[Lowfer] EAR tests this morning & early afternoon

[wa3tts at verizon.net]

JB & All:  I thought I would try some e-probe vs NW EWE tests before the afternoon QRN took over the spectrum.

First image below is my e-probe antenna driving a 300kHz LPF and then into a 2N3904 common emiiter preamp with a 470 ohm collector resistor and 22 ohm emitter resistor,  (via a pair of 185 kHz bridge T diplexers before and after the preamp)

Gain of 470/22 = 21 or 13~ (supposedly).  If I add the 100 ohms or so from the preamp B+ chokes the gain is more like 570/22 =25.9  and 10*log(25.9) = 14.1 dB....

So here is the filter>preamp>converter arrangement...

https://www.dropbox.com/s/popp6fe8uo02quh/IMG_1206.JPG?dl=0


And here is the e-probe capturing EAR...note the green bar level on the left....

https://www.dropbox.com/s/thi59jju1j8174k/IMG_1197.JPG?dl=0


Now I switch to the NW EWE antenna....

https://www.dropbox.com/s/z60f3v9g3raw4hh/IMG_1198.JPG?dl=0

Note how the e-probe is showing a -50.8 peak and the NE EWE antenna is showing a -54.6 peak, yet the background noise is lower on the NW EWE and EAR is visually stronger...

Now I switch to the e-probe antenna through the filters without the 2N3904 preamp and the prior two captures are on the waterfall as well...

https://www.dropbox.com/s/nvidvxfmixbwe88/capt00003.jpg?dl=0

At this point I will mention the combination of the 300 kHz LPF with the 185 kHz bridge T diplexers before and after the filter have a combined insertion loss of 
.6dB as measured with my Wavetek signal generator set at 188.83 kHz and Boonton RF millivolt meter....

In all these tests the AGC is off and the preamp is off on the FT-817 with the IF dial frequency 3.188.83 MHz  (3.0 MHz converter LO)

I can bring up the e-probe visual trace somewhat by turning on the FT-817 internal  preamp to increase the system gain, but it is not quite enough to make up the 
total background signal level to where ARGO works optimally for visual trace display.  It seems that ARGO really "likes" to operate well with the green level meter set at about 1/2" tall for weak signals and background noise...


I picked-up and SDRPlay RSP1A at Dayton, so here is my view of the AM Band on my e-probe with no filters other than the RSP1A AM band internal filter-attenuator and the LC shunt in the e-probe input which I have set near 1020 kHz (which take the  very local 1020 kHz and 1080 kHz AM stations down about 40 dB). Otherwise the e-probe is a single fet J310 W1VD modified AMRAD circuit....

https://www.dropbox.com/s/rqnxedgtvn6m212/IMG_1202.JPG?dl=0

Here is the e-probe and 300kHz filter-diplexer-preamp-diplexer combination with the RSP1A set at 273.0 kHz, which is the strongest local NDB station (UCP, New Castle, PA)...

https://www.dropbox.com/s/0g6xkew2znuw2dl/IMG_1205.JPG?dl=0

Having all the local AM stations down at -100 dBm or so seems to help the weak signal chasing for me...

Next thing to try is to roll the 2N3904 gain back a bit more, (another 2~3dB, etc.).  Going from a 4 ohm emitter resistor to a 22 ohm emitter resistor made a 1 S-unit improvement in my poor-main's 500Hz switched Zener noise source-to-variable attenuator setup in AM envelope detection mode with the FT-817...

73 Mike wa3tts