how does a DX commander work
everybody so
there's you gotta remember that there's some people who don't
watch YouTube videos okay they're on on Facebook or QRZ or whatever
and they hear about DXCommander and they don't know what it is all right so it's my duty
really to you know explain what my product is because I'm the owner I am Mr DX Commander
so it was an accident how it was discovered that I took a a vertical I was on hold at a time
it was a 40 meter vertical I had some radials and I've just done a video on radio so I'll put
a link to that somewhere radials on the ground so your coax came along okay the center go straight
up the pole and the radials I used some brass earthing blocks actually and just connected the
braid to that and then the radial still there put a bit of tape or Vaseline on it and it was fine
however what I did just experiment because I'm that way inclined is if that's my 40 meter there
I then just wrapped a bit of wire around and went up the other side of the pole with a 20.
okay now I didn't actually get a very good tune at the time so I abandoned it but the next day
I did it for 2015 10 and 6 I think I couldn't believe it I had this little multi-band antenna
which was which is really cool quite a long story short and that was 2013 2014 eight nine years ago
um I'll just show you some some pictures because that's a lot easier so this is this is a Rapide
this is based on a quite a small pole all right telescopic pole it's just uh seven meters high uh
23 four feet or something so you can see there's a number of elements that come straight up from
something called a driven plate at the very bottom all the elements go up through some spreader
plates these are the spreader plates and the rapid gets a little guy point here as well and at
the bottom there's no relays or anything else the the wigglies if you like come along your coax and
automatically select the right element okay now I spoke to both Mike M0MSN and Jonathan yesterday
uh M0JSX is how do I explain this without using words like high impedance blocks and things
but basically if you've got um I mean that's a hexagonal plate so I think we'll draw a sort of
a hex plate here we've got these holes here come ax is coming along to a ground plate and the SO239
I think we've got a picture there it is there's the SO239 bottom line the middle of that comes
along and just joins to the plate okay so every element is now live if you like if you put on that
multimeter across any element in the back of the SO239 we would get a short circuit which is good
the easiest way of explaining this is that if the RF on 15 meters has got a particular color
is orange it comes along and it hits the orange element and just goes I want to go up there all
right and off off it goes it's like the square hole Square Peg and the round hole system all
right all the other bands are the wrong shape basically and it doesn't go in reality is all
the other elements have probably got a high impedance so the RF just doesn't want to go
up there okay so this is the this is it and this is drawn in software okay so if I move this around
you can see there's a little hex plate at the bottom and all the elements go straight up it's
a little little red dots and so the coax is going so I can pick any frequency and show it to you and
you'll see we've got a reasonable match 1.38 to 1 it says in software in reality it's normally a bit
better and the far field plot looks like this so if we go low to the Horizon real DX down at five
degrees is the same almost within a whisker all right all around it doesn't matter if I pick 7.2
megahertz 14.2 megahertz you will see looks the same every time all right
that's because all the elements are a quarter wave apart from one element because the 40 meter
element if you measured it tip to toe to get let's say on 7.2 megahertz needs to be I don't
know let's just say 10 meters what we will find when we come to work out what the harmonic is of
that verticals and dipoles resonate every other harmonic okay so if you've got something at 7.2
megahertz three sevens are 21 so the next time it's going to resonate would be 21.6 megahertz
and what we found is if we just shortened this a whisker let's say buying that much and
we added a little Loop that came down we could still get a perfect tune on 7.2 but then 21.6
would come down to 21. let's say two all right so we got a perfect match there so it's not quite a
three-quarter wave on the 15 meter band so and I'll show you what that looks like uh 21 point
I don't think I've got the fold over configured on this we were just about to find out oh maybe
I have I don't know right I don't have the fold over configured in this so we'll just do it 21.4
this is really for the sake of the okay I'm going to SWR 1.05 by the way a three-quarter wavelength
element gives you a better match to 50 ohms than a quarter wave and yeah what does a far field plot
look like well it looks like all our gains going straight up okay but in fact if we measure down
at five degrees off the horizon we're getting minus 2.9 I'll make a note of that because that
sounds really bad doesn't it minus 2.9 but it's relative to another antenna so if we go to 14.2
and go to the far field plot and do my five degrees of horizon you will hear me talking
to New Zealand VK Alabama you name it on the 20 meter band on a straight vertical
and that's giving me minus 5.2 it says there so my 20 meter quarter wave most quarter waves are
about minus five right loads low down right it's a bit better up here into Germany for me as 1.8
that's fine right but low down it's still better than than a dipole all right and what did I say minus
5.1 minus 5.1 so call that three call that five so your three quarter wave is just over 2dB better
so the 15 meter band I mean it's it's pretty good and you'll probably hear me sometimes on
15 if you look at my live streams cracking on having a good time on 15 meters so that's how
a DX Commander works it's just a cut chart you get a kit you get a tape measure oh
um 20 meter band five meters and two centimeters whatever that is in old money all right cut it put
a full connector on and as you can see here you get a heat shrink and a few other odds and ends
and away you go so that's how a DX Commander Works nice and simple this is I've got some
radials on the ground and this is a working antenna right I use my I don't use any other
antenna well maybe a dipole you know things like that but uh there we are so that's how
a DX Commander works have faith easy isn't it right it couldn't be I mean I just don't know
another antenna but it's that simple with no components there's no traps no loading coils
nothing just a bit of wire that's why it works so well all right next video is coming up here
with jolly good day thanks for tuning in and I will see you on the next one bye for now