ICOM IC-7300 User Evaluation & Test Report - Adam, VA

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IC-7300 User Evaluation & Test Report

Reprinted by DX Engineering with permission of the author. 26 April 2016

By Adam Farson VA7OJ/AB4OJ

Iss. 1, April 14, 2016.

Figure 1: The Icom IC-7300.

Introduction: This report describes the evaluation of IC-7300 S/N 02001981 from a user
perspective. Appendix 1 presents results of an RF lab test suite performed on the radio. I
was able to spend a few days with the IC-7300 in my ham-shack, and thus had the
opportunity to exercise the radio’s principal features and evaluate its on-air behavior.

1. Physical “feel” of the IC-7300: The IC-7300 is fairly small and light, considering that
it is a full-featured 100W-class transceiver with a built-in ATU. The case dimensions are
240(W) × 238(D) × 95(H) mm and the radio weighs 4.1 kg.

The IC-7300 features a large color touch-screen display. This is an innovation in Icom’s

“base” HF transceiver product line, offering easy band/mode selection and navigation
through the radio’s menus. The placement of many control functions on the touch-screen

and in the MULTI knob menus has moved many controls off the front panel.

Owners of current Icom IF-DSP transceivers should find the IC-7300 quite familiar, and
should feel comfortable with it after a little familiarization with the touch-screen. In
addition to the display, the front panel has a number of feature keys in location similar to
those on other Icom radios as well as two concentric knobs (Twin PBT, AF Gain + RF
Gain/Squelch) and MULTI to the left and right of the display respectively. Pressing the
MULTI knob opens a context menu on the right edge of the screen; this menu changes
with the previously-selected mode or function, allowing adjustment of appropriate
parameters. The learning curve will be minimal for owners of other Icom IF-DSP radios.
The Twin PBT and MULTI controls are multi-turn and detented. The main tuning knob is
large and has a knurled Neoprene ring and a rotatable finger-dimple; it turns very
smoothly with minimal side-play.

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The standard 8-pin MIC socket, and the 3.5mm PHONES jack, is on the left side of the
front panel. The supplied HM-219 hand mic or any other compatible electret or low­impedance dynamic mic can be plugged into the mic jack. (A dynamic mic requires a
series blocking capacitor.) All the ports provided on other Icom radios are on the rear
panel, including a USB “B” port and the 13-pin DIN ACC socket. There is no front-panel
USB port. A large muffin-type cooling fan is also mounted on the rear panel.

The SD card slot for memory storage and loading, recording and firmware upgrade is
below the AF/RF Gain/Squelch knob. A screen capture function (enabled via menu)
allows capture of the current screen image to the SD card as a PNG or BMP file by
briefly pressing the POWER key. The image can also be viewed on the screen via menu.

The IC-7300 is solidly constructed and superbly finished. Like other Icom radios, it
conveys a tight, smooth, and precise overall feel. The die-cast alloy chassis also serves as
a heat dissipator, and the sheet-steel case is finished in an attractive black crinkle coating.
The front panel has a smooth, matte surface.

2. IC-7300 architecture: Icom is the first Japanese amateur radio manufacturer to offer
an HF/6m transceiver embodying direct-sampling/digital up-conversion SDR
architecture. In the receiver, the RF signal from the antenna feeds a high-speed ADC
(analogue/digital converter) via a preselector. This is a set of bandpass filters which
protect the ADC from strong out-of-band signals. The ADC digitizes a portion of the HF
range defined by the preselector; the digital output of the converter feeds the Field­Programmable Gate Array (FPGA) which is configured as a digital down-converter
(DDC) and delivers a digital baseband, 12 kHz wide and centered on 36 kHz, to the DSP
which carries out all signal-processing functions such as selectivity, demodulation etc. A
DAC (digital/analog converter) at the DSP output decodes the digital signal back to
audio. Figure 2 is a simplified block diagram.

Figure 2: Simplified block diagram of IC-7300.

The FPGA also delivers a 1 MHz-wide digital video signal to the Display Processor,
which manages the screen displays, including the fast FFT spectrum scope, waterfall,
audio scope and audio FFT (spectrum analyzer) as used in other Icom transceivers (7700,
7800, 7850/7851). The spectrum scope has a maximum span of ±500 kHz, adjustable
reference level (-20 to 20 dB), video bandwidth and averaging, and minimum RBW ≤ 50
Hz.

