AUTOMAGIC COMPUTER GENERATED SUBTITLES FOLLOW:
a very good day my name's Callum from DX Commander
OK.. a few days ago on this channel oh no it
wasn't we was I've got two films in my head you see we did a video I don't know
been a month ago on Delta loops right rotatable Delta loop sort of thing you'd
built and put on a small mast and then yesterday or the day before are released
to film or video we call on YouTube don't we all about impedance matching
and actions velocity factor but near the end of that film we discussed we nearly
go into impedance matching but we kind of didn't all right I've a did it
because I wanted to try and keep it on track so I'll put a link to that film
here for you to give I'll put a link here now there and I'll put a link at
the end of this film as well so you know to panic just to discuss that and now is
it normal to change one's mind I hope so because I was fairly committed to go
down the route of building a Delta loop originally for the house but with the
opportunity to build the new Shack down the farm I'm going off the idea because
if someone said what's the point of it all that lovely gear if you haven't got
a bit of game do you know the mean so we need some gay and I've been looking at
three or four options one just to pain Delta loop that I could match with
balance feeder to the 84k the big balanced tuna but that gives me gate in
two directions doesn't give all my gain over there but I've got a footprint I've
got a I can't go monstrous I don't think right without you know maybe the
landlord going on one other 540 years or something so then I thought maybe a hex
beam because that's multiband very nice I've got an a 3s sticking it's
collapsed at the moment but it's in the central heating pipes tearing my old
club I'm sure I could ask for it back because I kind of well I could put it on
permanent loan but I've had it back a3s is a 2015 and 10 and then years ago an
old fellow who Chris Pettit and I were giving him advice on his old towels on
me I think he had cast aluminium spiders two of them there in there the moment to
make a cubicle quad and and I just I just say that out loud to the man I'd
love to make a cubicle called it and he just picked a zit old fella just picked
you up said hey have it so I feel like I'm contractually bound to build that
cubical quad now a hex beam in the UK delivered and everything else it's about
500 pounds so I know for a fact I've got I thought she even spent a half that on
buying all the spreaders and and everything I could get this cubicle cord
up and running which got me back to VTN okay
so if you have a mono bandha which is presenting him and Pete and impedance
between 150 and 200 ohms which a loop will do a two element quad for instance
cubicle quad will present an impedance of about 150 ohms I seem to remember of
golly honorary 176 it says as its resonant frequency then we've got two
ways out the problem we could either put a four-to-one ballon which is
effectively would take a 200 line match and present 50 ohms to our coax which
will give us a really good match for a hundred and seventy six O's well I can
tell you that we would get next to nothing you know at 1.15 or something it
would be you know
close enough to run even transistor amplifier you know the other way out of
matching a a loop to a mono Bank this is now would be to use a 75 ohm maxing
matching section and now that's calculated at a quarter wavelength at
the velocity factor guru talking if remember on that film I'll show you the
end velocity factor we're talking about what why bother why why do why are we
interested we lost to be factor so if we've got a piece of correction it's
velocity is a hundred percent and our frequency is fourteen point two
megahertz and it just so happens that if we calculate three hundred divided by
fourteen point two that means our wavelength is twenty four point five on
another divided by four it says here that we could have a 75 ohm maxi section
at 6.15 it says it here a my little calculator meters long 75 ohms and then
connect it to our 50 own coax you'll get a bit of impedance matching
250 ohms it's just a bit of magic and you know what impedance is the one thing
that I can't use common sense about I feel inadequate or I haven't studied
Harvard it hard enough that I can't I couldn't debate it it's just a given
these are just numbers to me I just know that I'm looking for 50 bananas 50
apples 50 blue widgets 50 O's I understand why okay stupid I know for a
go of my Intel / anyway however that's a hundred six point one four seven five
meters 75 own coax that will be a hundred percent velocity factor
well the chances are I'll probably use Aircel seven velocity factor I think is
86 percent let's say it's two one three at 66 percent I'll just multiply that by
point six six so fat I'm after just over half call it four meters four meters
long which is odd twelve thirteen fourteen feet or something of our g21
375 own coax where wouldn't be RG to 1/3 cuz there's 50 ohms but the equivalent
seven yard g70 whatever it is okay I would buy that I'd buy some 75 n coax
and that would magically produce me 50 ohms just at the point at the quarter
wave less the velocity factor that's if you're matching a mono band if you
wanted a much you had a big loop for instance you know like the mega loop
that we had down a scout Hut it was 158 meters long or something we had a fourth
one Belen on there on that one and we just used to use it on 80 40 20 15 and
10 you know and with the with the inbuilt a to you on a rig you could get
the other bands but for high-power we got a great match on on the harmonics
you see and that was a four-to-one ballon because it was multi band because
