HAM RADIO: Vertical Antenna Size & Antenna Efficiency

In the second video of this series looking at ground mounted vertical antennas and how to make them efficient, I look at how the length of the vertical itself can improve or reduce efficiency.
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[@kellypaws]

Surprised I had missed this one. Very instructive.

[@timg5tm941]

Thanks!

[@aarontooth]

Good stuff! New ham here. I've mostly been focusing on QRM issues so far with my vertical. But lately I've become very aware of its poor efficiency as well, and I'm trying to understand that a bit better. This has been very helpful. Also thanks for crediting your sources.

[@timg5tm941]

My pleasure and thanks for stopping by!

[@MM0OPXFieldRadio]

Thoroughly enjoyed that Tim. Certainly keeping people on the hook for the next installment going further down the rabbit hole. People themselves need to have an understanding or they will never be content in what they have and believe any old marketing nonsense.

[@timg5tm941]

Thank you Colin and I totally agree 73

[@alzeNL]

Its great having you online as a teacher Tim - I wish we could have you at the club :D

[@timg5tm941]

Thanks Al! 73

[@dxscotland5901]

Hi Tim,I usually ignore the scientific graphs and build an test in my own location! Over the years I’ve found a 1/4 wave mono band antenna with 4elevated radials has allowed me to work dxcc on whatever band I’m working at the time.my own experience is don’t be put off and build and test! Thanks for all your great videos 73s Gm4zji Chris

[@timg5tm941]

Yes elevated radials are a game changer. Cheers Chris 73

[@HamRadioAdventures]

Excellent description, Thanks Tim!

[@timg5tm941]

Thanks!! 73

[@markramsay6399]

Excellent video TIm. Really appreciate this. Mark, 2E0MSR.

[@timg5tm941]

Thank you Mark! 73

[@markramsay6399]

Meant to add - with the DX Commander on 40m, the physical pole is about 10m, but the element is longer as there is a fold back. Given that the wire is coated, there is a real "length" extension to perhaps 12/13 m (I cannot recall right now). There is some interesting physics going on , the "length" of the wire is not the same as the desirable actual "height" of a 1/4 vertical, but it certainly does increase efficiency on 40m> Mark, 2E0MSR

[@brianfields4479]

Very good presentation Tim as always, but I must admit I didn't take anything like that into consideration when I put up my vertical, I simply got a 5m painters pole and some 5m radials and went on 20m, sort of suck it and see, and it's been there for 8 years now working dx Zl to eu every day hi , I just hope the painter doesn't want his pole back hi. Your info is always interesting, but we must remember sometimes ant can be very simple indeed, especially if we just want a quick qso at lunch time, as you demonstrate yourself very effectively whilst your mobile. Keep up the great work Tim 73.

[@markwhittington8198]

Another top vid Tim - keep 'em coming :)

[@timg5tm941]

Thank you Mark!

[@davemaier7]

Thank You! Very useful information.

[@timg5tm941]

Thank you Dave! 73

[@andyM7XTT]

Very good video 👍👍look forward to the next one

[@timg5tm941]

Thank you Andy! 73

[@DonDegidio]

Hi Tim, Awesome explanations and visuals. Looking forward to next installment. Stay safe. 73 WJ3U

[@timg5tm941]

Thank you Don, friend, you stay safe 73

[@donalfinn4205]

Very interesting to see!☘️👍

[@timg5tm941]

Thanks Donal

[@n5yiz]

Excellent

[@timg5tm941]

Thank you!

[@g0fvt]

Well done presentation. You may be surprised where this leads....

[@timg5tm941]

We shall see!

[@kc4cvh]

It occurs to me that, as a practical matter, there is more to be considered beyond radiation resistance and the sum of antenna losses. With several of these antenna lengths, there will be substantial reactance, the network which provides a reactance of opposite sign and transforms the impedance to that of the transmitter will have losses, too. If this network is distant from the antenna, there are losses associated with the circulating current in the transmission line. Combined, these losses may be greater than antenna inefficiency or radiated power.

[@timg5tm941]

Yes, where you match them is absolutely vital if the vertical is non resonant

[@mike94560]

I have a 43 ft vertical with 660ft of total radials. (22 x 30ft) Best vertical I ever used.

[@timg5tm941]

They work really well Mike

[@user-ss6zt2mo1l]

@@timg5tm941 instead of using a 4:1 balun, with these 43 foot verticals, could I use a 9:1 balun with the vertical Or could I disconnect the radials and use a 49:1 unun and increase the length of the radiator to an appropriate length ? Food for thought.

[@leonardogalloiz3atv474]

A bit of confusion between Radiation Resistance and feed impedance. A center fed half wave dipole and an end fed half wave antenna have the same radiation resistence and way different feed impedance.

