in this video series we are building a
ground station for a geostationary
satellite and try to talk to a swiss guy
in antarctica
it is a bonus series and not directly
related to the regular topics of the
channel
it is strongly suggested to start
watching at the beginning of the
playlist now showing in the top right
gritty youtubers here is the guy with
the swiss accent with a new episode and
fresh ideas around sensors and
microcontrollers
remember if you subscribe you will
always sit in the first row
you did not get an update for quite some
time
this has an expensive reason
i fried my power amplifier and had to
get a new one
now it's here and we can continue
like last time i was not lazy during
these weeks
the most important part was a visit to
the time and frequency lab at nujatel
university
when i got an invitation from subscriber
etienne to compare my gpsdo with their
atomic clocks for sure i said yes
but this is stuff for a later episode
because it was so exciting
i deviate this time i ordered the power
amplifier from sg labs in bulgaria i
already wanted to get my first amplifier
from there but during corona they were
not able to ship
so i ordered a similar one in china both
have around 30 db gain and a maximum of
20 watts output
the chinese runs on 12 to 24 volts and
has a built-in boost converter
the bulgarian runs on 24 to 28 volts so
i had to add an external boost converter
to replace the chinese with a bulgarian
but what happened with the chinese i did
some testing in my lab when the doorbell
rang
unfortunately i did not completely
switch off my test installation i just
switched it to receive and thought i get
a delivery and will be back in less than
five minutes
but it was a colleague who came for a
visit
when i came back to the lab i saw that
the ampere meter showed a quite high
current
when i touched the pa
it did not pass the swiss sky test
and i burned my fingers
we can have a quick look
it does not look horrible a few parts
are partly unsoldered and also the
solder around the power transistor was
fluid for some time so the temperature
was at around 300 degrees at least
this is why the device will go to the
engineering graveyard
it lost its life for my better
understanding of the world i can only
assume what happened
both pas draw quite some power without
any output signal i do no more remember
how much the old one needed the new
consumes 0.5 ampere while idle on 25
volts this is around 13 watts
and without cooling they can get hot
maybe this was the reason maybe
something else happened
anyway the new amplifier has an
advantage over the old one it switches
automatically on and off at a certain
level of the input signal
you can also switch it with a
push-to-talk input which will not be
used for the satellite because there you
work duplex so the new one should be
protected against overheating in idle
but during transmission it consumes up
to 40 watts
this is why after the first tests i
added two things
a fan and a temperature meter
now i know that after about 10 minutes
with 10 watts output it reaches a
temperature of around 55 degrees in my
lap that is okay with me
so this problem is solved
the next one was that my addon pluto did
no more react also here i do not
precisely know why but the second one
works now with my modification for an
external 25 megahertz reference provided
by the leo bodnar gpsdo
i added an attenuator to get the
reference signal to below 2 volts pp
like that i should have a stable
transmitter
to finish the transmission path
i purchased a used sennheiser gsp 350
headset it is made for gamers and seems
to be comfortable and most important it
has a usb connection
i did not want to have 2.4 gigahertz
bluetooth around my high power amplifier
the antenna also needed some attention
after my failure with my first try i was
contacted by achim he offered help and
because he was involved in the qo 100
project and built some stations
his input was valuable
according to his analysis i had to focus
on the antenna direction particularly on
the elevation of the potty
because i had to move it upwards to fit
the diameter of the potty it did no more
point precisely to the focus of the dish
and he told me that i had to do my
trials with my lnb attached
not by listening to the web sdr
if i hear the satellite i know the dish
points in the right direction also for
transmitting
so i calculated an angle of 2.5 degrees
and printed a new attachment for the
antenna
i saw that some dishes offer a different
mounting which should leave room for the
potty without modifications
so maybe this is a better solution for
you now i had to combine the potty with
an lnb
another colleague made this plastic part
on his lathe for me
and i'm sure it could also be 3d printed
first i wanted to cut the front of the
lnb but now i'm happy with what i have
the copper tube fits snugly into the
cone and mike the inventor of the potty
told me that this is okay
so i have an excellent combined antenna
the only thing i would do differently is
to cut the copper tube before soldering
the antenna
like that it would be a little shorter
now we still have one problem to solve
before the next try
the stabilization of the receiving
frequency
the plan was to inject a 25 megahertz
signal into the lnb
but for my first trial i wanted to use
another solution
the q0100 transmits beacons on three
frequencies two in a special morse code
and one on 10
489.700
in frequency shift keying or fsk
the addon pluto together with the sdr
console software can receive the whole
band with all beacons and all signals
transmitted by stations
a software add-on receives the middle
beacon and because it knows that it must
be on 10 489.750
it can correct all receiving frequencies
like that it should be stabilized
without any additional cost this is
software defined radio at its best
so everything is ready and even the
weather is better now
time for the next trial on the roof
the 80 centimeter dish is still waiting
and we can start
nearly
we have to do some math in the sdr
console
first we have to enable higher
frequencies above 10 gigahertz and
second we have to solve the problem of
the different frequencies used in this
project
let's use an example we want to
communicate on pin 489.700
the band plan shows that we have to
transmit on 2400 200 to get a signal on
this frequency
from former videos we know that the lnb
translates the 10 gigahertz signal down
to around 740 megahertz
this 9750 makes that the pluto listens
at
739.7 megahertz while sdr console
displays 10
489.700 as receiving frequency
this
8089.5 makes that the pluto transmits at
2400.200 while sdr console displays 10
489.705
as transmit frequency
now we couple the two and we have a very
comfortable transceiver wherever we set
our receiving frequency the transmitter
is also there cool
enough talked let's hit the transmit
button and listen to the signal
unfortunately it's not easy for me to
film the whole thing
test
one two three
test test test
hotel bravo nine probably alpha
but you should get an impression
really i hear my voice from the
satellite precisely on the same
frequency
just delayed by the 72 000 kilometers
travel distance
all viewers remember that this was the
same when we used satellites for
telephone conversations between the us
and europe in the 80s
it needs some concentration to listen to
our delayed voice while talking
so the whole thing works
as a general rule my transmitted signal
must not be stronger than the beacons
this is the case with around 8 watts for
the moment so my amplifier is big enough
also because my antenna cable is only 50
centimeters long of course
during the first evening i was able to
talk to four different stations in the
uk germany and france i had to stop
because it became dark and i did not
have the fan mounted for the first tests
i did not want to fly another pa
one of the stations by the way is a
viewer of this channel
so we are much closer to the initial
goal
to talk to the swiss sky in
antarctica during the next weeks
some tests and improvements will be made
and maybe i will find roman from
antarctica somewhere in space to talk to
him
i hope he has a little time for me
because i assume it is now dark for
nearly the whole day where he is
to keep the experiment interesting i
ordered a 120 and a 60 centimeter dish
so stay tuned if you are interested in
this comparison
i want to thank all my supporters on
patreon and viewers using my links for
their purchases for supporting the
channel without you it would be
difficult for me to do what i do now
especially frying pas and pluto's bye