Some really basic and stupid questions

[paulmohr]

Ok, I am just going to throw out a bunch of random stuff that I really don't understand completely. Some of them will seem very basic to a lot of you, some might even border on dumb or stupid. However I can't help but wonder if there are other people out there that are wondering the same things I am. Things that they figure most people just assume you know and they feel too ashamed or something to ask. Well I am going to ask them any way. Hopefully I can learn something and so can some others that are lurking around but don't want to ask because they feel it is too basic. These are in no particular order, just as I think of them.

What is the deal with signal pre amps and amplifiers as it applies to scanners? Is it even a thing? I haven't seen many, if any advertised and you don't see people talking about them or recommending them. You see a lot about low loss cable, keeping your connections to a minimum and using a decent antenna and getting it as high as you reasonably can. But unlike TV and cable you really don't see or hear much about your standard mast mounted pre amp, or indoor amplified signal boosters or splitters. I see them mentioned on occasion, but it is normally something along the lines of " you can try it and see if it works" kind of thing. And obviously as most of you know I am using them, and no one has said "oh god don't waste your time on those dumb things." It has been mentioned to me that while they may boost the signal they are also boosting the noise and it can trick you into thinking it works better, especially when looking at an RSSI meter or something.

The reason I ask this is because earlier today I mounted my new Discone antenna outside above my roof line. I did a piss poor job mounting it actually and will probably re do it tomorrow or this weekend. Not that I did a bad job on the cabling (in my opinion), but the option I chose to mount it doesn't look very secure to me and I am not sure I trust it for long. It seemed like a good idea at the time, but when I got down on the ground and looked at it I wasn't impressed lol.

And when I say I think I did a good job on the cable runs, remember I am thinking TV and cable type stuff, that is what I am familiar with. From the sounds of it scanners and ham radios are a different beast and the same things really don't apply. For instance, I have 25 foot of RG6 running from the antenna to the ground. Then I have a grounding block connector right before the next cable that runs into the house through the wall and into the basement. This is probably a 6 or 7 foot length of good quality RG6 with good connectors. That line plugs into a 10db signal amplifier with a line coming out and running the length of a room and into an amplified splitter, lets say 12 feet? From the splitter I have two lines that terminate in BNC compression fittings. One drops next to my computer where the scanner is plugged in most of the time, the other drops next to my bed so I can listen to it at night. The splitter is a 15 db gain with an adjustment. My understanding is it splits this between the two lines so it is actually more like 7db per line. So that is 5 separate RG6 lines and two amplifiers for basically one room lol. And these are just cheap RCA and radio shack amps, nothing commercial grade, I am too poor for that.

When I moved my new antenna outside and up on the roof and connected everything I was impressed with the results. It picks up very strong and it pretty much pegs out the signal meter in the freescan software and the analyzer built into the 325p2. I "thought" I did a good job on it and was happy. However a little while ago I was messing around and unplugged the amplifier and ran the line straight from the wall to my scanner. Basically straight from the antenna to the scanner with one connector in the middle. All of a sudden I started picking up channels I wasn't before. Like deerfield fire department which is well over 20 miles away, and some other small townships that I was complaining about not picking up before. From the sounds of it I over amplified the crap out of my system and it is just picking up the strong stuff that is fairly local. It picks them up really strong mind you, but I think they over power the weaker signals. So it is doing the opposite of what I actually wanted it to do. Does that make sense to anyone? Did I just learn a valuable lesson the hard way? When I re do my discone mount should I just go buy some really good quad shielded RG6 and run one line from the antenna right to the scanner. And just forget about the amplifiers and splitting the lines and all that fancy stuff I thought was cool because I was an ignorant newb?

My other questions are about the scanners themselves and the settings and adjustments. Sure, the manuals and the internet tell me what they do and how to adjust them. What I don't know is why? What do these adjustments do, and in what situations do I want to use them, or have them shut off.

Like the squelch, what does that thing even do? I know if I turn it all the way down all I get is static. But if I turn it past 2 there seems to be no difference from 2 to maxed out. I know they were useful when I had a CB back in the 80's, but I don't quite understand the function on a scanner.

And what is up with the attenuation. Mine has a built one that I can either leave off, or turn on and it attenuates the signal by 20db. I know what that means ( I think), but in what situation would I want to use that feature, or leave it shut off? The manual just says that it can do it, and how to turn it on and off. It don't see where it says why I would want to and what it would improve.

