Icom IC-7300 Manuale utente
GETTING THE MOST FROM YOUR HF
TRANSCEIVER
FRED KEMMERER, AB1OC
JANUARY 10TH, 2017
Topics
2
Not to Scale
•Its mostly about the receiver…
•Transmitter/amplifier operation tips
and tricks
•Common operating scenarios
3
VFO
Tuning
Audio
Gain
RF
Gain
”Roofing”
Filter*
Adjusts *’ed
Items
Preamp/
Attenuator
Notch
Filters*
Noise
Reduction/
Blanker*
Passband
Tuning
(DSP) Filter &
IF Shift
Pan Adapter/
Spectrum Scope
Its Mostly About The Receiver
Commonly Available Controls
Multi-Function Screen
Access
Function
Screen
CW Auto
Tune
Receive
Incremental
Tuning
Operating
Mode
Its Mostly About The Receiver - Some Terms
Bandwidth, Dynamic Range and Signal to Noise Ratio
4
Not to Scale
•Bandwidth – tools to limit your receiver so it “hears” only
what you want to hear and to protect it from overload
•Mostly about filters
•Dynamic Range –the difference between the loudest and
the weakest signal you rig can handle
•Want to maximize Dynamic Range for the target signal
•Mostly about adjusting for optimum RF gain and
operation of Automatic Gain Controls
•Signal to Noise Ratio –the relative power between the signal
you are trying to hear (good) and noise/interference (bad)
•Noise reduction processors to reduce noise along with
proper use of other controls
Its Mostly About The Receiver
Basic Receiver Elements (Single Conversion Analog)
5
Not to Scale
AGC Loop(s)
Bandpass
Filter
“Roofing”
Filter
“DSP”
Filtering
•Filters limit Bandwidth to reject unwanted signals, preventing them from
adversely effecting performance
•The Automatic Gain Control (AGC) System attempts to maximize Dynamic
Range within Weak Signal Receiver Stages
•Critical to maintain linearity to prevent distortion products
•DSP Adaptive Filters are use to reduce noise which improves S/N Ratio
(Pre)
Its Mostly About The Receiver
Basic Receiver Elements (Direct Sampling ex. IC-7300)
6
•Most filtering, all noise reduction and signal detection
steps are performed digitally
•AGC System must maximize A/D converter resolution for
the desired signal
•Many possible sources of non-linearity are eliminated
•A/D Converter Resolution and Oscillator Phase Noise become the
main performance limiters
•Digital processing speed and algorithm performance also matter
A/D
Digital
Proc.
(FPGA)
RF (Pre-)
Amplifier
Bandpass
Filter
D/A
Digital
Osc.
AGC Loop, IP+
Its Mostly About The Receiver
Controls to Optimize Weak Signals
7
Not to Scale
•Filters Limit Bandwidth and optimize adjacent signal rejection
•RF Gain Control, Preamp/Attenuator, and AGC Time Constant settings
optimize Dynamic Range
•Adaptive Noise Filtering is used to reduce noise; improving S/N Ratio
RF
Gain
Adjusts *’ed
Items
Preamp/
Attenuator
Noise
Reduction/
Blanker*
Passband Tuning
(DSP) Filter & IF Shift
Access Function Screen
(AGC Controls)
Its Mostly About The Receiver
Using Your Filters
8
Not to Scale
Minimize Noise BW/Interference:
•Roofing Filters – typically “fixed” BW
filters applied before IF stages
•DSP filters –Digital Signal Processing
after IF stages
•Both are realized in Digital Processor
of the IC-7300
IF Shift Example
Its Mostly About The Receiver
CW Reverse Sideband (CW-R)
9
Not to Scale
CW-R
Sideband
VFO
Freq.
Standard CW
Sideband
Desired Signal
Interference
VFO
Freq.
Reversing CW Sideband to Improve Adjacent Signal Rejection
Its Mostly About The Receiver
Dynamic Range –Its About Optimal Gain Control
10
A/D
Digital
Proc.
(FPGA)
RF (Pre)
Amplifier
Bandpass
Filter
D/A
Digital
Osc.
AGC Loop, IP+
A/D Range
00..0
11..1
+
Too Little Base Gain
(Preamp Helps)
A/D Range
00..0
11..1
+
Optimal Base Gain
A/D Range
00..0
11..1
+
Too Much Base Gain
(Preamp Off/Attn.)
AGC Acts To
Keep A/D in
Range
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