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A unique “touch-tune” feature allows quick tuning to a signal displayed on the scope by
touching the scope or waterfall field to magnify an area, then touching the desired signal
within that area.

In the transmitter, the audio codec converts mic audio to a digital baseband, which the
DSP then processes further and the digital up-converter in the FPGA then converts to a
digital RF signal at the transmit frequency. This signal is converted to analog by the high­speed DAC to the RF excitation for the PA Unit.

The IC-7300 incorporates a relay-chain type auto-tuner with a nominal 3:1 VSWR
matching range. The tuner is in the signal path on receive and transmit, and can be
bypassed when not required.

3. The touch-screen: The large (93 × 52 mm) color TFT touch-screen displays a very
clear, crisp image, with excellent contrast and color saturation, and an LCD backlight.
The home screen (see Figure 1) displays the current frequency in the upper field, the bar­graph meter in the middle and the spectrum scope in the lower field. The first two keys
below the screen, MENU and FUNCTION, are unique to the IC-7300. The third key,
M.SCOPE, moves the spectrum scope to the middle field; a different screen, selected via
the MENU key, can be opened in the lower field (e.g. a multi-function meter, RTTY
decoder or CW keyer controls, depending on mode). The waterfall is activated via the
EXIT/SET key at the bottom right of the home screen; a reduced-height scope and
waterfall can be displayed on the home screen via an EXIT/SET menu parameter.

When the Twin PBT knobs are rotated, a bandwidth/shift pop-up appears, and the
trapezoidal icon at the top centre of the screen changes, a dot appears to the right of the
icon. Pressing the inner PBT knob clears the Twin PBT setting. Pressing the MULTI
knob opens a menu with RF PWR, MIC Gain, COMP and MONITOR settings. A setting
is changed by touching its icon and rotating the MULTI knob. The MULTI knob menus
are context-sensitive; for example, pressing and holding the NB key activates NB, and
displays NB settings when the MULTI knob is pressed. RIT and ΔTX are adjusted by
pressing their respective keys on the top right of the front panel and rotating the MULTI
knob without pressing it. The CLEAR key clears these functions.

Pressing and holding the Notch, NR and NB keys makes their settings accessible from
the MULTI knob. These can be used to select notch width, NR level and NB parameters
respectively. When MN is selected, a pop-up displays its width.

TPF (Twin Peak Filter) can be activated via the MULTI menu in RTTY mode.

The menus are somewhat akin to those in other current Icom DSP radios. I found the set­up process fairly intuitive after consulting the relevant user-manual sections in cases of
doubt. Icom continues the use of a “Smart Menu” system which changes available
functions in a context-sensitive manner based on the mode currently in use.

Different screens are selected by pressing the MENU key on the bottom left of the screen.
Menu selections with default values can be returned to default by pressing and holding
their DEF softkey. Many of the screens have a “Back” arrow key to return to the previous
screen.

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The MENU screen includes a “SET” icon which opens a list of the 7300’s configuration

settings arranged in a hierarchy which is easily navigable. The desired line in the on­screen table can be selected via the MULTI knob or up/down arrows.

The FUNCTION key opens a screen with switches for functions such as AGC, COMP,
IP+, MONItor, VOX, BK-IN etc. Some of these (NB, NR, Preamp/ATT, NOTCH)
duplicate front-panel keys.

The QUICK key opens a context-sensitive Quick Menu for rapid configuration or default
setting of various menu functions.

Touching the leading (MHz) digits of the frequency display opens a band-selection
screen; the desired band is selected by touching its designator. Mode selection is similar;
touching the current mode icon opens the mode-selection screen. Tuning steps for kHz
and Hz are set by touch, or by touch/hold, on the respective digit groups.

The filter selection and adjustment procedure is similar to that on other Icom DSP radios.
Touch the FIL-(n) icon to toggle between FIL-1, FIL-2 and FIL-3. Touch and hold this
icon to adjust the filter bandwidth and select CW/SSB Sharp/Soft shape. All IF filters are
continuously adjustable. As in other Icom IF-DSP radios, filters with 500 Hz or narrower
bandwidth have the BPF shape factor, but a non-BPF filter can be configured via Twin
PBT.

