The dongle on the bottom is not even straight compared to the top one. Whats under it? Is there any protective skin on the bottom of the sdr? If not, looks like it could have shorted out.
Some photos of my RTL-SDR and its melted chips for your amusement. Request for cooling advice please.
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Looks like poster board.
A couple of thoughts, several of which have already been mentioned.
The RTL-SDRs were obviously taken out of their original case. Know that for some of them, anyways, the original, (often metal, not plastic), case served as the heat sink for the device. The boards with a “crystal oven”, (i.e. a heater for the Xtal, so that the frequency doesn’t drift with temperature), obviously generate a fair amount of heat, in addition to that generated by the chips and the power supply.
The chips and the small surface mounted components will likely tolerate a pretty high operating temperature, the tall electrolytic caps will dry out and go bad.
Since the devices are out of their original cases, they need a little heat sink, (RPi style, at a minimum), stuck on the chips.
If you intend to keep them in the black metal case then you need to add a bunch of ventilation holes, or an intake hole and an exhaust hole, with two small fans. You don’t actually need to move much air, but you do need to move SOME air, or the interior of the case will just keep getting hotter and hotter until the RTL-SDRs, the air, and the case all reach a steady state operating point. (The RTLs will be hot in this case).
Those aluminum boxes are great for some projects. They were originally designed primarily for projects that had large power transistors mounted directly on the metal case, (through a mica insulating washer, and using heat sink thermal paste). The large metal box then served as a very large surface area heat sink for the power transistors.
In this case there is no conduction of the RTL-SDR’s heat to the metal case, except through the large air gap, (the interior of the box). The air gap forms a much better thermal insulator that it does heat conduit to the case, which acts as a heat sink.
Enough on heat.
The “splitter” is a bit of a joke. The antenna and the RF front end of the RTL-SDR both have an impedance, and they ought to match for maximum transfer of the RF signal energy from the antenna to the receiver. Simply connecting the two receivers in parallel causes a tremendous mis-match of the impedance, and impairs the receivers’ sensitivity. It will work for strong signals… But it is surely a terrible hack.
Wiring stuff in parallel like that will work for house wiring and car wiring, (power buses), but not for RF signals. Some of the other photos in this thread show the use of an appropriate RF splitter, which matches the impedances of the various components. But you don’t get something for nothing. Depending upon your signal strength one might need a small RF amplifier before the splitter, as the splitter alone will attenuate the signal seen by the receivers.
I love the free floating LED… There are a dozen types of panel mounts for LEDs, all of which are dirt cheap. The lack of one is again reflective of the poor quality of this device. As a simple retrofit, you might mount (push) the LED into a small rubber grommet that fits in the panel hole.
If you are “re-building” this system, back onto the (very nice) black metal (aluminum) case, then I’d suggest:
Leaving your new RTL-SDRs in their original metal (not plastic) cases, and anchoring their metal cases directly to the large metallic box. Get a small tube of thermal paste and smear a thin layer on the RTL-SDRs cases where they press against the black box. Install at least one fan on the box, an intake and an exhaust fan will work better. If you install only one fan you still need holes on the opposite side of the box for the air to escape after blowing over the top of the RTL-SDRs.
If you were hard core you could add some additional power supply filtering to the USB provided power supply input, (i.e. a couple of 220 uF caps, for example). You should NOT to that if you power it directly off of a laptop or cheap PC’s USB port that doesn’t specifically have a high powered USB port. If you can run the receivers through a powered USB hub then you can add the extra filtering caps. The issue is that the USB spec doesn’t allow for a large “in rush” current when the device first turns on and sucks in a lot of current to charge up those caps. On some systems the USB port will be shut down if you exceed its current limit!
Interestingly, I have a couple of RTL-SDR receivers. One was dead out of the box. One worked for 6 months or so of continuous monitoring, (OP-25), and then died. Two others work for months on end before needing to be re-booted. I put a classic heat sink on their (metal) cases, but I tie them in place with a wire, as rubber bands get hot and brittle and then break. They provide additional cooling, and run warm to touch, not hot. (No fan required.)