Same thing with AGC setting. I have a vague idea of what I think it does. I think it is kind of like dynamic volume control on a tv or home theater receiver. Where it tries to level all the volumes automatically. If that is what it does, let me say hear and now the feature doesn't work very well lol. At least not on my unit. Is this what it really does? Do I want it on or off, and why would I want it on or off? I have a real problem with some voices being very loud, and some you can barely hear. In some cases you can use the volume offset, but that doesn't always work. Some times they are on the frequencies. One person in a car might be very loud, even to the point of distorting, and another person on the same frequency might be very soft. So the volume offset wouldn't do me much good for that. I assume it has to do with how they use the mic or how they have their settings adjusted. I remember you could do that with a cb fairly easy. I think it was called over modulation?

If anyone can clear some of this up for me it would be greatly appreciated.

 

[RF-Guy-El-Loco]

1). The boosters will over amplify local strong signals and the scanner will find these and lock on faster than a weaker signal. The boosters also have their own freq response curve boosting some freqs a bit more than others, they aren't Pro grade with tight specs. The best would be one with a line amp put in where the coax meets the antenna, so there is no signal lost in the coax before you Boost it. The bad answer to using them is "well if they work for you." I do all of this myself and view it all as experimentation.

2). The RG6 Quad shield would be great, but I would leave the grounding block and ground wire in line if the antenna is up on a tower outdoors. The ground block will only ground the coax shield and drain off the electrical charges in the air. But it won't protect from lightning on the center pin of your coax. For that you need an Opto-isolator too. Which is why I would just disconnect your antenna at the radio before any bad thunderstorms are forecast. The boosters and splitters in tandem seem to be too much. There is no perfect answer nor solution, as you are dealing with 155/460/800 Mhz bands and each will yield varied reception. I've tried it many ways, every 6 months I change it up, never satisfied with any of it. But I'm loco.

3). Think of squelch acting like a horse in a high jump contest. The horse is your RF signal, the jump bar is your squelch level. No bar is zero squelch level and everything (incl. noise) goes over into the receiver. Push the bar (squelch level) up and the horse has to work harder to go over the bar. Some RF signals can't clear a higher bar (squelch level), they are too weak in dBm. Only the strongest (RF signals) will clear a higher bar (squelch level at max). A local signal will always get thru on max squelch, for a weak static signal, it probably won't get over that bar to be heard. If weak signals annoy you, you crank up the squelch. If you want to hear those, leave squelch at just past the level where the noise stops being heard. 800 Mhz are finicky, use a very low squelch or zero if you can, you'll loose voice channels if it is up past "2". I monitor all digital on one scanner and leave squelch at zero level. If you set up PL/DPL tones on all your analog channels, you can use zero squelch too, as UPMan cleared this fact up. It works for me.

4). Attenuation is used if you have too much signal, as if you are right next to the actual transmit tower and it just wrecks havoc on the front end of the receiver. You hear distortion in the signal. You'll know it as you have already done it with the boosters. You could attenuate some channels if they distort (go by hearing) and not use attenuation for other signals. Attenuation also works as a poor man's squelch level, as if you have two analog channels sharing one frequency, one is always stronger, if you attenuate that channel, it may drop the weaker signal that annoys you off the map. Both signals will be weaker, but the stronger one will still be heard with a bit more noise now, as you reduced the signal level to the scanner. I don't use it with anything as you are just reducing your signal level. You will know by ear if you need it on. If you are near a broadcast tower you might use it if you hear problems on a certain frequency.

5). AGC is just what you think it is. I looked this up as it relates to the scanners. It is Audio Gain in this specific case and in the BCD325P2, it must be a very fine adjustment, as I can't hear it. I think it is a very small audio compressor circuit but I can't hear that it does much. The BCD396XT had a range adjustment on this function, and I noticed it didn't matter much either on that scanner. I use Volume Offset too, as you have found, some voices are weak, some are loud on the same (talkgroup) channel/frequency, depends on who is on shift. And what type of headset/mic they use. It worked great for a local PD's analog Aux channel which had lower audio levels than their main. Plus if you mix digital and analog channels together you may need it there too. AGC should fix the voice variation level on one channel, I have it set to On but maybe we aren't aware that it is really working. I can see the Uniden engineers laughing at me now!

