um you would have thought that a longer antenna performed better in fact i've got
so this is it's a wi-fi antenna that's very long that's just not it's not one wire going up there
there'll be lots of these inside it all stacked together with coils and little things that's not
quite what i want to talk about tonight though what we're going to do is um i'm gonna explain
from everything i've heard and done over the years what happens when we make antennas longer
and still get a match okay now look i'm going to use a piece of software here
but when i'm using the software i'm going to race through it if you want to
go through it slowly you'll have to hit the pause button and go frame at a time
because i'm just going to go whoosh probably i don't know yet it depends on how i edit it
uh so let's two two thing we'll do we'll do a straight vertical do a straight dipole then we'll
take the vertical we'll make it longer then we'll take the dipole make it longer now we'll make the
dipole extremely long and then we're going to get excuse me i'll bump to the camera the microphone
then we're going to get an end fed and we'll make that extremely long just see what happens because
there's some fascinating if you've got the space some really kinky things you can do with a bit
of rope no there's some really interesting things you can do uh with long wires all
right very long wires so i'm just gonna quickly make a vertical let's say for 40 meters okay
all right i've made a vertical and i've got an swr of 1.36 that's probably best
let's just have a look at the far field plot if we can picture what this might
look like okay so the plot on the left we're not that interested really it's looking down
plan view the one on the right is our elevation view and we'll it will that will change if you
like by the sea it will be a lot a lot you'll get more gain i can quickly do that for you
by the sea five thousand millisiemens per meter start you can see we get this huge gain really low
down okay anyway we're not here to do that what i'm here to do let's go back to 50 or is it five
average ground all right average ground where you grow your potatoes calculate right
uh we're just gonna come down five degrees off the horizon just give us a little baseline on
something five degrees says minus four point seven i'll just write that down i'm just going to write
that down minus 4.7 just so just so we don't we don't forget dipoles and verticals resonate on
every other harmonic every odd harmonic whatever which means you can take 7.2 and you can multiply
it by 3 which would be 21.6 thereabouts a few things happen height above ground mux that up
but effectively this will also be resonant on that's just for the sake of mass due 21.5
it says it's perfect at 21.8 in the real world that'll be actually about 21.5 21.6 but in terms
of software i'm just going to do 21.8 just to keep the numbers happy okay interesting notes
here do you notice how a three-quarter wave gives us a better match to 50 ohms if we go right to the
bottom here then a quarter wave just get a better match all right sw is 1.08 it's interesting so
the far field plot looks like that again on our average ground around 16 radials or something
and you can see that our um energy is is going kind of up at 45 degrees sort of thing you know
however if we come down low five degrees off the horizon where before we were having minus
uh 4.7 uh we've now got so that was a quarter wave a three-quarter wave is now minus 3.1 so depending
on how you cook the books on a few things you can get one or two extra db with a three-quarter wave
um by the way this would resonate on three-quarter waves also resonate on one and a quarter okay so
we'd have to multiply our 7.2 so i'm gonna fire up my calculator seven times three four five now
it would be next resonant on 35 megahertz would just be interesting on 35 ish it's going to
be 35 back to 36 a megahertz would be one and a quarter says the swr is a tiny bit wrong here swr
30 it says 36 and a half okay 36.5 not far out yeah start and there's the plot at one
and a quarter wavelength all right so you see these lobes have gone way up high there is a
little bit of going down here it says minus five point something whatever not not that good and
last one we'll do is we'll just move up the get my calculator back out and let's do uh 7.2 megahertz
seven that'll be one and three quarters all right yeah 50.4 it says so that'll be about 51 won't it
ah not far off and by the way yeah it'd be a shame it's not 50.15 because we a 40 meter element would
give you a tune then on 15 meters and six it will tune you just hit the atu but it's about normally
because i've tried this uh it's about a two to one sw it's just a bit higher anyway i'm waffling far
field plot the reason why it would be really cool is that one and a quarter you start getting these
