Topband: Slightly OT - amplifier noise

[Michael Tope]

Dave is that -112 dBm you calculated the output referred noise? If so, 
what is the gain behind it?

Thanks,

73, Mike W4EF.......

On 3/14/2020 2:13 PM, Dave Cuthbert wrote:
> Steve, I ran a SPICE model of the MFJ-1095 front end. What gain there is
> resides there. The next three stages have unity gain. The input noise is:
>
> 1.8 MHz, 50 nV/Hz^0.5
>
> 7.0 MHz, 26 nV/Hz^0.5
>
> 14 MHz, 19 nV/Hz^0.5
>
> 28 MHz, 13 nV/Hz^0.5
>
> Depending on the input stage gain (I'm modeling 1 to 2 depending on the
> transformer) the three following stages can up the noise by 4-5 dB.
>
> At 7 MHz the 26 nV/Hz^0.5 is 580 nV in a 500 Hz bandwidth, or -112 dBm.
> This is 2.5 S-units. *What receiver are you using, what band and what is
> the bandwidth? *
>
>       Dave KH6AQ
>
> On Sat, Mar 14, 2020 at 6:40 AM <n2icarrl at gmail.com> wrote:
>
>> This discussion of Hi Z amplifiers has been quite interesting. Excellent
>> information from W1FV and K7TJR.
>>
>> I have an RX amp question, related but slightly off-topic.
>>
>> I have an MFJ-1025/1026 noise canceler. I like to use it on the higher HF
>> bands
>> to cancel power line QRN. The noise is typically S3-S4, but I want it down
>> to S0
>> to hear the bottom layer of stations. My sense antenna works fine, and the
>> QRN
>> is canceled. However, the MFJ-1025 amplifier noise is quite significant,
>> often
>> negating the QRN cancellation. The MFJ amplifiers are J310's. Any
>> recommendations for something quieter ?
>>
>> 73,
>> Steve, N2IC
>>
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