QRPp WSPR

This post summarizes all the links to my version 1 WSPR QRPp transmitter project.

• QRPp WSPR – The catalyst
• QRPp WSPR – System Design
• QRPp WSPR – The transmitter
• QRPp WSPR – The Crystal "Oven"
• QRPp WSPR – PIC Controller
• QRPp WSPR – QRSS Software
• QRPp WSPR – Adding WSPR
• QRPp WSPR – WSPR Software

 

Version 2 is already under design and features multi-frequency operation using a DDS VFO to replace the crystal oscillator and with an output power configurable between 0 and 5 watts.

 

I'll post updates on version 2 as I make progress.

Comments

[Peter , PE1DCD]

Hi Stu,
I am interrested in ver2 (with the DDS).
Sinds I have a GPSDO (http://www.jrmiller.demon.co.uk/projects/ministd/frqstd.htm) I have the NMEA-data, the 1 sec pulse AND a extreme stabel/acurate 10Mhz signal. My ideal WSPR-beacon runs autonome, exact on time, exact on freq, extract the loc from NMEA and runs on more bands (i.e. 1st period 30 mtr, 2nd period 17 mtr and 3rd period on 12mtr.....) with a relay for antenna switching. But my problem is: I am a complete ZERO with programming PIC's. Keep up the good work and sorry for my ugly english...
'73 Peter , PE1DCD

[Harley Burton]

I jusst finished a WSPR transmitter with the DDS-30 board and although it works, minus a PA, I'm wondering how much trouble you have had with drift of the oscillator? I can stabilize it with a GPS stabilizer as you describe, but I'd rather not ad that much extra hardware. In your experience is that necessary?

Thanks,

Harley

[Stu Phillips]

Harley,

Can't comment on the DDS-30 but here's my experience with the DDS-60.

The DDS-60 uses a canned 30 MHz oscillator as the source of the reference clock. This is an SMT part on the reverse side of the board from the DDS chip.

There are two major sources of thermal energy on the board - the DDS chip and the voltage regulator. Both get quite hot in operation.

The canned oscillator does drift with heat - so the DDS output frequency will drift as a result.

There is enough thermal output from the board that the small aluminum box that contains the DDS-60, connectors etc gets warm to the touch after a few minutes.

Without some mitigation, I saw enough drift in a 2 minute period to be on the edge of WSPR stability.

Here are some options beyond using a GPSDO as the reference clock.

1. Gene (W3PM) uses a DDS-60 board with a heat sink glued to the DDS chip with epoxy. This keeps much of the thermal energy seeping through the board and heating the canned oscillator. Gene still sees some drift on his WSPR reports but typically +/-1 Hz level.

2. Use a heated enclosure as I did with my gen 1 WSPR system. The thermal mass of the enclosure (aluminum, board, air etc) should be high enough that the additional thermal energy from the DDS is mitigated.

3. Remove the canned oscillator and re-attach it via stiff wire to stand the part physically off the board. I use this approach to temporarily re-attach the SMT part when I'm testing without the GPSDO - it works fine. This might be sufficient to improve the stability as the major source of thermal energy is seep through via the board from the DDS.

4. Use a crystal heater to thermally stabilize the canned oscillator. Kuhne Electronics sells a product that does this - its the QH40A. I don't know how much this costs but several folks have used this approach to stabilize the DDS-60.

Hope you find this useful!
Stu