so in the last uh video in this series i did we modeled well we downloaded mma gal download
and we installed mma so i've got it running here
and here it is so today i thought we'd do a simple dipole again this is going to be under
five minutes i'm going to use you and i'm going to show you sorry a new tool so the first thing we're
going to do is going to head to the geometry tab and we're going to pick a dipole and let's say the
dipole can be for the 40 meter band let's we'll start off with a flat top dipole going uh north
south that will be on the y-axis so we'll do 10.2 meters one way and minus 10.2 meters the other way
now there's a drawing tool in this and it's actually clicking this button here if i hover
over it the tool tip is wire edit and there it is hey some buttons over here on the right
we're currently in a 3d look and i think with the control or shift button shift button we can move
that around okay control doesn't do anything x y that says looking straight down on the top of it
x z means we're on the x axis which is left to right and z is going straight up and then y z
now we're looking from the left hand side or the right hand side with z going straight up and you
can do stuff in here that'd be more difficult to do if you had to actually do the numbers
so we can right click this for instance and divide the wire into three pieces for instance
and then we can move this around so this button over here is draw a new wire and this one
is editor wired so i'm just going to grab this point here i'm going to move it over to there
because what i'm going to do is i'm going to create a little bit of wire in the very
middle that doesn't move can that be our feed point okay so we can zoom in a bit here and i
can make that fairly small because it we don't need to oops we don't really need to come back
come back to this there and then it'll tell us how long that is over here the length of that is point
two of a meter which is about eight inches so it's a bit too big really doesn't doesn't matter this
is just a model isn't it let me hit the ok button and now you'll see it's actually created some new
stuff all right and if i go to the view tab there it is and so that's wire three it says over here
this one says wire one so the middle one is going to be wire two so what i'm going to do is wire to
center that's where our coax is going to go so that's all i'm going to do i'll view that
and there it is it means i've cut it into three because we can make it inverted v in a minute
all right hit the calculate button this is for well i haven't told it over here actually yet it
might be easier to do 7.2 megahertz now so when i go over to here it'll bring it over for me 7.2
it says me typing it in so it's currently on the ground so we'll put it up about say eight meters
twenty four twenty five feet eight meters and we'll make it as a copper wire now it doesn't
make much of a difference what we make it out of here but anyway start um we've got a bit of
an swr issue going on it says 2.4 and but i'm not going to show you this bit so just stand by
because i'm going to show you that another day i don't want to confuse you now
it's actually that length is resonant on seven megahertz dead right and you'll see there uh
sw of one point one nine one point one point two to one okay and there's our far field plot
for our um 40 meter dipole and uh well it's easy isn't it and which is why one of the reasons if we
just go down around here at 45 degrees and that says the gain figure is 2.3 dbi there
and over here it's 6 db dbi so we're about a 3 db difference between north south east
and west the the um which is not a lot right you know s8 signal you're not going to know
if he's 3 db down or not all right so don't worry about the configuration north south
east west if it's for 40 meter dipole right we'll convert this for 20 meters in a minute
now in the main most of us don't have a flat top we've got a tree somewhere and it's more
normally inverted v so we'll go over here we'll unzoom this a little bit here we'll take a note
of roughly how long these things are it says each leg is 10.1 and i'm going to sort of invert it v
it there's 10.3 there so we're going to go down lower in frequency 10 10.3
i'm going to zoom in a tiny bit and i'm just going to make these tiny bits shorter 9.8
um you know you can get a bit fussy with this okay i would have thought the frequency would go up now
2.28 i reckon it's probably resonant about 7.2 now start it is 1.18 so has inverted v in it made much
of a difference so at 45 degrees off the horizon daytime 40 meters you know roughly where this is
going i've got whoops 3.1 there 5.7 there so there we are it's actually equaled out a bit isn't it
it's it's not much in it now when when i made the vertical the last time we did this
we you know we can have a look at it there and there it is now if we wanted to convert this for
20 meters well how do i do that well you could either raise the height by two
or if you really want to be fussy we can scale it so the new frequency wants to be 14.2 let's say
it will redesign all this and there's a trick we can get rid of some of the
decimal places one day if we want to but we'll do that when we go under the hood
at the moment that's about 4.6 meters what's that 20 feet somewhere just under
good it's still at 8 meters height it still looks like this eight meters at the top and in fact the
bottom of the oops the bottom of these is droops down one and a half meters ah five feet whatever
so now let's have a look at that if swr is wrong honestly we could fix it by adjusting
the lens it's not going to make an iota bit of difference iota when we look at the far field plot
so this is our far field plot now elevation we're after a little bit of dx yeah 10 degrees
not not heavy dx just you know average roughly where's my signal going and we can see we've
got this now it's important now you need to choose north south east west if it's a fixed
dipole all right and this is at eight meters so if we went up half a wavelength 20 meter band so
it's going to be 10 10 half a wavelength now 10 meters up inverted v on 20 meters far field plot
elevation heavy dx uh half a wavelength off the ground
uh so that's now that 4.7 there is roughly the same as a vertical all right so our
best gain east west is roughly the same as a vertical which is why vertical and 20 meters
works on blooming well on 20 because you've got all of this which the vertical is beating
all right instead of that so that's why we need to go above
a half a wavelength so if we went to you know 40 feet 12 and a half meters
40 feet now and we can see by the way we've got this lump coming up in the middle a little bit of
a waste five degrees of horizon yeah minus 1.4 now so you know you get your east-west you'll
be doing much better however from about here there to there you'll be uh a wee bit deaf good you have
now made your first dipole and that's probably a little bit more than five minutes i apologize
next time we're going to make a sky loop various loops and then gradually we'll get
deeper and deeper any deeper into some of the other tools okay in case you missed it i will
put a link in the description to the first one of these all right and uh and then stay
tuned and we'll make some more of this stuff all right lovely uh see you next time bye for now
stop recording