[Elecraft] [K3/K3s] RF Gain Control

[Bob McGraw K4TAX]

In all instances, 160M, 80M, & 40M, I run 15 dB Attenuation. For 10M & 6M I run Pre 1.  RF gain is then adjusted per band as needed depending on band noise. 

Bob, K4TAX


Sent from my iPhone

> On May 17, 2020, at 5:30 PM, donovanf at starpower.net wrote:
> 
> Hi John, 
> 
> 
> The K3/K3S "RF Gain" control doesn't control any RF stage at all... 
> It actually controls the gain of the 8.215 MHz IF amplifier immediately 
> following the 8.215 MHz roofing filters which then controls the 
> 8.215 MHz IF signal level feeding the 2nd mixer. 
> 
> 
> See the K3 RF Board schematic, page 4 of 4. The 8.215 MHz 
> IF amplifier is Q1. IF amplifier gain is controlled the front panel 
> "RF Gain" control (labelled as VIF Gain on the schematic) via U3. 
> 
> 
> This is why its so critically important to select the correct Preamp 
> setting (Preamp1, Preamp2 (in the K3S) or OFF) and proper attenuation 
> level because those are the only gain controls in the RF path of the 
> K3/K3S. If you select Prramp or attenuation incorrectly you've inserted 
> excessive signal levels into the roofing filters and IF amplifier. 
> 
> 
> 
> 
> 
> 
> 73 
> Frank 
> W3LPL 
> 
> ----- Original Message -----
> 
> From: "John Reilly" <reillyjf at gmail.com> 
> To: Elecraft at mailman.qth.net 
> Sent: Sunday, May 17, 2020 9:40:06 PM 
> Subject: [Elecraft] [K3/K3s] RF Gain Control 
> 
> Where in the K3/K3s Block Diagram is the RF Gain control located? We're 
> having discussions concerning whether is is better to reduce the RF 
> Gain, or turn on attenuation to increase dynamic range, especially on 
> 40m and below. 
> Thanks, 
> - 73, John, N0TA 
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