Re: 60 Meter homebrew rig IF frequencies
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In my BITX40 I used the VFO to switch USB/LSB for digital, so high side and low side. Worked great.Could I hear the difference? Yes. The filter skirt was different. Was it equally usable? You bet it was. And that was with just a 4 pole filter. Like this one. Check the plot on it.?
On Tue, Apr 29, 2025 at 11:48 PM, hwstar wrote:
If only it were so easy (it isn't) Sideband inversion: When the LO is above the IF the sideband gets inverted. The Crystal filter favors the LSB with the steepest roll of on the high side of the skirt.
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Steve
WA6ZFT
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But i think it? it is easy because will you hear the difference? I believe not.
I cant give exact figures because I do not have the precission equipment to measure it. Yes the roll off slope is greater on the high side. But many of the published plots do not show that much difference. So I just built the best xtal filter that I could using good parts and best matched xtals. So I have a 8mhz filter, 4 pole using 6 xtals (QER design ). My LO is at 15mhz for 40m so there is sideband inversion. But to my ears for a QPR tansceiver it sounds great. I do not believe I would? hear any difference.
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73
Kees PE9ST
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