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posted by
Fnord666
on Monday July 08 2019, @03:11PM
from the does-it-take-10-minutes-to-warm-up? dept.
from the does-it-take-10-minutes-to-warm-up? dept.
Antique radio receivers retain a significant charm, and though they do not carry huge value today they were often extremely high quality items that would have represented a significant investment for their original owners. This guy acquired just such a radio, a Philco 37-11 made in 1937, and since it was it[sic] a bit of a state he set about giving it some updated electronics. Stripping away the original electronics, he gave it a modern amplifier with Bluetooth capabilities, and a Raspberry Pi.
One of the coolest applications for a Pi I've seen.
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Updating a Vintage Radio With a Pi
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(Score: 2) by Knowledge Troll on Tuesday July 09 2019, @04:50PM (1 child)
I don't think anyone can listen to more than one thing at once and make sense of it unless what they are listening to is silence. I often have multiple radios receiving at once but not all of them are making noise. Note too that my example was putting wavs on disk not listening to many repeaters at once. The use case for multiple receivers I want is monitoring multiple frequencies for activity or running digital decoders like listening to four 2M packet frequencies at once and monitoring multiple repeaters and the simplex call channel. Using audio ducking you can assign priority to each audio source and then make them mutually exclusive. I already run audio chains that use multiple speakers and duck audio inputs so I can use my desktop PC, listen to music, listen to system event sounds, listen to the ham radio, and I even cut the music when I hit the PTT so I'm not sending that audio out onto the air.
I had not thought of time shifting the quadrature data from the SDR receiver that's a really good idea! I had only thought about time shifting the demodulated audio but I think both features are pretty good ideas.
I've got a 7610 sitting next to me here. Dual receive in it is not implemented the way you think it is: it's not done with 2 software receivers and demodulators running at once, it's done with two complete sets of RF gear each with their own filters and ADC. Though you can, finally, access the quadrature sampled data from the 7610 via a dedicated USB port I haven't yet tried to do it. The idea of bringing an entire HF band in at once to the PC is enticing but because the receiver does per band filtering like a normal HF rig I won't be receiving all of HF entirely, just the specific individual amateur bands.
Anecdotally I used an Icom IC-7100 for HF before the 7610 and after i switched over to the 7610 my audio quality reports from other stations increased dramatically. It went from "you sound good" to "that is a beautiful sounding radio" and each time it was just using the vendor supplied chicken choker mics. Icom also has the new SDR direct sampling VHF and UHF rig called the IC-9700 which is basically the VHF/UHF version of a 7300. It direct samples even the 70cm part of the band! There's a few hams around here that got one recently and they love it though it's got buggy firmware right now.
That's a good idea though there are also off the shelf SDR amateur receivers offering 14 bits and a few mhz of bandwidth and still come in at a reasonable price around $130 or so. When I talk to people they report that 14 bits is nice and that 12 bits doesn't quite cut it. Both of those units are available with a small price difference. If I was dedicated to running a more custom SDR setup in the shack I'd look to one of those things I think. Something like an SDRPlay.
(Score: 2) by fyngyrz on Tuesday July 09 2019, @06:45PM
Well, that buys you things too. Means you can have legit reception on bands outside the bandwidth of the one SDR. And you should still be able to run them both on one band if you like. It just takes more hardware.
On the 7300, what you get is very narrow bandwidth — I think it might be after the demodulator bandpass, but before the demodulation. It's only a few KHz worth of sampling. It would be terrific if it was the full wideband sample... but it's not. If it is on the 7610, that's a very worthy feature.
But... no general coverage. 🙁
It is. Among others, I run an AFE822x, which is a $200-ish, 14-bit SDR with 10 KHz to 1.6 GHz coverage. I really like it. The Ethernet connection is da bomb; you can (and I have done) remote it far away from the computer(s), and so keep the dense RFI that comes out of computers, routers, and all that junk down to a dull roar. USB connections are tethered right to the computer which does not make me happy. But as I said, because of those 14-bits, I had to go with a notch filter to make sure that everything it heard coming in from the antennas was within its dynamic range. Otherwise... clipping, aliasing... awfulness. On VHF I use a stepped attenuator because all that local stuff is quite strong and I have no need for much sensitivity anyway. If it isn't within ten miles, it's over 75 miles away in some other small town and I just don't care. I just use a discone. Hears satellites really well, all the local stuff too. VHF is fun. 😊
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Math: the only place where people buy 60 watermelons and no one wonders why.