The Time-Out Timer feature limits transmissions to a preset duration (3, 5, 10, 20 or 30
minutes, selectable by menu.) RF PWR can be turned down to 0. This feature is useful
when receiving via active antennas or mast-mounted preamplifiers without T/R
switching, or to avoid damaging test equipment when conducting receiver measurements.

The AUDIO screen displays an audio FFT spectrum analyzer and oscilloscope very
similar to those implemented in the IC-7851, IC-7800 (Firmware V3.00 and higher) and
IC-7700 (V2.00 and higher). This feature is very helpful in setting up one’s transmit
audio parameters, and also for visual audio assessment of a received signal.

4. Receiver front end management: The P.AMP/ATT key toggles between Preamps 1
sand 2, and an 18 dB RF attenuator. The RF Gain/Squelch control functions as an RF
Gain control when rotated counter-clockwise from 12 o’clock; an on-screen RFG icon
lights when RF Gain is active.

The input level limit for a direct-sampling receiver is the ADC clip level, where the

digital output of the ADC is “all ones”. When the ADC clips, the receiver can no longer

process signals. Thus, the 7300 provides means to prevent this condition from arising.
When the ADC starts clipping, a red OVF (overflow) icon lights to the right of the filter
selection icon. At this point, rotating the RF Gain control counter-clockwise will
extinguish OVF and restore normal operation. RF Gain should be set just at the point
where OVF goes dark, otherwise weak-signal reception will be degraded. If required,
ATT can be activated as well. When OVF lights, the preamp should be turned OFF. (In
general, use of the preamp on 7 MHz and below is not recommended, as the band noise is

almost always higher than the receiver’s noise floor and the preamp will only boost band

noise without improving signal/noise ratio.

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When receiving medium-wave AM broadcast stations below 1.7 MHz, interference from
strong stations can be mitigated by setting MF Band ATT to ON (Set/Function menu).
This is a 16 dB attenuator, which is inserted below 1.7 MHz and is ON by default. For
medium-wave AM listening on a quiet band, this feature can be turned OFF.

IP+ (Function key) activates dither and output randomization in the ADC, to improve the

IMD dynamic range of the ADC. It causes some loss of sensitivity, but the receiver’s

noise floor will still be below the band noise in most cases. When IP+ is active, an IP+
icon lights.

Being a current IC-7700 owner, I found that the IC-7300’s controls and menus fell
readily to hand. A user familiar with a radio such as the IC-756Pro3 or IC-7000 should
find the IC-7300 very user-friendly and its learning curve manageable. The IC-7300’s
default settings are very usable, allowing the radio to be placed in service with minimal
initial set-up.

The IC-7300 offers a configurable SWR Plot indicator with manual stepping rather than a
sweep function.

An front-panel AUTO TUNE key “tunes in” CW signals rapidly and accurately.

Touching the currently-displayed meter scale toggles between scales. Touching and
holding the meter scale opens the multi-function meter, which displays all scales
simultaneously.

5. USB interfaces: The IC-7300 is equipped with a rear-panel mini-USB “B” port. The
radio can be directly connected via the “B” port to a laptop or other PC via the supplied
USB cable. This is without doubt one of the IC-7300’s strongest features. The USB port
transports not only CI-V data, but also TX and RX PCM baseband between the IC-7300
and the computer. As a result, the USB cable is the only radio/PC connection required.
Gone forever is the mess of cables, level converters and interface boxes! This feature is
now standard on all Icom HF radios released since 2009. An Icom driver is required in
the PC; this is downloadable from the Icom Japan World website.

6. Filter selections and Twin PBT: As do the other Icom DSP transceivers, the IC-7300
offers fully-configurable RX IF selectivity filters for all modes. Three default filter
selections are available via the touch-screen for each mode, with continuously variable
bandwidth via the FILTER menu. In addition, there are selectable Sharp and Soft shape
factors for SSB and CW. The BPF filter configuration feature (for filter bandwidths of
500 Hz or less) operates in the same manner as on other Icom IF-DSP radios.

Twin PBT is one of the modes of the concentric multi-function controls. Pressing and
holding the inner knob [CLR] restores PBT to neutral.

