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HP EliteDesk 800 G1 running on 12 volts DC
Stefan Helander

Running HP EliteDesk 800 G1 USDT on 13.8 volts DC

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I got a HP EliteDesk 800 G1 USDT Ultra Slim Desktop computer for my ham schack. This is a small computer running on an external power supply just lika a laptop. It turned out to be the major source of RFI in my ham schack.

HP EliteDesk 800 G1 USDT

I suspected the power supply was the culrpit as those are switched ones and thought it might be possible to run the computer directly on my 13.8 VDC power supply that I use for my radios. The only voltages used in a computer is 12 and 5 volts, so there is probably a voltage regulator on the power input that regulates the voltage down from the 19 volts DC that the power supply outputs. Will it also run on 13.8 VDC?

Read more: Running HP EliteDesk 800 G1 USDT on 13.8 volts DC

The power cable to the HP EliteDesk 800 G1 USDT has a 3 pole connector, just the same as on laptops. One is negative, one is positive and the pin in the middle is a “power good” signal from the power supply. I read about people running 3rd party power supplies by connecting the power good over a resistor to the positive side, see this page.

Will it run if I just connect the power good to positive without a resistor? When I measured the voltages from the original power supply positive was +19 VDC and power good read about +12 VDC so it might be sufficient. Discussing it with a tech savvy friend, he suggested it might work and be worth a try.

I didn’t want to cut the cable on the original power supply but luckily I have a friend who hoardes old technical stuff and he happened to have an old broken HP laptop power supply, with the correct cable (who saves broken power supplies?, well it turned out to be useful in this case)

It works!

It turned out it works fine, no resistor needed. This might vary from model to model, but the HP EliteDesk 800 G1 USDT it works by directly connecting power good to the positive. This (image below) is the cable I now use to run my computer directly on 13.8 VDC. Black lead is negative, white is positive and blue is power good.

On 20 meters (14 MHz) my noise floor dropped from S5 to S0-A1!

HP EliteDesk 800 G1 running on 12 volts DC
Power cable to run a HP EliteDesk 800 G1 directly on 13.8 volts DC
IC-706 noise level on 20 m when running computer directly on 12 VDC
IC-706 noise level on 20 m (14 MHz) when running computer directly on 13.8 VDC
Yaesu FT-818ND QRP and CW keyer
Stefan Helander

How to operate QRP successfully

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Operating ham radio QRP, that is using low power, is probably not a good choise for the new beginner. To successfully operate ham radio QRP you need to use all your skills when it comes to selecting the correct bands, modes, propagation and evauluating current conditions. As a beginner to amateur radio it might be a better idea to start off with for example a 100 watt rig to get a lot of successful QSO:s and acquire knowledge about propagation and conditions first.

However, when you start to know how propagation and band conditions work, operating QRP from a portable location with a small temporary antenna can be an exciting and rewarding challenge. When operating QRP any contact is a success, not just far away DX stations. A contact just 500 or 1000 km:s away using a few watts is really exciting. But operating QRP requires patience. Don’t expect to come home with a log book with hundreds and hundreds of QSO:s.

  • Use CW. It comes through better with small amounts of power than SSB.
  • Listen around on the bands to estimate which bands are open and select the one with most or strongest stations. I usually start off on 10 meters and walk downwards on 12, 15, 17, 20, 30, 40 and 80 meters. If 10 meters is open, it can give you nice contacts with small amounts of power. That is during day time, if it is evening or night you might start off at 30 meters and walk your way down to 40 or 80. But as you know how propagation works, this is not news for you 😉
  • If you have Internet connection, send out a few CQ:s on each band and search for your call on Reverse Beacon Network (enter your callsign in the DX box) to see on what bands you show up and where your signals are strongest.
  • I prefer the WARC bands (12, 17 and 30 meters). They are contest free and generally less crowded.
  • Responding to CQ:s are way more efficient than sending CQ:s yourself. Even though your CQ might be heard, people have a tendency to respond to stronger signals and your will be weak when operating QRP.
  • If you decide to CQ yourself, use the QRP calling frequencies; 28.060, 24.906, 21.060, 18.086, 14.060, 10.116, 7.030 and 3.560 MHz. I usually add “QRP” one time before “PSE K” to indicate that I am operating QRP.

My QRP “go to” band usually is 30 meters. It is often open, it has propagation characteristics between 20 and 40 meters. And I usually get best results on RBN when I work 30 meters.

In the pictures below, I am operating QRP as SM0RGM/6 from a location nr Strömstad, Sweden.

Good luck and hope to see you on the bands! 73 de SM0RGM / OZ0RGM

Yaesu FT-818ND QRP and CW keyer
Yaesu FT-818ND QRP and CW keyer
HF-P1 10-80 meter portable antenna
HF-P1 10-80 meter portable antenna
EFHW 10-40 m on glass fibre fishing rod
EFHW 10-40 m on glass fibre fishing rod
Operating ham radio QRP as SM0RGM/6 from a temporary location nr Strömstad, Sweden
Cisco RV160 RFI fix
Stefan Helander

Cisco RV160 RFI-problems [fixed]

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Being an amateur radio operator (or HAM-radio operator) I need to use electronic devices with as low radio emissions as possible in order to keep a low noise level on the shortwave bands (or HF-bands). I found out that my Cisco RV160 router was one of the major sources of radio noise (RFI or Radio Frequency Interference) in my home. It turned out it was easily fixed as the culprit was not the router in itself, but it’s power supply.

The router runs on 12 volts DC (original power supply rated up to 1,5A) which is often available in the ham schack already. So in that case, get rid of the original power supply and hook up the router to your 12 volts DC supply in the shack. In my case, the router was located in another part of the house so I just replaced the power supply with another, transformer based power supply. In my case, a Mascot 6823, rated for 12 volts DC, 1A (intermittently up to 1,3A). Even though not the same amp rating as the original, it seems to be sufficient.