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VERTICALS

VERTICALS

Postby zs2cx » Thu Apr 21, 2011 10:27 am

:D I hate these things, but they do work if u get them right :?
so here goes... my adventure with these magical pipe organs.

Verticals

Some Hams swear by them and others swear at them…yeah u heard that before…
Well so have I! Personally I used to curse at them, just never could get it right.
Inexpensive and effective when we build them right, for a few bucks u get an antenna that bring the DX to your radio room. Always comparing a vertical to a dipole has given it a bad name, not understanding it is not a performer on shorter distances. 1000km onwards we are in business, now get that brain working and u will kick dust in any dipole’s eyes  True band conditions do not always favor the vertical and the dipole can hold its own. The pro’s and the cons… all that radials u need is a deterrent from a vertical radiator. Now the rule is to resonate that vertical, before adding any other mixture of things, like baking a cake which we hams know so little about. (Well at least me then)
For the record, the vertical antenna is a radiator with a electric field vertical in respect to the earth and whose magnetic field is parallel to the earth’s surface. This means the antenna itself is vertical mounted, some vertical antennas are mounted in the horizontal position, but they are used in Radar and more exotic antenna designs. Verticals like a dipole have two legs, shall we call the 2nd leg a radial in the ground or just above the ground (raised radials),they need to be in phase with each other, (meaning the vertical part and the radials)and the wave reflected from the earth by the real antenna is in phase with the direct wave from the antenna.(confusing  )The wave combinations produce a low angle of radiation close to the horizon for a vertical antenna, now this is good for DX work, but on short hauls disappoints the constructor of such a antenna.
The ground plane vertical is a popular antenna being a ½ wave long (the vertical part 1/4) the bottom part is divided into sections of equal parts, the antenna is fed in the centre. The vertical part acts as the antenna and the horizontal parts or radials, form an artificial ground plane. The radials do not radiate as each other radial cancels each other out.(only true if the radials are all equal and symmetrical) The voltage and current in the antenna are divided equally between the radials, which form a tuned system, it can be upset, or detuned by nearby objects.
Only true……When radials are installed above ground…..

For the average constructor, to be safe use PVC coated or plastic coated radial wires as these do carry current and high voltage, dangerous to our children and pets.
Verticals are omni directional (if we have a symmetrical ground plane)
Some operators reckon these antennas radiate equally poor in all directions and will have nothing to do with it; others work DX and are having a ball chasing the rare stations. The vertical is of easy construction and nothing can really go wrong with it. If u decide on a vertical antenna be prepared to go all the way installing many radials, the connections must be properly connected or soldered. The secret is out! If you don’t have enough radials don’t expect the antenna to work as u thought it might or heard of.
……….80m band……….
A vertical is not a compromise antenna it’s a killer on DX, I can work stations with my 80m vertical that is not heard by the dipole, don’t believe me? Get a vertical setup properly and run ring’s around that other antennas. That being said comparing a 10m long vertical for 80m band to a full sized dipole is not fair at all or is it?
Well here’s one u can try.


Image


Resonate the antenna first on 80m band, radials in my case ½ wavelength long ( +- 20m) u decide what u can fit in your yard, add the toroid , the beginning of winding goes to antenna, the end goes to the radials, tap the coax into the system for a perfect match.
One again I used the MFJ269B
I had 14 radials and most was 20m long (not symmetrical)

I built 2 of these and fed them with a phasing harness, 2 lengths 84 deg coax each 13,1m long to each antenna, the phasing harness was a 71 deg coax line. I could switch front and back as well as broadside, a killer antenna this was. Working DX with these short verticals was a definite pleasure, good reports yes, and on 80m the usual 5/9+ to 4/4 QRN reports.One of these verticals is now residing at ZS1L old man Alex, he made a comparison test between a delta vertical and the small 9,5m version, the small vertical held its own at times 1S point weaker than the full-size delta vertical.

PHASING
Now I know I will get frowned upon…but, how do we go about calculating this phasing harness thing?  I do it my way!
To start with I had tried my hand at phasing antennas and I failed, on 80m we are talking big, long and high from the ground, correct? Well no, not always… u know verticals have low radiating angles, yeah when perfect I suppose, mine was less than perfect.

Ok so here goes…let’s assume my frequency of operation is 3.795 MHz, antenna spacing is 9.8m apart. ( 1/8 wave +_ )
We need 2 phasing lines 50 ohm, 84 electrical degrees, now a full wave will be 90 degrees right, so a 50 ohm coax will have near 0, SWR when shorted at the far end and also, a full wave length of 50 ohm coax if the end is left open. Using the calculator I determined that I need about 13,5m of coax RG58u and using my MFJ trimmed it down, but u don’t have a MFJ… I once used 75 ohm coax for all applications with good results, altering the matching circuits a little bit.

