Monday, July 28, 2008

LCD Meters for Elecraft KPA100/KAT100 in EC2

This is an old modifications I did a few years ago. I moved the KPA100 amp of my Elecraft K2 together with the KAT100 antenna tuner into an EC2 enclosure. The front panel of the combo is normally occupied only by the LED indicators and SWR meter of KAT100 and it looks somewhat empty. I decided to install a digital voltmeter showing the voltage of the power supply and a digital thermometer indicating the temperature of the KPA100's heatsink. Both values are important for the proper operation of the amplifier.
K2 has a built-in voltmeter but it shows lower-than-actual value because of the voltage drop across the reverse-polarity protection diode. An accurate voltage is also needed for proper charging of the internal SLA battery. The temperature sensor of KPA100 "knows" only when to turn the fan on, but doesn't display the actual temperature of the finals, which is critical, especially during lengthy CW or digital modes sessions!
I got two LCD meters from Martel Electronics - - QM-100V (voltmeter 4 - 25V) and QM-110T (thermometer with internal and external sensors, Fahrenheit or Celsius).
UPDATE: The meters are now made by Lascar Electronics and are sold by various sources, including DigiKey - the new spec sheet is here HERE.

Installation is very simple! Each meter requires a single 5.5 mm (7/32") hole in the front panel. I left space in the middle, should I need to install other things on the front panel - switches, LEDs, meters, etc.

I made a custom wiring harness with shielded cable, which powers both meters. Ferrite toroids are installed to suppress any RF noise in the power. Small 3 pin jack is used toconnect the front panel meters to the KPA100 module ( ground, power and external temperature probe). This allows for an easy disconnect and removal of KPA100.
Bypass capacitors are installed on the female jack (KPA100 side)

This is the configuration jumper of the digital thermometer. The meter has two control inputs - when grounded, one is used to switch the display between Celsius and Fahrenheit and the other is used to specify which sensor is in use - internal or external. The meter has an internal sensor but for accurate measurements an external one should be installed. The external sensor is simply a 10 kOhm NTC precision thermistor, attached to the heatsink of the amplifier (near the speaker). I made a small bracket out of thick copper foil to attach the thermistor probe. I applied some thermal compound between the thermistor and the bracket and between the bracket and the heatsink. Small diameter shielded cable (RG-174) connects the thermistor to the female jack. I used thermistor from Mouser - Part# 594-2322-640-63103 (now obsolete part but there are other replacements).

This the final look of the front panel! Now I have an accurate voltmeter displaying the voltage of my bench power supply and thermometer for the finals of the amplifier.

Both meters are splash-proof (there is a thin rubber gasket between the meter and the front panel). They stick out just a little bit (5 mm) from the front face of the panel. On the back of each meter there is a small adjustment screw for calibration. I calibrated the voltmeter using my NIST traceable calibrated Fluke and it is "dead on" accurate now. The thermometer was calibrated using an accurate industrial thermometer. The external temperature sensor must be calibrated for the specific thermistor used to compensate for the manufacturing tolerance! The internal sensor is located in the meter housing and it is factory calibrated (there is calibration adjustment for it as well) - it can be used to show the temperature in the shack (if the radio is powered but not used for Tx). If used as a shack thermometer, there might be a small measurement error if the finals are hot due to proximity of the sensor. Small front panel switch can flip between shack/finals temperature. I don't need a shack thermometer since I already have one in my WavPro Luminator so I didn't install such switch.
I've been using this mod for about 3 years now with no problems!

Shack picture

Finally I am done with the reorganization of my shack. Late last year, I re-did all of the cables, reorganized them and made easier to navigate through the wires on the back. I have connected the Heathkit SB-200 in-line with my dipole antenna and I am almost done! The ACOM 1000 is connected to the vertical. The only things left to install are another LP-100A for more accurate measuring of the output power and an external antenna tuner (most probably Palstar) for my dipole antenna.
Now that I am almost done with the shack, I can focus on my other hobby - flying on Flight Simulator. So far I have 3 Dual-Xeon Pentium 4 machines to serve as render-engines. My plans are for 4 machines and total of 5 or 6 monitors - so much work needs to be done!

This shack perfectly fits my needs for now! It is a result of a couple of years in research for the best equipment/configuration and collecting it. I am really happy with the way it came out. The layout was changed a few times over the years until I got to this final version. This is an old picture of the shack - i'll try to post an updated one soon.

