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| To: | rsgb_lf_group@blacksheep.org |
|---|---|
| Subject: | Re: LF: Image-Cancelling Exciter |
| From: | Wolf DL4YHF <dl4yhf@freenet.de> |
| Date: | Sun, 16 Jan 2005 22:30:00 +0100 |
| In-reply-to: | <005801c4fc0a$c5526380$0500a8c0@charter.net> |
| References: | <005801c4fc0a$c5526380$0500a8c0@charter.net> |
| Reply-to: | rsgb_lf_group@blacksheep.org |
| Sender: | owner-rsgb_lf_group@blacksheep.org |
| User-agent: | Mozilla Thunderbird 0.9 (Windows/20041103) |
Hi John, Nice drawing, and much more complete than my "sketch" hi.. One question... Was the L.O. using 74AC74 + 74AC08 better than the simple 74 HC 107 method ? ...and one suggestion:To eliminate the need to adjust the offset voltage for the 4 input opamps, simply use AC-coupling. I found this very cute to reduce the number of trimpots to the minimum (namely zero). The TL084 which I used had an output offset error near 7 mV, the AC coupling (0.22 uF) between the OPAMP output and mixer input completely eliminates this. The 2.5 V bias for the switches was provided with a simple voltage divider from the 5 V supply. So much for today, further experiments will follow soon. Regards, Wolf DL4YHF . |
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