IC-7610_review_2018.pdf

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1、10 Practical Wireless April 2018 E-mail: practicalwirelesswarnersgroup.co.uk Review by Steve Ireland VK6VZ/G3ZZD T he new Icom IC-7610 must be one of the most anticipated new radios in the history of amateur radio. Just as the Elecraft K2 set the scene for an overhaul of the superheterodyne architec

2、ture and the release of its bigger brother K3 in 2008 which went on to dominate HF DXing and contesting for the next decade the first true Software Defined Radio with knobs the Icom IC-7300 (reviewed in August 2016 PW) has raised the curtain for the IC-7610 to challenge the K3 for its crown as argua

3、bly the most popular radio for demanding HF operation. In terms of how successful the IC-7300 has been since its launch in March 2016, the word is that currently about 20,000 have been sold worldwide. In contrast, I understand Elecraft has sold about half this number of K3 and K3S still a huge amoun

4、t for an amateur radio transceiver since sales started 1. Time will tell how this scenario plays out but as an HF DXer and contester, let me say from the outset that Im very happy with my IC-7610 and confident that digital architecture transceivers such as those from Icom, Apache Labs and FlexRadio

5、Systems are bringing to a close the days of the superheterodyne transceiver, even those with a digital signal processing back-end. Its Not Two IC-7300s Lets start by getting the biggest elephant in the room out of the way by saying that the popular idea of the IC-7610 with its dual receivers being l

6、ike two IC-7300s in one box is not only misleading but plain wrong. This comparison is often used to lead into to say that at currently around 3500 in the UK, the IC-7610 is overpriced in comparison to the IC-7300, selling at around 1200. To start deconstructing the elephant, the front-end filtering

7、 on each IC-7610 receiver is superior to the IC-7300, with better bandpass filtering and the one-pole Digi-Sel preselector module, which greatly improves the out-of-band rejection of big signals that can cause annoying intermodulation. If you are like me and have a powerful medium wave broadcast sta

8、tion relatively nearby, this is a really important feature. When it comes to working DX, particular the major once every 20 years DXpeditions such as the recent, sadly-aborted 3Y0Z operation, having two equally good receivers is priceless, because these expeditions will generally use up to a 5 to 10

9、kHz split between their transmit and receive frequencies. In the IC-7300, with its single receiver and dual VFOs, you can toggle back and forward between the receive and transmit frequencies but this is nothing like being able to listen to both frequencies simultaneously, by having one receiver in e

10、ach ear of your headphones, as you can on the IC-7610. Dual receivers enable you to know exactly what is happening in the pile-up and on the transmit frequency. The next point to make is that instead of getting the 14-bit version of the popular LTC2208 analogue-to-digital converter (ADC) that lies a

11、t the heart of the IC-7300, it looks though we get the 16-bit version 2 in each of the IC-7610 receivers - more of this later. 16-bit ADCs are used in the vast majority of high-end computer-assisted digital sampling SDRs, such as Apache Labs ANAN series 3 and Flex-Radios 6000 series 4 and the LTC220

12、8 was originally used in the ground- breaking HPSDR 5. For those like myself who are keen CW operators or who dislike clicking transmit- receive (TR) relays such as used in the IC-7300, the IC-7610 has solid-state, totally quiet, TR switching. On the IC-7610, the CW keying waveform generation and sh

13、aping is carried out in the radios RF Field Programmable Gate Array (FPGA) to minimise any latency (the delay between Morse characters being formed by a key/keyer and then actually transmitted). Unlike the IC-7300, the IC-7610 comes with superb audio peak filtering, adjustable in frequency, width an

14、d gain and available on both receivers, which is better than any analogue or digital audio filter that VK6VZ has ever used. This includes the excellent, well-regarded ones on the Elecraft K3, Ten- Tec Orion 2 and Yaesu FT-1000. The IC-7610 filter does an amazing job of cleaning up any CW or digital

15、signal not just in helping to dig weak ones out of the noise. The high definition touch screen (7in diagonal) is substantially larger and easier to use than the one on the IC-7300 (4.3in) and you have the additional ability to use an external VGA monitor by plugging a cheap DVD-I to HDMI socket adap

16、ter (typically around 5) into the IC-7610, which in turn plugs into a HDMI to VGA converter (usually around 20) into which the screen is plugged, giving you a massive view of the IC-7610 spectrum scope and transceiver functions. While it is possible to give the IC-7300 The Icom IC-7610 HF/6m Softwar

