Inverted V Dipole for 40 Metres: How Acute Should Your Angles Be?
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- Опубліковано 11 чер 2022
- A lot of us have made an inverted V dipole, especially for lower HF bands such as 40 metres. But how much of an angle should we allow between the dipole legs?
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Twitter: @Golf_5_TM
Email: TimG5TM@icloud.com - Наука та технологія
This is UT3UQK. Unfortunately can't go on air due to the war. But I was often using the inverted V. Had luck making a QSO on inverted V with Japan on 100W.
Glad it works for you and I hope you keep safe. 73
what a great intuitive demo tim, something i've wondered quite often👍👍
Thanks Joe - take care 73
A great explanation into the dipole and its idiosyncrasies of angle v SWR v Impedance. 👍
Cheers Gary!
Thanks Tim.
Very welcome! 73
Hi Tim, thanks for the data. I guess also, it the narrow angles, the radiation-resistance is rather low, so RF loss, of the antenna (wire) elements, might also become significant, especially the thinner the wire.
Very good explaination....so keeping in view all this...in case of a Multiband Doublet....that angle wont create much of a problem even up to 45 degrees angle due to the inherent nature of the ladder line .....
The only issue I still see with the narrow angle is the potential for increased common mode (maybe) - but, as you say the swr implications are largely offset by the ladderline used over the coax as the feedline. 73
Tim, you're a really smart guy. Could you possibly make a similar video on vertical coils? I'm really confused on basically everything about coils, their calculations, etc... Or, do you know a good resource for someone to get into making coils? I'm really interested in getting on 2200, 630, and even 160 while being somewhat space limited.
Looking at coils for later videos for sure
Hi Tim, nice informative video again. I didn't research this ant before putting it up, but I found at 10m firing to eu, it was 2 s points down into eu compared to my vertical on the 40m band, and the noise level was the same as the vertical. But when I dropped the height of the vee to 5m, it became a great rx ant on 40m, with next to no noise, which compared to a noisy vertical is a rx winner.
Not sure why it works like that, but it's a keeper hi.
I can now work s2 sigs on 40m but cannot hear them on the vertical, but the vertical long haul still out performs any other ant I've tried here.
73 zl3xdj
Great info Brian. I suppose you must be nulling out some vertically polarised noise source that your initially positioned dipole, being higher up and therefore a little stronger on lower angles, must have been receiving. Now having a lower noise rx/tx antenna is a big win! Cheers for stopping by 73.
@@timg5tm941 hi, I think most of my band noise comes from old street power
Lines, especially in summer when the connectors are very dry and arch over, and
There at the ends of the vee, so as you say, probably nullify them out.
Snow and 5c tonight, just been on 40m cw, 11:20pm local time and USA sigs are huge.
Cheers
Enjoy them Brian! Look forward to working you some day soon 73
H Tim, Love your videos. One question please re the 40m Inverted V antenna. Is it possible to feed an inverted V with window-line rather than coax, given that the radiating antenna elements and the 450 ohm window line are "balanced". I do realize the impedance of each will differ, so how in this situation would one address this disparity? I'm interested because of the lower loss of window line vs coax over over longer feed-line distances, and also in case a window line feed might confer some degree of multi-band performance to the antenna. (As with a doublet)
100% you can. It depends how you tune it. But a good wide range tuner will handle the impedance ranges across bands. (Probably)!
Awesome video, thank you. I just got my first 40 meter dipole put up yesterday. I'm running a flat dipole.. how do I know how much impedance my antenna has? I know would summon antennas impedance can increase I'm not sure about dipoles I thought they were pretty much balanced. Thank you in advance 73s
I wouldn’t worry about it … if it’s centre fed and cut for your Halfwave frequency all should be good
One thing to bare in mind at 45 deg. The inverted V becomes more omnidirectional than a flat-top dipole! At my QTH I use a folded terminated dipole that performs extremely well from 160m to 10m hung in an inverted V configuration. The downside is I'm losing up to 30% of my power on some bands!
73
GW6BXU
Yes it does become more omni but not massively so. Greater the feed-point apex height above ground, the more there is a marked difference in terms of the omni effect of the inverted V over the flat top. 73
Unless you are insistent on feeding with 50-ohm coax, your bandwidth reservations are immaterial. If you feed the same antennat with 600-ohm open wire through a matching network (stubs, matching sections or a "tuner"), you would still see the same patterns as MMANA shows. (With a "tuner", the SWR would always be 1:1 with virtually no detectable losses in the "tuner" and feedline.)
An interesting exercise would be to take this same 40m dipole and check the radiation patterns on other frequencies to see if there are any benefits to the acute angle on other bands (and ignore feedpoint impedance as long as it is not extremely high or low).
Another interesting exercise would be to repeat the model with the antenna elements horizontal. Some antenna farms may not allow the inverted-V configuration but may support a horizontal-V. An acute angle 40-m V-antenna would be a "V-Beam" on higher frequencies. (Of course, Murphy's Law says any gain realized by a V-Beam would be in a useless direction. ;-) )
Yes indeed. I considered mentioning the use of balanced line but just wanted to focus on the coax fed dipole in this instance. Your points surrounding the use of 600/450 ohm etc are valid and would of course give us a multi band antenna. I am big fan of doublets. 73
Hello Tim, you didn't mention the resulting impedance change. Your simulations are based on an impedance of 50 Ohms, I assume. Perhaps some form of transformer to bring it back to 50 would make the acite angle useable again.
Yes that cold occur - of course if you have the transformer at the shack end of the coax you will still have some loss in that feedline prior to the transformer. 73
I do not get it, why does no one consider inverted V in 3D? Sotabeams have one dipole that uses only one guying line. Tne inverted V lays a bit on the side which gives directivity. It's like half of a rhombic antenna. @Tim maybe you should make another video about that situation? What heigh should be that tripod antenna? should the feeder be a ladder line? at least at the part where it is supported by that single guying line?
Interesting for sure
As the angle becomes more acute, the greater the common mode current is impressed onto the coax as well
Good point
What would it be like if you flip the inverted V upside down into a V shape?
Hi Leo. Makes no difference. The angles in terms of impedance and swr remain the same as inverted V. So more acute than 90 degrees lowers the impedance below 50 ohms. More shallow than 90 means the impedance rises above 50 ohms. SWR begins to become a real issue when angles go belo9w 80 degrees. 73
@@timg5tm941 Thanks
Interesting, but I'd like to see this with a height of half a wavelength, which really is the minimum recommended for a dipole. Much lower angle of radiation.
Agree it is preferable. BUT - I wanted to use the example of a 40m dipole which many find tougher to squeeze into a garden and might attempt to do so with angles more acute than 90 degrees between the legs. 73
@@timg5tm941 I know, and it's valuable. But would be interesting to see the difference when higher.
@@andylinton2798 one to add for a future video 👍👍
Wha d sigh?
Not sure what you mean?
Hi Tim, I recently got a new antenna, well new to me, its a multi band 7/14/21/28 aluminium antenna, its not an inverted v it is a V that the angle can be changed from 180deg flat to 140deg to 90deg v, I now have it in the 90deg it works great and seems omnidirectional and swr is fine on all bands. What or would there be any advantage to change to 140deg or 180deg, am interested in long distance on some bands but inter G on 40mts, any opinion would be great. Thanks Martin..
I think I’ll model that and take a look .. how long is the antenna and how high above ground is the apex of the v?