Antenna selection

[psr600]

I'm asking for assistance / direction as to what type of antenna I need for my application. I currently have a BCD536HP scanner. To say I'm not happy with it's reception is an understatement. I live in Porter County located in Northwest Indiana, I work in Lake County. These two are neighboring counties. I get Porter County reception but get little to nothing for Lake County. I currently live approximately 5 - 6 miles away from Lake county. Here's the kicker, Chicago, Illinois is roughly 14 - 20 miles from my residence. I pick up more Chicago PD/FD radio traffic then I do Lake County. Lake county. Lake County has roughly 20 + agencies and I do not get a very sparse radio traffic.

I purchased a car magnetic antenna which helped. I anticipate on purchasing some type of antenna and mounting it in my attic. This is were I have my dilemma, I'm totally lost as to what type to purchase. So with that being said I'm not sure what to look for in an antenna when it talks about "plus and minus gains".

I know mounting an antenna inside an attic isn't ideal but at this time this is the only method that will work for now. So can you please help and assist me with a correct antenna I need for my application.

 

[mmckenna]

What frequencies/bands do you want to listen to?

With the exception of a discone antenna, most scanner antennas are going to be frequency dependent. That means they work better on one or a few bands. Knowing what you are looking for is the first step.

Gain has to do with how the antenna is designed. By making the antenna work better in certain directions or certain planes, it's said to have "gain". Don't automatically assume that more gain is "better", it's not. More gain often comes at a cost. The cost can be useable bandwidth (how wide a slice of spectrum the antenna will work over), size, etc.

Most of the frequencies used by public safety is going to be VHF, UHF, 700 or 800 MHz. In most cases, these frequencies are line of sight. In other words, if your antenna can "see" the transmitting antenna, chances are you are going to receive the signal. Many things are RF opaque, in that they'll pass RF signals without much impact.
Where this becomes an issue is if you have a lot of "dirt" between you and what you want to hear. If the transmitter you want to listen to is behind a hill or mountain, chances are you won't be able to hear it, no matter how big an antenna you have.
Putting antennas in attics can be an issue, too. Any metal component to the building will impact performance. Often insulation will have a foil vapor barrier backing, this can block RF pretty well. Metal lath behind plaster can be an effective block, too. heating/cooling ducts, metal pipes, wiring, etc. can all block signals.

Mounting in the attic can work fine, but know what's up there before you do the install. Outside and in the clear, as well as up high, is always going to work better. But, I understand that some locations have HOA limitations, neighbors, wives, etc. that get to dictate.

Discone antennas often get mentioned as being good scanner antennas. What is good for some may not be good for others. While discone antennas often have very wide useable frequency coverage, it comes at the cost of gain. In other words, they really don't do much to help the received signal. A frequency specific antenna with some gain will outperform a discone easily. Even some multi band antennas can easily outperform a discone.

Also, consider that the FCC, frequency coordinators and systems designers don't really want or need good RF coverage outside the agency's jurisdiction or operational area. FCC licenses these systems often for a certain radius around a center point. There's no need to invest money in trying to provide useable radio coverage 20 miles away if the officers don't cover that area. This can create issues for scanner listeners. Good antennas can help overcome this, sometimes.

Also, make sure you use good coaxial cable, higher grade cables get more signal from the antenna down to the radio. Cheap cable results in higher losses, and can result in the received signal being too weak by the time it gets to your radio.

So, knowing what frequencies you are looking to hear will help others make a suggestion. But know that it won't necessarily be a fix.

One easy thing you can try is to take your scanner with it's stock antenna up on the roof or in the attic. If you can hear the agency better, then putting an antenna up there is probably going to work well. On the other hand, if you go up on the roof and still cannot hear them, it's unlikely that any reasonable antenna is going to fix that.

 

[marksmith]

Not sure which specific systems you are trying to monitor. I see a P25 and Motorola system in Porter County, neither of which would necessarily produce issues. The Lake County public safety system is specifically noted as a phase II simulcast system. The phase II part your 436 should handle, but I suspect from your description that the simulcast distortion from the multisite system is your issue. All scanners other than the brand new SDS100 and SDS200 have a weakness when it comes to simulcast systems, as they are not meant to be able to pick out one site out of the numerous that are operating on the same frequency and inferfering with each other.

I suspect that when you scan that system you get what you would think are sufficient signal bars to receive transmissions, but just nothing comes in, or if it does it is a little choppy or cuts out. If you get yourself in a situation where your radio can only receive one site, it will generally work fine, but if you are within range of several, they will interfere with each other. This is called simulcast distortion,.

Ironically, putting the lousiest antenna you can (sometimes just a paperclip stuck into and touching the antenna will give you the best signal, since it is reducing the signal to just the strongest one and not all of them interfering with each other. The other option that people have had some success with is using a directional antenna to limit reception to one tower and not multiple towers or sites. Do a search on simulcast distortion on this website and there is tons of reading.

I have a similar situation where I live literally one mile from a multisite phase 1 simulcast site and I get 5 bars, but can hardly receive anything intelligible because I am right between two towers that are blowing each other away. Recently purchased the SDS100 and SDS200 and am shocked at how well that system and some others are now received just fine when my 536 and 436 won't recieve them unless I am mobile and in areas where one primary site can receive over all the others.

You should also be aware that new sites such as the phase II site in Lake County are new systems and are using the capabilities of these new systems to limit their communications range area to their specific are of operation. I think I remember seeing Porter County's system having a Lake County talkgroup that is used across systems to make the communication possible, rather than the brute force power and range used by the Porter Motorola system.

The Chicago stuff is relying on the old fashioned brute force range process, or a non-simulcast repeater system. Either have great range.

Hope this helps. Used to work at a steel plant in that area.

 

[JoshuaHufford]

You can also use your mag mount antenna on a cookie sheet in your attic to test reception there.

 

[marksmith]

You can also use your mag mount antenna on a cookie sheet in your attic to test reception there.

Yep. A very solid ground plane antenna design. Have used it many times.

Mark
SDS100&200/536/436/WS1095/996p2/996xt/325p2/396xt/psr800/396t/HP-1/HP-2 & others