In feet, a half wavelength in free space is 492 divided by the frequency in MHz.
492 / 3.795 MHZ = 129.64 feet *.304 = 39.4 meters
Now if we have a velocity factor of 0.66 take the 39.4m and times it with 0.66

39.4 * 0.66 = 26.01 meter for 3.795 MHZ
That’s a halve wavelength. How many degrees in half a wavelength? 180. Lets divide the length of the half wave of coax by 180
26.01 / 180 = 0.1445 meter per each degree, so 90 degrees = 13,005m
84deg = 12.138m and 71 degrees = 10.259m and so… on we go…
U still with me chaps? this is ¼ wave verticals right?
Vertical phasing sketch

Image

relay of the http://www.somewhere for an example
Image
Now what about the coax from the radio to relay box, can we just feed it with 50 ohms?
Unfortunately no, we need to correct the feed-line impedance; a vertical is normally 30 to 35 ohm. In my case I fed with 50 ohm to the relay from the relay to each vertical are 2 off 84 degree lines the phasing line is 71 degrees. Measuring it with the MFJ showed I was in the ball park, but not quite, I needed a L network to match my feeding 50 ohm coax to the relay box, the impedance was about 25 ohms + J 14,2. Matching with coax was an easy task; an L network seemed to be the way to go as I already had one.
3db on TX is worth while and on RX even better. On 40m upwards it does get easier as the antenna becomes smaller. This is not a perfect way of constructing the antenna and phasing lines but it did work and a definite 20 db front to back was noticeable at all times, if u want to go into all the details of phasing u need to get hold of ON4UN’s book on phasing. That said I get confused looking at all the measurements and formulas 
Now rule of thumb has just flown out the door, I thought I could just connect those darn wires up and bob’s your uncle u know 90 degree line and all…hope u learned something.
Having a MFJ269B or measuring instrument will be a plus to the antenna building side of things; both verticals need not be identical but should resonate on the same frequency and be ¼ wave length electrical at least. Impedance matching is important; we do not want to loose what we have just gained. So how do I know it worked? I transmitted a 1 watt signal at first on the operating frequency, then using my Field Strength Meter I walked in a big circle around the array, making notes as I went along and found a definite null on the reflector, the needle dipping to zero. On the front the reading showed 8.5, not S points, just relative signal received. This measurements on high power changed slightly by 1 behind the reflector, on 100 watt setting. I could switch broad side and be S9 in Cape Town and be S9 in Durban, or visa versa, facing north and south however the front to back was good and noticeable gain to the front noted as 1 S point to 2 S points stronger than east and west. This antenna was good for local and for DX although my intentions were to build a vertical for 80m DX-ing. All of this said: we are in year 2010 and conditions on HF is poor, at times a little better and are just awaiting the new sunspot But don’t get your hopes up to high many a bad day lay in front of us for HF communications. The angle of propagation at day and night make turns, favoring low and high angles at such quick rate that antenna testing with your buddy is rather meaningless, confusing u even more than u were before the test. I was having a QSO with JA5AQC Masaru on 80m 1july 2010, he would disappear on the vertical antenna and I switch to a dipole and he would be S5 to S7 just to go down in QSB again, switching to the vertical made it possible to finish the QSO.
The old saying: We cannot have them all, holds true.


well thats my take on it , it works, add that extra umf to that lineer and make it worthwhile
Croc
:let me just state this is not copied from some where, this is my work! i had to build the antenna and test it, to do a antenna book in 2010.
copy and save it if u need it, u are free to do so ,no copy this protection that, go for it :twisted:
if u can find a error let me know. :mrgreen:
Last edited by zs2cx on Sat Apr 23, 2011 5:31 pm, edited 2 times in total.
CROC
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Re: VERTICALS

Postby zs2cx » Fri Apr 22, 2011 1:10 pm

so the proof is in the pudding hey.
here recorded by PA3FUN tks chris.
http://www.zshare.net/audio/89289690e464be5e/
well its not playing the whole file by just rxing online, download it, 470kb file.
another short rec wking PA3FUN
http://www.zshare.net/audio/89290082111bd45f/
Verticals works :evil:
80m is not for sissy's :roll:
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Re: VERTICALS

Postby v51pj » Sat Apr 23, 2011 8:06 am

thank Johan fro this interesting input
make things more understandable and so easy

de v51pj
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Re: VERTICALS

Postby zl3dc » Tue Feb 05, 2013 8:32 pm

KI Ora from zl land,
I have been looking for a new 80m antenna that has some directivity,i have the usual dipole but , we have some land that should afford a better antenna on 80m so i have looking at phased verticals,
but being cheap and aliminium being dear, i anmlooking at what i have and that can be adapted.
Your Verical arrangement falls into this catagory,
I have 2 large 150mhz paging verticals and 2 small 440 colinlear, commerical fiberglass antennas that i hope to be able to join with the coil section,Do you have a photo of the one you constructed.
My other project is 4xc250 hf amp and I see you have some notes on thses so will look at those while awaiting your responce
cheers Ross
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Re: VERTICALS

Postby zs2cx » Sat Mar 02, 2013 9:01 pm

Hey Ross
i have not visited this site in some months,
which photos do u need ??
I do not use identical verticals as it is not necessary.
the one is 16.8m tall the other 9.8m with centre loading on both to resonate at 3.650,, with mutual coupling the resonance will rise to 3.795.
anyway let us know what u need to know,
Johan
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