Foxhunt VK3YNG Sniffer 4 User manual

VK3YNGSniffer 4 Instruction Manual (for V2.2 hardware)
© 2004, Bryan Ackerly, VK3YNG Rev2.2a Page 1
VK3YNGFoxhuntSnifferInstruction Manual
(Updated version for version 2.2 hardware***)
The VK3YNG FoxhuntSniffer is a speciallydesigned synthesised VHF direction
findingreceiver covering 120MHz and 144MHz bands.
The receiver is designed for quicklyfindingthe direction of beacons or hidden
transmitters. Anything fromdistantweak signals to veryclose “sniffing” of
transmitters runningmany watts of output power can be pin pointedaccurately
without suffering“overload”problems that plague other designs. Fullauto-ranging
operation allows theoperator to quicklyand intuitively locate the sourceofa signal
without twiddlingknobs or watchingmeters. Theoperator isfreed to concentrateon
more importantthings such as negotiatingterrain or readingmaps.
The unit is also available in afullytested Board levelformatfor thosewho wishto
integratethe unit into other equipment or build their own housing.
***Note: A number of features havechanged since earlierversions ofthe sniffer
werereleased. This manualreflects operation ofversion 2.2 hardware and cannotbe
used for earlier versions ofthe MK4 sniffer. For acopies of earlier sniffermanuals
please refer to theVK3YNG foxhuntweb site (see theend ofthis manual).

VK3YNGSniffer 4 Instruction Manual (for V2.2 hardware)
© 2004, Bryan Ackerly, VK3YNG Rev2.2a Page 2
Introduction....................................................................................................................3
Auto Power Down..........................................................................................................4
LowBatteryIndication..................................................................................................4
DisplayBrightness.........................................................................................................4
ReducedFunctionalitymode:........................................................................................4
Quick Button Reference:................................................................................................5
AlternativeKeyFunctions:............................................................................................5
Detailed Button Operation.............................................................................................6
Mode/Power switch: ..................................................................................................6
Power On: ..............................................................................................................6
ModeSelection:.....................................................................................................6
FM Mute:...............................................................................................................6
Power Off:..............................................................................................................6
Memories...................................................................................................................7
Recall functions. ....................................................................................................7
Store functions.......................................................................................................7
SyncButton................................................................................................................8
ARDF Sync:...........................................................................................................8
Band Scan: .............................................................................................................8
Other functions: .....................................................................................................8
D-Setbutton...............................................................................................................9
Uptimeindication: .................................................................................................9
RelativeBatteryVoltage indication:......................................................................9
Firmwareversion indication:...............................................................................10
Volume Control .......................................................................................................10
Range Control..........................................................................................................10
Peak Hold Mode ..................................................................................................10
Peak rangememory..............................................................................................10
Frequency Entry.......................................................................................................11
Configuring the Sniffer................................................................................................12
Tone (RSSI) Filtering: .............................................................................................12
Minimum filtering(1):.........................................................................................12
MediumFiltering(2): ..........................................................................................12
Maximum Filtering(3): .......................................................................................12
Peak Extend modeFiltering(6):..........................................................................12
ARDF/Scan Mode:...................................................................................................12
ARDF Mode(4):..................................................................................................12
Scan Ready Mode(5): .........................................................................................12
Reduced FunctionalityMode:..................................................................................13
MaximisingBatteryLife..............................................................................................13
Sample antennadesigns...............................................................................................14
Specifications:..............................................................................................................15
Links: ...........................................................................................................................15

VK3YNGSniffer 4 Instruction Manual (for V2.2 hardware)
© 2004, Bryan Ackerly, VK3YNG Rev2.2a Page 3
Introduction
The VK3YNG sniffer is designed to allow quick, easyand accurate determination of
thedirection of a transmitted signal in either the 120-123MHz or 143-150MHz bands.
The sniffer provides enough sensitivityto determine the direction of asignal from
manykilometres or miles away. This is useful for ARDF or Radio Sport use. Italso
provides enough attenuation to accurately determinethe direction of signals rightup
to thesource of the signal withoutsufferingfrom overload or compression effects.
Attenuation (signal reduction) is provided automaticallyin steps of approximately
15dB each time a particular signal strength threshold is reached. Thenumber of 15dB
steps of attenuationis shown on an LED display. For example, a displayvalue of zero
indicates maximum sensitivity, whereavalue of 9indicates a verystrongsignal that
requires approximately135dB of attenuation.
Signal strength indication is providedbyan audibletone that increases in frequency
(pitch) with increasingsignallevel. This is donebecausethe humanear is a much
more sensitive to changes in pitchthan sound level. Thereis also no inertiaor
overshoot problems as tend to occur with signal meters. A specialsoftware algorithm
ensures that thereceivedsignal strength tone does not suffer from “compression”
effects that occur at higher signal levels with somedesigns.

