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Messages - M R I

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Thank you for your great posts and for tuning into Best Smooth Jazz. If you would like a QSL send in your report to the email listed below.

General Radio Discussion / Re: Voice of Greece Shut Down March 31?
« on: February 12, 2022, 2209 UTC »
We also sent a email to them.


Nice AM at S9+ on SDR

Very good signal and music selection WTF

Thanks for all the fine reports!  :D

Equipment / Re: SW Receiver Recommendations
« on: January 26, 2022, 1614 UTC »
SDR’s have the best sound out of the box.

Had a copy on the R-390A

Listening on the R-390A in SAM USB.

2214 with Papa by Paul Anka

Now in AM mode

2224 Sunglasses At Night by Corey Hart.

That would not surprise me. Thanks for the info.

0010 Low signal in the noise. The best reception of my radios including SDR is the Collins R-390A with the automatic sideband selectable synchronous AM stereo detector.

Equipment / Re: R-390a Users
« on: January 05, 2022, 0036 UTC »
As far as stability on the R-390A I re worked the cosmos PTO VFO for mechanical stability and now after full warmup the drift is now 4Hz with the heaters off. Just amazing for a receiver that is 59-71 years old.

Equipment / Re: Parallel LC MW Notch Filter
« on: December 30, 2021, 1909 UTC »
Nice. Just enough to bring down the signal around one frequency.

The RF Workbench / Re: speech synth + Kahn ssb tx on arduino
« on: December 29, 2021, 1645 UTC »
I have been working with Arduino in my transmitters and receivers. Nice work. Keep us informed on your progress.

Equipment / Re: R-390a Users
« on: December 25, 2021, 0504 UTC »
Hello MRI, I would be very interested in the mod to make the R-390a go below the broadcast band. I have done only the AGC diode mod which works very well. Can you enlighten me on what that LF mod might be?


Hello Radioroom. All that is needed is a in a .01 disc capacitor connected to test point E209 going to your antenna with one end to ground. For best results use or make a bifilar antenna isolation transformer for ground loop hum and common mode rejection. The 390A will go down to 20Kc. Disconnect this antenna input when using higher bands.

Equipment / Re: R-390a Users
« on: December 19, 2021, 1924 UTC »
 I have a R390 Collins made that has original paint and meters. I have done very little repair work on it. I also have a R390A that I have restored it adding original meters to it. If you want to experience newer performance on both add a SDR interface to the 455Khz IF or add a tap on input BNC connectors before the filters for a wider spectrum display. Run your SDR software. The only thing is to keep in mind you will have some frequency drift over time which I minimized by adding a stable filament voltage regulator to the PTO VFO. I prefer the R390 performance over the 390A cost reduction version (except the mechanical filters) and by using the SDR you get the advantage of the brick wall filters anyway. One big advantage is you can use the 390 /A in a high RF field as long as it is not in your passband because of the excellent front end selectivity.

 For very good stability I may add a VFO stabilizing circuit to the PTO or switchable in out DDS VFO. This is just a possible future update but not necessary for most listening conditions.

 By the way you can add a simple mod that will allow the R390 to go below the broadcast band.

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