big loads off off here which is quite usable between 20 degrees off the horizon and you
know a couple of degrees off the horizon if we look at our five degree business which was there
it says 0.6 so very interesting we started off at uh minus 4.7 minus 3.1 one and a quarter
wasn't very good this is one on three quarters anyway so that's the vertical what happens if
we do the same thing with a dipole so let me just shut up a minute and i'll draw a dipole
so i've just drawn a dipole it's flat it's just sitting on the ground but we'll raise
it up i mean what sort of height you guess what number uh sort of 25 feet
i don't know what's that about eight meters something like that give or take
7.2 do you want to start a 40 meter band again uh do we fix the error
of the it says it's resonant at 7.1 all right well we'll just keep the numbers happy seven megahertz
swi is 1.22 all right so we're interested in these far field plots again aren't we so uh
just an interesting plot um how do you read this it looks like a bubble of rf by the way
and if it's sort of 500 miles away that's going to be about 35 degrees off the horizon
and we will see at 35 degrees off the horizon off one end you know we're getting 4.8 bananas
and off here we're getting 0.6 so north south or east west there's about 5 or 6 db
barely perceptibly noticeable on an s9 signal one would be sa 1b s9 all right so
but it looks fine we press a really cool button here actually and just see
how we'll zoom in a bit and we can just see what it looks like oh yes very nice bubble of rf
so i wouldn't be too worried about it north south east west and whatever because a low to
the ground dipole on 40 meters basically gives mostly again going straight up in the air okay
so great on a saturday morning if you just want to talk to your mates a couple hundred miles away
that will work a treat then we go up to 15 meters again let's see what happens again remember we're
going to go very long in a minute so we'll go to 21.3 ish i don't know where this is resonant at
okay so we'll go to 15 meters that will be resident actually about 21.8 we'll see swr 2.281
not bad because we've got an impedance here i can see it says 111 ohms but whatever let's go to the
far field plot so we've got this weird looking cloverleaf going on well that's sort of a six-leaf
clover i think uh let's uh we're more interested in dx on 15 meters and that will be probably
around about the five degrees mark so let's have a look over there it's a minus point nine
minus point four point eight there we've got some dips going on so we got this funny thing
and if we fire this thing up here so you can see what it's doing it's quite an interesting pattern
so there's a three-quarter wave so if you had a balance line it's a big long doublet what's
going to happen well let's go even higher up if you remember the next one was about 36.5
something like that that would be a one and a quarter wavelength swr is not bad so that'll
do fine what happens now we get more of these fingers so we've got our antenna is actually
running uh on this plot north south and we can see starting to get these north south
lobes here we go five degrees off the horizon where is the dx very healthy dx very healthy
indeed in four directions okay and then i seem to remember we go one and three quarters which was
51 52 ish whoops megahertz let me just check where the swr is correct there 51.1 there we are 51
we'll just have a look at what the far field plot looks like there so this is a maybe an 80 meter
doublet on roughly the 10 meter band there we are so these fingers in my opinion are starting to
come closer together but again we'd be using this let's say on six meters or 10 meters if it was
twice as long for the 80 meter band just reduce everything roughly 5 degrees off the horizon yeah
we're getting these very healthy lobes here what does that look like in 3d as a matter of interest
if you can see that very well just fascinating really isn't it so this is an antenna that's
basically too long all right so we've done the dipole we've done the vertical we've made them
a bit longer and we can what we can do is we're now going to make a very long antenna
so i had now rolly rolly zl1bq in his previous um qth previous location he's in new zealand
he noticed there was a very long telephone wire going for a couple of miles or something
rolly might come on leave a comment and we will i'll pin it to the top and he'll tell
us more about it there but he did have this very long antenna um well he converted it because it
wasn't connected to anything so he connected it i don't know probably with some sort like
a 64-1 transformer i don't know what he did but basically he made this very long end fit
and he was saying he could hear and have two-way communications with stations like in america
