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 11m elevated vertical and counterpoise question

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Ziplocbags
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Call Sign : 9-CT-025
Posts : 6
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Join date : 2020-06-09
QTH or Location : Shellbrook, Saskatchewan Canada
Equipment Used : President Ronald 10/12 meter with 11 meter modification.
Age : 45

11m elevated vertical and counterpoise question Empty
PostSubject: 11m elevated vertical and counterpoise question   11m elevated vertical and counterpoise question Icon_minitimeMon Aug 24, 2020 1:46 am

Hey guys, first off I'm pretty new to radio and antennas. While I've been around CB since the early 80s with my Dad being a CBer.
I have a question about 11m vertical, elevated, I want to add 4 counterpoise at a 45 degree angle. Now, the idea is a vertical dipole using 108 inch sections. My question is if I take the "grounded" 1/4 wave section and divide that up into 4 parts, use those lengths as 4 counterpoise, would that work? I'm taking what i know about 36 inch antennas having the rest of the antenna coiled to get a 1/4 wave etc. So for instance having four 27 inch counterpoise (which makes 108 inches if you stick them back together).

I currently just have a 108 inch copper pipe pushed up through a T.V. mast that still has the T.V. antenna on it. I basically was (with my limited knowledge) wanting to use the T.V. antenna as my "ground plan". I'll attach a photo. It works, my SWR is 1.3-6 across our 40 channels here in Canada. I can here pretty good skip coming in from the USA, but I don't seem to be getting out there. I'm using a president Ronald with the CB mod pushing around 12watts dead key.

Basically I want to put up a better antenna lol, and bring down that T.V. antenna, maybe make a yagi out of it.
Thanks for any help and advice, guys! 11m elevated vertical and counterpoise question Img_2011
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Victor
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11m elevated vertical and counterpoise question Empty
PostSubject: Re: 11m elevated vertical and counterpoise question   11m elevated vertical and counterpoise question Icon_minitimeMon Aug 24, 2020 10:44 am

Hi Mike,

Firstly, I'm not the most eminently qualified here regarding antennas, (probably Conor - Northern Crusader is judging by his postings so far).

I applaud you for experimenting with antennas and more importantly for asking questions, it is the way to learn such things. But I think we may be missing out some of the basics.


It sounds like you've taken the idea of a dipole but then want to split the ground section out, but to me that then sounds like a 1/4 wave ground plane antenna(?) Not only that, you want to 'cheat' physics by making the ground plane sections shorter(?)
It's not entirely clear from your description but the best guess I can hazard.

From what you have wrote and your posted image it looks like you've attached a 1/4 wave radiator to the top of a TV antenna to use that as a ground plane. It also seems that you've sort of pulled it off judging by your SWR readings, (but remember SWR is just the simplest way of measuring an antenna not the whole picture). That is a basic 1/4 wave GP antenna and not any different from a whip mag mount on a car, (except you can drive the car to a high spot Wink)

I think the simplest antenna you can build yourself for DX work is a dipole. I personally have an Inverted V dipole and it's performed quite well on this summer's 'skip'. It also doesn't take much to use those basic principles to construct a 'Moxon' beam which is essentially a folded dipole and reflector should you want more gain and directionality. The thing is, you may lose local copies in which case the 1/4 GP would be better.

It's all fun isn't it! Very Happy

The problem is that on CB most users are using low powers and we get away with not fully understanding or appreciating counterpoises, grounds and such. It's not until you pump up the power that we start seeing the effects of coax length etc. and get RF & voltages flying back to our rigs. This causes all sorts of problems including the fabled 'microphone kiss'!


As for hearing stations but not getting back to them, I'm not at all surprised but may not all be down to you.

There used to be an old CB term of 'Alligator' or 'Crocodile' stations, ie big mouth & small ears Wink
You can hear the 'big boys' but they can't hear you, all of them bending your needles with massive amounts of power pumped through an antenna that does little for their reception. The only way you can join in 'the game' is to start pumping out bigger powers yourself and the whole awful cycle continues.

American CB stations are renowned for it and so are Italian stations here in Europe, (Hola! Hola!)
It's all a little selfish though, either blocking out signals and stations in all directions or beaming across a flipping entire continent!

When propogation conditions allow you can get DX copies with the most basic of antennas and small amounts of power.
I've had copies spanning hundreds of miles with 4 watts using FM as have many others. It is possible Smile


Anyway, I hope that is of some use to you. 

Keep asking questions, maybe do a little more reading on antenna theory if antenna building is your thing. If it all seems a bit too much hassle there's nothing wrong with simply purchasing an antenna to do the job. But there's no better reward than getting a DX copy on an antenna of your own making Smile


All the best,
Victor

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The DB
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11m elevated vertical and counterpoise question Empty
PostSubject: Re: 11m elevated vertical and counterpoise question   11m elevated vertical and counterpoise question Icon_minitimeMon Aug 24, 2020 2:25 pm

Avanti used to make an antenna like that with three radials called the Starduster.   I'm pretty sure Sirio still makes a version of that antenna today, the Sirio version is called the M400.

