Saturday, January 22, 2022

Tonga volcanic eruption

On January 14, 2022 a large volcanic eruption resulted in an atmospheric pressure disturbance which was measurable on weather station barometers around the world. The energy from the eruption was estimated to be equivalent to 10 megatons of TNT (many times greater than typical nuclear bombs).
KL3RR-2 barometric pressure increased from 1003.5 mbar to 1005.2 mbar before dropping to a low of 1002.6 mbar. (Sensor measurement interval 15 minutes)

Satellite imagery of the eruption.

Tuesday, December 7, 2021

Furnace RFI affecting HF radio

Modern furnaces benefit from advances in technology allowing improved performance and higher efficiency.  However, if certain "good practice" aspects of design and implementation are not considered by the manufacturer, these technologies can also be a source of Radio Frequency Interference (RFI) which is detrimental to radio communication.  This is especially problematic when attempting to receive HF transmissions which have very low power levels after traveling long distances and are easily obscured by local noise.
The main emitter of RFI in this particular Lennox High Efficiency forced-air direct vent gas furnace seems to be the draft inducer fan.  This is a variable speed fan which acts to push the exhaust gases up the chimney since with high efficiency furnaces the exhaust temperature is too cool to depend on passive rising.  The voltage reaching the motor (and hence its speed) is modulated through rapid on/off switching (PWM), a technique which inherently generates and radiates RFI without proper mitigation.  The blower motor is also variable speed but does not seem to emit significant RFI like the draft inducer.
The goal of the fix should be to add impedance (resistance to Alternating Current) to any wires leaving the metal furnace enclosure so that any internally generated noise is significantly attenuated before traveling into (unshielded) wires inside the walls of the house which will radiate the noise and easily reach a nearby HF antenna.  These are the 120V power supply wires (Line, Neutral, and Ground) and 5 wires which run to the thermostat.  

Added clip on ferrite chokes (Fair-rite VO) to 120V supply wires (L,N,G). There are at least 2 chokes in series per wire (not all visible).

At the bottom of this control board we have the wires running to the thermostat upstairs.  Disconnecting at the terminals makes it easy to twist the wires (which also adds impedance) as well as add a toroid choke with about 4-5 loops.

This is the inducer fan motor itself.  Disconected pigtail to twist wires and added 3 clip on chokes in series.

Another view: chokes added to inducer fan wiring.  Where there was room I added a choke per individual wire.  Sometimes the chokes went over multiple wires; both ways add impedance.

Before this filtering every time the furnace came on 40m and above were wiped out by noise.  Now it makes no noticeable difference whether the furnace is running or not.

Igate upgrades

 Made some changes to APRS igate KL3RR-2 this summer:

  •  Radio: Baofeng UV3R to Yaesu FT-60r 
  •  TNC: Mobilinkd TNC2 to TNC3
  •  Antenna: Arrow J-Pole to Diamond X50A antenna 

The igate performance (stations & distance heard) immediately increased.  This was most notable when switching from the Baofeng to Yaesu radio.


Diamond X50A - bird approved.


Vertical X50A (VHF/UHF) and horizontal G5RV Jr. (HF)

Wednesday, June 30, 2021

Economical 12 Vdc power supply

Purchased an Xbox 360 power supply at the thrift shop for a few dollars. It has a relatively powerful 14.2A 12V output.  It is basically a computer power supply in a portable ruggedized kid-proof casing. For the Xbox 360 there are 3 versions: 16.5, 14.2, and 12.1 amp.  Others have reported converting them to general 12V power supply use.

First step was to cut the factory dc plug off.  When you plug the power supply into AC power you will get an orange LED.  To enable the 12V output connect the red and blue wires together (the LED will change to green).  You can wire them together permanently or even switch it electronically and have a remotely controllable dc power supply.  

The voltage is a bit low @ 12.2V, but is acceptable and does not drop too much under load. As far as noise it is surely not in the same league as a proper (much more expensive) power supply. However, I have tested it briefly on the HF bands and was still receiving quite a few signals. It's definitely superior to other low-cost switching power supplies and 12V chargers I have tested. Should work great for VHF and above.  May not be ideal for 24/7/365 application, there is a variable speed internal fan which would probably fail after some time. Still, considering the cost, it makes a decent portable or spare/beater 12V power supply.

Xbox 360 power supply with 30A Anderson connector installed.  Noise on HF could be further improved by adding more impedance in addition to the single choke that is on the dc output cable from the factory.

Tuesday, June 29, 2021

APRS Weather Station

Added weather station (WX) temperature, % relative humidity, and barometric pressure data to APRS igate. As with most APRS fixed stations KL3RR-2 periodically sent a packet out containing a position and static "comment" which has now been replaced with (more useful) weather telemetry.

Reading temp + RH over RF (433 MHz) from an Acurite wireless remote sensor using an RTL-SDR and rtl_433.  Many other brands and models of wireless weather stations are supported. Barometric measurements are from a Bosch BMP 280 communicating with the Raspi through I2C bus.  

