Upload
harold-greene
View
220
Download
0
Tags:
Embed Size (px)
Citation preview
Goal of this Presentation
• Arm you with a strategy to choose a radio that’s appropriate to your individual situation• A number of radios will be used to illustrate various
criteria, but any radio can be evaluated in the same way• NOT to promote or disparage any radio or brand vs. any
other……but my own definition of value will inevitably creep in• I invite you to comment on your own definitions of value!
Reference SourcesMost of this material came from somewhere else…• Sherwood Engineering: RMDR, IMDR measurements• ARRL • Product reviews: lab-grade testing, plus color commentary• “Test Procedures Manual”: measurement methods
• VA7OJ, I2VGO, Linearizer Technology Inc.: noise power ratio• Clifton Laboratories: AGC measurements• Audio Systems Group: compiled transmitter spectra from ARRL Lab• Company and distributor materials• eHam classifieds: used equipment prices
Situations
• New ham – bewildering amount and variety of information• Capability upgrade – more effective communications• Use modes• Casual vs. competitive• Home vs. road• Standalone vs. transverter• Dominated by CW / SSB / Digital• Your predilection here!
How did you choose your last radio?… and how do you feel about that decision today?• Opinions of personal or on-air acquaintances• On-air observations• Online, magazine reviews• Company web sites, hamfest exhibits, email reflectors• Online chat room, special interest group web site• Technical blogs• Previous experience with a brand or model• e.g., at your local / favorite multi-multi contest operation!
Radio Selection Criteria
• Price and “features” – one piece of an entire station• Receiver – you can’t work ‘em if you can’t hear ‘em• Transmitter – you mean, this matters?• Interface – logging programs, digital modes• Ergonomics – initial setup, on-the-air operation• “Intangibles”
Price and FeaturesA Balancing Act
• Price• New vs. “pre-owned”• Recent models may have significant hardware revisions
• Band coverage, transverter interface• Output power, ATU• Display
• “Character” vs. “Graphical”• Bandscope, touchscreen menu buttons
• Interface convenience• Upgrade path: filters, functions, features• Power supply: internal vs. external• Size, weight
Receiver-Specific Criteria
• Ability to hear desired signals• Sensitivity• No longer an issue at HF vs. atmospheric noise• May be important if you want to use with transverter
• Selectivity• Hardware – L-C, ceramic, crystal, mechanical filters• Software – DSP – bandpass, notch, noise reduction
• Distortion – audible “junk” created in the receiver• Listening fatigue – how it “sounds”• Audio distortion• Response to impulse noise
Contesting: a Dynamic Environment• “Running” produces higher scores than “S&P”• “Loud” stations do more running• “Not loud” stations do more S&P
• If you’re running, “not loud” stations will be calling you …• … while you are surrounded by other “loud” stations
• When you S&P, you may be calling “not loud” stations…• … while they are surrounded by “loud” stations
• CQ WW 2014 log submissionsPower CW SSB
High 3011 (41%) 3240 (41%)
Low 3821 (52%) 4337 (55%)
QRP 505 (7%) 344 (4%)
Simplified Receiver Block DiagramWhat Could Possibly Go Wrong?!• Active stages are not
perfectly linear• Active and passive
stages can overload• Mixing is multiplication:
inherently nonlinear!• Mixers mix everything
at their inputs
Local Oscillator
IF Amp, Detector
Audio Amp
Preselector IF Filter
Antenna
Speaker
RF Input
Local Oscillator
Image
Desired IF OutputAm
plitu
de
Frequency
IF Filter Passband
Mixers Mix Everything at Their InputsPhase noise, distortions “smear” spectra• Real world oscillators produce
noise sidebands• Amplifier nonlinearities, ALC, CW
rise/fall times spread the spectra of input signals• Multiple signals appear at the
mixer’s RF input• Result: noisy jumble in the IF
RF
LO
Image
Desired IF Output
Ampl
itude
Frequency
Reciprocal Mixing (RM)• “…noise generated [by] the mixing of the First Local Oscillator’s Phase Noise and a strong adjacent, steady signal.”
“Clean” RF source
RF
LO
ImageDesired IF Output
Ampl
itude
Frequency
Step Atten
Receiver 14.02314.027
14.025MHz
ANT
Audio Distortion
Meter
Low-noise
XTAL Osc
SPKR
Measurement Setup
TS590
IC7700
IC7700
FTDX3000
IC9100
TS990
TS990
Flex3000Eagle
TS590Flex5000
FTDX5000
KX3
K3?
Flex6300
Flex6700
Pric
e* (U
SD)
756P2(IR)
IC7600
K3
RMDR (dB) = SRF (dBm) - MDS (dBm)
Notes:* RED = retail,
BLACK = used
Intermodulation Distortion (IMD)• “…range of signals that can be tolerated by the [receiver] while producing essentially no undesired spurious responses.”