The TPF menu item in the RTTY SET menu selects the Twin Peak Filter (TPF) in RTTY
mode. No CW APF (Audio Peak Filter) is provided. However, the CW RX LPF and HPF
in the TONE SET menu are a reasonable alternative to the "missing" APF; their ranges
are 100 - 2000 and 500 - 2400 Hz respectively.
The HPF and LPF can be set to "bracket" the received CW tone in a tight 100 Hz audio
bandwidth. The DEF softkey restores these filters to default (off).

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7. BPF vs. non-BPF filters: As in other Icom IF-DSP radios, the IC-7300 allows the user
to select two additional shapes for 500 Hz or narrower filters, in addition to SHARP and
SOFT. These are BPF (steeper skirts) and non-BPF (softer skirts).

To configure a BPF filter, select a 500 Hz or narrower CW, RTTY or SSB-D filter with
Twin PBT neutral. To set up a non-BPF filter, select a filter with BW > 500 Hz, and
narrow the filter to 500 Hz or less by rotating the Twin PBT controls. When Twin PBT is
displaced from its neutral position, a dot appears to the right of the filter icon at the top of
the screen.

8. Notch filters: The tunable manual notch filter (MN) is inside the AGC loop, and is
extremely effective. The MN has 3 width settings (WIDE, MID and NAR); its stopband
attenuation is at least 70 dB. The manual notch suppresses an interfering carrier before it
can stimulate AGC action; it thus prevents swamping. To adjust the notch frequency
precisely, press and hold the NOTCH key, then rotate the main tuning knob.

The auto notch filter (AN) is post-AGC. It suppresses single and multiple tones, but
strong undesired signals can still cause AGC action and swamp the receiver. MN and AN
are mutually exclusive, and AN is inoperative in CW mode. The NOTCH key toggles
OFF – AN – MN. When MN is selected, a pop-up field is displayed on the screen,
allowing selection of WIDE, MID or NAR (narrow) notch by pressing and holding the
NOTCH key.

10. NR (noise reduction): The DSP NR is very effective. In SSB mode, the maximum
noise reduction occurs at an NR control setting of 10. As NR level is increased, there is a

slight loss of “highs” in the received audio; this is as expected. The measured SINAD

increase in SSB mode was about 13 dB. For precise NR adjustment, press and hold the
NR key, then rotate the MULTI knob.

11. NB (noise blanker): The IF-level DSP-based noise blanker is arguably one of the IC­7300’s strongest features. I have found it to be extremely effective in suppressing fast­rising impulsive RF events before they can stimulate AGC action within the DSP
algorithm. The NB completely blanks noise impulses which would otherwise cause AGC
clamping. I found its performance comparable to that of the IC-7700’s NB. The NB menu
(threshold, depth and width) is accessed by pressing and holding the NB key. The NB
works very effectively in conjunction with NR.

12. AGC system: The IC-7300 has an in-channel AGC loop. The digital AGC detector for
the AGC loop is within the DSP algorithm. Level indications from the detector are
processed in the DSP, and control the DC bias on a PIN-diode attenuator at the RF ADC
input. This architecture prevents strong adjacent signals from swamping the AGC, and
allows full exploitation of the ADC’s dynamic range.

The AGC menu is similar to that of other Icom IF-DSP radios. The Slow, Mid and Fast
AGC settings are customizable via menu for each mode, and AGC can be turned OFF via
menu.

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13. Receive and transmit audio menus: The IC-7300 TONE SET menu offers the same

Mic

Band

Conditions

Mic Gain

TBW

COMP

Bass

Treble

PR-781

40m

S9+

85%

WIDE 100-2900

8

+1

+5

HM-219

40m

S9+

50%

WIDE 200-2900

5 0 +3

NATO

40m

S9+

20%

WIDE 100-2900

5

+1

+1

generous selection of audio configuration parameters as that of the IC-7600 and IC-7700:
TBW (low and high cutoff frequencies), RX and TX Bass/Treble EQ, RX HPF and LPF,
transmit compression, etc. All audio settings are grouped under the SET/Tone Control
menu.

14. Metering: The on-screen bar-graph meter displays the S-meter at all times; touching
the scale toggles between PO, SWR, ALC and COMP. Touch and hold displays the multi­function meter.

15. RTTY decoder and memory keyer: The IC-7300 features an on-screen RTTY
decoder/display as well as an 8 x 70 chars RTTY memory keyer for transmitting short
messages.