 

[bob550]

I'll try to address your questions on signal amplification and attenuation. Some amplification can be helpful, especially if splitting your antenna signal among multiple scanners, or using a long length of cable. I use a cable TV amp with adjustable gain to connect to up to 4 scanners. However, as they say, too much of a good thing can be bad. I find, for example, that amplifying the signal is necessary for 700 to 800 MHz signals, but can cause overloading (too much signal) on the VHF-High band. The overloading causes the scanner to literally desensitize, and reduces the received signal. My solution is to selectively attenuate (reduce) those VHF signals that may be affected by the overloading. Most of today's scanners will let you choose either global attenuation (applied to all memory channels) or selective attenuation (applied to memory channels of your choice). When the attenuation is applied to an affected VHF signal, such as NOAA Weather, the signal and clarity improves, sometimes dramatically. I know it's counterintuitive, but it works!

 

[paulmohr]

Thanks guys, that helps a little. Someone shot me a PM as well to explain some stuff. I will have to look into the PL/DPL tone thing. No clue what that is either lol.

So it kind of sounds like some stuff is sort hit and miss, and a little trial and error. Just because a signal sounds like crap (which I really don't seem to have a problem with) or doesn't come in consistently don't just assume it is a weak signal and needs boosted. It might be the other way around. Sort of like driving a 500 hp muscle car in the rain, sometimes you can have too much of a good thing lol.

Is what I am kind of getting out of some of my answers and research is that Scanners are a bit of compromise because of what we ask them to do. A radio that is actually designed to tune into and lock on to a frequency does a much better job of receiving than one that is made to scan a whole bunch of frequencies really fast and look for a "hit". I guess a good analogy would be to compare it to optics. A really nice high powered optic is great for zooming in on something and seeing it better. And the better the glass and design the more clarity and resolution you will get. The down side is very hard to find something with that much power. You have to sort of know where to point it to begin with. Where as if you want to scan an area like a field or something less magnification and a wider field of view works much better.

 

[hiegtx]

Thanks guys, that helps a little. Someone shot me a PM as well to explain some stuff. I will have to look into the PL/DPL tone thing. No clue what that is either lol.

See these Wiki pages:
Continuous Tone-Coded Squelch System - The RadioReference Wiki
and
DCS - The RadioReference Wiki

These tones or codes are used to differentiate multiple users on the same frequency. In my area, for frequency 154.4000, there are two cities using that. One is 15 miles south of me, the other 15 east of me. and the third is maybe 25 miles to my northeast. Without using either CTCSS (PL is Motorola's term for the same thing, for Private Line) or DCS (which Motorola calls DPL, Digital Private Line), if I programmed the frequency I could receive either of them. However, by using the correct tone or code, I can program them separately, so that I can tell which of the two is transmitting.

Is what I am kind of getting out of some of my answers and research is that Scanners are a bit of compromise because of what we ask them to do. A radio that is actually designed to tune into and lock on to a frequency does a much better job of receiving than one that is made to scan a whole bunch of frequencies really fast and look for a "hit". I guess a good analogy would be to compare it to optics. A really nice high powered optic is great for zooming in on something and seeing it better. And the better the glass and design the more clarity and resolution you will get. The down side is very hard to find something with that much power. You have to sort of know where to point it to begin with. Where as if you want to scan an area like a field or something less magnification and a wider field of view works much better.

That's why you see comments regarding, among other things, Simulcast Distortion. A 'real' professional radio, costing several times what a scanner sells far, is equipped to deal with that. It's also programmed for some specific frequencies that are in use in the area.

A scanner, on the other hand, is trying to listen to any number of frequencies, in more than one band (such as Vhf, Uhf, and 700/800MHz), and scan rapidly through them. Could a scanner be produced that is better against simulcast issues? I suspect so, but the cost could be significantly higher than most people would want to pay. If you read some of the many posts where someone is asking for help programming their new (to them, if not brand new) scanner, you'll see comments where they are expecting a ~$100 radio to receive their local system(s). And they're shocked when informed that their equipment cannot handle digital and/or trunking. If the increased cost was not excessive, at least some of the members here would pay more for a scanner that handled simulcast. But that's not where the biggest part of the customer base is. So, you're seeing 'serious' users, with simulcast issues, buying one of the Unication pagers. These are up to $200 more than the currently most expensive scanners. They can only monitor one system at a time, from what I've read, but to some folks, it's worth it.