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Test with unlocked DUO as a standalone 144MHz receiver, 144.002MHz, 100Hz BW, CW, using my DXing ears and Heil Pro7 earphones as a detector, I can hear down to -132dBm using my E4421B with additional 30dB attenuator as a source.
When I compare with my Kuhne TR144H transverter into the DUO, the MDS using the same ears is -156dBm. Perhaps with a good masthead preamp the DUO might be OK for 144. Using WSJT JT4A mode or PI-RX I can hear down to -163dBm with the Kuhne and no LNA.
Works fine in SW2 on WBFM 88-108MHz, but I can’t see any signals in 144MHz, and more worrying, I don’t see any increase in noise when I enable my masthead LNA. I *can* hear meteor pings from GRAVES on 143.050 with the preamp enabled, but the noise floor with or without the antenna plus LNA is unchanged.
On GB3VHF, with the LNA and DUO I get *some* JT65B decodes at 281km, but it is right at the limit of decodability
003400 1 -20 1.1 -5 3 * GB3VHF JO01EH
003800 2 -20 1.1 -5 3 * GB3VHF JO01EH
Certainly not state of the art 2M DX gear, also there are some very VERY big FM broadcast alias images in the 2M band unless I use the LNA with its sharp helical filters. I am 51km from the BC transmitter.
Useful backup maybe if I lose/forget the Kuhne. Simple enough to add a linear with 0dBm input for 70MHz or 144 and an LNA, but I’ll keep the Kuhne thanks.
Compare result with the Kuhne. 15dB better C/N ration. All JT65/PI-RX tests in 2.4kHz bandwidth
005600 9 -5 1.1 -5 3 * GB3VHF JO01EH
From the FAQ: http://support.eladit.com/kb/faq.php?id=4
FDM-DUO 2m Operation
To unlock the DUO (up to 165MHz): low pass filter must be off, check menu #2 “RX LP” and output must be set to 0dbm in menu #33 “TX OUT”
output is on the 0dbm sma socket
to unlock SW-2 open FDMSW2SwSetup.xml with an editor and search for UnlockDUOt at the bottom of the file. Set it to 1.
RX antenna jack can be used for VHF antenna (so HF ant on RX/TX and VHF on RX can be connected at the same time)
external preselector needed & amp if you need more than 0dbm output (this is 1mW).
Been doing some tests of my Elad FDM-DUO on HF bands with my noise-ridden lab environment. Using my HP E4421B sig gen with 30dB screened attenuator, the minimum discernable signal using PI-RX and JT4A is:
I was wondering if I was getting noise from the local environment up the coax outer or power/control leads, but those measurements were made with the coax screen of the HF antenna connected to the radio, so I guess not.
With the antennas connected (at 2200utc), I see a noise floor of -142dBm on 28MHz, only a couple of dB more than with a dummy load. On 18MHz, about the same. Across the bands from 18MHz to 30MHz, I see a few tones and squiggles, worst tones about -120dBm. Looks like I don’t have any significant local noise, at least between 18MHz and 30MHz. Interesting. Bit different on LF and VHF, where I have some work to do!
As ever, this was MY Duo and MY lab, YMMV!
Recording of GRAVES MS pings at 11:00 on 17th Nov using FDM-DUO SDR rx with Kuhne TR144H 14MHz IF, 9-ele LFA and 0.6dB LNA