if I'd used just a quarter wave matching section that's the velocity vector it
would have only words on the one band you see now interested is just design
considerations for a quarter I'm not quite sure from what what this film
video is supposed to be so I might cover a few things here I'll just head on back
to the screen now so I had in in the software the Mme a givers they happen to
give us a quad and it's a if we look at it it's a cubical quad looks like this
and you can either feed it there they're all there so that is the the 20 meter
one okay any unique turn around and you could look at it
from the top and then we've got 15 meters here and that's 10 and I'm
thinking well we could have 20 17 15 12 and 10 maybe or could I do something
kinky for 30 maybe not on a quad a couple of pixel dipoles folded dipoles
but anyway now we're always very when I got this spider I did a lot of research
about this and some people they take these these wetware these feed points
are and some manufactures you can buy you could take these feed points and to
bring them all together and they put a false one bail in there and they feed
all aerials at once just like a fam dipole it kind of works now I have
looked at that model that and spent days actually trying to get a single feed
point with a four to one ballon and I was I was getting my knickers in a twist
which is maybe a British expression but I was just getting all mixed up now I
happened to have on this this rat pack it's got a six way switch remote switch
I could put a remote switch up at the up up here where the this that all the
contraption would be the hardware that would hold it all all up I would just
manually switch 20 meters 1715 and actually that's my preferred route to be
frank with you now those that go I think he was a Canadian and I'm sorry I've got
the link you have to do some Google searches cubical quad whatever he had
all these matching sessions and then he had some disaster struck I know ice
storm or something but he ripped out all the match excuse me he ripped out all
the matching sections and he just he just directed moron 5000 racks and there
wasn't much change and a reason being there was who was that
save it they would say that an antenna geek in America I believe poor chaps
dead doubt but he when SK about seven or eight years ago apparently still got a
website with a load of resources on it and you can pay someone who will say in
the comments he wrote to him and he said what do you think's happening and it and
they reckoned there was enough copper up there that actually changed the
impedance so on a five band or six band cuz I could put little six meters in
here as well you see in fact I can extend the cord out a bit and give me a
for element for six meters just for fun that it was that he wasn't getting it
wasn't getting 175 zone own ohms anymore he was getting 70 80 ohms which way it
was it was a do I want to bother putting all the matching stubs back in when I
could just switch him okay click 2017 but even maybe that's just in the scheme
of things helped your consideration I didn't have a long email trail when I
was in Cornwall last year with a chap who had found an old blog article of
mine and talked about this as well and and I'm not quite sure who he was
anymore that many emails and what his conclusion conclusion was might be the
same of mine actually build it and see I suppose in these building these things
and by the way this this happens to match at fourteen point four one of the
reason quite keen to build this is that the elevation profile at five degrees
off the horizon is one point two which is slightly better than a two-element
just a plain two element two yagi at the same height so if I just reopen I had
one open a minute ago I think was that one it was calculate real add 10 meters
which is what's the heights gonna be on this get their own and chips or about
this whoa
it's enormous and I we had a rush everything goes
wrong doesn't it far-field far-field will look too far fit well I've I got it
like this why don't I just have it that's better right elevation five so a
two-element would give me point five and a quad at the same that my - LM saying
my quad has to be built like that to get the same height the feed where the
government says the mechanicals so in fact some of the quad will be
lower and some of the cobble be higher so I'm not cheating anyway our big deal
I'm getting 1.7 DB better off but a really nice pattern really nice pattern
on the quad whereas the beam gives me quite a lot off the pack but at the end
of the day if I can get something up at 10 meters pointing in the wiper
direction I want to point it in it'll work okay whether is a hex beam so I'm
thinking this - element yagi over here is probably
representative by about one DV probably of a reality so it's probably a bit less
so I'm probably gonna get one and a half maybe two DB better or a full-size
cubical quad then I would order hex beam and think about Hayek's beam is I worry
about my time I just buy it and put it up that ruins the fun doesn't it to
actually build a cubical quad will be a severe hassle to be frank with you but
well be fun I'd be able to say wouldn't you oh yeah I've built one and it worked
and and I've got the switch I'd rip it out of here because I don't need it here
for most of our said stay on the road I don't need a coax which revoked coax
switch here that would be ideal top of the tower wouldn't it anyway so I've
card a couple of things today so I've got
what title of this film should be cubicle Court design considerations days
right that's all for now see you next time - my name is Callum
..a very good day.
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