17、e Defined Transceiver Steve Ireland VK6VZ/G3ZZD was one of the first to get his hands on the eagerly awaited Icom IC-7610. He reports his findings and explains why SDRs make good DX/contest-grade HF transceivers. Icom IC-7610.indd 1026/02/2018 08:25 April 2018 Practical Wireless 11 an external displ

18、ay by plugging it into a personal computer running the N1MM logging software 6, as most IC-7300 users will know, you cannot simply plug a monitor screen into it. Other advantages of the IC-7610 over the IC-7300 are its larger physical size, which results in a much more comfortable, spacious and easy

19、 to use front panel. It is great, for example, to have a large Independent Receiver Tune control directly adjacent to the main tuning knob. The rear panel offers much better connectivity than the IC-7300, particularly where antennas concerned you get two PL-259 antenna ports, plus a BNC-format recei

20、ve antenna input and output. While the IC-7610 is not a dual IC-7300, the interface of the original software written for controlling the IC-7610 is very similar to that of the IC-7300. What this means in practice is if you have used a IC-7300 and customised its menu settings, in particular the spect

21、rum scope and receiver filtering parameters, setting up the IC-7610 how you want it is a breeze. Even if you havent, the super videos on setting up and using the IC-7300 available on YouTube in particular, my favourite ones by Steve Ellington N4LQ 7 make life very easy for new IC-7610 users. Design

22、and Construction The Icom IC-7610 uses a direct sampling SDR architecture, with two identical, independent digital down conversion (DDC) receivers and a digital up conversion (DUC) transmitter. By independent, I mean that the receivers can operate independently on different frequency bands and diffe

23、rent modes. As standard, the receivers both share the same main tuning knob but you can buy a second stand-alone tuning knob (Icom RC-28) to tune the second (designated SUB) receiver (UK price to be announced but probably around 250). The tuning of the two receivers can be tracked/coupled together,

24、enabling you to carry out diversity reception by, for example, plugging separate horizontal and vertically polarised antennas into each receiver and then listening to one receiver in your left ear and the other in your right ear. A look at the block diagram and schematics which come on the CD suppli

25、ed with the IC-7610, Fig. 2, shows that each receiver front-end has its own ADC, ADC driver/preamplifier, stepped attenuator, group of bandpass filters and Digi-Sel automatically tracking preselector. If you listen very carefully while tuning one of the receivers, you can faintly hear its associated

26、 preselector operating/tuning. In addition, there are separate digital- to-analogue (DAC) converters, using 14-bit ISL5961 chips, and audio chains on each receiver, enabling binaural reception of signals. The encoding of the analogue transmit audio and the decoding of the receive audio bitstream is

27、carried out by an Ashai-Kasei AK4621EF dual 24-bit 192kHz stereo audio CODEC, which interfaces with the FPGA. As most who have read about direct sampling receivers will know, it is the ADC that forms the heart of any digital up/down conversion or digital sampling radio, converting RF signals to digi

28、tal data by rapidly sampling them. The symmetrical data lines coming from the two LTC2208 ADCs go to the main IC-7610 AlteraRF Field Programmable Gate Array (FPGA) which then carries out most of the RF and digital signal processing and frequency management in the IC-7610. Ive recently discovered 8 t

29、he FPGA is configured as a digital down converter and delivers a digital 12kHz IF to each of the receiver DACs, which converts the digital signal back to audio. All signal processing functions are performed in the FPGA. The use of the FPGA after an ADC in this manner is the conventional, time-tested

30、 way to deal with the huge amount of data that comes out of an ADC a crucial and difficult task that takes a huge number of gates and some very special programming ability. My good friend and regular co-writer on SDR Phil Harman VK6PH uses the analogy of drinking from a fire hose when it comes to ca

31、rrying the necessary function of an FPGA. In the case of a 16-bit LTC2208 ADC that samples analogue signals at the rate of 130 mega samples per second (Msps), the data output stream would be 16 x 130Msps - over two gigabytes per second! To deal with this huge amount of data and take advantage of the

32、 high dynamic range the 16-bit LTC 2208 offers, the FPGA first carries out a specialised form of filtering, known as decimation, using digital filtering formed from gates in the array, before carrying out other processing tasks, using further gates. In addition to the main FPGA that supports the two

33、 ADCs, each IC-7610 receiver has a separate Lattice common FPGA, which carries signal processing tasks that specifically relate to the associated receiver. Other separate, independent functions for each receiver include spectrum scope/ waterfall displays with 100dB dynamic range, audio and squelch c

34、ontrols and external speaker jacks. Measurements and On-Air Performance Just about every radio amateur who is interested in receiver performance and the associated measurements would be aware of the famous receiver test data table 9 published by Rob Sherwood NC0B, founder of Sherwood Engineering, wh