Good luck with your project(s) !
JC
The RTL-SDRs were obviously taken out of their original case. Know that for some of them, anyways, the original, (often metal, not plastic), case served as the heat sink for the device. The boards with a “crystal oven”, (i.e. a heater for the Xtal, so that the frequency doesn’t drift with temperature), obviously generate a fair amount of heat, in addition to that generated by the chips and the power supply.
The chips and the small surface mounted components will likely tolerate a pretty high operating temperature, the tall electrolytic caps will dry out and go bad.
Since the devices are out of their original cases, they need a little heat sink, (RPi style, at a minimum), stuck on the chips.
If you intend to keep them in the black metal case then you need to add a bunch of ventilation holes, or an intake hole and an exhaust hole, with two small fans. You don’t actually need to move much air, but you do need to move SOME air, or the interior of the case will just keep getting hotter and hotter until the RTL-SDRs, the air, and the case all reach a steady state operating point. (The RTLs will be hot in this case).
Those aluminum boxes are great for some projects. They were originally designed primarily for projects that had large power transistors mounted directly on the metal case, (through a mica insulating washer, and using heat sink thermal paste). The large metal box then served as a very large surface area heat sink for the power transistors.
In this case there is no conduction of the RTL-SDR’s heat to the metal case, except through the large air gap, (the interior of the box). The air gap forms a much better thermal insulator that it does heat conduit to the case, which acts as a heat sink.
Enough on heat.
The “splitter” is a bit of a joke. The antenna and the RF front end of the RTL-SDR both have an impedance, and they ought to match for maximum transfer of the RF signal energy from the antenna to the receiver. Simply connecting the two receivers in parallel causes a tremendous mis-match of the impedance, and impairs the receivers’ sensitivity. It will work for strong signals… But it is surely a terrible hack.
Wiring stuff in parallel like that will work for house wiring and car wiring, (power buses), but not for RF signals. Some of the other photos in this thread show the use of an appropriate RF splitter, which matches the impedances of the various components. But you don’t get something for nothing. Depending upon your signal strength one might need a small RF amplifier before the splitter, as the splitter alone will attenuate the signal seen by the receivers.
I love the free floating LED… There are a dozen types of panel mounts for LEDs, all of which are dirt cheap. The lack of one is again reflective of the poor quality of this device. As a simple retrofit, you might mount (push) the LED into a small rubber grommet that fits in the panel hole.
If you are “re-building” this system, back onto the (very nice) black metal (aluminum) case, then I’d suggest:
Leaving your new RTL-SDRs in their original metal (not plastic) cases, and anchoring their metal cases directly to the large metallic box. Get a small tube of thermal paste and smear a thin layer on the RTL-SDRs cases where they press against the black box. Install at least one fan on the box, an intake and an exhaust fan will work better. If you install only one fan you still need holes on the opposite side of the box for the air to escape after blowing over the top of the RTL-SDRs.
If you were hard core you could add some additional power supply filtering to the USB provided power supply input, (i.e. a couple of 220 uF caps, for example). You should NOT to that if you power it directly off of a laptop or cheap PC’s USB port that doesn’t specifically have a high powered USB port. If you can run the receivers through a powered USB hub then you can add the extra filtering caps. The issue is that the USB spec doesn’t allow for a large “in rush” current when the device first turns on and sucks in a lot of current to charge up those caps. On some systems the USB port will be shut down if you exceed its current limit!
Interestingly, I have a couple of RTL-SDR receivers. One was dead out of the box. One worked for 6 months or so of continuous monitoring, (OP-25), and then died. Two others work for months on end before needing to be re-booted. I put a classic heat sink on their (metal) cases, but I tie them in place with a wire, as rubber bands get hot and brittle and then break. They provide additional cooling, and run warm to touch, not hot. (No fan required.)