Sunday, July 20, 2008

Mission: Organization

Late last year I went through a complete re-organization of my station. Over the years I was trying to keep it neat and organized but constant modifications, new equipment installations and what not created a big mess behind the operating desk. This is what it looked when I pulled the desk away from the wall:

As one can see it was almost impossible to find or trace cables, especially since there is not much room to work with.

Yet another view of the "wire salad"!

After I disconnected every single cable and made a few custom ones, it took me about a day to create the current, more ergonomic layout of the equipment and reconnect everything.

Now everything is way more organized and accessible. I used huge amount (literally - pounds) of ferrite toroids and split-core ferrite beads to form common-mode current chokes on almost every cable. This resulted in a electrical noise-free environment. Most of the chokes are installed on cables connected to the PC. Right in the middle of the image is visible the copper ground bar. I used wide straps made of copper foil to ground each piece of equipment to the ground bar.

Wednesday, July 16, 2008

Station layout and equipment

Here is a list of some of the equipment I am using. I am really happy with my current configuration and I am not planing any major changes in the near future.
Icom IC-R75 - AM synch detector mod (Rado 2.1), AGC mod, FL-103 (2.8 kHz/9Mhz 2nd IF) and FL-257 (3.3 kHz / 455 kHz 3rd IF) SSB filters, UT-102 voice module. This is my main SWL receiver and station Tx monitor.
Yaesu FT-1000MP Mark V Field - 70 MHz IF amp InRad mod, CW clicks mod, 2nd IF (Yaesu YF-114SN 2kHz / 8.2 MHz) and 3rd IF (InRad #702 -C 2.1 kHz / 455kHz) Narrow SSB filters, 2nd IF (InRad #708 250Hz / 8.2 Mhz) and 3rd IF (InRad #704 250Hz / 455kHz) Narrow CW filters, FH-1 remote keypad. My primary HF SSB transceiver.
Elecraft K2 with KPA100/KAT100 in EC2 enclosure. K2 has all of the options installed - KSB2, K160RX, K60XV, KNB2, KDSP2, KAT2, KIO2, KBT2. The radio is updated will all factory updates and mods. KPA100/KAT100 combo has some extra front panel meters installed (voltage and temperature). This is my primary HF CW radio (also portable/QRP when needed)
Yaesu FT-920 -FM-1 unit, TCXO-7, YF-116A 6kHz AM filter, YF-116C 500Hz CW filter. FT-920 is my secondary/backup HF radio, digital modes and 6 meters tranceiver.
Yaesu FT-100D - cooling fan mods, chasiss ground mod. XF-117A 6kHz AM filter. My VHF/UHF radio and backup portable/mobile radio.
Yaesu FC-20 - external antenna tuner for FT-100D
Palstar AT2K - high power external manual tuner for matching the G5RV
Alinco DM-340MV main power supply (linear) - powers FT-1000MP, K2, KPA100/KAT100 and Yaesu FT-100D.
Alinco DM-330MV secondary power supply (switching) - powers FT-920
Radio Shack 3A linear power supply - powers Icom IC-R75, LED desktop lights and both LP-100 wattmeters.
Telepost LP-100 vector wattmeter - used to monitor amplifier's input RF power.
Telepost LP-100A vector wattmeter - used to monitor amplifier's output RF power.
Bird 43 wattmeter - used to monitor the RF output.
ACOM 1000 - Primary HF+6m linear amplifier
Heathkit SB-200 backup linear amplifier with Palstar DL1500 dummy load.
Tigertronics Signal Link SL-1+ connected to FT-920 for digital modes work.
SteppIR BigIR Mark III /w 80 meter coil vertical antenna and G5RV dipole.
SteppIR antenna controller connected to one of the computer's serial ports.
N8LP SteppIR Tuning Relay - Tx protection for the SteppIR antenna.
2x Diamond CX-210 2-position antenna switches and custom patch pannel for RF signal routing.
4 position RCA audio/video switch for audio routing, 2x 2-position RS232 switches
4x RCA 40-5000 die-cast speakers, Motorola comm speaker and pair of powered Acoustic Designs speakers.
Yaesu MD-100A8X microphone, second homebrewed desktop mic, Sony MDR-2506 headphones.
Begali Signature Edition morse paddle and Bulgarian Military "Voroshilov" straight key.
Griffin PowerMate knob controller.
WavPro Luminator station's master clock.
Pentium 4 / 1.7 GHz computer with nVidia Quadro graphics card anddual monitors, Sound Blaster Audigy 2 audio card and 4 x RS-232 serial ports for tranceiver control . Windows XP Pro.