If you are considering the purchase of a 50MHz transceiver with HF facility then the ICOM IC736 may well be on your short list.
The purpose of this article is not to review every feature of the transceiver but to answer the questions that a six metre enthusiast is likely to ask. Key amongst these are, just how good is the rig at 50MHz and what are its weaknesses?
If the reader requires an independent and in depth review of technical specifications, the article by Peter Hart G3SJX in RadComm May 1995 can be recommended.
The transceiver is loaded with features including all HF Bands with extended general coverage receiver, 100 watts PEP output on 50MHz, built in ATU and power supply, electronic keyer with full break-in, very sophisticated VFO and memory channel control and much more. A selection of optional filters are available and remote transceiver control is possible using a PC.
The IC736 operates from 230 Volts and given its larger size, 330W x 111H x 285D it is best seen as a base station, contest or DXpedition rig. Portable or mobile operation is likely to be prohibited by the absence of a DC power option. It remains a surprise to the author that the rig was not made dual voltage by ICOM, as the HF only variant the IC738 operates from 13.8v and shares common circuitry.
What about Six?
It is clear that 50MHz was taken into account during the design of this transceiver by the ICOM engineers, although some design changes would have greatly added to its usability on the band.
The general coverage receiver covers 30KHz to 30MHz and then 45MHz to 60MHz. This allows for monitoring of European TV carriers and, looking forward to the peak of cycle 23, trans-continental signals just below the band.
However the absence of receive coverage from 30MHz to 45MHz is a limitation for monitoring the rise of the MUF. I have wondered if anyone knows of a modification that will extend the receiver coverage?
In band receive sensitivity is good, although in practice the transceiver is operated with the pre-amplifier permanently in circuit. The analogue S meter is very linear and easy to read although ungenerous in its reading. Out of band receive sensitivity above 54MHz is markedly reduced. Sensitivity between 45MHz and 50MHz seems very good.
The in built power supply introduces some background noise which can be heard as a gently pulsating "mush-mush" when the band is quiet. I found this rather annoying at first, but as with living next to a busy road you get used to it after a while.
Buying an optional CW filter (there are several available) is essential for serious DXing at 50MHz and this can be used very effectively with the PBT (pass band tuning) facility. The notch filter is useful in getting rid of local QRM such as 49MHz domestic devices and the noise blanker is moderately effective on ignition type noise.
CW operation is, however, in LSB and this is a major irritant, requiring re-tuning onto the CW signal when it has been monitored in USB (the mode most operators will use when tuning across the band).
This also means that cross mode contacts are nearly impossible. This is a draw back as calling a DX station on CW (when he is working USB) is a useful technique to get noticed. Whilst I couldn't claim to have lost any contacts because of this, it does not assist the operator interested in weak signal DXing and seems to have been an oversight or regrettable cost saving by the ICOM designers.
An interesting effect of this tuning is that FSK beacons are copied in reverse CW. The first time I heard this I thought that my CW skills had suddenly left me!
Reports on speech quality and CW transmissions have always been very good and I am led to believe by local stations that there are no noticeable sproggies.
The power output of 100 Watts PEP is a very useful level when fed into a reasonable beam and may well be about the maximum that many stations will be able to run without EMC problems. A rise in SWR has the immediate effect of reducing output power, which the in built tuner can be used to overcome. Do note however that the in-built tuner is only in circuit on transmit.
There is an audio speech processor which is adjusted from the rear panel. To make an appreciable difference to transmit audibility the setting has to be 3/4 maximum, somewhat higher than instructed in the manual. As with all processors you are well advised to seek the help of a nearby station to set the level correctly.
CW operation is really excellent and the electronic keyer easy to use and adjust. The full QSK facility can be used with great effect to run a beacon from a memory keyer. The in built electronic keyer has no memory function.
The main tuning knob is large making frequency shifting straightforward. One minor grumble is the power output control, located on the front panel. This is a very small knob and not ideal for regular adjusting. In my view this is necessary on 50MHz, to avoid unnecessary QRM during big Es openings (using the minimum power necessary for a solid QSO is very friendly to other band users).
Despite some limitations the IC736 is a good rig for 50 MHz and should allow you to work plenty of DX.
It may represent best value for money in terms of features and performance on the band at the present time and has acquitted itself well when used by DXpeditions such as 4L6PA.
The lack of receive between 30MHz and 45MHz and the CW tuning arrangement are the most notable disadvantages for the six metre operator.
The next step forward on 6m will be the introduction of DSP technology. This holds considerable promise for the enthusiast although prices, at least initially, are likely to be high.
The major benefit will be to improve receive performance by providing more powerful filtering of the considerable local QRM that effects 50MHz in urban areas.
Coincidentally at the time of writing this
review ICOM launched their new IC756 in Japan. An HF and 50MHz
transceiver with full DSP. No doubt the other major manufacturers
will be doing the same in due course.
To return to the archives page click here