Good luck with your project(s) !
JC
I took the led out before it could short anything and I'll probably leave it out. I've finally managed to get my rsp1 clone (the one with the switches) to work quite well with DSDplus FL and it stays very cool. I believe I'm going to rebuild it using two msi sdr as I think I can get by without adding additional cooling. Could you suggest a 4 port rf splitter and amplifier that would suit my needs?
BTW, thank you for your post. If I sounded hostile it was not at you, it was at the individual who was selling this crap!
Have a look at the link posted in Comment #5 in this Thread, "Ghetto SDR Setup".
It shows a nice 1 - to - 2 way splitter, with a bandwidth of 5 MHz - 2.4 GHz.
It also shows the RTL-SDRs connected directly to the splitter, without any intervening cables.
There is a loss in the signal, and some additional signal reflections, every time one adds a connector to the signal chain.
In the photo there is an adapter for the connector types on the splitter to the connector types on the receivers, such is life.
In the perfect world the splitter and the receivers would have the same connector types and one could even eliminate these.
I don't know of any 1-to-4 way, wide band, splitter to suggest off hand. Others might certainly chime in here with their favorite!
Do look around and make sure the splitter's bandwidth includes the frequencies that you are interested in receiving.
For example, if you are listening to an 800 MHz public safety system, then a cheap, low bandwidth, "TV" splitter that doesn't include the 800 - 900 MHz range isn't going to work for you.
Regarding the RF amplifier, the same comments apply.
Look around at several models, and check carefully to see their bandwidth, and the connectors used.
You would likely be best served by a unit that has an adjustable gain.
You want enough gain to overcome the losses of the splitters and connectors and cables and, and, and...
and yet not too much gain that you overload the front end of the receiver with too strong of a signal.
The RTL-SDRs are great little radios, but they don't go overboard on frills.
There is minimal, if any, automatic gain control on the RF front end.
That means that with a strong signal and an RF amp you can overload the front end, which will make the system work poorly.
Likewise, there are many posts where people note that the RF gain on the RTL-SDRs, (typically 0 - 48 range), works best in the mid levels at best. When set too high, it causes significant distortion and internal interference itself. So if one is listening to a weak signal, and needs the higher gain, then using an external RF amp and not setting the RTL-SDR's internal gain too high will work better.
In your case, with the splitters, you will likely want some extra gain because of the losses from the antenna to the receivers induced by the splitters, so you can easily set the RTL-SDR's gain to a low / mid setting, and make up for all of the front end losses with the external amp.
If you are using 4 RTL-SDRs, and you have trouble finding a reasonable 1 - to - 4 way splitter, then consider using TWO antennas, each feeding their own RF amplifier, 1 - to - 2 way splitter, and then feeding two RTL-SDRs. Unless you have an outside tower and a very expensive antenna and coax cable the 2 antenna system would likely be less expensive and better overall for you.
If you use two antennas, make sure that you keep them separated by several feet, so that they don't interfere with each other.
Yes, there are rules-of-thumb for the antenna separation based upon the antenna type and the frequencies involved, but my old brain can't recall them at the moment. The point is, bottom line, don't stick them right next to each other.
In the photo referenced above, the black heat sink, (on the left receiver), is similar to what I have on my RTL-SDRs. Like the ones in the photo, mine are in the open, (not enclosed in a case), so I don't have a fan on them.
Good luck with your system!
JC
Have a look at the link posted in Comment #5 in this Thread, "Ghetto SDR Setup".
It shows a nice 1 - to - 2 way splitter, with a bandwidth of 5 MHz - 2.4 GHz.
It also shows the RTL-SDRs connected directly to the splitter, without any intervening cables.
There is a loss in the signal, and some additional signal reflections, every time one adds a connector to the signal chain.
In the photo there is an adapter for the connector types on the splitter to the connector types on the receivers, such is life.
In the perfect world the splitter and the receivers would have the same connector types and one could even eliminate these.
I don't know of any 1-to-4 way, wide band, splitter to suggest off hand. Others might certainly chime in here with their favorite!
Do look around and make sure the splitter's bandwidth includes the frequencies that you are interested in receiving.
For example, if you are listening to an 800 MHz public safety system, then a cheap, low bandwidth, "TV" splitter that doesn't include the 800 - 900 MHz range isn't going to work for you.
Regarding the RF amplifier, the same comments apply.
Look around at several models, and check carefully to see their bandwidth, and the connectors used.
You would likely be best served by a unit that has an adjustable gain.
You want enough gain to overcome the losses of the splitters and connectors and cables and, and, and...
and yet not too much gain that you overload the front end of the receiver with too strong of a signal.
The RTL-SDRs are great little radios, but they don't go overboard on frills.
There is minimal, if any, automatic gain control on the RF front end.
That means that with a strong signal and an RF amp you can overload the front end, which will make the system work poorly.
Likewise, there are many posts where people note that the RF gain on the RTL-SDRs, (typically 0 - 48 range), works best in the mid levels at best. When set too high, it causes significant distortion and internal interference itself. So if one is listening to a weak signal, and needs the higher gain, then using an external RF amp and not setting the RTL-SDR's internal gain too high will work better.
In your case, with the splitters, you will likely want some extra gain because of the losses from the antenna to the receivers induced by the splitters, so you can easily set the RTL-SDR's gain to a low / mid setting, and make up for all of the front end losses with the external amp.
If you are using 4 RTL-SDRs, and you have trouble finding a reasonable 1 - to - 4 way splitter, then consider using TWO antennas, each feeding their own RF amplifier, 1 - to - 2 way splitter, and then feeding two RTL-SDRs. Unless you have an outside tower and a very expensive antenna and coax cable the 2 antenna system would likely be less expensive and better overall for you.
If you use two antennas, make sure that you keep them separated by several feet, so that they don't interfere with each other.
Yes, there are rules-of-thumb for the antenna separation based upon the antenna type and the frequencies involved, but my old brain can't recall them at the moment. The point is, bottom line, don't stick them right next to each other.
In the photo referenced above, the black heat sink, (on the left receiver), is similar to what I have on my RTL-SDRs. Like the ones in the photo, mine are in the open, (not enclosed in a case), so I don't have a fan on them.
Good luck with your system!
JC
I appreciate the advice no offense taken. I kind of knew what to expect when I bought it. Their website is sketch and I couldn't find the cases or similar setup in the usual Chinese stores. I suspect some yocals are responsible for this nonesense (if you search around you'll find their videos). I ended up with 2 cheap RTL-SDRs two USB-A male to female pigtails a 3 port USB hub and a neat little project box with rubber gromits, worth every penny I paid just needs some improvements.
I haven't ran the two that were installed in the unit long enough to destroy them yet, however if I don't have some active cooling they get hot to the touch and DSD fastlane starts displaying sync errors. I've been fooling around with the RTL-SDRs for around 10 years or so and I just recently got into trunking. If I count the two in this unit, plus the two that failed, I also had a nooelec smartee, and two more of the blue RTL-SDRs over the years so I'm on number 6 and 7. I will admit I don't know much about getting the signal to the device. I just know when it works and this site has been a great resource.
I also have one of the little msi.sdr SDRplay clones with the switches I'm really liking it stays nice and cool without active cooling. Will probably order a couple more of those. I can't find a use case where the SDRPlay clone can't do what the RTL does for me and if I do I've got two of them.
Sync errors are usually signal related. What are you using for an antenna and after those are warmed up, are they on freq or is the ppm off and needing an adjustment?
I'm using this antenna on a metal roof.
https://www.aliexpress.us/item/3256...t_main.23.54e41802tCkNOx&gatewayAdapt=glo2usa
It stays on frequency but the signal strength seems to drop like I'm lowering the gain. If I blow across the chips the sync errors clear up momentarily.
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