Anything I may need to know?

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Motoballa

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Hello. I ordered my first SDR from ebay ( DVB-T + DAB + FM Radio Realtek RTL2832U R820T software defined SDR HDTVwbGT15 ) and I'm going to hook it up to monitor a trunking system. Is there anything I'd need to know or any tips that would be helpful? Anything is appreciated! Thanks.

73
 

br0adband

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Only tip I can offer: get ready to order a second RTL stick 'cause if you intend to monitor a trunked system - whether it's pure analog or using digital formats like P25 or something else or a mixture of each on the same system - doing so with just one RTL stick is possible but not nearly as easy or consistent as having two of them working together to do the job. With a trunked system you need to be able to maintain a fairly constant monitoring of the control channel (CC) which provides the necessary info for hopping the trunks (frequencies) when communications happen on the voice channels/frequencies.

It IS entirely possible to do this with just the one RTL stick, sure, I've done that myself, but it doesn't work as well with one stick trying to pull in the CC, hop to a frequency when a voice transmission happens, then hopping back to the CC and picking things up, over and over again. With two RTL sticks (or two SDR devices, whichever, and sometimes just one if it has bandwidth wide enough to cover all the system frequencies), you can then dedicate one to control channel monitoring exclusively and use the second stick for dedicated voice channel/frequency tuning resulting in a much more efficient monitoring setup.

You'll also end up using Unitrunker to decode the trunked system control channel - Unitrunker can be used to control both the RTL sticks simultaneously (one as the Signal or CC receiver, one as the Voice receiver) and voila, a "proper" trunked monitoring system for not a whole lot of money at all. ;)

You could, of course, already have another device to add to the RTL stick you just bought, like an older scanner with a discriminator tap for monitoring the CC (those are excellent for such purposes, actually, since the CC frequency never really changes on most any trunked system) so, either way getting a second RTL stick just makes this whole process a lot easier. I had just one RTL stick for quite a while before I finally did buy a second one, and as soon as I started using both at the same time I realized I shouldn't have waited that long to do it.

Actually I do have a second tip: get pigtails (MCX or SMA depending on the connector used for the RTL stick(s) you end up owning so you can attach real antennas to them. The tiny little antennas they include with these "cheap USB TV tuners" are effectively useless for any serious monitoring, truly, and getting some proper antennas with pigtails to connect them will make a dramatic difference in the experience all around. If the RTL stick you bought comes with a telescopic whip (some do) then that's going to be better than the little 4-5" one, definitely, but still you'll want to get a pigtail (or two) and do some proper antennas.
 

radio3353

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...

Actually I do have a second tip: get pigtails (MCX or SMA depending on the connector used for the RTL stick(s) you end up owning so you can attach real antennas to them.

Any recommended source for quality 1 to 2 foot long SMA pigtails? Thanks.

Edit: Actually, pigtails with 1 male SMA and 1 male BNC would be better since I will be coming out of a splitter with female BNC's on it.
 

br0adband

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eBay, Amazon, take your pick, no sense paying extreme amounts of money for the same stuff - a ton of these pigtails are made in the same factory or factories and just labeled for different resellers so, the same stuff from most companies. Typical length is 6" with 12" being a bit more pricey (like a buck more, maybe two), with 2 foot versions being custom made so even more expensive.

But then again I see a bunch of SMA to BNC Male or Female 13" pigtails on Amazon right now for under $3, go figure. ;)

Do a search at either site or wherever and you'll find something that works great. I have two 6" MCX to BNC pigtails I bought about 2 years ago, been connected/disconnected many times, still working just fine and purchased from eBay for about $6 each.
 

natedawg1604

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It IS entirely possible to do this with just the one RTL stick, sure, I've done that myself....

You only need one dongle for P-25, if using OP-25. Admittedly, that program is not for the faint of heart, and probably not recommended for new SDR users. Regardless you still need 2 dongles for DMR Connect+ and so forth. I wished I would have bought 2 dongles much earlier than I did. Also I would second, third and fourth your comments about the antennas!! The connectors, antennas and cabling attached to your dongle, are just as important as with hardware scanners or any other radio system.
 

br0adband

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Yah, I figured that OP25 wasn't in the mix at this point hence me not mentioning it - I've had several people ask about that recently and I continue to point them to the OP25 thread here in this subforum because it contains all the info necessary that most anyone would need to get it operational but it's not for the faint of heart, no, certainly not. I like it, in the relatively small amount of time I used it, but the limitations in general - and the fact that someone put up an actual stream on Broadcastify of the very system that I was going to use OP25 to monitor, the LV Metro PD, just had me not using it much at all after I went through all that trouble getting it functional.

But it's there is people wish to make use of it, definitely.
 

fleef

Kristin Cavazos Phoenix Arizona
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Hello. I ordered my first SDR from ebay ( DVB-T + DAB + FM Radio Realtek RTL2832U R820T software defined SDR HDTVwbGT15 ) and I'm going to hook it up to monitor a trunking system. Is there anything I'd need to know or any tips that would be helpful? Anything is appreciated! Thanks.

