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Author Topic: Using an Old Scanner to Extend the Frequency Range of SDR Receivers  (Read 10253 times)
HAMMYGUY
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Posts: 86




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« on: September 24, 2011, 09:40:17 AM »

I noticed the thread on IF outputs and figured this probably deserves a thread of it's own. 

Most SDR receivers only cover the HF range and some do include coverage up to the 50Mhz range. Though their sensitivity is lacking up in the very high end ranges.  My Perseus while an excellent HF receiver only goes up to 40mhz.  My Flex-Radio SDR-1000 and Flex-1500 both do include coverage up to 6 meters.  The 1500 seems to have reasonable sensitivity up there. And I can't leave out my RF-Space SDR-IQ which only goes up to 30Mhz. 

Now I have quite a bit of interest in having a spectrum analyzer for 2 meters, 440, and the aircraft band.  The only SDR receiver that I've seen capable of doing that so far the FunCube USB "dongle" radio.  But I've seen that it really requires external preamps and filtering to make it usable.  Micro-Telcom was working on a project "Genesis" a while ago which would have had these frequency ranges, but I haven't seen much on it lately.   And of course transverters could be employed but are more money than I'm willing to put toward the result. 

Plus most hams are real frugal.  OK cheap.  Most want to do a project with the least amount of dollar output.  I'm certainly in that group.

Enter the lowly analog signal scanner.  Available on eBay for less than 1/4 of retail in most cases.  Most have 10.7Mhz IF's which can be readily tapped, but will need to be amplified to bring the signals up to a usable level, and have no roofing filters which allow a large swath of spectrum to be watched.  Using the scanner as a cheap converter really opens up a different aspect to SDR which isn't being offered yet at a reasonable price. 

I'm posting this as more of a thought process to see if others have done this, their results, and are some scanners better than others? 

This video on Youtube shows how this gentleman has done it using a Radio Shack Pro-2021.  I've purchased this scanner to try this experiment out.  I'll post what the results are. 

http://www.youtube.com/watch?v=pBlChNwNkjE









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KA4POL
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Posts: 2086




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« Reply #1 on: September 24, 2011, 11:57:15 AM »

Sounds interesting. You may also consider a TV tuner as a frontend: http://www.surplustraders.net/a/0142.shtml

If you were not so frugal  Wink I'd recommend you: http://www.winradio.com/ They offer a wide field of frequencies (9 kHz to 8599 MHz).

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W6RMK
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Posts: 659




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« Reply #2 on: September 25, 2011, 10:58:33 AM »

another approach is mixer + PLL or VCO+DAC.

Pick the frequencies right and you could do some sort of repeating harmonics off a 50MHz or 66MHz LO
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WS4E
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Posts: 232




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« Reply #3 on: September 25, 2011, 09:03:44 PM »

>The only SDR receiver that I've seen capable of doing that so far the FunCube USB "dongle" radio.  But I've seen that it really requires external preamps and filtering to make it usable.

Softrocks now can be built to cover the 2m, 6m, and 4m bands.


Good deal for $58. 

I have a 2m kit sitting on my work table as the next project to build.

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KS4JU
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Posts: 18




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« Reply #4 on: September 28, 2011, 10:27:03 AM »

The Alinco DJ-X11 has an IQ output and covers 0.05~1,299.99995MHz all mode and is very reasonably priced  Grin
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HAMMYGUY
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« Reply #5 on: September 29, 2011, 07:58:39 PM »

The Alinco DJ-X11 has an IQ output and covers 0.05~1,299.99995MHz all mode and is very reasonably priced  Grin

I do own one of them. While it's an excellent scanner, getting the ERW-8 cable to work has been a real challenge.  Several days later of playing with drivers etc, it still doesn't function.  Alinco's documentation on the IQ output is pathetic at best.   
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W4HIJ
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Posts: 367




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« Reply #6 on: October 01, 2011, 04:46:44 PM »

I think if the amateur satellite service hadn't gone virtually belly up that a 2m/440 and possibly even higher coverage transceiver along the lines of Flex 1500 would be a big seller. The capabilities of an SDR integrated with the PC  would  be a tailor made "building block" for a low cost sat station. Unfortunately though, the sats up there are dying off left and right, P3E will likely never see a launch and things like the ARISS SAT are just novelties. Doing what you are suggesting might be a neat experiment because I don't think we will see any manufacturers  put any serious development resources into a VHF/UHF SDR.
73,
Michael, W4HIJ
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W6RMK
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Posts: 659




