I never got the memo. 🙂
Crikey, only a couple days later, I stumble across an example in the wild. In reference to a 22m Part 15 beacon, "...the limits are 4.6 mW into a half wave dipole, or 2.3 mW into a quarter wave ground plane antenna." So a 3dB 'advantage' to the quarter wave antenna over the half wave antenna. Error (I presume) might be either of the two causes I've outlined above, more likely the latter one. Interesting that this supposed 3dB 'advantage' of a quarter wave antenna over a half wave antenna, defying common sense, is still going on even decades later. Someone should really get to the bottom of it. Double check the applied power, beware voltage source, confirm impedance. Then try trimming the ground plane from infinity to just quarter wave, or (as was recommended years ago) quarter wave +5%. Step 1 would be to reproduce the anomaly. Then see if it has a logical basis. Maybe try a vertical dipole split by an infinite ground plane, but will require two feeds, out of phase, beware total power. All of this is right at the very foundation of antenna modelling. Either there's a rational explanation (which I cannot imagine) for the supposed +3dB 'advantage' of a quarter wave antenna over a vertical dipole, or we have a 3dB unconstrained error loose in the wild, potentially leading people astray for decades. Interesting eh?
OMG. When people are burying hundreds of meters or even km of wire, I hope that they're not unknowingly trying to cut-off the lower half of the universe... "Yep, my computer model says I'll get +3dB from my vertical if I can just put the bottom half of the notably-finite virtual Universe into a Faraday cage." ...Continues digging... P.S. the other slightly-embarrassing hidden assumption: the Earth is flat, as the DX antipode is still in the upper half. This would likely cause red-herring distractions during any discussion. It's an odd discrepancy. Odder still that it's been kicking around for decades. I've never heard of any logical explanation why it's actually not an error. So I assume it's an error. 3dB !! 73.
For the 40m band using a 49:1 use 66ft of wire - it would work well on 40 20 15 10. For a 9:1 reduce the length to around 58ft so the impedance is lower and can be brought down to a better swr by the 9:1. You will need a tuner for these bands however with the 9:1, unlike the 49:1.
@@timg5tm941 this is helpful. Am I right in interpreting that the radiator length which is likeliest to achieve the lowest SWR specifically at 40m through a 9:1 is ~58ft (when factoring in the ground radials)? I’m trying to figure out if I can dial in the radiator length for a shorter vertical (or near-vertical) for 40m that I might get away with sans tuner (yet retaining the 9:1 matching box at the feedpoint). Then I might use it well with my QCX-mini 40, while perhaps gaining some additional bands with a larger rig. I guess you’ve already shown that 31ft doesn’t get us there… so I perhaps shouldn’t expect this at any measurement
2:00 "...12 quarter wave radials..." Since they're all "quarter wave", is that 12 radials per band? Seven bands = 84 radials = getting close to half a km of wire (~432m). The back garden can't simultaneously be so small that the resident can only be allowed maybe one square meter for a single vertical element, and yet the same back garden is somehow also big enough to allow 12 quarter wave radials for the 40m band (i.e. 10m in 12 directions = at least 20m width and depth). That's a good size yard for the UK, a tenth of an acre for just the back garden. I wonder if that same 432m of radial wire might be better used up in the air (instead of buried). Perhaps a multi-element vertical to have fewer compromises, or more than one vertical antenna and a coaxial switch. Optimization is good, but bypassing the compromises might also be an option for most people.
Yep. In general, I don't see the need to actually bury hundreds of meters of ground wire *for the higher HF bands*. 160m sure. 80m perhaps, 40m maybe. Anything higher than that, people should strongly consider the advantages of other options: raised feed points and far fewer radials, or various more-balanced options. To clarify thoughts, would anyone have their 70cm (440 MHz UHF) antenna mounted on the ground (dirt) with endless numbers of buried radials, or is it more common to raise the antenna way up as high as possible? Same thing begins to apply even at (roughly) the 30m band, or arguably 20m if you prefer. But if one lives on a tall cliff overlooking the sea, then okay - go for it. No need for any antenna height (AGL) for at least one side. 🙂
Yes I’m aware of that. I’m using it to paint a picture of a set up that many (by no means the majority) use. I think you might be confusing this with me advocating it’s usage. 73
