Filament Change Gcode

Just found this nice Gcode to help you set up a filament change for multiple colors in a print at a certain layer. Quoted from the original site which is linked below.

How to pause printing to switch filament

Posted by carlos, 16 November 2015 3:47 pm

In order to do multi color print with one extruder. You can pause the printer at a specific height. Make sure your machine supports the M600 command otherwise just see what they use for said firmware. Just insert the following after the layer height call in the gcode file. For example search for “; layer 5” and add the following after it:

;Pause Code
G91 ;Set Relative Mode
G1 E-5.000000 F500 ;Retract 5mm
G1 Z15 F300 ;move Z up 15mm
G90 ;Set Absolute Mode
G1 X20 Y20 F9000 ;Move to hold position
G91 ;Set Relative Mode
G1 E-40 F500 ;Retract 40mm, this can be commented out if you just want to pause to insert magnets or something.
M300 ;Beep (marlin)
M600 X0 Y0 Z10 E10
G90 ;Set Absolute Mode
G1 F5000 ;Set speed limits, depending on slicer this can be set to your initial mm/min speed or it can be used for the following move only then the next layer will set the speed
G28 X0 Y0 ;Home X Y
M82 ;Set extruder to Absolute Mode
G92 E0 ;Set Extruder to 0

Running on smoothieware, make sure to have the following set up in your configuration file (from:

## for switching filament
leave_heaters_on_suspend true
after_suspend_gcode G91_G0E-5_G0Z10_G90_G0X-50Y-50 # Gcode to run after suspend, retract then get head out of way
before_resume_gcode G91_G1E1_G90 # Gcode to run after temp is reached but before resume – do a prime

Please refer to for more information at

There is also the G4: Dwell command

Example: G4 P200

In this case sit still doing nothing for 200 milliseconds. During delays the state of the machine (for example the temperatures of its extruders) will still be preserved and controlled.

Lastly if you use simplify 3D check this forum post on how to do it from the slicer:

Nozzle Purge and Wiping Gcode

Found this useful little snippet of Gcode that can be added to the start of a print to make sure the nozzle is well primed and clean. Original post linked below.

Purge and nozzle wipe starting gcode

Posted by carlos, 2 September 2015 2:01 pm

Use this gcode to purge and wipe filiment before printing.

Simplified version

M107 ;turn off fan
G28 X0 Y0 Z0 ;home X, Y and Z axis end-stops
G29 ;initiate z-probing
G1 X0 Y0 Z.10 ;move to corner of bed
G92 E0 ;zero the extruded length
G1 F200 E3 ;extrude 3mm of feed stock
G92 E0 ;zero the extruded length

Advanced wipe and purge

M107 ;turn off fan
G28 X0 Y0 Z0 ; home X, Y and Z axis end-stops
G29 ; initiate z-probing
G0 X0 Y0 F9000 ; Go to front
G0 Z0.15 ; Drop to bed
G92 E0 ; zero the extruded length
G1 X40 E25 F500 ; Extrude 25mm of filament in a 4cm line
G92 E0 ; zero the extruded length
G1 E-1 F500 ; Retract a little
G1 X80 F4000 ; Quickly wipe away from the filament line
G1 Z0.3 ; Raise and begin printing.

3D Printed Antenna Radial Storage Spools

My larger multi-band antenna, a Wolf River Coil, comes with a trio of pre-cut radial wires to attach to the legs. No matter how carefully I roll them up into a tied off bundle, the next time I get them out and setup the antenna, I spend a significant amount of time untangling them.

I’ve been thinking about solving this problem with my 3D Printer for a while, but I have a ton of projects like this in the works and it’s taken me a while to get around to it.

While shopping for some other radio parts the other day however, I saw a commercial radial storage spool design in a portable antenna kit that I really liked. It was elegant, practical, and not overly complicated. So I dove into Fusion 360 to draw my own version of the design.

Finished Antenna Radial Storage Spool Design

I exported the design to a .STL file, sliced it up in Cura using the draft .2mm layer height profile and 20% infill with a brim, and zipped it off to my OctoPi for printing in a dark blue PLA+ filament on my silent-steppered (mod) Anet ET5X.

The spool about halfway printed. The nozzle was just a little too far away so I used the blue tape to hold the brim down to the bed!

The resulting spools (I printed three) came out great!

Finished 3D Printed antenna radial spool.
Much better antenna radial storage!

I’ve uploaded the design to Thingiverse if you want to print your own 🙂

FT8 QSOs from Utah!

Working HF from my current base location has been a bit difficult due to the available locations for antennas being rather limited and all indoors. (I live in a tiny apartment.)

However, last week I spent a few days in Utah for a wedding in the family and had the opportunity to make quite a number of HF contacts on FT8 from a park in Ogden, a church lawn in Orem, and even from the roof of my parked car outside my hotel!