16. VFO/Memory management: The IC-7300 offers the same VFO and memory
management features as other current Icom HF+ transceivers: VFO/memory toggle and
transfer, memory write/clear, memo-pad, Split, VFO A/B swap [A/B] and equalize [touch
and hold A/B], etc.

17. Brief “on-air” report: Upon completing the test suite, I installed the IC-7300 in my
shack and connected it to my 1 kW amplifier and multi-band HF/6m vertical antenna

a) SSB: I spent several hours chatting on 40m SSB with friends who are familiar with
my voice and the sound of my signal. Distant stations reported that the audio quality of
my transmissions was "excellent” when using the Heil PR-781 desk mic plugged into the
radio’s MIC socket via an OPC-589 adapter cable. Two stations I worked on 40m SSB
assisted me in optimizing transmit audio settings for the PR-781 and supplied HM-219. I
tested the IC-7300with two other mics; the supplied HM-219 and a British Army NATO
dynamic mic. I noted that the PR-781 required higher Mic Gain and COMP settings than
either the HM-219 or the NATO mic. The reported audio quality with the HM-219 was
very good, with some popping on plosive sounds. The NATO mic yielded a bright and
highly articulate sound, if somewhat lacking in lows. (No surprise there!)

The following are the transmit audio settings I used in the SSB trials:

Table 1: Transmit audio settings.

As discussed in 11. above, the DSP-based noise blanker is superb. It does not distort the
signal at all, and can be left on at all times; it is every bit as good as the IC-7700 or IC­7600 blanker. At my QTH, with Level 5, Width 8 and Depth 80, the NB suppressed fast­rising noise spikes and almost completely eliminated locally-generated electrical noise
from HV power lines and industrial processes.

As discussed in Section 10 above, I found the NR very effective on SSB. Even at 10, NR
did not attenuate “highs” excessively. NR is very effective in conjunction with NB.

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Preamp 1 (7 dB gain) brought weak stations up to very comfortable copy without S/N
degradation. The SSB filters and Twin PBT were excellent, as we have come to expect
from other Icom DSP radios. MN and AN were extremely helpful. I was able to notch out
single tones with MN; also, AN reduced the levels of multiple tones. I did not use
Preamp 2 on 40m, as it is optimized for 50 MHz and higher.

The superior phase-noise performance of a direct-sampling SDR (as compared to a
conventional superhet) and the absence of passive IMD due to crystal filters in the signal
path really showed in the 7300’s clean reception in the presence of strong adjacent­channel interference during my on-air SSB tests.

Overall, I found that band noise on SSB at my QTH was sufficiently obtrusive to require
the use of NR (Level 10) at all times. Still, SSB operation on 20m with a mix of strong
and weak signals was quite comfortable and pleasant. Receive audio quality was crisp
and smooth. Subjectively, I was impressed by the clarity of received signals.

b) CW: I made a brief CW QSO on 40m using a straight key.. With 500 and 250 Hz CW
filters (Sharp, BPF) and NR/NB on, ringing was minimal with Preamp off. I then set up a
250 Hz filter (Soft, non-BPF) with NR on and Preamp off. Again, there was virtually no
audible ringing, and the received CW note was very smooth. Activating Preamp 1 or 2
raised the noise level slightly, but did not cause significant ringing.

In a brief test of full-break-in operation at 20-23 wpm, I found this mode quite smooth,
with fast receiver recovery. On keying transitions, a slight “thump” was audible in the
headphones.

c) AM: In a quick check of AM reception, I listened to various MF and HF broadcast
stations. A local station on 690 kHz and a music broadcast on 5995 kHz sounded good on
the IC-7300’s internal speaker, but much clearer (as one would expect) on my external
speaker or on the headset. I did note that the AM IF filters cut off quite steeply below 200
Hz.

The 9 kHz AM filter offered the best frequency response, but the 6 kHz setting sounded
somewhat “smoother” and 3 kHz cut the “highs” excessively. The IC-7300’s Twin PBT
is fully functional in this mode. Mid AGC was best for average to good signal conditions,
but Fast AGC handled rapid selective fading more effectively. NR was quite effective in
improving the S/N ratio of weak AM signals.

