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What’s best? A dipole or a doublet ham radio antenna

action! welcome live long and prosper! listen I was down the farm the other
day contemplating the difference between a dipole and a doublet so a dipole is generally a coax comes up to a point the center of the coax conductor the sent
the very center the this would Center goes out this way if you like and the
braid goes that way and each leg is a quarter of a wavelength so that’s about
well the whole thing is about half a wavelength long give or take depending
if it’s close to the ground or further away from the ground things happen
not a lot enough however in the main that’s a dipole okay it’s it’s a one
band it’s a one band antenna although it works
on the third and the fifth and the seventh and a ninth multiple as well so
a 40 meter dipole force F and megahertz seven point one megahertz depending on
the height a few other variables will work again or 21.3 if you know to me
that’s a third multiple one of the harmonics where as a loop all the way
around is every harmonic so it’s 7 14 21 28 maybe that’s why they designed the
bands the way they are who knows ah where the hell well the only way oh
yes any in the main it’s just two legs now I have designed them in the past I
saw of Zed shaped you know sort of potato shaped and in the main you can
get away with it and it won’t screw up if you like you tune but the more
further away you go from you know this strange reality the more you’re gonna
have problem to nyan now a doublet is slightly different a doublet should not
be an exact multiple of any band that you’re trying to use therein so for
instance if you hadn’t if you had to 20 meter legs fed with ladder line or with
open wire feeder or window line whatever you call it that’s balanced line into a
big tuner and your twin your knobs to get the perfect match you tuner the
ladder line and the aerial becomes if you like part of the whole area it’s
part of the circuit to represent 50 ohms 50 bananas 50 apples to you to your
radio you say and and it can’t be an exact multiple because your current
distribution ends up potentially the very ends with high voltage in the
middle all sorts of things happen you can just be the wrong frequency okay so
we need to pick a length that isn’t 480 meters it isn’t the forties isn’t for
160 and there’s favorite doublet lengths but don’t get your knickers in a twist
old British expression where the hell where we have forgotten again shapes
balance line yeah it just means that we can end up with some weird and wonderful
shapes without worrying too much and we can use these shapes to our advantage
so first of all the doublet that I’m trying to put up must give me a good
line my to 90 degrees on the compass that’s if you like north west and I also
need about 45 50 60 degrees on the compass roughly for Australia that’s
very difficult to get off dipoles it’ll either be one or the other
you see let me just show you this really cool thing I coming but I don’t know who
wrote this I’m sure there’s an about somewhere but anyway you can just put in
your I’ve done it before so IO 92 Delta India this is a bit accurate for a world
map okay but it does show you the problems I’ve got with having a single
dipole we’ve just had some technical problems but I’ve cut that out so you
don’t need to be bothered with it so this is a great circle map based from
the farm of all places but and he’s fantastic and that’s the link and I’ll
put that down in in the description so we could see my problem is I’ve got my
means unzoom this slightly my 290 brings me right through kind of Newfoundland
and the whole west coast 300 takes me all the way through the middle of the
u.s. to the the top of Mexico’s Southern California here and 310 would you scroll
up a bit you can see here brings me through right through the middle of the
US I need to get to 330 to get into British Columbia 320 is going to be sort
of the Seattle region so I need this top left okay it’s cut a long story short
Simon Australia over here on the right I’ve got anywhere between 40 and 90
degrees I’m trying to trying to now bear in mind
so my dipole hopefully it’s not that one there we don’t need that we need the
other one that backs it from there that’s moved this is my actual 40 meter
dipole okay and it I’ve drawn it specifically I’ll go to the 3d plot I’ve
drawn it specifically slightly off axis because I am that the path and
everything are on a farm is 13 degrees south of West if you don’t I mean which
is why it’s point Southwest a little bit so if I take a
datum point okay if you’ve never seen a plot like this before by the way the one
on the left is your bird’s-eye view looking at the top at say 40 wrong
button and say all right 45 degrees off the horizon
it’s a slice taken through it and it’s displayed as if we’re a bird flying over
the top and that’s what the pattern looks and number one on the right is the
same but from the road side okay so that’s this is what is shy and you can
run your cursor around so at five degrees which is kind of my personal
baseline for understanding how an antenna works really low off the horizon
five degrees we can see the actual so it to 70 which is Wes and if we like we’re
after 290 really I’m aiming for about 300 which is about there so it’s minus
eleven point four what this minus eleven point four mean will a true at vertical
with a decent ground system will give me about minus five six seven eight nine
