WARNING - COMPUTER GENERATED SUBTITLES
cameras everywhere I'll use my little hourglass stay under 10 minutes
ladies and gentlemen welcome to DX COMMANDER up my name is Callum now I've got
microphones and cameras everywhere because we've got a paper here I want to
discuss and that a fella called Rudy Severns prepared for us now I've read
part four and it's pretty heavy okay how many radials does my verts
could really need and I'm not gonna go through this oh it's very good there's a
little bit of wallpaper looks like Fortran it looks like Greek to a lot of
us so let's dispense with that from in it
and I want to tend to concentrate on this one here vertical antenna ground
system experiment number two okay I've got it on the screen as well now what
really did is a nice thing about mr. sevens and 6lf is that he has not only
got the science he does the real-world experimentation as well now I'm more
with just an experimenter and I rely on people like Rudy sevens to give me the
maths the the kind of backup it's all very well an experiment working but you
know how efficient was it really now what really actually did is that and it
says it here if you read his paper he used five different antennas but I'm
really interested in the first antenna he did because he then used 64 32 16 8 4
and one radial and physically measured the impact of the DB gain or otherwise
on a radial basis in terms of numbers and plotted that for us which is which
is good but he also interests and we're lucky that he did this for us
is that he told what would happen if I cut these radials in half so he's used
quarter wavelength radials so in other words for the most of experimentation
for 40 meters these will be 10 meters long but wait before you tune out
the original work on radials was done in the 30s I forget by who so understand
that's 90 years ago and it remained the benchmark for the broadcast industry
which was 40 percent of the wavelength for radials
so for the 40 meter band for that be 60 meters long a hundred and twenty of them
and that was the benchmark and a lot of people in amateur radio thought that
maybe we've got to go down that route after all don't we want efficiency as
well but as you'll see in a minute where they calming themselves for that extra
quarter of the DB but in fairness it will probably cheaper to put out
hundreds of miles of radials than it was to them because their
license was probably you know ten kilowatts and that was it so maybe every
whisker helped after all these would be commercial broadcast stations in the US
and like the BBC at Rugby and places like that so let's dig in whoops dig
into Rudy's experiment because he says here quarter wavelength of one-inch
aluminium tubing Heaney adjusted to resonate at 7.2 megahertz and and then
he improved it progressively by adding 33 feet number 18 insulated wire which
is what's said about point seven mil I mean just then thin wire nothing heavy
and he ordered he initially just used the coax only as one radial which he
called zero and then he went up to let me expand this up so you can read a bit
better how do I can I am zoom in his resume button that's better we're really
now look where are we he went from zero to four eight sixteen thirty and he
stopped at sixty four radials and he repeated for each aerial now we're not
interested each aerial because I'm interested in called a wave okay as many
of you know I have an interest in quarter waves because
I do so on the product is basic a load of cooler ways so anyway he he reckoned
his he's got on these other experiment chocolate on the floor now
and he's got an average soil so he's got a 0.02 Siemens per meter conductivity
and relative dielectric constant of 13 now that's not far off a regular meadow
pastureland British back garden not the desert and not by the sea which is even
better okay but you know it doesn't matter because it's all relative anyway
it doesn't matter where he tested it we're actually only really interested if
you think about it on the number of radials and he made two measurements
each the input impedance and the value for transmission gained a point one
point eight wavelengths one point eight wavelengths away so if it's forty meters
he was one point eight times forty well 248 about seventeen meters away if it's
forty meters right so let's get to two graphs and we can i zoom in this a bit
further for you because couldn't look at it on here as well
the first graph was number of radials so for instance let's pick sixteen which
will be this one here all right coming down there and that's his quarter wave
this first one just above the dotted line we're interested in all the rest
were top loaded in mobile whips and everything else I've noticed in that so
what he's got is the signal improvement and this is the key thing okay the
signal improvement by adding from starting off at zero radials in other