The NR did not distort the recovered audio. NR Level 6 was the “sweet spot”, providing
optimum noise reduction with minimal attenuation of highs. Higher NR settings cut the
highs excessively. Above 10, the NR control had no further effect. (Note that the AM
bass and treble EQ settings were both 0 dB, with HPF off.)

AN was effective in suppressing interfering tones and heterodynes, but MN caused some
distortion when tuned across the signal. The reason for this is that MN suppresses the
carrier in a manner similar to selective fading.

Slight hiss was evident when receiving weak AM signals, but NR largely suppressed it.

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d) RTTY: I tuned in some 40m RTTY signals and was able to tune them accurately with
the FFT tuning aid and decode them reliably using the internal decoder.

18. ACC/USB AF Output Level Check: During receiver testing, I checked the receive
AF levels at the USB port using a spectrum-analysis program, and at ACC Pin 12 using a
true RMS voltmeter. All levels were well within specifications. The 32% level setting
(SET/Connectors menu) yielded lowest THD at the USB port.

18a. ACC MOD and USB MOD Input Level Check: During transmitter testing, I also
checked the AF input levels at the USB port using a tone-generator program, and at ACC
Pin 11 using an audio signal generator, for 100W PEP output. All levels were well within
specifications. To use the USB port, I installed the Ver. 1.2 Icom USB drivers
(downloadable from the Icom Japan world-wide support site).

http://www.icom.co.jp/world/support/download/firm/

19. Case temperature: The radio showed no signs of excessive heating even after 2
hours’ “rag-chew” SSB operation at 100W PEP output. Average case temperature was
33°C, rising to 35°C at the hottest point after several minutes’ key-down transmit at
100W during transmitter testing (temperature indicator blue).

20. Concerns: Three items warranting further analysis were encountered during the tests:

excess background noise and MDS degradation with IP+ on, several receiver “birdies”

(mainly in the 0.5 – 3.6 MHz range) and transmitted IMD performance on 50 MHz.
These will be discussed in more detail in the relevant sections of this report.

21. Conclusion: After a few days’ “cockpit time” on the IC-7300, I am very favorably
impressed by its solid, refined construction, clear and informative display, easy
familiarization experience, smooth operating “feel”, impressive array of features and
excellent on-air performance. This radio is unique in that it is a true, stand-alone* direct­sampling/digital up-conversion SDR in an attractive, compact package. Yet again, Icom
has a winner with the SDR performance, intuitive touch-screen and the straightforward
USB computer interface. This is certainly a lot of radio for its price category.

22. Acknowledgements: I would like to thank Ray Novak N9JA at Icom America, and
Paul Veel VE7PVL and Jim Backeland VE7JMB at Icom Canada for making an IC-7300
available to me for testing and evaluation.

*Stand-alone SDR: self-contained, not requiring a computer as a prerequisite for
operation.

Adam Farson, VA7OJ/AB4OJ

e-mail: [e-mail]

http://www.ab4oj.com/

April 11, 2016.

Update history:
Iss. 1: Pre-release, April 15, 2016.

Copyright © 2016 A. Farson VA7OJ/AB4OJ. All rights reserved.

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Appendix 1: Performance Tests on IC-7300 S/N 02001981

MHz

1.905

3.605

14.1

28.1

50.1

70.1

Preamp

SSB

CW

SSB

CW

SSB

CW

SSB

CW

SSB

CW

SSB

CW

Off

-125

-131

-124

-132

-127

-134

-122

-129

-124

-131

-124

-131

IP+

-113

-121

-114

-121

-114

-122

-110

-118

-116

-123

-113

-121

ATT

-114 1

-133

-141

-133

-141

-135

-142

-131

-139

-134

-141

-133

-140

2

-134

-142

-134

-142

-136

-143

-133

-141

-135

-142

-133

-141

As performed in my home RF lab, April 1-12, 2016.

A. HF/6m Receiver Tests

1: MDS (Minimum Discernible Signal) is a measure of ultimate receiver sensitivity. In
this test, MDS is defined as the RF input power which yields a 3 dB increase in the
receiver noise floor, as measured at the audio output.

Test Conditions: SSB 2.4 kHz & CW 500 Hz SHARP, ATT off, NR off, NB off, Notch
off. AGC-M. Max.RF Gain. Levels in dBm. IP+ off except where shown.

Table 2: MDS (HF, 6m).