zero heavens so I’m going to be 6 DB quieter on my transmit than a good
vertical ground mounted 40 meter vertical and if I had a two element
phased array I’d be getting another 3d better off again so I am way down on 40
meters however going the other way I’m minus eight point nine still about 3
DB under a plane vertical and the farm can’t cope with a vertical cut know
where to put it so I’ve got to get something up in the air how can I get
better than minus six better than a single vertical going both Northwest and
northeast if possible well that’s what I thought until I started mucking around
with a design a very strange design to push the RF in a lots of different
directions and I was lucky I’ve come up with something I think might work so
let’s just view this that’s a the red dot here
that’s my oak tree and at the moment I’ve got my dipole
coming down sort of here and here or looks a bit shorter than that in this
version I come down slightly south of the top coming down a little bit steeper
on this side here just over halfway up the aluminium pole where I’ve got my two
meters on and then I drop down to only Z two meters off the ground
okay so I’ll have to do that with a little bit of fiberglass or something
and a little thingy a little bit of wire you know tape to it and this is much
longer than that I got at the moment it comes all the way down here and then
I’ve got this little piece sticking down now I promise you if I move this just a
foot you would see the pattern would cock up took me ages to get this and
that is Z and that’s three meters off the off the ground now I’ve already
calculated as few times as well just show you again if I fit that with coax
that would give me SWR of 12.9 because i’ve got AA
resistors 591 and I’ve got this reactance here just I’ll go do it right
but I can feed it will open when I feed a ladder line or something into the big
tuna create part the tunica becomes part of the area of the car it’s part of the
tuning circuit the SWR on the balanced feeder would be negligible yeah well
what does it do in real life so I go to my far field plot here it doesn’t look
any different to normal but if I go down to I think just say it’s a thirty thirty
degrees which most of Europe I’m doing fine so I’m getting this quite and not
not what I would imagine to be a fairly nice pattern did I say 35 degrees so
into Germany which is about their 4.8 okay I’m 3 DB short into Germany but you
know that’s a single hop I don’t really care about that so it’s go back to my 5
degrees there and let’s go down to 5 degrees here and you could see where
I’ve got a bit of luck going on so whereas over here I was let’s take 290 I
was – 10.3 we should up here at the top of the screen
and if I go there again which is 290 I’m now – 4.8
so I’m a DB better off the mother cool so that’s cool and I am 560 be better
off than my current dipole so that’s really good
and by the way a DB’s mount up so if I’m running my amplifier as well all of a
sudden I’m I’m gonna be let’s say another six or eight DBS
it will all add up and I know that I’ll be much better now into the US then I
was over 150 beats better off and into V Kaela let’s take it a verage of roughly
over here I’m about minus 3.9 so again a couple of DB better off than the
vertical and he’ll I’m well three seven certainly six six and a half T be better
off on that so it’s it’s interesting learning MMA na and I’ve done quite a
lot of tutorials in the past I did a sort of a zero to expert in 30 minutes
I’ll see if I can find a link I’ll put it here for you which is well it shows
you all the tricks now to draw your aerial and everything else if you’ve got
some balance line it means that you can um you can create some weird shapes and
get some gain you see so anyway what’s the difference between a dipole and one
and a a doublet which is what the title of this film is and one is a tune for a
tuned aerial that you’ve kind of stuck with and the other is something you can
muck around and push about if I’m gonna tweak this a little bit more and see if
I get another DB air at the thing at five degrees alright I might have to
have a 40 meter low-to-the-ground dipole it sort of 20 feet for the big bubble
stuff that thousand-mile stuff okay so um I have to switch my sweet some coax
in well I’m okay with that would this work on a tee as well three point seven
I got funny Feeny it’ll just work that was right three point seven yeah that’s
why I expect a bubble of RF because it’s about 40 meters 42 feet 45 feet whatever
and at 5 degrees it’s nothing not doing anything particular
yeah us would be minus 11 but in fact a lot of DX angles on a team
at 20 degrees not all of it but some of it can be and I’m getting it fairly
omnidirectional pattern at about zero you know so I’m happy with that at all
Dylan for my Envy stuff my short my short range stuff I’ve got mine I’ve got
five point six up here at 30 degrees two point four forty degrees four point
three five point five and my near 200 mile stuff is you know he’s huge six
point eight that’s that’s absolutely fine okay
hopefully I inspired you I’ll see you back down a farm and next time I won’t
take the b-roll with my cheap camera so my name’s Callum from DX Commander – enjoy your radio chaps and enjoy YouTube.. and let me know your thoughts and see if
we can get this built next couple of weeks. A very good day

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