Review: Icom AH-705
Richard Constantine G3UGF takes a critical look at the new tuner from Icom.
Richard Constantine G3UGF takes a critical look at the new tuner from Icom.
When I first reviewed Icom’s feature packed IC-705, QRP transceiver, back in December, there was comment around how disappointing it was that it didn’t contain an auto-tuner. My response was, “With all that tech’, do you really want a bigger box?”
Chinese ATU manufacturer mAT was quick to produce a compact add-on for the IC-705. However, although there were some photographs on the net there was nothing concrete from Icom, until now.
On Arrival
When it finally arrived on my desk I was expecting a similar unit to the mAT-705, something like the size of the old St Bruno pipe tobacco tins. What a shock!
A 10W maximum tuner unit, the size of a large paperback book at 190w x 104h x 40d mm, twice the weight of its competitor at 505 grams, with batteries installed (not included) plus a third more costly.
Nevertheless, I immediately sensed that the ABS type case had a reassuringly solid feel, protective covers over the control and external power sockets, BNC RF input socket and an SO239 antenna connection point. The addition of a wing nut earth/ counterpoise terminal was a nice touch for longwires or verticals, a favourite of the /P user. Practically, though, might it have been better on the other end?
While not containing the lithium iron, rechargeable batteries of the mAT-705 Mk2 version and recommending the use of two Alkaline AA batteries, there was provision for external power. Opening the coin screw battery compartment didn’t expose the inner workings and both the top cover and battery door included sealer gaskets, making the whole unit IP54 rated.
That may sound impressive but, IP54 means it’s protected in normal use from dust ingress and splashproof from any angle, not water or weatherproof. This classification means that it’s not suitable for remote operation in inclement weather, without additional protection.
Looking at the accessories it was disappointing to see that at this price point (circa £300.00 at time of press) only a DC Pro-plug and not a compete DC lead was provided.
Why on earth is the power plug a different size to that of the IC-705 transceiver? Surely it would have been more useful for it to be compatible. Doing so would have made it possible to continue operating the IC 705 from its battery pack if the Alkaline cells in the tuner unit died, simply by just transferring the supply cable.
2m length, terminated, control and coaxial cables are included in the package. For backpacking or desktop operation they’re more than adequate. For a greater distance between operating point and the antenna feedpoint, longer cables can easily be made up by the operator. Optional 16ft cables are said to be in the pipeline, at time of press. The control and RF connections to the IC-705 are on opposite sides of the radio. If you add a microphone, a key and a power cable it gets a little untidy, but no worse than other radios, such as the KX3.
The biggest initial let-down for me was that the instruction leaflet shows a wire antenna connected via a special PL259 plug adapter. This incorporates a 4mm combined screw post terminal/socket. What’s actually in the box is a rather average quality PL259 plug, suitable only for large diameter coax. Closer reading of the instruction leaflet footnotes reads, “connection adapter, depending on antenna tuner version.”
The only choice is to connect a 4mm plug directly into the centre pin of the SO239 socket, or buy an adapter separately. Puzzled and for what such items cost, it was extremely disappointing and I’m being polite. It is included in the US version, retailing for less.
My immediate reaction was that this omission fell short of Icom’s otherwise high standards and excellent reputation. That was until I had a conversation with my contacts at Icom. The answer appears to be that the available adapters are not CE compliant and would void compliance on the whole package in Europe. Don’t worry this review gets better!
Fig. 1: AH-705. Lightweight. Handheld – just. Fig. 2: Tuner secured to a vertical by bracket and tie wrap. Fig. 3: Desktop operation, with mAT tuner for comparison. Fig. 4: AH-705 hidden secrets.
Read On!
Something I didn’t expect to find was a rather curious and dedicated, mast adapter. It’s shaped to mount against the side of a pole. Locating lugs prevent it from twisting and it’s presumably intended for a 25mm (1in) mast, looking at the cut-out. I tested it on my 2in and it was OK. It didn’t really fit on my favourite and larger 10m telescopic, unless mounted higher on the tapered pole, shortening the antenna.
The rear of the tuner unit has a universal ¼in camera, threaded socket to which the adapter fixes.
Here is another trick missed. The attachment screw and washers aren’t captive as in many camera fittings – standby to lose them in the long grass!