73

Do you frequent the rtl sdr reddit forum? https://www.reddit.com/r/RTLSDR/ not sure if already posted, if so apologies

I will say this, and it may not be much help- but all the rtl-sdr did was give me another reason to buy a "real" trunking scanner. Having to use two sticks, and the whole software installing and trouble getting everything installed on the computer so I could just hear some P25 dispatch calls, and it STILL not working like a scanner would- well, I basically use the USB stick sdr for doing frequency searches and "fun stuff" than for listening to trunk scans. Sorry it may not be much help- but that is my honest opinion. A scanner is WAY more robust, easier, and you just switch it on and go! No computer to turn on, no big processes that use up memory and overheat my ancient laptop, etc etc.

SDR for digital decoding, scanner for SCANNING.
 

br0adband

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Some folks just don't have much success with using the "cheap USB TV tuner" approach to things aka RTL sticks and with SDR software of various kinds, that's true, but many of us have great success using such tools. I myself don't even own a physical scanner anymore (but will get another one someday when the price is right or a great deal comes along at the right time) and I use my two RTL sticks for monitoring everything these days from the basic AM stuff on the Civilian air band to the most current digital formats including P25 Phase II.

Is it for everyone? Of course not, but I think that many people in this hobby, especially those of us that have been participating and "listening in" for many decades now, would agree that it's the simple idea of doing something new and interesting that makes the SDR side of things so appealing. Along with the extremely low cost nature of using such RTL sticks coupled with free software being able to do things that the best scanners on the market today still can't do natively that's a pretty powerful "one-two" punch of sorts that can't be dismissed just because it's not easy or simple to set up and use. With the RR database, the need or requirement to actually scan for the main things people want to monitor - police, fire, EMS, local government, etc - is passe since all the info is there, relatively accurate and relatively up to date as well because people contribute the info from their monitoring in the first place: the RR database didn't suddenly just appear out of thin air one day filled with all that info (which is quite significant and continues to grow).

Years from now when SDR hardware and software is even more advanced we'll probably have interfaces that work exactly like a modern high end digital scanner like the 436HP or 536HP happens to do. Unfortunately we're not there just yet and believe me I'd love to have something that looks like a basic physical scanner interface where I can just program it with whatever I want and that's that: one app that can and mostly does it all or comes pretty close to it.

So far yes we're dealing with one or multiple sticks, and with those needing one or multiple pieces of software to make use of them to monitor the content we're interested in but that's part of the fun. It's not a requirement to take on SDR hardware and software, it's just an option that again because of the extremely low cost makes it almost silly to not get involved with it in some manners.

The lack of decent documentation and tutorials out there - even in spite of there being almost no end to the videos on YouTube and other places with instructions on how to get this stuff working - is holding a lot of people back too and I know I try my best to help people when they ask for it (with long posts like this one, I'm wordy, what can I say). There are two books out there on Amazon (available as eBooks too) currently on helping people using RTL-based sticks with SDR software and while they're both "ok" in my opinion they're not exactly what they could be in terms of ease of instruction as well as just flat out making things simpler for people to understand overall. They're better than nothing and I do recommend them, but sometimes I think I could do better (and probably should have years ago). :D

I've helped people start from nothing but a laptop and end up a few days later (not that it takes days to do it but those people do have lives with other things going on) with a working OP25 installation tuning in trunked P25 Phase I and II systems where before they simply could not ever monitor those systems at all because of not owning a digital capable scanner - and of course getting a P25 Phase II scanner these days is practically an instant $350+ investment. The guy paid $50 for the laptop, $12 for one RTL stick, and $5 for a pigtail he attached to an old cellular magnet mount antenna and voila, in less than about 12 hours of his actual time he was monitoring a system he'd never been able to monitor before so, I consider that a positive thing. :)

It's a learning process like any other. 18 months ago I could barely do much of anything with the RTL sticks and Unitrunker much less adding in virtual audio cables to patch signals to DSD (great app for what it is/was capable of) and then to DSD+ (which changed things dramatically for most of us and still does with each new version). Getting a P25 system monitored was a challenge, but getting a trunked P25 system monitored was pretty much impossible for me.

A few days ago I created a new trunked P25 Phase I system with Unitrunker and DSD+ in about 2 mins, start to finish, completely from scratch, and when I enabled the Signal receiver it worked flawlessly and as soon as I enabled the Voice receiver sent the signal to DSD+ and voila, audio in my headphones as expected. It's become habit to create working systems with Unitrunker now and it just takes time and repetition like all skills learning does.

But if you're happy with a handheld physical scanner, fantastic, ain't nothing stopping someone from using both types of hardware in their monitoring hobbies. When you can monitor DMR/TRBO, NXDN, or several other formats on such a device and with no "outside help" from computers - especially if such systems are trunked, let me know. ;)
 
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