The pressure measurement is corrected to sea level barometric pressure and all parameters are fed into APRS client XASTIR through a "networked WX" interface using a combination of shell + python scripts and the network utility nmap.  (Inspired by


KL3RR-2 Raspberry Pi igate + WX


Bosch BMP280 absolute pressure sensor on Adafruit board in "custom" enclosure. Accurate to ±1 hPa / mbar. 


KL3RR-2 sending a WX packet (XASTIR on Raspberry Pi OS).

A week of weather data as presented by  KL3RR-2 sends out a WX packet every 15 minutes.    

This weather data can also be provided to the Citizen Weather Observer Program directly through APRS-IS.  Submitting WX data to this program provides useful quality analysis which can help detect problems and improve the accuracy of the station.

Wednesday, October 28, 2020

APRS over DMR with the Anytone 878

Recently setup APRS over DMR on the Anytone 878...

The first step is to enable GPS and APRS in "Options" under the "Tool" menu in the CPS software.  Then proceed to the "APRS" options window through the "Public" settings tree:

APRS setup window in Anytone 878 CPS.
 Red dots highlight important configuration options:

  • "Fixed beacon location" - "Off". Current location will be sourced from GPS.
  • Channel settings - "Report Channel" and "Report Slot" set to "Current Channel" and "Channel Slot" respectively.  We will be creating a seperate channel to use APRS over the local DMR repeater.  "APRS TG" is 310999 for APRS-IS through Brandmeister.  "Call type" set to "Private call". 
  • "Repeater Activation Delay" - 300 ms   

Talk group "DigitalAPRS" created (BM TG 310999).
Channel settings.
  • "Digital APRS PTT Mode" - "On".  APRS beacons are only sent when PTT is pressed
  • "DMR MODE" - "Repeater". Required for syncing of  timing when using a multiple timeslice repeater.  Ensure receive and transmit frequency are correct.
  • "Contact" - "DigitalAPRS".  Sets Talk Group to 310999 which sends APRS traffic into APRS-IS through Brandmeister. 

Made it in to!

Monday, June 29, 2020

Field Day 2020

KL3RR/P QTH BP53gd. East Fork Chulitna river. G5RV jr strung up back in the trees.

Icom IC-7300.  Laptop for WSJT-X and JS8Call digital modes on 10, 20 & 40m.

Wednesday, June 17, 2020


The NanoVNA is a tiny, self contained, portable, but low cost Vector Network Analyzer.  It features a touch screen and built in lithium rechargeable battery.

NanoVNA with included accessories (minus SMA to UHF adapter).

Of interest to the radio operator is being able to measure reflected power and calculate the Standing Wave Ratio (SWR) over a frequency range.  The NanoVNA automates this resulting in an easy-to-interpret graphical summary of antenna radiation efficiency vs. frequency. 

Hooked up to the Firestik 2MCKB 2m antenna. 

Triangle "1" at 143.400 MHz showing 1.05 SWR.  Should work well on the 2m band 144-148 MHz.

This information is crucial for effective antenna building or diagnosing and many antennas can be adjusted to improve SWR around a desired frequency.

Monday, June 15, 2020

-Hermes-Lite 2 - HF SDR transceiver

Minor assembly required.
Hooked up to power, antenna, and ethernet for interface to PC.
The Hermes-Lite can listen on an unlimited number of virtual receivers which can concurrently monitor 4 bands at up to 384 kHz x 4 total bandwidth. 

HF digital modes allow many simultaneous transmissions to fit into a relatively narrow slice of bandwidth. 

The receiving capability of the Hermes-Lite coupled with specialized software and the processing power of the computer allows for monitoring a significant chunk of the HF digital mode frequency range using a single radio. 

SparkSDR - Transmitting on 20m with the built in 5W amplifier and N2ADR filter board. Just over 20 virtual receivers monitoring HF digi modes with one DigiU dedicated to JS8Call.

It is somewhat intensive for the PC and LAN.

I was initially using a 2014-vintage i5 laptop which handled it but was a bit strained and the cooling fans were noisy in that state.  Since then I have switched to a i5-3470 desktop machine which handles it better and with less noise.  I am seeing about 2.5 TB/week (45 Mbit/sec) of data transfer between the HL2 and SparkSDR in the above receiver configuration with 192 kHz sampling bandwidth. The gigabit LAN has plenty of capacity left.

24/7 automated decoding of these signals contributes to an online reporting database allowing visualization of world-wide HF propagation activity:

Pskreporter stats - HL2 with about 20 receivers over a 24 hour period.  Each marker represents a station heard and color denotes the frequency (40m, 30m, 20m, or 17m).  Transmissions between Alaska and Europe travel over the north pole.
On Raspberry Pi 4:

VNC into Raspberry Pi 4 with about 16 receivers (SparkSDR).  Sampling bandwidth 96 kHz. 26 Mbit/s going between HL2 and RPi4.
The Raspberry Pi 4 May be comfortably usable with up to about 4-6 receivers.  Of note is the fact that VNC server uses a significant amount of CPU.  I already disabled the "waterfall summary" for each virtual receiver with some CPU savings, but it seems driving the waterfall graphics adds a significant load especially over a remote connection. 

