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Radio amateurs and Microwaves

• An overview of– Basic principles– Techniques used– Activities – Results

This is an invitation to join the microwave activities !!

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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,...

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Everybody says• Microwaves are

– Difficult– No activity– Very specialized– Home made equipment needed– Etc…

But our motto is: Microwave are …. Fun!

LOOK FURTHER

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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

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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

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4

2

2

222

111

c

f

dP

dPP ttr

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Noise

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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

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Atm

osp

her

ic a

bso

rpti

on • <10GHz

the absorption is neglect- able

• >10GHz absorption becomes significant

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Graphical presentation of atmospheric absorption

* 100 KM

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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

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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)..

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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

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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

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23 cm modules examplesDB6NT transverter

30 Watt power

amplifier with

Toshiba modules

Pre amplifier Nf < 1dB

150 Watt power

amplifier

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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 (…?...)

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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

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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

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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

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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:

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24 GHz components

Antenna relayToshiba 24

GHz amplifier

DB6NTX-tal

Oscillator

24 GHz station components

Exciter 2m – 24 GHz

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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)

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10 MHz frequency standard

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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

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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

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Contests – the ON4SHF sites

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Contests – the ON4SHF antennas

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Contests – the ON4SHF operators

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Activity days - ON4SHF/P

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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!?)

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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

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702

6m

913

9036-3cm

12-6mm

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Thats’s all

JOIN THE CLUB

It is question time

on4cdu, on4iy

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Back-up slides

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Detailed Photos 10 GHz stationTransverter DB6NT

2m -> 3 cm10 GHz

Pre-amplifier

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Attenuation at 24 GHz

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Beacon

• 10 GHz beacon ON0KUL/B