Note on IP+ and MDS: With IP+ on, 10 – 13 dB MDS degradation was observed. In
addition, the AF background noise level rises by ≈ 10 dB. This effect increases on bands
below 7 MHz, and can readily be seen in Figure 3.

It is understood that IP+ activates ADC dither and randomization. On other direct­sampling SDR receivers previously tested, little or no increase in noise floor was
observed with dither and randomization on.

It is recommended that this phenomenon receive further analysis.

Figure 3: Audio noise output with IP+ off and on. ANT input terminated in 50Ω.

11

Preamp

OVF (Clip) Level dBm

Off

-10

IP+

-10 1 -23 2 -27

1a: ADC Clip Levels. In this test, the receiver is offset +25 kHz above the test signal
frequency and the input level required to light the on-screen OVF icon is noted.

OVF indication occurs only when a strong out-of-channel signal is present. In-channel
signals cause AGC action which attenuates the signal at the ADC input.

Test Conditions: RX tuned to 14.1 MHz, test signal freq. 14.125 MHz, CW 500 Hz
SHARP, ATT off, NR off, NB off, Notch off. AGC-M. Max.RF Gain.

Table 3: OVF (Clip) Levels.

1b: AM Sensitivity. Here, an AM test signal with 30% modulation at 1 kHz is applied to
the RF input. The RF input power which yields 10 dB (S+N)/N is recorded (Table 4). At

0.9 MHz, readings are taken with the 16 dB MF Band Attenuator off and on. (This
attenuator is valid only for f ≤ 1.7 MHz).

Test Conditions: ATT off, NR off, NB off, Notch off. AGC-M. Wide (9 kHz) AM filter.
(-Levels in dBm.

12

Table 4: AM Sensitivity.

Preamp

MF Band ATT

0.9 MHz

3.9 MHz

14.1 MHz

Off

OFF

-105

-107

-109

ON

-89 1

-112

-113

-114 2

-113

-115

-115

Preamp

29.5 MHz

52.525 MHz

70.5 MHz

Off

-109

-109

-109

1

-120

-119

-121

2

-122

-121

-122

Δf kHz

RMDR dB

Phase noise dBc/Hz

1

100

-127

2

109

-136

5

115

-142

10

117

-144

20

119

-146

Notes:

1. Very clean demodulation; full quieting ≈ -75 dBm (preamp off).

2. NR suppresses high-frequency hiss at low signal levels. Unmodulated carrier at

-115 dBm (preamp off, NR off) increases noise floor by 4 dB.

1b. 12 dB SINAD FM sensitivity: In this test, a distortion meter is connected to the
PHONES jack, and an FM signal modulated by a 1 kHz tone with 3 kHz peak deviation
is applied to the RF input. Input signal power for 12 dB SINAD is recorded (Table 4).

Table 5: FM 12 dB SINAD Sensitivity in dBm.

2: Reciprocal Mixing Noise occurs in a direct-sampling SDR receiver when the phase-
noise sidebands of the ADC clock mix with strong signals close in frequency to the
wanted signal, producing unwanted noise products in the detection channel and degrading
the receiver sensitivity. Reciprocal mixing noise is a measure of theADC clock’s spectral
purity.

In this test, a test signal from a high-quality 5 MHz OCXO with known low phase noise
is injected into the receiver's RF input at a fixed offset from the operating frequency. The
RF input power is increased until the receiver noise floor increases by 3 dB, as measured
at the audio output. Reciprocal mixing noise, expressed as a figure of merit, is the
difference between this RF input power and measured MDS. The test is run with preamp
off. The higher the value, the better.

Test Conditions: CW mode, 500 Hz filter, preamp off, ATT off, NR off, AGC-M,
NB off, max. RF Gain, positive offset. Reciprocal mixing in dB = input power – MDS
(both in dBm). Phase noise in dBc/Hz = -(RMDR+10 log 500) = -(RMDR + 27). Note:
For Δf > 20 kHz, OVF lights before noise floor increases by 3 dB.

Table 5: Reciprocal Mixing Noise in dB (HF/6m).

3: IF filter shape factor (-6/-60 dB). This is the ratio of the -60 dB bandwidth to the -6

dB bandwidth, which is a figure of merit for the filter’s adjacent-channel’s rejection. The
lower the shape factor, the “tighter” the filter.