I logged contacts from Canada, California, Washington, Mexico, Oregon, to name a few.

But my favorite one was made with a station (K7NWF) here in Arizona that I just can’t hit from Arizona due to the bounce distance being about 500 miles on 20m. We sail right over each other’s heads normally, and we had unsuccessfully been trying to make a FT8 or FT4 contact for 4 days, but Saturday night as the sun was going down, we watched our signals shorten, hitting closer and closer till we finally popped up on each other’s digital signal reports.

WSJT-X QSO Window with K7NWF
PSKReporter – KJ7DJR Signal Received by K7NWF
Daylight almost gone when we finally made contact on 20m

I was using my Comet HFJ-350M compact multi-band antenna planted on the roof of my car right outside my hotel room and my radio in the trunk. The radio I was using was a Xiegu G90, along with a SignaLink USB Soundcard.

Operating out of the “Ham Shack in the Trunk” earlier in the week

Other QSO’s over those few days also used a Wolf River Coil Screwdriver antenna where space permitted a pretty large radial ground plane footprint, but that really wasn’t possible to set up at the hotel since the space is tight in the parking lot and there is not much lawn. (I really didn’t want anyone running over my radial wires or antenna!)

All in all it was very rewarding to finally be on my way to my first award (I’m within 5 confirmed contacts of the World Radio Friendship Award) and it’s terrific to finally be working HF.

Thank you to Norm, Don, and all my other Elmers who’ve helped me graduate into the Skywave arena.

Xiegu G90 Digital Modes with SignaLink Setup

The Xiegu G90 is a great little affordable radio which has digital capabilities. While Xiegu (CEE-eh Goo, not Zy-Goo for you non-Mandarin speakers) does supply a break out module, the CE-19 for connecting to a soundcard with digital modes, many hams prefer to use a little more robust plug-n-play setup like the Tigertronics SignaLink.

However setup information if you want to use the G90 and SignaLink together is sketchy and incomplete. I’ve spent a lot of time searching, and cobbling together the pieces from various sources including help from a couple of Elmer friends (Norm K7NWF and Don WQ1E) to get it working, so I’m going to document my own digital setup in this post in the hopes that it might be useful to someone else to have it all in one place.

What you will need:

  • Xiegu G90 Radio
  • SignaLink USB (SLUSB8PM) properly jumpered (SLMOD6PM) for the G90
  • SignaLink 8-pin Mini Din Cable (SLCAB8PM – included with the SLUSB8PM SignaLink, but you can buy one separately if needed)
  • USB B to USB A Cable
  • WSJT-X Software

(Note: No rig control – You’ll need to tune the radio to frequency yourself because the closest thing you’ll find to the G90 rig control commands are in the ICOM family of radio profiles, and not everything works properly in those profiles.)

Cable Connections:

Connect the Radio’s rear Accessory port to the SignaLink RJ45 jack using the 8-pin min-Din cable. Be careful to line up the arrow on the 8-pin connector of the cable pointing DOWN. The cable fits one way only and you can damage the socket or cable pins if you try to force it in the wrong way. (Ask me how I know that, I dare ya =) )

Connect the SignaLink to your computer’s USB port using the USB B to USB-A cable.

The computer should automatically install the drivers and treat the SignaLink as a USB Audio Codec device.

Computer Audio Configuration:

In your control panel, set the default Sound Playback and Recording devices on your computer to the regular speakers and microphone. (Your SignaLink should NOT be handling the regular computer system sounds, just the communications for the radio through the WSJT-X software.)

G90 Radio Configuration:

These settings come from OH8STN’s helpful video.

VOX – Enable VOX for the PTT setting

Line Input – Change the input from Mic to Line Input

Input Audio Levels – Set input Audio levels to 10.

Audio Out Level – Leave set to 15.

AGC – Turn AGC Off (Should Show AGC– on the display)

Power Level – Set to around 18w

SignaLink Settings:

Set the TX knob about halfway.

Set the RX knob about halfway.

Set the Delay knob to 0.

Software Configuration:

Open the WSJT-X Software.

In File > Settings

General Tab – Fill in your Callsign and Grid Square

Radio Tab – Set Radio to NONE. Set PTT Method to VOX

Audio Tab – Set the Soundcard to select your SignaLink USB Audio Codec in the Input and Output dropdowns.

Set the Power between the top two marks in WSJT-X on the right hand part of the screen.

WSJT-X Power level setting

You should now be ready to tune up your antenna to the chosen band, run the auto-tuner on your G90, and start making contacts!

Happy QSO-ing!


Random Wire Antenna Lengths

A very simple type of antenna is a plain random length of wire, but making one that can be used on multiple bands has been complicated.

Here’s an excellent article with a chart showing the best wire lengths for multiple band operations.