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« Reply #7 on: October 01, 2011, 06:02:06 PM »

What's this about no VHF/UHF SDRs?   There's a fair number of them around.  A coworker uses a DSP-10 on 2m and 23cm.  The USRP is being used by hundreds of people, a lot of them on 70cm. You can do all sorts of interesting stuff with novel modulation schemes, innumerable coding schemes, and so forth.

OTOH, if you're looking for a "turnkey" VHF/UHF rig that's an SDR, I think you're right.  The market is way too small to justify it, and the FCC certification aspects are going to be pretty onerous.  It's a lot harder to prove that your 140-150 MHz, 400-450MHz receiver can't receive cellphones as an image, or on a harmonic of the LO, than it is on something with a 30 MHz low pass filter in front of it.

There are people contemplating a purpose designed satellite or EME rig that would use a PC as the backend signal processor, but that's down the road aways
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W4HIJ
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Posts: 367




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« Reply #8 on: October 01, 2011, 06:49:15 PM »

What's this about no VHF/UHF SDRs?   There's a fair number of them around.  A coworker uses a DSP-10 on 2m and 23cm.  The USRP is being used by hundreds of people, a lot of them on 70cm. You can do all sorts of interesting stuff with novel modulation schemes, innumerable coding schemes, and so forth.

OTOH, if you're looking for a "turnkey" VHF/UHF rig that's an SDR, I think you're right.  The market is way too small to justify it, and the FCC certification aspects are going to be pretty onerous.  It's a lot harder to prove that your 140-150 MHz, 400-450MHz receiver can't receive cellphones as an image, or on a harmonic of the LO, than it is on something with a 30 MHz low pass filter in front of it.

There are people contemplating a purpose designed satellite or EME rig that would use a PC as the backend signal processor, but that's down the road aways
Yes, I was talking more or less a "turnkey" version. Only a few years ago when the outlook for sats wasn't quite as dismal as it now appears to be, I would have killed for something along the lines and price range of a Flex 1500 for 2m/440 sat work. Would have been a lot of fun and made that part of the hobby more accessible for some.
 I think the cellphone stuff is ridiculous, the onus to insure privacy should fall on the cellphone companies, not scanner and amateur radio manufacturers but that's another debate and another thread for some other day.
73,
Michael, W4HIJ
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N3LCW
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Posts: 152




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« Reply #9 on: September 27, 2012, 07:02:53 AM »

Has anyone had recent success tapping the 10.7MHz IF output with any scanner and feeding an SDR receiver like the SDR-IQ?

Andy
N3LCW
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KE5JPP
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Posts: 0




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« Reply #10 on: September 27, 2012, 07:45:06 AM »

Here's what I am setting up:

https://sites.google.com/site/amateurradiointerferometry/file-cabinet/QS1R%20microwave.pdf?attredirects=0&d=1

https://sites.google.com/site/amateurradiointerferometry/file-cabinet/QS1R%20mixer%20basic%20configuration.jpg?attredirects=0&d=1

https://sites.google.com/site/amateurradiointerferometry/file-cabinet/QS1R%20UHF.pptx?attredirects=0&d=1

https://sites.google.com/site/amateurradiointerferometry/file-cabinet/SETI%20horn%20of%20plenty%20and%20hardware%20layout.pdf?attredirects=0&d=1

https://sites.google.com/site/amateurradiointerferometry/file-cabinet

I am building the BPFs needed instead of buying the Minicircuits ones since they are easy to do.  I will have 65 - 4400 MHz coverage. 

Gene


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KA4POL
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Posts: 2086




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« Reply #11 on: September 27, 2012, 07:54:34 AM »

Has anyone had recent success tapping the 10.7MHz IF output with any scanner and feeding an SDR receiver like the SDR-IQ?
This is not a big issue. You also can use the IF of old TV tuners. See http://www.geocities.ws/how_chee/cx23881fc6.htm
Using the IF in your case should be much easier.
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