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K3S Preamp 2 Six Meter Noise Figure

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stengrevics

K3S Preamp 2 Six Meter Noise Figure

Does anyone know what the preamp 2 noise figure is on 6 meters? I have not been able to find it in the owner's manual or in Fred's book.

Thanks,

John
WA1EAZ

ab2tc

Re: K3S Preamp 2 Six Meter Noise Figure

Hi,

According to the ARRL review in November, 2dB! Deaf no more.

AB2TC - Knut

stengrevics wrote

Does anyone know what the preamp 2 noise figure is on 6 meters? I have not been able to find it in the owner's manual or in Fred's book.

Thanks,

John
WA1EAZ

Charlie T, K3ICH

Re: K3S Preamp 2 Six Meter Noise Figure

I'll bet its a lot better than that.

A 39¢ GG junction FET pre-amp will do under well 2dB on 6.

Charlie k3ICH

-----Original Message-----
From: Elecraft [mailto:[hidden email]] On Behalf Of ab2tc
Sent: Monday, May 01, 2017 2:08 PM
To: [hidden email]
Subject: Re: [Elecraft] K3S Preamp 2 Six Meter Noise Figure

Hi,

According to the ARRL review in November, 2dB! Deaf no more.

AB2TC - Knut

stengrevics wrote
> Does anyone know what the preamp 2 noise figure is on 6 meters? I
> have not been able to find it in the owner's manual or in Fred's book.
>
> Thanks,
>
> John
> WA1EAZ

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stengrevics

Re: K3S Preamp 2 Six Meter Noise Figure

That was my reaction as well, but that is what the QST review states.

John
WA1EAZ

> On May 1, 2017, at 3:02 PM, Charlie T, K3ICH <[hidden email]> wrote:
>
> I'll bet it’s a lot better than that.
>
> A 39¢ GG junction FET pre-amp will do under well 2dB on 6.
>
> Charlie k3ICH
>
> -----Original Message-----
> From: Elecraft [mailto:[hidden email]] On Behalf Of ab2tc
> Sent: Monday, May 01, 2017 2:08 PM
> To: [hidden email]
> Subject: Re: [Elecraft] K3S Preamp 2 Six Meter Noise Figure
>
> Hi,
>
> According to the ARRL review in November, 2dB! Deaf no more.
>
> AB2TC - Knut
>
>
> stengrevics wrote
>> Does anyone know what the preamp 2 noise figure is on 6 meters? I
>> have not been able to find it in the owner's manual or in Fred's book.
>>
>> Thanks,
>>
>> John
>> WA1EAZ
>
>
>
>
>
> --
> View this message in context:
> http://elecraft.365791.n2.nabble.com/K3S-Preamp-2-Six-Meter-Noise-Figure-tp7
> 630221p7630223.html
> Sent from the Elecraft mailing list archive at Nabble.com.
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>
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>
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>
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Wes Stewart-2

Re: K3S Preamp 2 Six Meter Noise Figure

Just because a "device" will do under 2 dB (or whatever) doesn't mean an
amplifier necessarily will. Circuit losses, mismatch and bias settings will
affect the circuit NF.

Additionally, something like an HP noise source is made to be a good source
match, both on and off. Those with lower excess noise, indicating the presence
of an attenuator are better at this than higher noise sources. Nevertheless,
there can be a difference. If one of these sources is used to both tune and
measure an amplifier, the NF can, and probably will be, different when connected
to an antenna. These differences are probably in the noise, excuse the pun, at
6 meters but can be significant at higher frequencies.

Many years ago when GaAs FET were just arriving a friend designed and built a
preamp for 1296 MHz. I measured the NF at 0.6 dB, but after looking at the
undercertainties the number was something like (going by memory) 0.6 dB +1,
-0.6, in other words, it could be perfect. This was all due to the 10:1 input
SWR. With a vector network analyzer these uncertainties can be resolved, but
it's not trivial.

I had to chuckle after HP donated an HP8970 to the ARRL lab years ago and they
reviewed an ARR preamp and listed the NF to two decimal places, presumably
because that's what the instrument reported.

Wes N7WS

On 5/1/2017 12:15 PM, John Stengrevics wrote:

> That was my reaction as well, but that is what the QST review states.
>
> John
> WA1EAZ
>
>> On May 1, 2017, at 3:02 PM, Charlie T, K3ICH <[hidden email]> wrote:
>>
>> I'll bet it’s a lot better than that.
>>
>> A 39¢ GG junction FET pre-amp will do under well 2dB on 6.
>>
>> Charlie k3ICH
>>
>> -----Original Message-----
>> From: Elecraft [mailto:[hidden email]] On Behalf Of ab2tc
>> Sent: Monday, May 01, 2017 2:08 PM
>> To: [hidden email]
>> Subject: Re: [Elecraft] K3S Preamp 2 Six Meter Noise Figure
>>
>> Hi,
>>
>> According to the ARRL review in November, 2dB! Deaf no more.
>>
>> AB2TC - Knut
>>
>>

Edward R Cole

Re: K3S Preamp 2 Six Meter Noise Figure

In reply to this post by stengrevics

I did some checking on this.

QST article shows K3S MDS using preamp 2 as -145 dBm for 6m which is
pretty good.
Calculating MDS for a NF of 2 dB provides -146.5 dBm using a bandpass
of 500-Hz (which is what Elecraft cites for MDS).

The NF for 14 MHz is 8 dB (which is nominal on most new HF
receivers). MDS = -139 dBm measured by ARRL for preamp 1

I use the PR6-10 on my K3 which the same as preamp 2 in the K3S (I believe).
My external ARR GasFet preamp is cited 0.5 dB NF which corresponds to
-155.1 dBm (with PR6-10 off)

-145 dBm is quite respectable MDS on 6m. -155 dBm is eme level.

73, Ed - KL7UW
http://www.kl7uw.com
Dubus-NA Business mail:
[hidden email]

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