SoftRock TXRX and WSPR using I/Q

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K9IQY's picture
Last seen: 2 years 11 months ago
Joined: 2011/02/23 - 21:55
SoftRock TXRX and WSPR using I/Q

Can someone please help clarifying the process to adjust the suppression of the transmit image for an old ham but a newcomer to this technology? Here is my understanding of the process but it doesn't seem to be right:

Ref: WSPR 2.1: Supplement to User’s Guide

Image Rejection

To adjust TX image rejection you need a separate communications receiver. Start WSPR, select the desired band, check the Idle box, set TX fraction to 100%, and click the Tune button. WSPR will send a series of long dashes at the selected frequency Tune in the main signal on the separate receiver; then find the unwanted image, which will be offset in frequency by twice the sum of Fiq and the Rx BFO frequency. (For the example setup described above, the image is 27 kHz below the desired signal.) While listening to the unwanted image, slowly adjust the sliders labeled TX I/Q Balance and TX Phase on the Setup | I-Q Mode screen, seeking a null. There are two sliders for each parameter — the upper one for coarse adjustments, the lower for fine. New settings are applied at the start of each transmitted dash. When you have found the best null you may exit WSPR. The program will remember your last settings of TX I/Q Balance and TX Phase.

Selected frequency (for TX?): double click in the waterfall to select?

Dial frequency: 10.1387 MHz

Fiq = 12,000 Hz

Rx BFO = 1,500 Hz

Desired signal: 10.140200 MHz

2 x (12,000 Hz + 1,500 Hz) = .027 MHz

So then, 10.140200 – .027 = 10.113200

Undesired TX image = 10.113200?