VK3YNGSniffer 4 Instruction Manual (for V2.2 hardware)
© 2004, Bryan Ackerly, VK3YNG Rev2.2a Page 4
AutoPower Down
The sniffer willautomatically power down if either of the followingtwo conditions
aremet:
1) There has been no keypressed for at least 10 minutes.
2) There has been no “upward” progression in range for at least10minutes.
The sniffer willgive fiveshortbeeps just beforethe unit powers down.
LowBatteryIndication
The sniffer functions accuratelyto supplyvoltages down to approximately2.7 volts.
Below this the accuracybecomes compromised or the sniffer maypower itself down.
When power has dropped to 2.7 volts or lower, thedisplaydecimal point is enabled to
warn theuser that batteries areinneed of replacement.
DisplayBrightness
A high efficiencySevenSegmentRed LED is usedfor therange display. It has two
brightness settings, one for daytime useand asignificantlyreduced brightness level
for nightuse. Alight sensor locatedimmediatelyabovethe displayautomatically
determines thebrightnesslevel.
Reduced Functionalitymode:
This mode maybeusefulfor children or first time operators. Itallows the sniffer to be
used in its mostbasic format and hides all programmability options from the user.
This mode is veryuseful for scout foxhuntingfor example. For this reason, many
refer to this modeas “Scout Mode”.

VK3YNGSniffer 4 Instruction Manual (for V2.2 hardware)
© 2004, Bryan Ackerly, VK3YNG Rev2.2a Page 5
Quick Button Reference:
The followingtable gives quick index to key functions in both normalandreduced
functionalitymodes.
Button
Operationin Normal mode Operationin reduced
functionality mode
1 Recall channel 1 (Hold to store frequency/mode) Recall onlychannel1
2 Recall channel 2 (Hold to store frequency/mode) Recall onlychannel2
3 Recall channel 3 (Hold to store frequency/mode) Recall onlychannel3
4 Recall channel 4 (Hold to store frequency/mode) Recall onlychannel4
5 Recall channel 5 (Hold to store frequency/mode) Recall onlychannel5
6 Recall channel 6 (Hold to store frequency/mode) Recall onlychannel6
7 Band Scan or ARDF mode Startof cycle
Synchronisation function. No function
8 Range down DelaySet/Display. 1 to 5 seconds.
0=peak hold mode. (7-9 are special functions) Batterylevel
9 Volume Down No function
0 Volume Up No function
R Manual Rangeset/disable No function
F FrequencyEntry(4 digits follow) No function
M Power/Audio ModeSelect (Tone/AM/FM, Hold
for power off) Power On/Off only (instant power off)
AlternativeKeyFunctions:
The default operation mode of the sniffercan be reconfigured byholdingdown
certain keys whilepoweringup the unit. Thesniffer will maintain this operation mode
for subsequentpower up/down cycles.
Button Displayduring
power-up Function if pressed during power-up
1 n Filter “A”, Minimum Tonefiltering. (fastestresponse)
2 o Filter “B”, MediumTone filtering
3 P Filter “C”, Maximum Tone filtering(slowestresponse)
4 A ARDF mode. Synchronised at power-up. Sync key is
used to re-sync thetransmitter cycle.
5 S Scan mode. Sync key is used to scan for strongest signal
between frequency stored in channels 5and 6.
6 J Filter “D”, Tone Extend Mode. Used for veryshort
duration signals. (New function in V2.1 firmware)
7 H Normal operation. Selects normal tone range and
disables reduced functionalitymode if set.
8 L Low-Tone mode(RSSI tones atquarter frequency.
Resolution slightly reducedatlow tone frequencies)
F S Reduced key functionality mode(“scout” mode)
R t Toggle (Enable/disable) auto rangechange
announcementtones

