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@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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