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Low Angle Radiation - HF 5 Degree Angle A Myth?
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- เผยแพร่เมื่อ 22 ก.พ. 2024
- In previous Videos, Peter G3OJV has doubted the existence of any significant far-field radiation at angles as low as 5 degrees, particularly on the higher HF bands. A number of well qualified Hams have written papers in QST and QEX that throw doubt on the existence of significant ultra low angle radiation. In this Video Peter looks at some data that seems to support the probability that the very low angle radiation shown in some popular software programs and design claims is misleading, and does not represent real-world performance.
W4RNL Brewster Angle
on5au.be/Cebik-2/ThePseudo-bre...
W7SX Brewster Angle
www.arrl.org/files/file/QEX_Ne...
Good to see someone talking sense about this subject for a change, whereas others mislead people to believe our verticals radiate in a unrealistic way.
Thanks for sharing. 73 Peter.
This is an excellent example of how a lifetime of experience can enlighten those of us who accept on face value what a software package is telling us but actually fails in design. Thank you Peter for sharing!.
Thanks for sharing.
Very good video Peter. Les Moxon also went into this quite extensively in Chapter 10 of "HF Antennas For All Locations". Your points about multi-hop (I'd add chordal hop) for really long DX paths make sense also.
Yes Moxon was very good with knowledge which he translated into antenna designs. 73 Peter.
Thank you Peter. It's a very intetesting subject. My tutor often emphasised the importance of using an antenna with good low angle radiation for DX. I only have small garden, so have never been able to make a good practical comparison for myself. I cannot put up a full size horizontal antenna for 40 m or a full size G5RV.
Although I have used verical antennas, I have mostly favoured the Inverted L format. Initially 1/4 wave fed against ground, but more latterly an EFHW as an Inverted L. This works well for me.
My assumtion is that the Inverted L has a mix of vertical and horizontal radiation that can cover a range of propagation circumstances.
I concur with the basic conclusions in this and other your videos that we should put up the best / most efficient antenna that will fit in the 'back yard' and have fun! That might make the 5 degree / low angle / Brewster Angle seem rather esoteric, but it's worth keeping in mind.
Thank you for the detailed presentation! 73, Mike. M0MTJ
Iam just working on a 2 ele parasitic vertical for 20m in a small garden, gives nearly 2 S points gain long path.
Hi Mike, the EFHW inverted L is a good antenna and has the polarisation mix. I worked ZL yesterday on 40m with half size G5RV up 25ft. There's mo 5 degree there and he was an S-point down on my vertical!
Sounds good.
@@watersstanton Thanks Peter!
Thank you for bringing this back to light from the 60s. I think this was missing piece around how I should visualize ground reflection (which in my mind had to have some cancellation and assumed model software was taking that into account). Surprised they don't already incorporate it and texture the area where loss will occur and how low depending on frequency.
Does it pull the highest gain part of the lobe downward some or does that tend to stay at same angle when accounting for Brewster?
The software is primarily an excellent educational tool, but unfortunately has shortcomings which should not be translated into real-life performance claims or illustrations. 73 Peter
To "activate" the angles
Unfortunately this is not achievable for ‘normal” hams” and even sea water is not a perfect ground!
Appreciate you addressing the takeoff angle importance.
The difference between average ground and "perfect" at 1 degree is somewhat close to 6 dB.
I enlarged my ground-radial system from 1/4 wave wires into 2 waves one night, and on 80 m CW the signals from W6 California came up some 6 dB in comparison with the W1 - 4 from eastcoast. The difference remained all time after.
So I achieved the "theoretical" 6 dB improvement by my radial wire addition.
I had a W1CF 4 el phased vertical with 400 radials at the time 1979-1984, and towards W6 via short path (NW-direction) I had a bunch of 3 wires that I lengthened. That was the ONLY thing I did.
To achieve a "perfect" ground in this direction was not that difficult.. after all.
The guy sucting for that Dxpedition (on 160 or 80m) can "walk out with the dog" late evening in the right direction to the DX. Equipped with a roll of some 40 -80 m long single wire instead of the dog, laying this wire upon the ground (streets, gardens what ever). After a success QSO with this DX, "go out with the dog" again with a smile on his face, and roll back the wire on the spool.
