1 Radio amateurs and Microwaves An overview of –Basic principles –Techniques used –Activities...
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Transcript of 1 Radio amateurs and Microwaves An overview of –Basic principles –Techniques used –Activities...
1
Radio amateurs and Microwaves
• An overview of– Basic principles– Techniques used– Activities – Results
This is an invitation to join the microwave activities !!
2
Figures
• Microwaves are the frequencies above 1000 MHz– More than 99% of the radio amateur
frequency allocation is in the microwave bands….
• Amateur frequencies– 23 cm, 13 cm, (9 cm not in ON), 6 cm, 3 cm
(= 10 GHz), 1.2 cm (= 24 GHz)– 47 & 76 GHz,...
3
Everybody says• Microwaves are
– Difficult– No activity– Very specialized– Home made equipment needed– Etc…
But our motto is: Microwave are …. Fun!
LOOK FURTHER
4
Signal strength• The power received can be calculated with the formula of
Friis:
• WIKIPEDIA:
• Conclusion: The power received decreases at higher frequencies, but……
dfL
df
cGGPG
dGPP rttrttr
log20log2045,32
44
22
5
Signal strength with equal antennas
Formula of Friis is not “fair": at higher frequencies the dimensions of the antennas decrease!
• Alternative: compare signal strength with equal antenna dimensions
Assume an antenna area of 1 m^2: the equation is now:
Conclusion: the received power increases with the frequency!!
effAG
2
4
2
2
222
111
c
f
dP
dPP ttr
6
Noise
7
Microwave Propagation
• Troposphere– Good location is an advantage
• High altitude & “free horizon”
• Reflection (rain & snow) – For microwave amateurs with a “bad” location
rainscatter on 6 cm and on 10 & 24 GHz is an alternative
8
Atm
osp
her
ic a
bso
rpti
on • <10GHz
the absorption is neglect- able
• >10GHz absorption becomes significant
9
Graphical presentation of atmospheric absorption
* 100 KM
10
Rainscatter
• Antennas become efficient when their dimensions are in the same range as the wavelength
• Water is polarised• Raindrops dimensions are typical 2-3mm At 10GHz raindrops are (small) antennas which relay
the incoming signals Doppler ! Caused by random (wind) movement of the
‘antennas’.
Examples
• USA DX is 1015 km 8/2005
11
Some considerations about components
• De dimensions of “components” have big influences at microwaves – Classical R’s, C’s, PCB’s etc. cannot be used in many
places (parasitic effects)• “Special microwave” components are needed E.g. GaAs
Fets, SMD components, Teflon PCBs, .... – At microwaves antennas with dimensions of several
wavelengths are possible; e.g. a dish can be used.• The attenuation in coax cables can be extreme;
pay attention to it and use special coax or, if possible, use waveguides (the dimensions of waveguides is at frequencies of 8 GHz and up reasonable)..
12
Microwave transverter setup
Transmit mixer
Transmit amplifiers
Antenna relay
Antenna
Receive amplifiers
(very) stable X-tal oscillator
Frequency multiplier
To transceiver
2 m, 70 cm
receive mixer
13
23 cm
• Lowest Microwave band
• Transceivers for this band are available, but you can also use transverters (E.g. DB6NT)
• Modes used: – DX tropo, EME: CW/SSB – ATV, FM relays stations: FM
• Typical contest ODX ~ 750Km
14
23 cm modules examplesDB6NT transverter
30 Watt power
amplifier with
Toshiba modules
Pre amplifier Nf < 1dB
150 Watt power
amplifier
15
23 cm Antennas
yagiLoop yagi
2 meter dish
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13 cm
• Behavior is comparable with 23 cm
• Transverters (E.g. DB6NT design) are frequently used
• Not a lot of activity outside the contests– DX-ing during contests (ODX ~ 600 km)– Oscar Mode S down link…..(dead now)– ATV (…?...)