VK3YNGSniffer 4 Instruction Manual (for V2.2 hardware)
© 2004, Bryan Ackerly, VK3YNG Rev2.2a Page 6
Detailed Button Operation
Mode/Power switch:
Power On:
Pressingthis button once powers on the unitto the frequencyand mode stored in
memory channel 1.
Mode Selection:
Pressingthis button momentarilywhile theunit is powered up cycles the unitthrough
its operatingmodes and brieflydisplays the selection on the display. Themodes cycle
through in the followingsequence:“A” – AM reception, “U” – Unmuted FM
reception, “F” – MutedFM reception and “t” – Signal strength Tone. Thecyclethen
repeats. When headphones are used, onechannel is always set to givesignal strength
tone, while the other channel follows the selectedmode. This is usefulfor hunting
different continuous carrier transmissions where thetransmitters’ identification is
given usingeither AM of FM modulation.
FMMute:
The Muted FM mode offers apseudo FM mutefunction to muteall receiver audio
when thesniffer is notreceivingasignal. This is a signal based (rather thannoise
based) mutethat activates whenever thereceivedsignal is below thelowerrange
threshold on ranges 1 upward and is always activeon range 0.
Power Off:
Pressingand holdingtheMode button for greater than 1 secondwill power down the
unit. In reduced functionalitymode, the unit will power off immediately when the
Mode button is pressed. Themode switchoperates onlyas a simple on/off switch in
reducedfunctionalitymode.
M

VK3YNGSniffer 4 Instruction Manual (for V2.2 hardware)
© 2004, Bryan Ackerly, VK3YNG Rev2.2a Page 7
through
Memories
Buttons 1 through 6allow storing and recallingof memory modes and frequencies.
Recall functions.
Pressinganyof the buttons 1 through 6innormaloperation modewill recallthe
frequencyand mode stored in non-volatile memory. In normal operation mode, the
displaywilldisplaythelast 4 digits of the selected memories frequencyin kilohertz.
For example, a stored frequencyof 147.425MHz will flash up thesequence “7 4 2 5”.
The first two (100 and 10) megahertz digits areinferred byfirstentered digit as per
thefollowingtable:
Setting of “MHz” digit Band selection
0, 1, 2 120-122.995MHz
3 through 9 143-149.995MHz
The recalled frequencyis not displayed in reducedfunctionalitymode.
Storefunctions
Pressingand holdingany of buttons 1 through 6 will resultin the selected frequency
andmode beingstored inthe selected memory. The button must be pressed and held
until two short beeps areheard in succession. This confirms that thedata has been
committed to memory.
The Store function is disabled in reduced functionalitymode.
1
6

VK3YNGSniffer 4 Instruction Manual (for V2.2 hardware)
© 2004, Bryan Ackerly, VK3YNG Rev2.2a Page 8
Sync Button
ARDF Sync:
This facilityis used to synchronisethe receiver for useininternationalstyle (ARDF)
foxhuntingfor a one-minute cycle, five-transmitter system.
In ARDF modethis timer is automatically synchronized when the receiveris switched
on. Threeshortbeeps are generated as confirmation of this mode.
PressingtheSyncbutton re-synchronises this timer. Threeshortbeeps are given to
confirmthis button has beenpressed. Thesync button should be pressed at thestart of
transmitter one’s cycle.
At 50 seconds into thecycle, the sniffer willgeneratethree short beeps giving10
seconds warningthatthe current transmitter’s cycle is abouttoend. If the sniffer is
currentlyreceivingat range1 or lower, at four seconds beforethe completion of the
current transmitter cycle the sniffer broadcasts anumber of beeps correspondingto
thenumber of thetransmitter in the cyclewhich is about to commence. The pitch of
these beeps is set slightly lower than the “50-second”beeps. Thedisplayalso briefly
flashes the number ofthe nexttransmitter.
Band Scan:
When ARDF modeis notselected, the “7”keyperforms a basicband scan operation
wherethe sniffer hunts for thehighest signalbetween the two frequencies stored in
channellocations 5 and 6. Thehighest signal found is stored inchannel 4. The scan
will ignoreanysignals within approximately 10KHz of the frequency stored for
channel1 and the signalmustbedetectableat range2 or higher to bestored.
This operation takes some time to complete, especiallyif thereis large frequency
difference between channels 5 and 6. The scan function works bestfor continuous
signals and maynotproperlydetect intermittent transmissions. Channel5 must be
lower in frequencythan channel6 andbothfrequencies mustbewithin thesame band
(i.e. 120MHz or 140MHz)
Other functions:
In ARDF mode, if a rangedown delay(d-Set) of zero is selected and thesniffer is not
currentlyconfigured for manual ranging, the sniffer willautomatically selectrange
zero at thestart of the nexttransmitters’ cycle regardless of the current signal
strength.
Holdingthe “7”keyduringpower-up cancelsthe Low RSSI Tonemode and the
ReducedKeyFunctionalitymode. In this mode the signal strength tones function
normallyand the maximum signal strength pitchis 8KHz. This mode is set as the
factory default.
This keyis disabled in reducedfunctionality mode.
7