Ofcource he is using a vertical antenna, hopefully not located at ground, but up 1 or so meter above ground, making the radials sloping down to ground. This concentrate the radiation towards the horizon.
73 de Bjorn
Peter, that was fascinating. Thank you so much for taking the time to go through this with us.
You are welcome.
Spot on as always Peter, how about the end fed inverted V for some of us with small gardens as the weight at the centre would be less (no feeder pulling it down) and the width across the bottom as would only be about 3/4 of the length at the base of a straight dipole.
Regards
Dave.
Yes good example. Put it on my list. 73 Peter
Again another excellent video. I have always said that there are a lot of “half truths” out there in Ham radio. A large void in the knowledge of how verticals ( and grounds) work! This video dispels some of that and you are doing a great service.
73,
Don
N4DJ
Thanks for sharing!
south south west of me lies Argentina (south america) and Australia new Zealand (antartica) North is EU, west brasil, and USA, east north east japan..
over the years i have had many vertical versions, including phased for 80m and 40m, Christman method.... my 2 contenders were dipole / vertical too name 2 of them...
my most difficult contacts, ZL1iu 80 m band, but he did peak one year at 5/9 youtube has my recording for that... very seldom did the vertical/s out perform my dipole up at 20m high, i always had my doubts just as you Peter, then one year i raised my 40m vertical atop the mast 12 m high, sloped the 4 radials and wow! i was suprised but sort of expected the result, getting clear of the buildings around me made a huge difference, a week or so later the western cape had a strong storm with high wind , by by vertical, topband eu from ZS on a dipole no problem 80m as well, i needed about 250 watts to work a station in netherlands on TB... the mountain range north of me (close) blocked the vertical low angle(that's what i thought) so i build 2 phased vertical for 80m facing JA and PY it did outperform my dipole but not always at times the dipole are way better, like 2 spoint's... then one early morning i worked into USA and Argentina chile, brasil the verticals beat the dipole hands down, but USA was Dipole s...the King... to the North lay my friend ZS 6HA we always worked 80m dx at 3.795 , he had a advantage being north of me to europe, i always had to wait a few minutes (like 30 min) before i could work EU, Ja i was stronger and south America i was stronger than him, but most of the times weaker towards EU. then along came Greenland one evening i worked him and busted a eu pileup was funny, i could not help but think my signal traveled around the south pole :)
topband has been the band with the most surprises fan dipole 20m high and a vertical yet the dipole always win... now remember dx to me means outside of Africa!
so USA, SOUTH America, EU, VK, ZL etc a bit farther then across the ocean from G to stateside.. hmmm.
ZS2CX
Great info there. Lots to ponder and it does question radiation angles and whether we really appreciate that ultra low angles are of little practical use. Dipoles often beat verticals! We are still learning!
Interesting information.
I count myself lucky that my area is relatively flat and my antenna has a clear path to the horizon at a low angle.
Yes, you are fortunate, but the Brewster Angle and its effect remains.
In reviewing the conclusions in the second article by Zavrel, unless I misunderstood the text, the PBA is insignificant for ground mounted verticals?
Quite the opposite!
@@watersstanton Thanks for the reply, I'm having trouble with the conclusion in that article and what it is really saying. Best Regards
The paper specifically states that the PBA is irrelevant for ground mounted vertical antennas of 1/4 wave or less. It’s right there in the first sentence of the second paragraph. The conclusion nicely summarises the author’s reasoning for loss of gain we see at low angles. It’s not the Brewster effect - that’s the point of his argument.
@@watersstantonincorrect as the paper quoted clearly explains
@@watersstanton Peter, with the greatest respect, both forgediron and M0RMY are absolutely correct in what they said. From that article. . .
"The commonly published explanation is that ground reflections reverse the phase, and thus wave cancellation occurs in the far field, and produce the pseudo-Brewster angle . . . . . However, this explanation is not possible with ground-mounted vertical antennas ¼ wave or shorter in height. Simple geometry instructs us that this is not the case"
And in the conclusions, referring specifically to the Pseudo Brewster Angle . . .
"There is insignificant influence of reflected waves on the antenna pattern of ground-mounted vertical antennas that are aquarter-wave or shorter height"
Excellent Excellent video and very interesting, what will happen if you put a vertical antenna 10 meters up in the air with radials, will the Brewster Angle change to be lower or higher or the same or will the radials have something to do with this Brewster Angle. LA2VLA
The suggestion is that elevated verticals still have the same problem but no specific examples of elevated radials.