words only the coax and he would then measured it at four DB which is two bars
in here and up so he got a one DB by the look of its have a look and it's that
line yes sir four radials he achieved one DB
gain over no radials okay at eight radials he achieved 1.8 just over DB
gain over no radial so that's new to DB isn't it at 16 radials which is this one
just here so 16 go up and where it stops and then Read Across we're at 2.2 DB
gain over no radios at all and then all the way up to 64 radials he gets to 2.6
so the difference between 16 radials and 64 radials is I'll just double check
that 2.2 to 2.6 2.5 actually 2 at 52.4 16 radials 2.2 so 16 to 64 rinser maybe
half a DB okay you'd lose that by breathing okay so it's up to you as
several at 32 radials it seems to be flattened out in fact the difference
between 16 radials and 32 radials is only point four point three of a DB so
if you know UD B's you'll know that three DB is you can of doubling your
power or doubling you received 3 DB is double right 2 DB is it's about half
that and 1d B's next to nothing and 10 DB is a factor of 10 actually now there
is a DB table on the internet but I drop that in the fuckin if I can find it
that's the improvement in secret second all he says over a single ground steak
with no radials for each oh he used a single ground steak and no read radials
that was his zero point it doesn't compare the relative worth of each
antenna but in fairness were not interested
in the relative worth of each antenna only interested in the quarter wave
this was his impedance so for number of radials 16 quarter wave we get an
impedance of about 40 ohms and then it stays just just just under 40 ohms
that's what I get that's why I'm getting an SWR about 1.2 or something it's just
it's just fine if you really wanted impedance of 50 ohms you'd be into 4
radials but if we go back up to here for radials is giving us the difference is 4
and 16 is 2 points at 1 point 2 DB so it's worthwhile getting to about 16 if
you can okay but there's any improvements you still getting a signal
out what else did he write home about they changed the number of radials
number of radials and resonant frequency so and this is where maybe some of my
customers are getting stuck they tell me that the that I normally
use X number radials and on my quarter wave and you'll use a different set of
water waves a different set of radials and if we look down here if Joe's soap
uses with my mouse come so we turn the page back x number of radials it's that
one there isn't it so it's just read the plot carefully here so at 7 megahertz or
round number of radials say he's plotted 16 there 16 radials was resonant at 7.1
as 1 5 2 so 1 7 point 1 1 if you like ok and then if you double amount of radials
the resonant frequency goes up slightly the aerial is effectively becoming
slightly shorter that's what it's looking like so depending on how many
radials you used if you used there is a potential to go from
six point nine seven five to seven point so this potentially about a hundred
kilohertz in it if he used 4 or 16 radials actually probably not too much
you're hardly gonna notice that where the dip is okay so there we are ah what
else did he say resident frequency vertical inverter
he's going on about loading and everything else we're not really
interested in that but I am interested in one thing that I can't find now
because the wages are lying on the ground surface I'm happily recording
here minutes have gone by as I've edited this because I'm trying I'm quite a
fussy I like my I like my data you know I like the Builder prove things um I
like to build a demonstrate that I've got my songs right wonder where it is
one if I'm fine on the internet here we go I found it I mean ages trying to find
there's some running our memory card in addition to the tests he says Rudy did
something really cool he compared 16 quarter wave radials versus 32 eighth
wave radials and in line with the modeling and calculations the signal
strengths were almost the same maybe I found it so in other words you can use
the same amount of copper right but more radials less size there are
found it it was in there all along I've spent nine and a half minutes trying to
find that for you and I'm running screen-capture three cameras all in high
res while waste of memory but there we
are Sami can write home bounce something to
think about none of us don't fret too much about how many radials okay just
don't fret about it I've tried it with four and I would still work in the world
and having a laugh but I would say somewhere around 10 and 20 you're gonna
have a laugh if you want to add more it's up to you
my name's Cal a map from Diaz commander m0 MCX
have a jolly good day thanks for tuning in I'll see you on the next one don't
forget to Like and subscribe to this channel bye bye for now
dddd
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