Re: More Radio Articles and Designs


Gary Kinsman
 

Phil,

What I meant to say is that the S/N meter doesn't work when offset tuned. The RSSI meter still works in this case.

I tried using offset tuning with my PL-380 last night on SW. For me, the best combination is the 2 kHz filter with a 1 kHz offset. This provides very intelligible audio, and seems to reduce fading distortion a bit. I guess in theory a 2 kHz offset should be better, but it makes the sound too shrill, especially on fades. A 1.5 kHz filter with a 1.5 kHz offset might be ideal, but this is not possible with a stock radio.

A slower AGC would help quite a bit for fading distortion and pumping, but I'm not aware of any small radios that offer selectable AGC speeds.

A nice feature of the DSP filters is that they seem to be perfectly symmetrical. This is usually not the case with physical filters, unless they are very expensive.

Regards,
Gary

--- In ultralightdx@..., "gkinsman1" <gkinsman@...> wrote:

Thanks, Phil.

I especially enjoyed your article "Si4734 Offset Tuning." I'm going to give these techniques a try on my PL-380. It's too bad the signal meter isn't functional when doing offset tuning.

I find that offset tuning is often necessary on my PL-380 to minimize internal-generated hets on MW AM, but I haven't tried it for reduction of selective fading distortion (on MW or SW) yet.

Regards,
Gary

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