A company called Workman also sells a hub that is designed to screw in a standard vertical, and three or four more at a 45 degree downward angle, however, I'm not sure if they are still operating.  Their web site is up but all of their images are broken, which is odd as they are all hosted on their web site.  The link is https://www.workmanelectronics.com/

At HF frequencies, its not uncommon to see a variant of this antenna design where you have a 1/4 wavelength vertical at the end of a mast, and part of the antenna's guy lines double as antenna radials.  I've also seen some that use as few as two wires that follow the roof line down as the antenna is mounted on the corner of a roof.

Its actually a fairly common design, although it is used more at VHF frequencies than HF.


The DB


Last edited by The DB on Mon Aug 24, 2020 4:07 pm; edited 1 time in total

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Northern Crusader
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Call Sign : M0GVZ / 26CT1760
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Join date : 2019-11-13
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Equipment Used : Icom 7300, TS480, President McKinley, Albrecht AE6110, CRT Mike
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11m elevated vertical and counterpoise question Empty
PostSubject: Re: 11m elevated vertical and counterpoise question   11m elevated vertical and counterpoise question Icon_minitimeMon Aug 24, 2020 2:33 pm

If you take a vertical dipole and make 4 legs out of the bottom you've converted a vertical dipole into a 1/4 wave groundplane antenna. The whole concept of the RF ground planes is we want RF to flow over a more efficient conductor than the lossy earth (as in ground, soil etc) below the antenna - the more efficient it is, the more current flows in that meaning more current can flow in the radiating element means stronger signals. In an ideal world you'd have a solid metallic disc with the antenna sticking up out of the middle of it. Basically because most of the RF and magnetic field is concentrated nearer the antenna you want the greatest coverage there as that's where the majority of the current flows.

Four 1/4 wave long radials is considered a near perfect ground on an elevated antenna. You can shorten them but then you need to use more of them, this is the path that Sirio take - when you look at the difference betwee the Sirio 2016, Sirio Tornado 27 and Sirio 827 the main difference is that the radials shorten and increase in number as they do.

Given your current antenna set up I would just add four wires 9ft long (shorten by 4% if using insulated wire due to skin effect / velocity factor of insulated wire), bring them out at maybe a 30-45 degree angle. You could even just connect them to the same point that the coax braid is currently connected to in your configuration you have now. You'll find that it does alter the antenna tuning and the angle the legs are at will also have an effect but as it's a 1/4 wave antenna they're quite broadbanded and as long as it was below 1.6:1 on on all the channels you intend to use I'd not bother adjusting it.

Don't bother trying to make a Yagi out of the TV antenna, you'll need to rework everything and realise it's not really feasible. For a quick to make beam make a Moxon Rectangle, you can find plenty of online calculators. When using the online calculator then building it remember to reduce cable lengths by 4% if you're using insulated wire as the calculators assume bare wire.

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Ziplocbags
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Call Sign : 9-CT-025
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QTH or Location : Shellbrook, Saskatchewan Canada
Equipment Used : President Ronald 10/12 meter with 11 meter modification.
Age : 45

11m elevated vertical and counterpoise question Empty
PostSubject: Re: 11m elevated vertical and counterpoise question   11m elevated vertical and counterpoise question Icon_minitimeMon Aug 24, 2020 3:09 pm

Thanks guys for the replies.
I spent a good chunk of time reading about the idea of 1/4 wave ground plan after posting my original post. I even went so far as to learn how to use MMANA-GAL and modeled my idea - which seemed to work out in theory with all things ideal but high SWR. Reading your replies suggest that I was at least heading in the right direction lmao.

Northern Crusader, I understand I'd have to completely rework the T.V. antenna if I was to try and make a yagi from it. I was thinking of using it to make a 3 element yagi or even just a 2 element.

Thank you guys for the information, it is very helpful.

I would like to get that T.V. antenna down though and get a proper antenna up there. I did have the idea Northern Crusader mentioned about adding 4 wires, however that mast is 40 feet, and pretty close to my neighbors house, so besides shitting my pants climbing the mast I don't really have anywhere to anchor the wires. Which was the reasoning for trying to make a 1/4 wave ground plan with short ground plan wires.

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BoB4jjjj
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11m elevated vertical and counterpoise question Empty
PostSubject: Re: 11m elevated vertical and counterpoise question   11m elevated vertical and counterpoise question Icon_minitimeThu Sep 03, 2020 5:29 pm

Hi Mike,
To be honest, it would be better at the start if you went out and bought a Silver Rod either 1/2 wave or 5/8 wave, the 5/8 being slightly better.  They are as good as anything else on the market, but you can make a good vertical aerial/antenna yourself.
See here  https://youtu.be/5VxHNTttpEc  A copy of a Gainmaster, all you need is a fibreglass pole.
Here is the updated version, but watch the other first as he assumes you have watched it, so does not go into so much detail.   https://youtu.be/-0s4La1MElQ
You will find that a lot of Americans are using a bit of power, however, that does not mean you need to.
It is far more satisfying to get through with a standard set with standard power.
Go for the best aerial/antenna you can afford before adding power.
Good coax will help, long cable runs are very lossy, RG58 has a lot of loss in a long run, get the best coax you can afford.

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