[@tristan4777]

Hi Tim, My copy of the RAE Manual from 1988 (page 57) says "The 'radiation resistance' of an antenna is a fictitious resistance which would dissipate the power radiated by it.". A good reminder that everyone needs to double check their 'facts' from time to time. It's wierd that I remember that, that's in there it's probably because it stuck out as being a bit odd.

[@timg5tm941]

I agree, facts are very important. Thankfully we have the work of people such as DJ2YA to support the theory. I was glad to use his data. 73

[@Kinetic79]

Super interesting. It’s curious to me how much worse the 1/4 wavelength vertical is as you go down to lower bands (as compared to the higher bands)… since I think the ground system you described is proportionally the same.

[@timg5tm941]

One of the many mysteries!

[@francoguanziroli7867]

Hallo Tim, thank you for nice video, I'm waiting for the next👏. Only a clarification: in Half Wave configuration impedence is abt 3Kohm, and a tranformer is mandatory: for monoband application best results with 64:1, in multiband configuration 49:1 is using as a compromize.

[@timg5tm941]

Hi Franco. I deliberately used the lower end of the radiation resistance figure for the half wave. You are correct that it can often be higher 73

[@francoguanziroli7867]

@@timg5tm941 👍

[@Lastaii]

Hi Tim, interesting series! I was wondering, you're mostly concerned about radiation pressure WRT transmitting, but is it also important for receiving as well?

[@timg5tm941]

Hi there its a unit to assess the radiation efficiency therefore TX 73

[@briantrask8173]

Hi Tim, It seems like the 1/2 wave vertical has the best efficiency. Do 1/2 wave verticals need radials and what is the best way to match them? Thanks for another great video. 🙂

[@timg5tm941]

Hi Brian, stay tuned for the next video in the series (radials), all will be revealed! 73

[@klas-erikwimanoz1dtf967]

Vy good presentation. If I take the 43 foot vertical and turn it 90 degrees... this is my endfed random wire antenna out of my window. Instead of radials a 4:1 UNUN is grounded in a water pipe for the heating (works great for what it is). Suppose all this theory applies.

[@timg5tm941]

Yes and a nice antenna you have too

[@ericdee6802]

Life begins at 1/2 wavelength!!😏👍

[@timg5tm941]

Well for radiation resistance, it could be said so yes! Lol

[@2EOGIY]

@Tim how to measure radiation resistance? or efficiency? Can it be calculated out of any NanoVNA measurements like power loss?

[@timg5tm941]

The few who have, have compared field strengths as well as taking into account overall feedpoint impedance and thus determining loss resistance as part of this. It’s a complicated measure and in most part is based upon the inevitable differences in the feedpoint impedances between say a 1/4 and a 1/2 wave.

[@user-ss6zt2mo1l]

Can I shorten or lengthen the antenna

[@stevet7522]

So am I understanding this right? Half wave verticals with quarter wave radials have the best radiation resistance?

[@timg5tm941]

We cover radials on the next video, but 1/2 wave verticals fed at the base require minimal radial fields and exhibit an appreciably higher radiation resistance compared with a 1/4 wave. 73

[@stevet7522]

@@timg5tm941 thanks for the reply and info. Another question: would this only work as mono band verticals? I'm assuming that it would not work well in a fan dipole (DXcommander) since the signal would most likely radiate at the quarter wave radiator, assuming you have something like 20,17,15,10. Or does the signal radiate on the most resonate radiator?

[@timg5tm941]

Hi Steve you need to use 1/4 waves in a DX commander configuration owing to their lower impedances. 1/2 waves wouldn’t work. Of course you could also use one vertical and have a tuner near the feedpoint. So for 20-10 a 20 foot plus vertical would do well for example.

[@stevet7522]

@@timg5tm941 fantastic. Thank you for all that. Love the video and keep up the good work.

[@timg5tm941]

@Steve T that’s very kind Steve thank you for your support

[@45auto]

On a completely unrelated note, may I ask is that a West Country accent?

[@timg5tm941]

Nearly, it’s South Walian

[@45auto]

@@timg5tm941 some definitely sounded Welsh to my American ear but I've been watching an old TV show called Hinterland and was afraid I was projecting.

[@brianfields4479]

Very good presentation Tim as always, but I must admit I didn't take anything like that into consideration when I put up my vertical, I simply got a 5m painters pole and some 5m radials and went on 20m, sort of suck it and see, and it's been there for 8 years now working dx Zl to eu every day hi , I just hope the painter doesn't want his pole back hi. Your info is always interesting, but we must remember sometimes ant can be very simple indeed, especially if we just want a quick qso at lunch time, as you demonstrate yourself very effectively whilst your mobile. Keep up the great work Tim 73.

[@timg5tm941]

Wise words Brian. My focus here mainly was on non resonant multiband verticals. It’s amazing how many manufacturers claim great efficiency for very short unloaded verticals!!73