As featured April 2018, Practical Wireless
Steve Ireland VK6VZ/G3ZZD

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.

The 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 architecture 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 arguably 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 amount 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 I’m very happy with my IC-7610 and confident that digital architecture transceivers such as those from Icom, Apache Labs and FlexRadio Systems are bringing to a close the days of the superheterodyne transceiver, even those with a digital signal processing back-end.

It’s Not Two IC-7300s

Let’s 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 like 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 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 station 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 10kHz ‘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 each ear of your headphones, as you can on the IC-7610.

All of my transceivers for the last 20 years have had dual receivers for this reason and there is no way I’d go back to a single receiver. 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 at the heart of the IC-7300, it looks like getting 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-Radio’s 6000 series [4] and the LTC2208 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 shaping is carried out in the radio’s 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 and 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 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 adapter (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 an external display 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 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 receive antenna input and output, which can be switched between the two receivers.

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 spectrum scope and receiver filtering parameters, setting up the IC-7610 how you want it is a breeze.

Even if you haven’t, 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.

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