RF1 2
LO
ImageIMD 2 1
Desired IF Out
1 2 IMD
Ampl
itude
Frequency
Hybrid Combiner
Receiver 14.002
ANT
Audio Distortion
Meter
RF Gen 214.000
SPKR
2-kHz Measurement Setup
Signal Analyzer
Hybrid Combiner
RF Gen 3 14.002
Step Atten
RF Gen 113.998
IC7000
FT2000
FT1000D
FT1KMPV(IR)
IC756P
FT1KMP(IR)
756P2 TS590*
IC7700*
IC7700*
IC7800*
K2*
OmniVI+
FTDX3000*
IC9100
TS990
TS990
Flex3000*
Eagle*
ArgVI*
TS590*Orion
OrionII
Flex5000
FTDX5000*
KX3
K3
Flex6300
Flex6700Pr
ice*
* (U
SD)
756P2(IR)
IC7600*
K3*
OmniVII
IM3DR (dB) = SRF (dBm) - MDS (dBm)
TS830S/YK88
Noise Power Ratio (NPR)• “… white noise is used to simulate the presence of many carriers of random amplitude and phase.”
NPR Measurement Setup
Tune RX to fnotch
IC7000FT1KMP-V
IC7700
IC7800
FTDX3000
IC9100FT950 TS590
KX3
Flex6700
Noi
se P
ower
Rati
o (d
B) (V
A7O
J)
IC7600
K3
• No clear correlation vs. IM3DR• A new “numbers race?”
Listening FatigueHow the Radio “Sounds”• Commonplace “10% THD” spec produces tiring audio
• Distortion -20dB from desired signal
• Example• IC756 Pro III must be driven into clipping to meet the 2 W
into 8 ohm brochure spec.• Many audible spurs
• Spurs disappear at lower audio output• <0.1% distortion• Easy to listen for long periods
Listening FatigueHow the Radio “Sounds”
• Early K3 users complained about “scratchy” audio• 40dB down = 1% distortion• Many audible spurs
• Adding output choke attenuated spurs• 0.1% distortion• Easy to listen for long periods
AGC Controls• Purpose
• Reduce distortion• Prevent damage to operator!
• Implementation: reduce gain in presence of strong signals• How fast and how much?• Then what?
• Optimizing AGC parameters key to performance in wide range of signal environments• e.g., shape of decay action can affect
AGC-related IMD C L
Transmitter-Specific CriteriaKnow the properties of your transmitted signal• CQ WW rules: “Signals with excessive bandwidth (e.g., splatter, clicks)” may
disqualified for unsportsmanlike conduct”• SSB: optimize audio chain for communicating effectiveness
• Mic: “pin 1” problem• Frequency tailoring: accentuate the positive, eliminate the negative• Amplitude compression: AF vs. RF, level• Background noise: clean transmission and clean reception (AGC)
• CW: control rise/fall for “appropriate” bandwidth• Digi: internal vs. external signal generation• ALC behavior• (ATU matching range)
Transmitter: ARRL Lab Test Data*Revealing side-by-side comparisons
* Mfgr data for Flex
60WPM Keying Spectral Data
CW Rise TimeA Little Goes a Long Way
TR=3ms
TR=10ms
• 1 “dit” time = 1.2/WPM (W5ALT)
• 30WPM 1 dit = 40ms• 50WPM 1 dit = 24ms
10ms rise, fall fast enough!
TR=3ms TR=10ms
ALC
• ALC too fast: distortion, IMD• ALC too slow: overshoot could
damage linears that only need 40 to 60 watts of drive• ALC overshoot often
worse at reduced power• ALC “artifacts” can be
very troubling
No ALC
ALC Half Scale
60 dB down 1.8 kHz away
4 kHz -60 dB
Rig power set to 50W
PC-to-Rig “Direct” Interface Example• Analog Interface: Line In / Line Out• “Soundcard” digital modes• SSB “digital voice keyer” (DVK)• Digital voice (e.g., FreeDV)
• Digital Interface: RS232, USB, FW• CW: LPT is dead!• SSB: built-in DVK• Digi: “native” DSP capabilities
Soundcard-to-Rig Interface Example• Isolates transmit and
receive audio• PTT, CW, FSK rig
control• COM or USB• Essential:
compatibility between interface S/W, OS, interface and rig
ErgonomicsAccess to radio controls
• Setup: menu confusion?• Most-used operational controls• Knob/button/readout size,
spacing, grouping• Confounded multi-functions?
• Visibility from operating position• Display – too “busy?”• Controls – label size, color?
• Keyboard-radio reach fatigue• Physical size, weight
ergo.human.cornell.edu/AHTutorials/typingposture.html
Where is the radio?
“Intangibles”
• Reliability• What breaks?• How often?
• Serviceability• Foreign vs. domestic service depot• Discontinued support• ROHS and older radios
• Manufacturer, distributor longevity• “Crowd” support and online discussion groups
Decisions, Decisions, Decisions
• There’s a lot to consider when choosing an HF transceiver• Winner may not be obvious• Make a list of your priorities• “Score” candidates against your
priority list• Tally up the score to select a winner…
• … or choose a different radio for “intangible” reasons• “I just had to try that radio!”
Parameter Importance (1-5)
Score(1-5)
Parameter Score
A 5 4 20
B 4 4 16
C 3 5 15
D 2 2 4
Total 55