35、ich is compiled from equipment testing carried out in Robs extremely well-equipped laboratory. Robs table rates receivers/the receive sections of HF transceivers produced over the last 30 years or so according to their ability to deal with strong signals that are relatively closely spaced (mostly 2k

36、Hz apart). He calls this parameter Dynamic Range Narrow Spaced or DRNS and if a radio has a DRNS of 75 to 80dB in his table, my experience is this is good enough for general (DX and ragchewing) operation unless you The IC-7610 in use at VK6VZ. Icom IC-7610.indd 1126/02/2018 08:25 12 Practical Wirele

37、ss April 2018 Review: Icom IC-7610 are unlucky enough to have a radio amateur who lives a kilometre or two away, runs (at least) the legal UK power limit and is active on a daily basis when you want to go on the air. If this is the case, then you are likely to need a radio with a DRNS of at least 6d

38、B higher (81 to 86dB) to operate within a kilohertz or two of your high-powered neighbour. Just before Christmas, Rob put an Icom IC-7610 through its paces in his laboratory 10 and was kind enough to allow me to use the associated measurements in this review. The sample IC-7610 performed very well,

39、displaying a DRNS of 98dB (with the IP+ control switched on) and 90dB (with the IP+ switched off) at 2kHz spacing. When it comes to Robs very long and thorough table, this DRNS currently puts the IC-7610 in eleventh place - some five places above the IC-7300, which has a DRNS of 94dB (IP+ on) and 81

40、dB DRNS (IP+ off). However, to put this into context, the leading radio in Robs table is a FlexRadio 6700 that he measured at 108db DRNS (preamp on) back in 2014. A second Flex 6700 sample measured by him in March 2017 measured 96dB DRNS (preamp on) and 99dB DRNS (preamp off). As Rob said in a recen

41、t interview 11 on the Ham Talk Live internet programme with Neil Rapp WB9VPG, the top direct sampling/digital down conversion receivers and transceivers he has tested all have similar, consistently-high DRNS figures. The 2017 Flex 6700 sample measured 99dB, the Apache Labs ANAN 200D 99dB, the Microt

42、elecom Perseus receiver 99dB, the Icom 7610 98dB (IP+ on) and the Icom R-8600 98 dB (IP+ on). Now I have my own brutal means of on- air testing how well a receiver performs on very strong signals, which is: “Can I operate within 1kHz of the formidable contesting station of my good friend Kevin Smith

43、 VK6LW, who lives just a couple of kilometres away, whichever way Kev is beaming and whatever band he is operating on?” To give an idea of his signal strength, on the 160m band where Kevs signal is loudest, he is a true S9+40dB. To get a feel for how receiver DRNS has improved over time, in the 1990

44、s I used top- of-the line radios for that decade, including the FT-1000MP (68dB DRNS) and FT-1000 (69dB DRNS), neither of which were Kev- proof. Nowadays DRNS for new top HF radios produced by all the manufacturers are well over the 81 to 86dB milestone and the problems of front-end overloading have

45、, as a result, generally faded into history, at least at my QTH. My IC-7610 was tested out during the 2017 CQ WW CW contest and the 2018 CQ 160 CW Contest and proved totally Kev-proof, as did a friends ANAN 200D (99dB DRNS in Robs table), which was used alongside the IC-7610. Not only I could tell n

46、o difference in Kev- proofness between the two radios, but they performed at least equally well in this regard to their predecessors at VK6VZ, the Ten-Tec Orion 2 and Elecraft K3. However, for me, using the IC-7610 on-air was more fun and effective than any of its predecessors. As Rob Sherwood said

47、in the Ham Radio Live interview: “It is crazy to judge a radio by one parameter” and, to me, its particularly crazy to do this just on DRNS when all new contest/DX-grade radios work so well on strong signals. Why SDRs Make Good Radios One of the reasons why the Elecraft K3S, Icom IC-7851, Yaesu FT-5

48、000D and other superhet-based transceivers are at the top of Rob Sherwoods table is because they use crystal filtering as the first point in their architecture after the antenna to provide signal-width selectivity. Crystal filters placed in this position are known as roofing filters and protect the

49、rest of the receiver from very strong signals outside of the very narrow width of the multi-pole filter. However, what may seem to be the strongest point of this latest variation of the superhet architecture can also be arguably its Achilles heel when it comes to producing very clean and clear-sounding audio in your speaker or headphones. All radio frequencies that radio amateurs use are covered in noise atmospheric, ionospheric and man-made. When noise spikes or pulses pass through a crystal filter, the phase response of the filter varies, depending of the frequencie