Search found 59 matches

by aurgathor
Mon Oct 15, 2018 2:32 am
Forum: RTL-SDR Discussion
Topic: Question about FPGA and signal reception / ADS-B
Replies: 1
Views: 2176

Re: Question about FPGA and signal reception / ADS-B

First, you need to understand how programmable logic (PLD, FPGA, etc.) works. That's not very complicated. Next you need to get a development kit and need to learn how to program an FPGA. I haven't done any FPGA work lately, but previously, I used Verilog to write code for it, then used the manufact...
by aurgathor
Sun Oct 14, 2018 5:44 pm
Forum: RTL-SDR Discussion
Topic: Custom 400-406 MHZ bandpass filter?
Replies: 2
Views: 3180

Re: Custom 400-406 MHZ bandpass filter?

As it was already mentioned, making a suitable filter is not easy, but in case you still want to try it, you probably want an elliptic (Cauer) filter since that's the steepest, or an inverse Chebyshev filter. Unfortunately, the math for filter design is kinda (?) ugly. Methinks the best way to reduc...
by aurgathor
Sat Oct 13, 2018 11:49 pm
Forum: Other SDR Devices
Topic: Why Tx/Rx devices are so expansives ?
Replies: 9
Views: 20173

Re: Why Tx/Rx devices are so expansives ?

I assume that in the future all smartphones will be using SDR based radios. Disagree. Current smart phones can already do CDMA/GSM/LTE with traditional ASICs at a reasonable price, so aside from upgradeability and additional flexibility, there is not a whole lot to gain by using an SDR instead. And...
by aurgathor
Sat Jun 16, 2018 1:50 am
Forum: RTL-SDR Discussion
Topic: RTL-SDR's in an outdoor box
Replies: 3
Views: 2017

Re: RTL-SDR's in an outdoor box

I have a couple of sets of USB over Cat5 extenders, and I found that their performance is very poor. They would barely work with my 50 ft Cat6 and weren't very reliable with 25ft long cables (Cat6 or Cat5) either. But other extenders using a different chipset may work better. In any case, currently ...
by aurgathor
Thu Jun 14, 2018 11:49 pm
Forum: RTL-SDR Discussion
Topic: RTL-SDR's in an outdoor box
Replies: 3
Views: 2017

Re: RTL-SDR's in an outdoor box

USB 2.0 max cable length is a bit over 15 ft, so depending on the actual distance you may either need an extender cable, or one or more USB hubs. Since the RTL-SDR dongles can draw well over 300 mA, the last cables that connect to he dongles should be sized accordingly to avoid excessive voltage dro...
by aurgathor
Thu Jun 14, 2018 4:38 am
Forum: RTL-SDR Discussion
Topic: Weak reception when in movement!
Replies: 11
Views: 5835

Re: Weak reception when in movement!

An LNA will increase signal level, but in itself it can't fix multipath distortion. Wikipedia and the patents I linked above should give you some idea on what is it, and some ways to fix it.
by aurgathor
Tue Jun 12, 2018 1:25 pm
Forum: RTL-SDR Discussion
Topic: Weak reception when in movement!
Replies: 11
Views: 5835

Re: Weak reception when in movement!

It is most certainly multipath. BTW, my car radio does the same thing in some places. I think there are some DSP algorithms and other solutions that can correct it, but I don't think you'll find that in free SW, or in an $20 dongle. Here are some patents on it: https://patents.google.com/patent/US61...
by aurgathor
Fri Jun 08, 2018 3:33 am
Forum: RTL-SDR Discussion
Topic: V3 warms up even when computer is shut down
Replies: 9
Views: 5590

Re: V3 warms up even when computer is shut down

Methinks it's definitely not normal, and I just tested 4 PCs and none of them have USB power when they are shut down. I guess that could be a new feature I was not aware of. Another possibility is that the shutdown state was only hibernate, not a true shutdown which may very well be the case with Wi...
by aurgathor
Thu Jun 07, 2018 2:54 am
Forum: RTL-SDR Discussion
Topic: V3 warms up even when computer is shut down
Replies: 9
Views: 5590

Re: V3 warms up even when computer is shut down

USB ports should be off (no power to them) when the computer is shut down, so I find this a little (?!) strange, to say the least. If it plugged into a powered hub, the hub may still have power regardless of the PC, and if he PC is only sleeping, USB ports are usually powered. But I have yet to see ...
by aurgathor
Tue Jun 05, 2018 7:10 am
Forum: Antennas
Topic: Yagi Antenna for "death" Spot?
Replies: 4
Views: 3771

Re: Yagi Antenna for "death" Spot?

Usually there is a bit of scatter, so you'll still get some signal even without LOS. If you look in SDR# and see some signal at the right frequency, but if it's too noisy to be useful, a Yagi will probably help. However, If you see no signal at all, then the Yagi may not see enough signal either. Of...