VK3YNGSniffer 4 Instruction Manual (for V2.2 hardware)
© 2004, Bryan Ackerly, VK3YNG Rev2.2a Page 9
D-Set button
Rangingup on the snifferhappens automatically with minimaldelay. To implement
short term peak detection, there is an intentionaldelaybefore the sniffer ranges down.
This delay is programmablebetween 1 and5 seconds usingthe D-Setbutton. For
beginners, avaluebetween 3 and5 seconds is recommended. For more advanced
users, 1 or 2seconds gives better results. When huntingintermittentand veryshort
durationtransmissions such as those used on wildlife, 5 seconds or “peak hold” mode
(seebelow) is recommended. The factorydefault is 2 seconds.
Tosetthe rangedown delay, press the“D-Set” button. The displaywill respond by
displayingthe letter “d”. Pressing buttons 0 through 5 will then set andstorethe new
range down delay.
PressingtheD-set(7) button twicewill brieflydisplaythe current range down delay
in seconds. Thedisplaythen reverts to displayingthe current range.
Setting a range down delay of zero disables down ranging.In this casethe sniffer
operates ina“peak hold” modeand down rangingis disabled. Manual rangingis
disabledand pressingthe “range”button willresetthecurrentpeak hold range to
zero. This mode is usefulwhen huntingextremelyintermittent signals suchas wildlife
or model aircraftbeacons.
Holdingthe “D-Set” keyduring power-up causes the sniffer to operate in lower tone
RSSI mode. This modemayprove usefulto thosewho havedifficultyhearinghigher
audio frequencies. In this modethe signalstrengthtonefrequenciesare divided by4.
The top tonepitch is limited to about2KHz and resolution becomes slightlylimited at
thelowest tonefrequencies. (Note: this mode has no effect onthe pitch of supervisory
beep and tonefrequencies)
This keyis disabled in reducedfunctionalitymode.
Uptimeindication:
Pressingthe“D-Set” button then pressing “7” will display4 digits indicatingthe
number of hours andminutes since thereceiver was powered up. This can be useful
for ARDF events where theuser mayhave forgottentosynchronise their watch.
RelativeBatteryVoltageindication:
Pressingthe“D-Set” button then pressing “9” will displaytwo digits giving an
indication of therelativebatterycapacityin percentageterms. 99% indicates a full
batterywhile 0% indicates the point where sniffer operation is significantly
compromised. The sniffer maypower itself off before reaching0%.
8

VK3YNGSniffer 4 Instruction Manual (for V2.2 hardware)
© 2004, Bryan Ackerly, VK3YNG Rev2.2a Page 10
Firmwareversion indication:
Pressingthe“D-Set” button and thenpressingthe “F” button will display4 digits
which indicatethe installed firmware version.
Volume Control
During normal operation, the “9” and“0” buttons allow the settingof volume. The
displaybrieflyshows thenewlevel and reverts to displaying the current rangewhen
thebutton is released. These buttons are disabledin reduced functionalitymode.
Range Control
Normallythe sniffer automaticallyselects thebestrange for the currentlyreceived
signal. In somesituations it maybe necessaryto range the sniffer manually. Therange
control button canbeused for this purpose. This button also controlsanumber of
other features dependingon the mode selected.
In auto-rangingmode, pressingthis button brieflydisplays theletter “r”in the display,
andthen the displayreverts to displayingthe currentrange. Pressinganydigit then
manuallyselects therange. The displaybrieflydisplays “r”followedbythe selected
range. The sniffer remains in manualranging mode until defeated by pressingthe “R”
button a second time. This re-enables auto-ranging.
Holdingthis keyduringpower-up toggles thestateof the“rangetone announcement”
flag. When this flagis set, the sniffer generates a “be-bop” tonesequencewhenever
thesniffer ranges up or down. The frequencyof thetones gives theoperatoraudible
indication of thecurrentrange and thedirection of thechange. When this flagis
cleared, range changes happen without announcement.
This keyis disabled in reducedfunctionalitymode.
Peak Hold Mode
This range button also resets thepeak rangehold function if the down range delay (D-
set) is set to zero. In peak hold mode, manual rangingis disabled.
Peak range memory
If the range button is pressed twice in succession, the display will brieflyshowthe
maximum range the sniffer has achieved sincepower up or thelast successful
frequencychange.
In ARDF mode, (see Sync button section) the peak rangevalue is automaticallyreset
at30 seconds into the current transmitter cycle. This is very usefulifthereis a need to
check whatrange thesniffer got to just beforethe previous transmitter finished its
cycle.
This function is not available when Peak Holdmode(dSet=0) is selected.
R
9 0