Sunday, October 6, 2019

-APRS applications

Overlooking Anchorage, Alaska 3510 ft ASL.  Anytone 878-UV transmitting APRS beacon.
On the way up/down some location beacons were not recorded. APRS tracking is limited to where you can be heard by an igate or repeater.  On VHF this is basically line of sight to town.

Sunday, April 28, 2019

-Install/upgrade external antennas, coax into house, & ground system.

2x galvanized conduit (1 & 1.25" EMT) + hose clamps & exhaust clamp saddle + extended ubolt to connect the two sections.  Arrow OSJ 146/440 Mhz J-pole now @ ~30 ft HAAT.

Safety and compliance inspector Jay collecting fee after approval of a Steller installation.  Always seal exposed UHF connections with rubber splicing and electrical tape.

2x Comet CTC-50M window feed-thru jumper with vinyl sliding windows. Final setup will go through wall.

Ground rod installation.  Easily bore down 10 ft in 2 minutes using metal tubing & home water pressure.

Sunday, March 24, 2019

-Raspberry Pi 3 and Mobilinkd TNC2 for APRS duty

  • Setup XASTIR on Raspbian to act as an Igate using Mobilinkd KISS TNC.

XASTIR doing RF -> inet gating.  Terminal highlights commands to activate Bluetooth serial link after paired to Mobilinkd.

Update 6/2020 - Have been running an APRS Igate KL3RR-2 for about 1.5 years. Initially had some issues with bluetooth stability on the Raspi3.  The BT link would fail after a few weeks. I found this was a known issue and solved in the Raspi3 B. Indeed it fixed the problem and now has run stable for many months without any intervention.

Current hardware for KL3RR-2 is a Baofeng UV3R, Mobilinkd TNC2, Raspi3 B running Raspbian and XASTIR.  Antenna is an Arrow J-Pole at approx 30' height.

I appreciate the GUI of XASTIR both for visualization (which is a key outcome of the data produced by APRS) as well as being able to interact and use the station for APRS functions such as messaging.  Coupled with connecting to the raspi via VNC this makes for a functional APRS Igate that is remotely accessible and controllable. 

KL3RR-2 APRS Igate interface via remote connection (VNC).

Sunday, March 17, 2019

-12 Vdc power

Current home setup for powering radio equipment:

Electrical hardware mounted on a cutting board.  Samlex SEC-1230UL 30-A charger, Optima Blue Top 55-Ah battery.  Blue Sea Systems (marine) fuse panel and various other components intended for car audio.
  • The SEC-1230UL is a switch mode supply but quiet enough to not interfere with HF reception.  
  • With the SEC-1230UL and a battery, the system behaves as a dc Uninterruptible Power Supply.
  • With 120 Vac available, the system can maintain a <30 A draw indefinitely (limited by the charger).  However, higher amperages can be sustained intermittently (limited by the battery).

Monday, March 11, 2019


New Mobilinkd TNC 2.2 . Working well so far.  Very quick to setup.  
It links to a tablet, phone, or computer (via Bluetooth) and a radio (via cable).  

The Mobilinkd is a KISS TNC.  It MOdulates/DEModulates between the radio audio in/out and a digital signal sent over the Bluetooth-serial link while facilitating switching of the radio PTT.

The end functionality is completely dependent upon software.  One of the most common uses is for APRS:

Mobilinkd TNC 2.2 w/ Baofeng UV-3R and APRSdroid on a tablet.
The high resolution screen is ideal for mapping APRS data.

The radio and TNC are a compact package.
The Bluetooth is nice as the tablet is not constrained by a physical link to the TNC.

Sunday, February 10, 2019

-DMR hotspot operational

TP-Link TL-WR802N (Travel Wifi AP router) and SharkRF openSPOT 1
Local digital radio internet gateway. 20 mW max output (UHF)

(radio) <-> (openSPOT) <-> (worldwide DMR networks via internet)

-APRS troubleshooting. Anytone 878UV

Anytone AT-D878UV as heard by rtl-sdr+gqrx. Garbled coordinate data in APRS position transmission causes it to be ignored by receiving stations.

A second example showing other stations' APRS traffic for comparison

Update 2/27: Found some information here leading me to a solution for the APRS issue.  Below is a screenshot of my 878 APRS settings which have resolved the unintelligible transmission problem:

Take note of the time delay settings (with red dots) as well as the lack of a coma in "APRS signal path".  These changes resulted in my APRS transmissions clearing up and finally showing up on


Update 2020: Updating the CPS and radio firmware to the latest (and matching) versions seems to have eliminated the above issues.  Through the last year I have been using the 878 with to transmit my position in a number of challenging outdoor environments and it has performed and held up well.  Looking forward to APRS messaging capability in the future.

Anytone AT-D878UV DMR & Analog VHF/UHF radio

Sunday, May 24, 2015

Sunday, April 12, 2015

-Portable HF in Alaska

Finished customizing the new protective case:

New setup, Pelican 1495
(Yaesu FT-857D and LDG Z-11 Pro II)

Old setup.  Backpack portable. Chugach Park AK.