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Re: LF: Image-Cancelling Exciter

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
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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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