Random Wire Antenna Lengths

The trick is to make sure that the wire is not a multiple of 1/2 wave length on any band you want to use.

Vertical Antenna Theory: Loading and Ground Planes

Because of the sheer length of the radio waves in certain bands, portable antennas or antennas in low space/stealth applications use a number of tricks or compromises to get resonance and radiating power sufficient to make contacts.

Two of these tricks and compromises used with vertical antennas are Loading and Ground Radials.


Loading is a technique where electrical length is added to the antenna by using coils of wire placed in the middle of the antenna. In effect, part of the antenna is compressed into a smaller space but the electrical current still “sees” a longer path.

There is a cost for this technique however, in the adding of more inductance to the antenna.

Loading most often is implemented at the base of the antenna for practical reasons– such as stability, but that is not the most efficient place compared to loading at the middle or top of the vertical.

Here are a couple of resources discussing how loading at different points in the antenna differ.

Base vs. Center Loading Vertical Antennas – Discussion of loading using different positions in the antenna at

Center vs. Base Loading Antennas – Similar discussion of antenna loading positions, including the loading of fiberglass masts at

Ground Planes:

“The antenna ground plane acts as a simulated ground. It is found that for a monopole antenna like a quarter wavelength vertical, the ground acts as a plane to reflect the radio waves so that an image of the top half of the antenna is seen in the Earth.

It is possible to simulate this function by replacing the real earth with a conducting plane. To function as an antenna ground plane, the conducting surface must extend for least a quarter wavelength from the base of the antenna.”

Antenna Ground Plane: theory & design (At – excellent discussion of how ground planes work, how impedance is altered depending on the angle of the radials.

Soda Can Battery From Trash

I really love DIY projects and proof of concepts with electricity and radio so when I saw this little project using soda cans, cardboard, copper wire, sand, and saltwater to build a battery, I was all over it.

(video from, an alternative to YouTube’s increasingly anti-free speech platform)


  1. Cut the tops off of old soda cans carefully and deburr the can edges.
  2. Draw circles around the bottoms of the cans on a sheet of cardboard to create the bottom insulators.
  3. Cut out the circles, and place each one inside the cans at the bottom.
  4. Cut out rectangles of cardboard to just slightly under the height of the cans and wide enough to form a tube inside the can. These will be your insulators for the sides of the can battery cells.
  5. Insert the cardboard tubes into the cans.
  6. Create a coil out of copper wire for each can with about an inch of the wire sticking above the can top.
  7. Place the coils inside the cans and center. Fill the cans with play sand around the coils nearly to the top.
  8. Add 2T of salt to 16.9oz of water, and mix well.
  9. Fill the cans with the saltwater mix until the sand is completely saturated.
  10. Check the voltage and amps of each cell by clipping tester leads to the center copper wire and the can top edge.
  11. Use hot glue to fasten the cans down in place to a piece of foamcore board or plastic. Leave a little space between each cell to avoid shorting out across the cells.
  12. Wire the cells in series, from center conductor of one cell to side of the next cell. (The side of the can is negative, the center conductor is positive.)

MagLoop Antenna Construction Resources

Surprisingly, though ham radio operators usually have a ton of radios, antennas are even more important. You can have the most expensive radio in the world, but without a good antenna for your location that is tuned properly, you’ll have a hard time getting contacts at all. So hams are always testing, building, and fiddling with antennas.

MagLoop antennas are useful for confined spaces, indoor, or stealth installs such as in apartments.

Here are some really excellent resources for designing and building MagLoops.

80-20m MagLoop Antennas – Very in depth discussion on the different variables and principals that make for a good MagLoop.

Multi-Turn MagLoop Antenna – Comparison table of variables for a 6.5ft magnetic loop antenna for 40 meters.

3-Band Magnetic Loop Antenna Design – Short schematic design for a 20-30-40 meters Magnetic Loop antenna. Includes construction details.

How to Update Your Address on Your Ham Radio Operator License

A requirement of maintaining an amateur radio operators license is that you must update the FCC with your current address if you move.

Failure to keep your address updated and accurate can result in losing your ham radio license, so you’ll want to make sure you don’t forget to update it.

There are a number of independent companies that will do this for you, for a fee, but you can actually do this yourself online for free if you know how.

The FCC provides instructions on how to update your address here.

You will need your FCC Registration Number (FRN number). If you have forgotten what it is, your can look it up by searching the FCC License Database for your call sign.

Go to the FCC’s Online License Manager to file your change of address.

Login with your FRN and your password you created when you got your FRN.

Find your license in the list and look to the right hand side of the screen where it says Work on this License.

There is an update link in the box. Click the link to start the process to update your address.

Follow the prompts to update your address, and certify the application.

You’re done! Easy and free.

A few useful FCC links: