Shack re-wiring: RTL-SDR options?
Hi folks,
Has anyone used an RTL-SDR dongle on the 10.7 MHz IF output from another receiver? Is that better than going direct?
My cable TV provider is forcing us to go all-digital. With the new "cable box" comes the opportunity to re-wire the shack and simplify the many layers of cables, splitters, and lash-ups that have accumulated over the years. The proverbial camel is crying out for help.
What this has to do with Ham Radio is that part of the lash-up mess is an old pre-CATV deep fringe TV antenna that I have in the attic, aimed to the southern horizon. We are well outside the range of any of the digital OTA stations, and never one to leave a perfectly good piece of RF equipment go to waste, I currently have it fed to an old Icom R-7000 scanning receiver (previously used as the AO-40 downlink IF) and to an RTL-SDR dongle by way of a TV 2:1 splitter. I've tried hooking the dongle directly to my 2m ham antenna for satellite use, but for some reason that was less than satisfactory. Never really did hear much of anything, and never could figure out why. At least with the TV antenna, I can copy some stuff with the dongle, though the Icom is generally better. But the Icom doesn't do the various digital modes that are better suited for SDR.
Looking at the back of the Icom, I see that it has a 10.7 MHz IF output, so the thought is that the SDR dongle might perform better hooked there (with a DC bias block) instead of to the antenna itself through the splitter. Both receivers have similar frequency coverage, but perhaps the Icom, while somewhat deaf by modern standards, might still make for a better front-end to the dongle?
I think the down-side is that the Icom's IF bandpass is narrower than the Dongle's, so I'd lose some flexibility there. I would also lose the ability to software-control the frequency of the receive chain, outside of the IF bandpass.
What do you think? Would this be a net win or loss for the RTL-SDR?
Thanks,
Greg KO6TH
On 03/02/17 16:46, Greg D wrote:
Hi folks,
Has anyone used an RTL-SDR dongle on the 10.7 MHz IF output from another receiver? Is that better than going direct?
I would hope (but perhaps not assume) that your R-7000's front-end is better than the silicon tuner within the RTL dongle. The IF will already have AGC applied to it, so overload of the dongle won't be a concern once you get the level from the IF tap down to something that doesn't over-range the dongle's AGC input on typical signals. That can be done with a simple inline attenuator.
Here's some information about a hardware mod which allows "direct sampling mode" on the dongle:
http://www.rtl-sdr.com/rtl-sdr-direct-sampling-mode/
By doing this, you are essentially creating a Panadapter for the R-7000.
Let us know how it works!
--- Zach N0ZGO
I don't think an RTL dongle will tune down that low.
Jim KQ6EA
On 03/02/2017 10:46 PM, Greg D wrote:
Hi folks,
Has anyone used an RTL-SDR dongle on the 10.7 MHz IF output from another receiver? Is that better than going direct?
My cable TV provider is forcing us to go all-digital. With the new "cable box" comes the opportunity to re-wire the shack and simplify the many layers of cables, splitters, and lash-ups that have accumulated over the years. The proverbial camel is crying out for help.
What this has to do with Ham Radio is that part of the lash-up mess is an old pre-CATV deep fringe TV antenna that I have in the attic, aimed to the southern horizon. We are well outside the range of any of the digital OTA stations, and never one to leave a perfectly good piece of RF equipment go to waste, I currently have it fed to an old Icom R-7000 scanning receiver (previously used as the AO-40 downlink IF) and to an RTL-SDR dongle by way of a TV 2:1 splitter. I've tried hooking the dongle directly to my 2m ham antenna for satellite use, but for some reason that was less than satisfactory. Never really did hear much of anything, and never could figure out why. At least with the TV antenna, I can copy some stuff with the dongle, though the Icom is generally better. But the Icom doesn't do the various digital modes that are better suited for SDR.
Looking at the back of the Icom, I see that it has a 10.7 MHz IF output, so the thought is that the SDR dongle might perform better hooked there (with a DC bias block) instead of to the antenna itself through the splitter. Both receivers have similar frequency coverage, but perhaps the Icom, while somewhat deaf by modern standards, might still make for a better front-end to the dongle?
I think the down-side is that the Icom's IF bandpass is narrower than the Dongle's, so I'd lose some flexibility there. I would also lose the ability to software-control the frequency of the receive chain, outside of the IF bandpass.
What do you think? Would this be a net win or loss for the RTL-SDR?
Thanks,
Greg KO6TH
Sent via [email protected]. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
Doh!
Well, that answers that question. Thanks, Jim. You are correct! 24.00 is the minimum Gqrx will let it go.
Greg KO6TH
Jim Jerzycke wrote:
I don't think an RTL dongle will tune down that low.
Jim KQ6EA
On 03/02/2017 10:46 PM, Greg D wrote:
Hi folks,
Has anyone used an RTL-SDR dongle on the 10.7 MHz IF output from another receiver? Is that better than going direct?
My cable TV provider is forcing us to go all-digital. With the new "cable box" comes the opportunity to re-wire the shack and simplify the many layers of cables, splitters, and lash-ups that have accumulated over the years. The proverbial camel is crying out for help.
What this has to do with Ham Radio is that part of the lash-up mess is an old pre-CATV deep fringe TV antenna that I have in the attic, aimed to the southern horizon. We are well outside the range of any of the digital OTA stations, and never one to leave a perfectly good piece of RF equipment go to waste, I currently have it fed to an old Icom R-7000 scanning receiver (previously used as the AO-40 downlink IF) and to an RTL-SDR dongle by way of a TV 2:1 splitter. I've tried hooking the dongle directly to my 2m ham antenna for satellite use, but for some reason that was less than satisfactory. Never really did hear much of anything, and never could figure out why. At least with the TV antenna, I can copy some stuff with the dongle, though the Icom is generally better. But the Icom doesn't do the various digital modes that are better suited for SDR.
Looking at the back of the Icom, I see that it has a 10.7 MHz IF output, so the thought is that the SDR dongle might perform better hooked there (with a DC bias block) instead of to the antenna itself through the splitter. Both receivers have similar frequency coverage, but perhaps the Icom, while somewhat deaf by modern standards, might still make for a better front-end to the dongle?
I think the down-side is that the Icom's IF bandpass is narrower than the Dongle's, so I'd lose some flexibility there. I would also lose the ability to software-control the frequency of the receive chain, outside of the IF bandpass.
What do you think? Would this be a net win or loss for the RTL-SDR?
Thanks,
Greg KO6TH
Sent via [email protected]. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
Sent via [email protected]. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
Greg,
There are modified versions of the RTLSDR dongle that support direct sampling. That is to say, a signal is fed directly into the RTL2832 chip, bypassing the tuner/down-converter chip. This enables reception of signals from 0 to 14.4 MHz (half the 28.8 Msps sampling rate of the analog-to-digital converter). Perhaps you could make use of one of these. Search for them on Ebay or through Google in general. You may need to attenuate the 10.7 MHz IF signal prior to feeding into the dongle, as too strong a signal will damage it. Hope this helps.
73,
Mac / AE5PH
On 03/02/2017 10:40 PM, Greg D wrote:
Doh!
Well, that answers that question. Thanks, Jim. You are correct! 24.00 is the minimum Gqrx will let it go.
Greg KO6TH
Jim Jerzycke wrote:
I don't think an RTL dongle will tune down that low.
Jim KQ6EA
On 03/02/2017 10:46 PM, Greg D wrote:
Hi folks,
Has anyone used an RTL-SDR dongle on the 10.7 MHz IF output from another receiver? Is that better than going direct?
My cable TV provider is forcing us to go all-digital. With the new "cable box" comes the opportunity to re-wire the shack and simplify the many layers of cables, splitters, and lash-ups that have accumulated over the years. The proverbial camel is crying out for help.
What this has to do with Ham Radio is that part of the lash-up mess is an old pre-CATV deep fringe TV antenna that I have in the attic, aimed to the southern horizon. We are well outside the range of any of the digital OTA stations, and never one to leave a perfectly good piece of RF equipment go to waste, I currently have it fed to an old Icom R-7000 scanning receiver (previously used as the AO-40 downlink IF) and to an RTL-SDR dongle by way of a TV 2:1 splitter. I've tried hooking the dongle directly to my 2m ham antenna for satellite use, but for some reason that was less than satisfactory. Never really did hear much of anything, and never could figure out why. At least with the TV antenna, I can copy some stuff with the dongle, though the Icom is generally better. But the Icom doesn't do the various digital modes that are better suited for SDR.
Looking at the back of the Icom, I see that it has a 10.7 MHz IF output, so the thought is that the SDR dongle might perform better hooked there (with a DC bias block) instead of to the antenna itself through the splitter. Both receivers have similar frequency coverage, but perhaps the Icom, while somewhat deaf by modern standards, might still make for a better front-end to the dongle?
I think the down-side is that the Icom's IF bandpass is narrower than the Dongle's, so I'd lose some flexibility there. I would also lose the ability to software-control the frequency of the receive chain, outside of the IF bandpass.
What do you think? Would this be a net win or loss for the RTL-SDR?
Thanks,
Greg KO6TH
Sent via [email protected]. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
Sent via [email protected]. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
Sent via [email protected]. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
I don't know what your budget is, but an SDRPlay would work fine at those frequencies and is a higher performing SDR as well.
-Scott, K4KDR
--------------------------------------------------------------------------------
-----Original Message----- From: Mac A. Cody Sent: Friday, March 03, 2017 12:03 AM To: [email protected] Subject: Re: [amsat-bb] Shack re-wiring: RTL-SDR options?
Greg,
There are modified versions of the RTLSDR dongle that support direct sampling. That is to say, a signal is fed directly into the RTL2832 chip, bypassing the tuner/down-converter chip. This enables reception of signals from 0 to 14.4 MHz (half the 28.8 Msps sampling rate of the analog-to-digital converter). Perhaps you could make use of one of these. Search for them on Ebay or through Google in general. You may need to attenuate the 10.7 MHz IF signal prior to feeding into the dongle, as too strong a signal will damage it. Hope this helps.
