[Elecraft] [K3/K3s] RF Gain Control

[Dave Cole]

I looked at my K3, (not S), and I have a single step of ATT 10 DB, 
should I have more, or is it just the K3S that has multi steps.

73, and thanks,
Dave (NK7Z)
https://www.nk7z.net
ARRL Volunteer Examiner
ARRL Technical Specialist
ARRL Asst. Director, NW Division, Technical Resources

On 5/17/20 5:11 PM, Bob McGraw K4TAX wrote:
> 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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> 
> 
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