Are we sure that such reflection does not appear in modelling software? Adding a ground does make the sort of difference that is shown in the diagram from the RSGB handbook.
Not in the elevation ploys I have seen.
Very interesting information, Peter. The link is not working it says Not Found
The requested URL was not Found on this server.
OK I will check it and correct it.
Outstanding
I concur
The only time i had luck with a verical was over salt water
Rest of time prefer a horizontal antenna
Plus you get ground gain
Yes that has been my experience as well.
Excellent Report, Thank you
You are very welcome
The performers off the antenna imo depends on conditions ...top 3 for me are conditions... antenna .. coax ...at last he rig the antenna that works for me may not for you ... depends on circumstances at youre QTH
Thanks for sharing your thoughts. 73 Peter
Thank you. This forgotten information from the past is importent. I think that no one wants a cloud heater so low angle is good but look where the maximum is, there is your far feld not at any other angle. Great video.
Glad it was helpful!
Great video and links. Thanks!
Glad you like them!
Peter no disrespect implied or intended...i dont understand fully why frequency varies the Brewster effect sorry,, im asking not critising ,why is this please. over ground quality i grasp that.. but if you have best quality ground then why would freq change it please.. i love your input videos and theyre honest and factual Sir..only sayin
In simple terms the ground reflection changes with frequency and thus the phase cancellation and intensity changes. There are more details in the papers I linked below the video. 73 Peter.
@@watersstanton TY Sir
I have always had great luck with inverted v antennas. The g5rv is my favorite.
Thanks for sharing
Low angle ground reflection angle = The Brewster angle/reflection, quite important....
Yes.
Greetings from Orlando, FL
Hi there. Can you send over some of the sunshine please!
Very informative as usual Peter...W6QR
Great to hear from you. 73 Peter.
tnx fer input - my brain will have enough to handle over the weekend ;) 73
A glass of wine helps!
Greetings from Switzerland 👍
Hello there!
Great video enjoyed it keep them co ing
Thank you, I will
Greetings from Colombia
You are very welcome.
really expensive tea cup coaster you have there :)
Or chopping board!
Ancient wisdom (from the 1960’s😂). The ground is an unknown constant for most of us, so though critical it is left out. Reminds me of our current times! The wisdom of the past is ignored and therefore is taken off the map of consciousness….. hence our Godless condition. 😂😂 Thanks for this video it has partly answered the very same question that has been rattling around in my puny brain 🧠 73 de VK2AOE George
Nice to hear from you. Thanks for sharing. 73 Peter.
Interesting Peter, but in reality I think ‘it does not matter with that reflection angle because:
No Antenna I have seen have a stronger radiation a 5 degrees than 15. So - if you attempt to optimize for 5 in the modelling software - you are given an even more optimized antenna at 15-20 degrees.
Those 5 degree patterns are for people at the beach, with a counterpoise in saltwater - and only tiny waves 😂
Thanks for sharing.
At the end of the day, either way, if propagation is good you will get dx, if not it's still a great hobby.
Yes that is the fun of HF
@@watersstanton yes that's right, iam not sure so many get so up tight about the hobby.
After being a full time carer for my wheelchair wife, the radio relaxes me, but many worry about swr velocity factor etc etc, just get on the air ant enjoy. Best wishes Peter, enjoy your weekend.
Makes complete sense. Thanks Peter
Grüße aus Deutschland. 73, walter
Greetings to you. p
Yes it's not normally shown on the free be sortware untill you start paying lots of money for professional based software.
Afraid that is the case! 73 Peter
The DX con man and his good buddies say you are wrong.....
It hit a raw nerve I think! But you cannot deny the facts and the results that many users of verticals observe. Nothing wring with a vertical but you have to be realistic
@@watersstantonkeep sticking it too him I would but he deletes all my messages so he is living in a world of no alternative views...
@@user-gj5iv5kv2git’s Jim! Hey Jim, that replacement liver of yours must be nearing its final chugging. All that vitamin B draining away, get your moans in (the ones not yet associated with physical pain anyway) while you can x
Many thanks for sharing your knowledge of an amateur radio life with us / 73
CS7BDO
My pleasure!,