The bracket has side slots allowing suspension on a tree branch, using a loop string or Velcro type strap to a vertical mast but where’s the double-sided hook and loop or hanging cord? Value-added touches like these make all the difference to the user experience. In market speak, they enhance the ownership experience.
It might be a small point but there are no feet on the unit to stop it sliding around on a desk and it does. Nothing in the packaging but easily fixed by adding those tiny transparent plastic cupboard door stops from the DIY emporium.
Having overcome my initial misgivings, I fitted two AA batteries. There’s no onoff switch as such on the tuner and no provision to charge batteries in situ. Icom say that standby current is less than 1mA and around 300mA when the latching relays are briefly working. After that, I suppose battery life depends on how often you push the Tune button on the rig and what is stored in its memories. I must confess to using Ni-MH batteries as I had them to hand.
Alkalines are known to retain their charge better when not in frequent use. It wasn’t an issue, even after extensive testing and I haven’t changed them yet.
Keeping an open mind, I moved to the next phase. Removing six deep set screws only reveals the underside of the PCB. Six more and the circuit board lifts out, with no wires attached.
It reveals an elegant and highly professional, largely surface mount, nine inductor design. There are some 23 relays, all microprocessor controlled, linked to a VSWR sensor and what looks like a reference load, plus changeover for receive (Nine Inductors, in preference to seven in some others may be its secret weapon).
It’s clear that this unit has been well designed and engineered for both production and servicing, should the need ever arise. Trailing wire connections have been eradicated and the board simply lifts out complete, leaving behind input and output sockets and battery contacts. It’s certainly a cut above what I’ve seen from other sources, thus far.
For anyone brave enough or foolish enough like me to want to see inside the black box, ignore some of those selfpromoting YouTube videos and take a look at Amateur Radio Shorts 4, from Ham Nation. Thankfully, it is short and you can take a warranty-safe look inside, without a trembling screwdriver in your hand, like me.
In Use
How does it perform? In a word, it’s amazing. It’s amazing at its job of providing a low impedance connection for the radio and thus protecting the all-important PA stage. It does this at speed and with little noise. Using its memories, repeat cycles get shorter and quicker, as you move across the same band.
But like the old truism, “You can lead a horse to water but, you can’t make it drink.” You can match the impedance, but does it radiate?
Of course, matching to relatively low impedance, coaxially fed antennas is easy. The real test comes with half-wave endfeds, having impedance ranges anything from 2kΩ to 3kΩ and even higher. Wire antennas are a staple for /P activity and makers don’t like to be too specific about such things; Icom is no exception.
Using shorter end-fed wires between
40-6m, avoiding half wavelengths, is usually no real issue, but it’s the LF bands that are the real test. Icom specify a minimum of 30m of wire for 160m and 7m or greater for 80m and higher.
Icom have a wealth of experience in this department and have been making similar products for many years. The AH-4 is a classic example. Using their knowledge and experience, they have clearly underclaimed and over delivered here – always a good option.
It’s enough for me to say that I’ve used doublets (with a balun to transform from balanced to unbalanced), longwires, short verticals, loaded verticals and purposely looked for matches at half wavelengths on every band. Understandably, it only ran out of steam on 160m with 10m of wire, tuned against ground, after making a valiant attempt. Apart from that it worked every time and on halfwaves and frequency multiples. Even though the instructions say it doesn’t work on halfwaves it does, but I don’t intend to risk it long term, for reliability reasons.
Taking it with me on my first away trip of the year I did find using just 10m of wire on 80m somewhat challenging, but managed CW contacts into Eastern and Central Europe. That said, it will most certainly be my tuner of choice for my next trip, next month.
In Summary
To summarise, I can now see why it’s larger than some others. I appreciate that this is a premium product that commands a premium price. It’s just a shame it’s limited to a conservatively rated 10W and retailing at a similar price to 100W alternatives.
Having spent some time in electronic manufacturing many years ago, I understand that bringing products to market involves collaboration between designers, engineers and marketing. It’s my personal belief that unfortunately some opportunities have been missed here, in the small details that affect the user’s initial experience. On that score it falls a little short at 4.8 stars.
However, there is no denying this device is amazing, performance-wise, and in that department, it’s well worthy of 5 stars and the Icom name
My thanks to ML &S for the early supply, thereby making this in-depth review possible.