Something new again, something not working again, and yet a record result for VKVPA. I had already tried out the Kenwood TS-2000 in the previous round. It’s known to have certain flaws, but it delivers up to 100W of power on 2m, a speech processor, and several filters that help combat interference.
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TIP: Why make modifications to the Kenwood TS-2000?
Problematic Filters in the Kenwood TS-2000
A certain series of this TCVR has problematic filters at 455 kHz. This issue affects not only the TS-2000 but also devices from other brands. This manifests as crackling during reception, dropouts, or even a complete loss of sensitivity. The owner will therefore have no choice but to have the device serviced.
Low Sensitivity at 144 MHz
The second reason for making modifications to this device is its low sensitivity at 144 MHz. This is caused by low voltage at the G2 stage of the preamplifier. Again, some versions have the preamplifier’s operating point set differently, and the sensitivity is fine.
Fan Replacement
The fan in the TS-2000 turns on during both transmission and reception. This is because many circuits remain powered even during reception, causing the device to generate heat. If the fan control circuit detects that the temperature is high, the fan turns on. However, the original fan is relatively noisy. Therefore, it is advisable to replace it with a quiet fan, such as a Noctua.
INRAD Filter
To improve reception and increase durability, you can replace the factory filter at 10.695 MHz. The INRAD #92 filter is narrower and has a better stopband, but it is installed in the device via cable connections.
SDR Panadapter
All modern-generation TCVRs feature the ability to display the frequency spectrum using SDR technology. The TS-2000, however, does not belong to this generation; nevertheless, by adding a buffer amplifier and an SDR receiver, this capability can be achieved.
There are, therefore, quite a few reasons to make modifications to this device.
Upgrades Before the VKVPA
Immediately after the last round of the VKVPA, I set out to modify the power supply. It was not rated for the required current draw. I added two more stabilization transistors to the pair already in the power supply, which improved heat dissipation and simultaneously reduced the power supply’s internal resistance.
It was also time to start using a headset with a microphone and a foot switch. The wiring is described in another article.
I also installed a quiet Noctua NF-R8 Redux 1200 fan. The difference in noise level compared to the original fan is significant. The same fan also replaced the classic Sunon fan in my 13.8V/40A home power supply.
I built a decoupling amplifier based on G4HUP’s design. It’s similar to the amplifier I installed in the R2CW TCVR, but this one also includes an output low-pass filter. The isolating amplifier is fed before the filter at a frequency of 41.895 MHz. Here I made a mistake and accidentally connected it after the filter. As a result, I saw a spectrum of about 15 kHz on the SD. When I realized my mistake, I naturally changed the connection point; however, after reassembling the TCVR, it powered on but was completely silent.
Finding the cause took several hours of troubleshooting and testing. Interestingly, the TCVR wouldn’t transmit in any modes other than FM. I managed to determine that most of the receiver’s RF circuits were functioning, but the conversion to 455 kHz wasn’t occurring. No oscillator signal was reaching the mixer. This signal is generated by a DDS. The transmitter circuitry also includes similar DDS circuits. They also require a clock signal to function—and that was missing. The clock signal is generated on the PLL board but is passed to the adjacent RX2 board, where there is also a single-transistor amplifier. While I measured approximately 410 mV on the PLL board with an RF probe, there were only a few millivolts across this transistor. Why? Because it had no power supply. Power is supplied via a flat cable from the RX1 board. Due to handling the TCVR, I had plugged and unplugged that cable from the connector several times. The paradox is that the supply voltage is roughly in the middle of this cable. An ohmmeter measurement showed no fault in the cable. However, a test connection using a separate cable brought the TS-2000 back to life. Phew.
I managed to make one more improvement—CAT control from N1MM+.
Windy VHF PA
The weather forecast promised sunshine, warmth, and wind. It turned out perfectly. Even from a distance, I could see that the wind turbine at nearby Suchý vrch was spinning fast. I figured I’d still manage to get the 4×5-element DK7ZB Yagi up in the air. And indeed, I did. It was more difficult to set up the single 8-element DK7ZB Yagi on the second mast. The wind was twisting it around as it pleased.
Thanks to the improvements I’d made and the skills I’d gained in building antennas, I had everything ready ahead of time. All that was left was to calibrate the rotator. I turned it on—and it wouldn’t rotate. I thought I was dreaming. But no. It wouldn’t rotate. So I manually adjusted the antennas to 180 degrees.
The VKVPA contest begins, and I notice another problem with the modulation. Maybe it’s the headset with the microphone, maybe the TCVR, maybe the power supply… I don’t know yet. The wind is picking up, and I’m holding the mast with the 8el.DK7ZB antenna in one hand, taking notes with the other, operating the equipment and the KST chat… and even holding the handheld microphone? I tried adjusting the modulation (reducing both power and modulation, even though the ALC was barely noticeable).
A major advantage, however, is CAT paired with SDR. I practically don’t miss any signal. Not even when a given station isn’t transmitting and I’d be tuning through it. I saw it on the spectrum, so I’ll just wait a moment for it on the frequency.
Activity from the southeast is quite pronounced—whether from Romanian, Hungarian, Serbian, or Bosnian stations—and even in response to calls. Probably because these stations are off to the side of the epicenter of activity, they’re scanning the band more and pointing their antennas this way more actively. For me, they also represent valuable multipliers.
When I called out a single call sign, a station ending in “/4” responded. After checking the call sign, it turned out to be I5MZY/4 from JN64. I tried both antennas, but the quad was pointed in a different direction, and the signal was equally strong on both. However, the contact was successful. I immediately contacted two other Italian stations via the KST chat—IK4GNG actually came through!
For the last half hour, I manually rotated the 4×5-element DK7ZB Yagi to an azimuth of about 270 degrees and tried contacting more Czech and Moravian stations. Apparently, there were also German stations on the band, but the wind was so strong that at times I had to hold the mast with both hands to keep it from turning. The wind was also blowing into the microphone.
DXCC Countries in VKVPA June 2022
Physically, this was a very demanding VKVPA. My left shoulder is probably the worst it’s ever been. But in terms of results, this VKVPA was a record-breaker—I managed 74 contacts, 266 points, and 22 multipliers, for a total of 5,852 points. The average distance also increased, reaching 204 km. The longest contact was with IK4GNG (657 km).
The key now will be to resolve the issues—repair the rotator or use a different one, and figure out why the modulation wasn’t right. Many thanks to everyone for the multipliers, for example OM2JK for JN87 and OM8OM for KN09!