17
Technical parts of 13 cm contest station ON4SHF13 cm
transverter DB6NT
Transverter
Power amplifier 80 Watts out (GSM tuned to 13cm)
Medium power amplifier
Antenna relais and sequencerOther example of
GSM amplifier
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6 cm• Amateur band “in between” 23 cm en 3 cm
– One hand 13 cm tropo behavior– Other hand rain scatter possibilities
• Transverters are commonly used (E.g. DB6NT kits)• Low activity on this band; in practice only activity during
contests• DX ~ 600 Km• 2 examples
19
10 GHz• Popular microwave band with reasonable
amount of activity– CW/SSB mode is used for DX-ing– ATV uses FM modulation
• Propagation– 10 GHz is the highest frequency band which does not
suffer from atmospheric absorption– Troposferic ducting frequently possible– Rain & Aircraft scatter possible
• Contest and activity day distances: > 500 Km– European record 1400 km
20
10 GHz technics• The “plumbing” time is over, a modern 10 GHz
station contains PCBs with SMD components!• Building a 10 GHz station is not a project for
starters, but on the other hand those who can handle SMDs is able to assemble a 10 GHz transverter PCB in a few evenings.
• Tuning and testing such a PCB is not simple; the help of an experienced amateur is recommended.– Note: ‘complex’ measuring equipment is useful but
not needed at all
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Box with transverterDish 48 cm
10 GHz station example
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Pre-amplifier
Oscillator2.5 GHz
Power amplifier4 Watt
Transverter DB6NT2m -> 3 cm
Transition coax to waveguide
Medium power
amplifier
Antennarelay
Waveguide to antenna
23
24 GHz
• “Difficult” amateur band due to absorption by water vapour ( ~0.2 dB/Km)
• Propagation experiments needed– The behaviour and dependencies of conditions on 24
GHz are not completely clear.
• Our (ON4SHF) best DX is 260 km• Reasonable amount of components and
equipment is available at surplus markets• Example 24 GHz QSO:
24
24 GHz components
Antenna relayToshiba 24
GHz amplifier
DB6NTX-tal
Oscillator
24 GHz station components
Exciter 2m – 24 GHz
25
Examples of 24 GHz stations
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Microwave operations• CW frequently used (but very slow is good
enough ....)• Site (use e.g. Radio Mobile)• Weather (e.g. scatter possibilities)• Frequency accuracy
– OCXO, GPS• Antenna direction AZ/EL
– Calibration is important: Sun, beacons, 1st contact with known station.
• Talkback!!! - /P– To UK: 144.175 MHz; To F: 144.390 MHz; IARU EUR 432.350
MHz; – DXCLUSTER; CONVERS; WWW.ON4KST.COM (also via
GSM/GPRS)
27
10 MHz frequency standard
28
In the box
10 MHZ PLL
GPS RX
Display processor
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LO PLL
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LO driver for microwave frequencies
G8ACEOCXO
LOPLL
124.500 MHz out
Locking the OCXOs to the 10 MHz frequency standard
31
Microwave activities
• Contests 4 times a year – March, May, July & October
• Activity days– In France, in UK, NAC (SM, LA, ..)
• Special activities– E.g. Ysselmeer contest
32
Contests – the ON4SHF sites
33
Contests – the ON4SHF antennas
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Contests – the ON4SHF operators
35
Activity days - ON4SHF/P
36
Microwaving in the US (1)
• Differences:– More bands: 222 MHz, 903 MHz, 3.4 GHz– Topography: mountain topping (East-West
coast)– Possibilities for coastal ducts (Nord-South at
east coast, California-Hawaii at west coast)– Bigger and better surplus– Contest rules: much advantages for mobile
stations: /R suffix (to be introduced in Europe!?)
37
Microwaving in the US (2)
Rover example– W3IY/R “shack
in a van”– 50,144,
432,903,1296, 2304, 3564, 5760, 10368, 24192, 47088
– 1000Qs/contest
23
702
6m
913
9036-3cm
12-6mm
38
Thats’s all
JOIN THE CLUB
It is question time
on4cdu, on4iy
39
Back-up slides
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Detailed Photos 10 GHz stationTransverter DB6NT
2m -> 3 cm10 GHz
Pre-amplifier
41
Attenuation at 24 GHz
42
Beacon
• 10 GHz beacon ON0KUL/B