and stuff which his friends couldn't actually didn't believe he was actually talking to them
but he was he was getting a healthy signal and it was a very long like a two-mile thing
i spoke to a guy on 80 meters a couple of years ago and he had i think it was two kilometers
of wire not very high off the ground just through the trees with some big you know
tensioning elastic things he genuinely did and he told me that he could talk to this guy in
canada every night of the week on 80 meters so i he said he gave me all the dimensions i modeled it
but i couldn't on qr said his email was bounced or something so he never got my results but i will
just do this for you so we'll make an incredibly long antenna so let me shut up and i'll do that
okay so this is our x and y i'm i'm i've made this along the x left right east west axis it's
2 000 meters one leg and 2 000 meters another leg now let's go to 80 meters
now you could walk a mile that way and a mile that way and start chopping bits and tune it
for a for a coax you know however easiest way of running this would be some balance line
to a big fat tuner in my opinion but whatever okay let's just hit the start button see what happens
might take a while because this is enormous even though i've got a super fast machine
there's a lot of calculations let me shut up and let's run this calculation
okay we're done uh so yeah we need to trim it we've got a big high swr
and i've put this at eight meters high so but assuming we could get a tune and you can use your
big fat tuner or whatever else let's see what this does well this is why he was talking to the guy in
wherever he was well these look very very high off the ground let's just do this at five degrees of
horizon okay so there's it splits into we've got a super high pitch gain there 16.4 dbi which it's
an enormous amount of power put your 100 watts in there you two know it in fact we could do that now
let's just quickly do 16 so you've got 100 watts if we had 100 watts we got 16 dbi so
a thousand watts uh 10 db is we've given them a thousand watts 13 dbi is equivalent to 2 000
watts and 40 16 dbi fourth okay so yeah yeah 16 is a lot okay um it's a lot so if you've got a zero
db gain antenna fairly low to the ground right over the horizon a fairly low to the ground dipole
eight meters versus this guy your hundred watts is the same as his four thousand
watts in that direction which is probably the only reason he could speak to you know
quebec or something it might be lucky that could have been florida from us because they're slightly
different angles fascinating now we've all got an end fed knocking around and we little enfit
so let's just quickly model a really long head fed before i go
this would be a very long low to the ground and fed inverted l okay for some reason i can't get
a match let's let's ignore the match all right i'm not actually that interested in the match
i mean i've got 90 to 1 swr here i could probably get a better match
if i hit this button here somewhere it's going to be resonant i just don't know where yeah it is
further up so we would have to go out and cut bits off and add bits or whatever else
it doesn't matter okay i'm just going to say on top band 1.9 ish megahertz
what does the far field plot look like on a very long whole wavelength where it looks like this
that's fine so interesting isn't it so let's go up let's miss 80 because i just think we're
going to get a couple more lobes but let's go up to 7.2 whatever megahertz and have a look at
that and look at the far field plot so we can see we've got more of these coming up now elevation
five degrees any dx potential all there is a little bit so we're you know from there to
there's a nice big spread we are averaging zero okay if you remember our quarter wave gave us
um minus 4.7 so that's quite nice there it is what about on 20 meters 14. uh three fourteen
point three might take a bit of a while far field plots oh you can see in the direction
of the l we've got at five degrees off horizon a couple of little lobes here look nice it's about
10 db more than a vertical look very good indeed and uh well what happens then if we make it super
long okay that's going minus 16 to minus 320 meters of wire what the hell would happen okay
far field plot please oh fascinating fascinating five degrees look at this
i'm looking at this game these game figures are up here so there we are very long antennas
quite interesting if you've got the space or a fence line with a neighbor try a long nfed
you might be surprised who knows i'm going to give it a go all right so stick with the program if you
follow this channel then in within a month or so we're going to put a big long head fed
and see if we can get a little bit more gain to the us on 40 meters particularly
on a receive might be nice wouldn't it so enjoy your radio i'll see you next time bye for now