73,
Mac / AE5PH
On 03/02/2017 10:40 PM, Greg D wrote:
Doh!
Well, that answers that question. Thanks, Jim. You are correct! 24.00 is the minimum Gqrx will let it go.
Greg KO6TH
Jim Jerzycke wrote:
I don't think an RTL dongle will tune down that low.
Jim KQ6EA
On 03/02/2017 10:46 PM, Greg D wrote:
Hi folks,
Has anyone used an RTL-SDR dongle on the 10.7 MHz IF output from another receiver? Is that better than going direct?
My cable TV provider is forcing us to go all-digital. With the new "cable box" comes the opportunity to re-wire the shack and simplify the many layers of cables, splitters, and lash-ups that have accumulated over the years. The proverbial camel is crying out for help.
What this has to do with Ham Radio is that part of the lash-up mess is an old pre-CATV deep fringe TV antenna that I have in the attic, aimed to the southern horizon. We are well outside the range of any of the digital OTA stations, and never one to leave a perfectly good piece of RF equipment go to waste, I currently have it fed to an old Icom R-7000 scanning receiver (previously used as the AO-40 downlink IF) and to an RTL-SDR dongle by way of a TV 2:1 splitter. I've tried hooking the dongle directly to my 2m ham antenna for satellite use, but for some reason that was less than satisfactory. Never really did hear much of anything, and never could figure out why. At least with the TV antenna, I can copy some stuff with the dongle, though the Icom is generally better. But the Icom doesn't do the various digital modes that are better suited for SDR.
Looking at the back of the Icom, I see that it has a 10.7 MHz IF output, so the thought is that the SDR dongle might perform better hooked there (with a DC bias block) instead of to the antenna itself through the splitter. Both receivers have similar frequency coverage, but perhaps the Icom, while somewhat deaf by modern standards, might still make for a better front-end to the dongle?
I think the down-side is that the Icom's IF bandpass is narrower than the Dongle's, so I'd lose some flexibility there. I would also lose the ability to software-control the frequency of the receive chain, outside of the IF bandpass.
What do you think? Would this be a net win or loss for the RTL-SDR?
Thanks,
Greg KO6TH
I know there are plans for simple upconverters out there, but I've never built one.
I've owned most of the SDR receivers out there, from $5 dongles to both FunCube dongles, the HackRF One, SDRplay, and now the AirSpy. Depending on what you want to use them for, and *where* you're located, they can be really cool, or a disappointment.
Here in the RF Alley of SoCal, the cheap dongles can really fold up on strong signals many, many MHz away from the signal-of-interest.
Jim
On 03/03/2017 04:40 AM, Greg D wrote:
Doh!
Well, that answers that question. Thanks, Jim. You are correct! 24.00 is the minimum Gqrx will let it go.
Greg KO6TH
Jim Jerzycke wrote:
I don't think an RTL dongle will tune down that low.
Jim KQ6EA
On 03/02/2017 10:46 PM, Greg D wrote:
Hi folks,
Has anyone used an RTL-SDR dongle on the 10.7 MHz IF output from another receiver? Is that better than going direct?
My cable TV provider is forcing us to go all-digital. With the new "cable box" comes the opportunity to re-wire the shack and simplify the many layers of cables, splitters, and lash-ups that have accumulated over the years. The proverbial camel is crying out for help.
What this has to do with Ham Radio is that part of the lash-up mess is an old pre-CATV deep fringe TV antenna that I have in the attic, aimed to the southern horizon. We are well outside the range of any of the digital OTA stations, and never one to leave a perfectly good piece of RF equipment go to waste, I currently have it fed to an old Icom R-7000 scanning receiver (previously used as the AO-40 downlink IF) and to an RTL-SDR dongle by way of a TV 2:1 splitter. I've tried hooking the dongle directly to my 2m ham antenna for satellite use, but for some reason that was less than satisfactory. Never really did hear much of anything, and never could figure out why. At least with the TV antenna, I can copy some stuff with the dongle, though the Icom is generally better. But the Icom doesn't do the various digital modes that are better suited for SDR.
Looking at the back of the Icom, I see that it has a 10.7 MHz IF output, so the thought is that the SDR dongle might perform better hooked there (with a DC bias block) instead of to the antenna itself through the splitter. Both receivers have similar frequency coverage, but perhaps the Icom, while somewhat deaf by modern standards, might still make for a better front-end to the dongle?
I think the down-side is that the Icom's IF bandpass is narrower than the Dongle's, so I'd lose some flexibility there. I would also lose the ability to software-control the frequency of the receive chain, outside of the IF bandpass.
What do you think? Would this be a net win or loss for the RTL-SDR?
Thanks,
Greg KO6TH
Sent via [email protected]. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
Sent via [email protected]. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
participants (5)
-
Greg D -
Jim Jerzycke -
Mac A. Cody -
Scott -
Zach Metzinger