VK3YNGSniffer 4 Instruction Manual (for V2.2 hardware)
© 2004, Bryan Ackerly, VK3YNG Rev2.2a Page 11
Frequency Entry
The sniffer can operate atany frequencyin the range120.000-122.995 and143.000 -
149.995MHz in 5KHz steps. Pressingthe “F” button initiates frequencyentry. The
displayconfirms this bydisplaying“F”. The sniffer then expects four digits to be
keyed in to set thedesired frequency. If anerror occurs whileenteringfrequency, the
letter “E”is brieflydisplayed and the sniffer then reverts to the previous operation
frequency. Thefirstdigitsets both the 1MHz frequencyand the band. 0 through 2 sets
the120MHz band. 3 through9 set the140MHz band.
Factorydefaultfrequencies
Memory Frequency Mode
1 145.300MHz Tone
2 145.700MHz Tone
3 144.250MHz Tone
4 146.500MHz Tone
5 121.500MHz Tone
6 146.575MHz FM
Note: 121.5MHz is used as aninternationalpersonal, maritime andaeronautical
distress beaconfrequency. With an appropriate antenna, the sniffer can be used to
locate ELT and EPIRB emergencybeacons.
For the scan functiontowork correctly, thefrequencies stored inchannels 5 and 6
should be in thesame band. This is not thecase for the factorydefaultconfiguration.
Direct frequencyentryis not permitted in reduced functionalitymode.
F

VK3YNGSniffer 4 Instruction Manual (for V2.2 hardware)
© 2004, Bryan Ackerly, VK3YNG Rev2.2a Page 12
Configuring the Sniffer
The MK4 sniffer has a number ofconfigurablefeatures. Some of thesehave already
been described in theprevious sections. Therestare explained here.
Tone (RSSI) Filtering:
There arefour levels of filtering available on theMK4 sniffer. These areselected by
holdingbuttons 1, 2, 3or 6 when poweringup the sniffer. Thesniffer will retain this
settinguntil thenext time itis changed.
Minimum filtering (1):
This leveloffilteringis the sameas the original MK4. It offers the fastestand most
accuratetrackingof the received signallevel. On transmitters with ahigh AM
component, the tone can become quite “thick” soundingas the tonetries to partially
track themodulation. This settingis thefactory default.
Medium Filtering (2):
This leveloffilteringoffers thebestcompromise betweenresponsetimeand
Amplitude modulation (AM) filtering.
MaximumFiltering (3):
This mode provides maximumfilteringof the received signaland is similarto thatof
theVK3TJN/XAJ Ultra-sniffer. While this modeoffers the best smoothingof
received signals itcan tend to “blur”the definition of shortduration pulses.
Peak Extend modeFiltering (6):
This is a specialmode for usewith veryshort duration repetitivesignals such as those
emitted fromwildlife or modelaircraft transmitters. The transmitters used are
typically verylow power and transmit for around 40 milliseconds every second or
two. The tone pitchand therefore signaldirection can be veryhard to determineusing
theabove filteringmodes.
This special modeextends the timeof the peaklevelof thereceived signal so that the
user can easilycompare thesignal level fromdifferent directions.
ARDF/Scan Mode:
ARDF Mode (4):
Holdingthe “4”button while poweringup puts the sniffer into ARDF mode. In this
mode the sniffer will power up giving three beeps and will synchronise the ARDF
timer. For more information see thesection on the SyncButton.
ScanReadyMode(5):
Holdingthe “5”button while poweringup puts the sniffer into scan readymode. In
this mode thesniffer gives a singlebeep during power up and thesyncbutton
executes aband scan function. This is the factorydefault. For more information see
thesection on the Sync Button.

