WSPR-TX XP Plus Transmitter

The WSPR-TX XP Plus is a standalone all band WSPR transmitter with built in GPS for the radio amateur experimenter.
This Plus version is pretty much the same as the WSPR-TX XP except for two additional features in the Plus model:
1 WiFi
2 External frequency reference input

 
Some quick features:
1: Standalone operation, PC required for configuration but not for operation.
2: Works on any Ham band from 136kHz to 70MHz
3: Is powered from 5V.
4: Pre-built and tested except for the output low-pass filter that needs to be added.
5: Comes with built in GPS module and included external GPS antenna with a 3m (10 feet) cable.
6: Set up your call-sign and apply power and off you go!
   Timing and Maidenhead position is automatic from the GPS network.
   Take it camping, move it to another QTH, use it mobile.
   Needs only 5V 250mA so can be powered from a phone charger or USB power pack.
7: Open source software and Schematic is published on Github.
Low-pass filters are sold separately and can be either on-board or external filters.
Check out the Mezzanine boards for some automatically switched filter options.

 

 
The WSPR-TX XP Plus works on any Ham band from 136kHz to 70MHz and is powered from 5V.
Once you have set up your call-sign it will operate independently indoors or outdoors with minimal requirement of interaction from the user.
There is no need to have it connected to a computer, no need to set the time or to interact with it in any way. The WSPR-RX_LP1 takes care of everything needed automatically for you.

 
The GPS provides the timing necessary to ensure that the WSPR transmission is occuring at the correct time. The GPS also provide the position information needed to calculate the Maidenhead code that is transmitted. This is a great feature as it means the users don’t have to know the Maidenhead grid before getting on the air. This can be very convenient if you take the transmitter to a new location or use it in a mobile application.

The output power around 250mW is in my opinion just perfect for WSPR operation. With a dipole antenna it will give you continent coverage most of the time but when the conditions are favorable it will give you trans-continent contacts so at this power level it easy to see how the daily conditions change.
The input power requirements are 5V 100mA at idle and 250mA when transmitting.
This makes it possible to use a laptop computer, phone charger or a USB Power pack to power it in mobile or stationary operation mode.
What better way to test out your portable antennas than to stick this in your backpack with a USB power pack and try out different antennas or mobile QTHs?

 
Advanced but not high cost, minimal assembly required by the user.
To keep cost down and to minimize the amount of version I need to build and keep in stock I have not populated the Low Pass filter on the output.
The buyer will have to build this filter to complete the transmitter. Everything else is built, calibrated and tested.
The low pass filter is sold separately, see the shop for options.

 
For more information including links to the Source code and Schema - see the product page.  https://www.zachtek.com/1048

 
The product comes with an external GPS antenna, a WiFi antenna and a USB cable but without a power adapter. (USB phone charger can be used)

 
At the time of this writing (October 2023) there is now support for the WiFi in the Firmware.
Future firmware may include support for WiFi to be used for timing from NTP servers and/or to be used for configuration of the device.
These improvements may take a long time to be included or may not be included at all.

 
The frequency reference input is typically used with a 10MHz OCXO.
The firmware can be configured to use other frequencies by the user but the current firmware (V2R18) have only been tested with a 10MHz reference.
Using other reference frequencies may result in the PLL becoming unlocked or outputting the incorrect frequency.
Input waveform for the reference signal can be either a sinus or a square wave.
Minimum level for the reference signal is 8dBm, PLL unlock conditions occur below this level.
Maximum level is 18dBm, damage may occur if this limit is exceeded.