Finding trimmers and using srectrograms.

An image really is worth a thousand words when it comes to precision handiwork such as aligning the ATS-909 HF receiver. The radio is small, with small trimmers and associated components. Fortunately, they are only a few and not hard to locate. Alignment requires setting the trimmers, watching a spectral display, and readjusting as necessary until the receiver tunes to within a few hertz at both low and high ends of its tuning range. The trimmers are delicate, so work gently and methodically on this fine radio. Click on the images to enlarge.

Where to find T14, VC4, and VC5:
(be gentle with the coils and trimmers!!)

ats-909 main board circuitry

Where to Find TC301

ats-909 secondary board circuitry

Spectrograms below were created with Spectran

WWV seen in USB mode, 14999 kHz; beat note = 1028 Hz (receiver error = - 28 Hz)

spectrogram of alignment signal

WWV seen in USB mode, 14999 kHz; beat note = 1007 Hz (receiver error = -7 Hz)

spectrogram of alignment signal

Tags: ATS-909, DX-398, receiver mods, radio hacks

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