Electronics > RF, Microwave, Ham Radio
Are there any off-the-shelf 1.4 GHz SSB AM FM receivers?
Ben321:
I'm looking for a receiver that can receive in AM, FM, USB, or LSB mode, for frequencies at least as high as 1.4204057517667 GHz (this very specific frequency is the 21cm hydrogen radio spectral line, typically used in radio astronomy). Of all the modes though, the one that's most important is USB. If I tune to 1kHz below this frequency while it's in USB mode, if there is hydrogen gas near the receiver's antenna, I should hear a 1kHz tone. Is there an off-the-shelf receiver I can buy that will tune to frequencies that high, and be able to listen in USB mode? I know ICom has some receivers that can tune that high, but they are limited to AM and FM reception in those bands, and USB reception is only permitted in bands below 1.3 GHz. I have an ICom PCR-1000 (computer controlled receiver) and it can use all modes in all bands, but the highest frequency it can receive is 1.299999999 GHz (just short of 1.3GHz). There are other receivers that ICom offers that can tune up above 1.3GHz, but in those higher bands, USB and LSB reception is disabled.
Can anybody here recommend a receiver that is being sold commercially (no custom equipment, no modified equipment) that can tune in to the hydrogen 21cm emission, while in USB mode? And if so, what would it cost?
cdev:
I have had very good luck with a $10 off the shelf RTL2832 R820T DVB-T dongle I bought on ebay. Its the mid size one with the PAL antenna connector (not MCX) It comes in either white or black and has a curved row of holes in a parabola pattern.
What could be more appropriate for radio astronomy. I think Markus Leech who is a software developer who works on the Gnuradio project has standardized his hydrogen line reception setup on this particular dongle.
That was several years ago.
The specific dongle is a good one for mods because it comes on a postage stamp sized PCB and all four corners are ground plane and so it lends itself well to mounting on a larger PCB as a carrier. Also the connections you can make to the capacitors to improve its filtering are easy. (not as important for VHF and above but important if you want to use it for HF reception, (which requires soldering two tiny wires to the chip and having them stay there which is hard, even for an experienced solderer.)
Actually, I see its now $6.50 with free shipping.
Performance, durability (of the antenna connector) and frequency accuracy of that model is quite good. It receives from 24-1766 MHz.
I use it with CubicSDR software and a Planar Disk antenna.
An LNA is useful for radio astronomy. You can buy a very good MMIC based LNA with a noise figure well under 1 db for around $35 from Adam in Croatia, if you search on "LNA4ALL" You definitely should use one. You can actually benefit greatly from a double stage LNA in that particular application.
You should download some of the plans for inexpensive radio astronomy antennas. You'll need a high gain antenna to get any kind of resolution on your plots. You can build a horn out of cardboard and foam core inside of a discarded refrigerator box. Feed it with a cantenna/waveguide adjusted for optimal performance.
David Hess:
The usual solution is to use a transverter with an existing HF, VHF, or UHF SSB receiver. Receivers intended for use with a transverter have an offset function so they display the correct frequency.
AOR makes SSB receivers which can receive 1.4 GHz but I do not know how well they work and they are not cheap.
There is a good list which includes wideband SSB receivers here:
http://www.universal-radio.com/catalog/widerxvr/chartw.html
Ben321:
--- Quote from: David Hess on January 27, 2017, 05:08:43 am ---The usual solution is to use a transverter with an existing HF, VHF, or UHF SSB receiver. Receivers intended for use with a transverter have an offset function so they display the correct frequency.
AOR makes SSB receivers which can receive 1.4 GHz but I do not know how well they work and they are not cheap.
There is a good list which includes wideband SSB receivers here:
http://www.universal-radio.com/catalog/widerxvr/chartw.html
--- End quote ---
Where can I get one of these transverters that you speak of? Does any company sell any such item commercially? Or is this something that has to be custom built by the person who's going to use it?
David Hess:
--- Quote from: Ben321 on January 27, 2017, 08:15:09 pm ---Where can I get one of these transverters that you speak of? Does any company sell any such item commercially? Or is this something that has to be custom built by the person who's going to use it?
--- End quote ---
They are somewhere between custom built and commercially available. The problem will be finding a already built one which covers 1.4 GHz because they are usually designed for as narrow a frequency range as possible to prevent intermodulation problems.
QST and QEX magazines occasionally include kit based transverter designs which could be modified for 1.4 GHz.
These guys make a kit which could be used with a 2 meter SSB receiver if the local oscillator frequency is changed:
http://www.minikits.com.au/eme23-trv.htm
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