Kenwood TS-590 Impressions

When announced the Kenwood TS-590 didn’t caught my attention, it was later when I was looking for small radio with good performance for Multi-2 and SO2R operation and read the first reports from users that I got interested. I decided to get one and put it to the test at the SE0X station.

The following is a report of my impressions of this new contest grade transceiver ranking in the top 10 of Rob Sherwood’s receiver test when it comes to dynamic range.

I ordered the radio in February to get it in good time for the WPX SSB Contest, but when it showed up on the doorstep it quickly became clear that a bad apple had slipped through Kenwood’s quality control as there where three technical problems identified right out of the box.

First of all the Noise Floor was measured at -128 dBm which is way behind the TS-590 measured by Rob Sherwood at -135 dBm. Second problem was a huge drop in signal when switching in the 500 Hz roofing filter and the third issue was that the frequency reference was misaligned. In addition to this the metal work of the VFO knob was was not completed as it had sharp edges.

The radio was returned to Kenwood Germany who after a few days decided to replace it. I was told that both my supplier and Kenwood was out of stock and that I had to wait for a new radio being sent from Japan. The earth quake disaster further delayed the replacement radio but eventually it showed up but a few days after the WPX contest.

The replacement radio performed considerably better, the noise floor was at the expected level and signal levels when switching between 500 Hz and 2.7kHz filters remained fairly stable with about 1 dB gain at 500 Hz bandwidth. Still there is noticeable difference in signal when switching between up and down conversion, 5 dB or about 1 S-unit which seems much but should not really make any practical difference for normal use.

The 590 has been measured by Rob Sherwood to have a dynamic range of 88 dB at 2 kHz spacing which puts it at a #9 rank in Rob’s list of tested receivers. For reference a Yaesu FT-1000 MP MKV Field with the Inrad roofing filter mod comes in at 71 dB and and an Icom IC-7800 at 80 dB. Ahead of the 590 is pure contest machines like the FT-5000 at 101 dB closely followed by the K3, Orion II and some SDR receivers.

To hear how the receiver performs under real contest conditions I took it for a spin in the recent Gagarin Cup. I was really pleased with the receiver which feels a little calmer and less noisy than the K3. I did not use the preamp, not even on 15 and 10 meter, and this probably boosted the perception of a quiet receiver. The received audio felt clean and clear and was easy to listen to for an extended time.

The DSP filters works great, both on CW and SSB. It is easy to narrow down the passband to 200, 100 or even 50 Hz in CW without noticeable ringing. The filter effectively cuts off offending QRM and although the Gagarin Cup don’t generate the same high levels of QRM as CQWW I expect the TS-590 to perform well in an even more crowded environment. Only at one time that thought I heard some DSP artifacts in SSB, something I haven’t noticed with the receivers in the K3.

Other useful features in the TS-590 are the noise blanker and noise reduction that both comes in two versions. NB 1 is an analog blanker and NB2 is a digital blanker, I found NB2 being efficient on key clicks and in some situations blanking strong clicks enough to improve copy of a weaker station. This is especially useful when clix from a pileup covers the DX or in a contest situation where clix might reduce your hearing. NR1 is noise reduction specifically for SSB and NR2 helps reducing noise in CW. I found NR2 efficient in reducing some pulsing QRM covering the lower part of 15 meters, most possibly an OTH radar. The noise blanker also blanked the noise, but only without a CW signal in the passband. As soon as the signal was back the pulsing QRM was brought up in amplitude again. In this case the NR2 was a lot better solution, so the advise is to experiment with both the noise blanker and noise reduction, one might be more useful than the other depending on the type of noise.

On transmit the TS-590 is pretty straight forward. One feature that I do like is the ability to change the between a soft and hard setting for the voice processor. With my background in broadcasting I have come to appreciate the power of decreased dynamics to increase the average loudness level. In addition to the different mic level settings, transmit equalization and compression levels, a menu setting toggling between a soft and a hard processing sound makes it possible to change between a razor sharp pileup busting mic sound and a more relaxed but still sharp conversational sound.

There have been a lot of discussions about a an initial power spike generated when starting transmit. I have not really noticed this problem, on the contrary it seems like power is dropping out for a second or two about a seconds into every SSB transmission. I have yet to verify this but with normal talk the LP-100 meter is registering a drop in power that I haven’t seen with other radios.

On the negative side the sidetone (monitor) volume is a little high for my taste. For casual operating this might not be an issue, but when contesting and listening for hours I would prefer to have my sidetone a little lower in level to avoid tiring the ears.

The radio has two serial connections, one RS-232 and one USB connector that also serves as an audio port making the TS-590 a radio with its own internal sound card. Kenwood provide the necessary drivers and remote control software on their website and it all works well with the exception of one peculiar thing; when transmitting digital modes using the VOX the microphone is still connected to the transmitter. To mute mic audio the PTT has to be activated through the accessory connector on the back panel. This is true even when using the USB audio interface, a rather strange arrangement in my opinion.

The ergonomics of the TS-590 is good considering its small form factor. The radio is in the size of a K3, the build finish is great and the weight of 7.5 kg make sure the radio won’t move around when buttons are pushed. The buttons are slightly smaller than on a K3 and backlighting would be a nice addition to aid operation in dimmed or dark situations. Even with the small buttons the radio is easy to use and with most of the button punching happening in the contest software I really don’t see a need for a bigger box or larger buttons.

Another helpful feature is the ability to program the two PF buttons, PF A and PF B, with any menu function that you would use often. In my case that would be TUNE on PF A and Processor soft/hard toggle on PF B. You might find other useful options that you like to bring to the front panel.

It is great to see a radio with the price tag of 1795 EUR/USD beating the many times more expensive radios from Icom and Yeasu. It seems like the development team at Kenwood has aimed to be in the top 10 and hit that target while at the same time lowering the price in this performance range. Compared with the “big boys” the 590 lacks the second RX and some other bells and whistles, but it is certainly compensated for by the lower price.

Update September 13, 2011: There have been a long discussions in the Yahoo! TS-590 group about the fact that the TS-590 on WARC bands, 10 and 6 meter use the SSB filter as the most narrow roofing filter in up-conversion mode. This might lead to attenuation of weak signals caused by the AGC adjusting to strong signals that are outside the DSP passband but still inside the roofing filter passband. For contesting use this could be an issue on 10 meters CW, but on other “contest bands” the radio works in down-conversion mode using the 500 Hz roofing filter in narrow modes like CW.

Update 2 December 2011: Kenwood have release a fix that is promised to address “improves desensing level caused by strong out-of-passband signals on up-conversion bands”, the problem described in the previous paragraph. This is good news to contesters as the solar cycle improves and 10 meter becomes crowded.