VK3YNGSniffer 4 Instruction Manual (for V2.2 hardware)
© 2004, Bryan Ackerly, VK3YNG Rev2.2a Page 13
Reduced Functionality Mode:
In this mode, most of the special features of the sniffer are disabled. This mode is
usefulwhenanewcomeror a scoutgroup etc uses the sniffer. (Hencewhysomeusers
callthis “Scout Mode”)Memoriescan onlybe recalled and mostof theother keys,
includingvolume controlare disabled. Thepower button onlyacts as a simple on-off
andthe modeof operation is defined bywhat is stored for each channel.
Tosetthe sniffer in reduced functionalitymode, press and hold the “F”button while
poweringup.
Tocancel reduced functionalitymode, press and hold the “7”keywhile poweringup.
Maximising BatteryLife
There areanumber of solutions for extendingbatterylife with thesniffer. The most
criticalone is the volume setting. Batterylifeis reduced considerablywhenusingthe
internal speaker onahigh volumelevel with a continuous signal. Usethe lowest
volumelevelpossible when usingthe internal speaker or use external headphones.
The displayalso operates at a higher intensitylevel for daytimeusethat puts more
load on the battery. Typicallynighttimeonlyoperationincreases alkalinebatterylife
byabout30%.
Users who would like to get thelongest use between batterychanges should consider
usingLithium AA batteries. These batteries have a verylongshelf lifeand capableof
providingwellover 14 hours of continuous daytimeoperation.
Do not usesingle cell NiCd or NiMh batteries as their terminal voltage (1.2V) is too
low. ZincCarbon and General Purpose Manganese batteries are also not
recommended. (For the technicallycapable however, it is possible to modifythe
sniffer to runoff three AA NiCd or NiMh batteries bythe external addition of an extra
single cell AAbatteryholder. Capacityof NiMh batteries nowadays is rapidly
approachingthat ofstandard Alkalines)

VK3YNGSniffer 4 Instruction Manual (for V2.2 hardware)
© 2004, Bryan Ackerly, VK3YNG Rev2.2a Page 14
Sample antenna designs
The antenna design is largelyamatter of personalchoice. For portable use, designs
varybetween two and four elements. Moreelements give better directivity and more
precise bearings but aremore difficult to carryaround. For most situations, three
elements offer a good compromise. Hereis an example of antenna designs for 120
and146MHz.
Director
Driven Element
Reflector
Frequency:
Director
Driven Element
Refelector
121MHz
1118
1178
1237
146MHz
930
981
1029
Tap Length 138 115
Element Spacing 373 311
Balun Length 815 680
Tap Length
25mm
(centre tocentre)
A B
Sniffer Mounting Plate
73 x80mm
Element Lengths fromTiptoTip
All unitsinMillimetres (divide by 25.4for inches)
Element Material: 10mm aluminiumtubing
Tap lengths are typical and may require adjustement
Typical 3-element BeamAntenna (based on VK3VT design)
Balun
(RG174 coax cable)
BNC Connector

VK3YNGSniffer 4 Instruction Manual (for V2.2 hardware)
© 2004, Bryan Ackerly, VK3YNG Rev2.2a Page 15
Specifications:
FrequencyCoverage 120-122.995MHz, 143-149.995MHz in 5KHz steps
Channel Bandwidth 16KHz
Sensitivity Better than -120dBm
Maximum signallevel +30dBm
Power Supply 3VDC (2xAA Alkaline orLithium penlight cells)
BatteryLife* Typically 3+ hours (alkaline), 14+ hours (Lithium)
Memories 6, programmable (stores modeand frequency)
Receivemodes AM, FM, Signal strength Tone
Max RSSI frequency Programmable2KHz or 8KHz
Size 76mm(W), 80mm(H), 25mm(D) not includingBNC
connector
AntennaConnection BNC
HeadphoneConnection 3.5mmstereo
*Note: Battery life is dependant sound level and displayintensity. See section on
batterylife.
VCO
PLL
Atten RF
2nd L.O.
10.7MHz 455KHz
Detector
Regulator
CPU
Keypad
Pwr Supply
5V
3V
3V Batt
DAC
FM
AM
Tone
RSSI
LDR
Gain
Tune
Ant.
120-150MHz 120-150MHz
VK3YNG Sniffer MK4 - Block DIagram
2V5
Links:
More information on foxhuntingand techniques can be found on these websites:
Australian ARDF website:
http://www.ardf.org.au
Joe Moell’s Foxhuntingwebsite. (A verygood foxhunters resource)
http://www.homingin.com
Author: Bryan Ackerly,VK3YNG
Web page: http://www.foxhunt.com.au
Email : [e-mail] (please includethe word “MK4”or “sniffer”in the
subject title)
Phone [phone] Fax:[phone]