[ARC5] A Heterodyne Sweep Generator

[Geoff]

Mine used audio AGC to the MC1350 IF amp. Built one for 80-15M including 
WARC, fun little things.

Carl




----- Original Message ----- 
From: "Fuqua, Bill L" <wlfuqu00 at uky.edu>
To: "David Stinson" <arc5 at ix.netcom.com>; "ARC-5" <arc5 at mailman.qth.net>
Sent: Thursday, March 13, 2014 1:18 PM
Subject: Re: [ARC5] A Heterodyne Sweep Generator


>  In some QRP transceivers they feed the AGC back into the input pins.
> By reducing the input bias voltage the gain is reduced. I can't recall the 
> exact radios
> that used this scheme but they derived the AGC voltage from the audio and 
> applied
> it to the mixer which had a transformer directly connected to the input 
> pins and a bypass to ground
> on one side. The AGC was applied to the bypassed side of the input 
> transformer.
>  However, I would suggest that you set up the system for constant output 
> and use a variable
> attenuator between the output and device to be tested along with the 
> appropriate series resistance
> to match the input impedance of the device under test.
>
> 73
> Bill wa4lav
>
> ________________________________________
> From: arc5-bounces at mailman.qth.net [arc5-bounces at mailman.qth.net] on 
> behalf of David Stinson [arc5 at ix.netcom.com]
> Sent: Thursday, March 13, 2014 11:20 AM
> To: ARC-5
> Subject: Re: [ARC5] A Heterodyne Sweep Generator
>
>> The NE602 has a useful amount of conversion gain - an advantage
>> in
>> receiver applications (which is what it was designed for) - and
>> often a
>> disadvantage in frequency-conversion applications,...
>
> Can the gain be throttled with negative feedback?
> I've used them but never looked into this.
> Back to yard work!
>
> 73 Dave AB5S
>
>
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