Tram Multiple antennas

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I'm going to warn you that I'm going to sound stupid to many of you. Where I live I have two National Forests and a statewide fire department that covers the area near me. We have frequent fires both in either the national forests or in the Cal Fire area of Southern California. I live for those of you that know the area in Menifee on a 2,000 hill which puts me next to the Cleveland National Forest as well as the San Bernardino National Forest. All the hills around me are covered with yellow grass that burns fast and I have to keep a hundred feet of clearance around my home at all times. I'd like to know what's happening before I hear about it on the news.

I have a new scanner, a Uniden 996P2, that lets me listen to everything including the County fire departments in the neighboring County. I'm a perfectionist that wants the best. Cal Fire is at 151 megahertz and the forest service is at 170 megahertz. And then there's of course the helicopters that dip out of the lake down at I think it's 122 megahertz.

I went to Scanner Master looking for an antenna and I can't find something that covers these bands all at one time. There's mobile antennas but I mean I don't have a mobile. What kind of antenna do I need? I was told that I could take a Tram and cut it for 160 megahertz and it would be like in between Cal Fire and the forest service. I've been told I might be able to hear the helicopters if they're operating close enough. Or do I need something called a discone? I want something with a little bit of gain.
 

W9WSS

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A Laird, EM-Wave, Antenex, ComTelCo, or other better brand should have a VHF whip you can cut in the mid-range of what you wish to monitor. Remember this is for receiving, so it shouldn't be too critical for comms in the 122/151/170 MHz. spectrum. I strongly recommend EM-Wave because the whip is very thick, making it ideal for wide-band coverage. I have two cut for 146 MHZ (1/4 wave). It's also 3/4 wave for the UHF Ham range, centering at 446 MHz. I can transmit and receive in both the UHF and VHF bands with a great match and excellent receive.
 
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I'm not a ham so that doesn't mean to me what it means to you. I was looking at a tram base station antenna and it was a ham that told me if I got one and cut it for 160 megahertz that would be in the center of the 151 and 171 range and should be able to still hear the helicopters fighting the frequent grass fires that burn very fast up in through here. I overlooked the lake where the helicopters grab their water. When you say I could cut a whip I don't know what I would do with it. So if I got a Laird or Antenex base antenna I think you called it tuned at 160 megahertz wouldn't that do the same thing?
 

prcguy

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Since you seem a little new to scanning, I believe your needs will change in the future and you might like scanning aircraft or public service stuff on other bands. So at this point I might recommend an antenna that covers more than just the 151 to 171Mhz range and your typical scanner type Discone is a good place to start. I will receive everything from aircraft down at 118MHz to your VHF stuff between 151 and 171MHz plus anything else like UHF mil air (since your not that far from March AFB) and police/fire/hospital/ambulance/etc, through 512MHz. A Discone will receive all of those with roughly the same performance and no gaps in frequency, unlike any other antenna that is frequency specific. The Discone will also work for 700/800MHz stuff but with reduced performance but probably much better than pushing a VHF only antenna to do the same.
 
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Thank you for your reply. We don't have any police or fire on 700 / 800 megahertz here. Actually we do but they are encrypted on the police side and fire is provided by Cal Fire and they are on 151 megahertz. From the hill I live on I can hear San Bernardino County Fire where I enjoy hiking and of course I can hear Cleveland National Forest right next to me. San Bernardino National Forest is also right next to me since they seem to have an outcropping if you will that's not connected to the main mountain range. But they're on 170 megahertz. Their air tankers are at 169 megahertz so I have no problem hearing them. It's just there's a difference between hearing the tactical versus the repeaters. I've been using this site to figure out the tacticals and they seem to have an awful lot to choose from between County, state, and federal. You guys really get into this I don't know how you remember all this stuff. I don't imagine I'll listen much during the winter although I do listen to CHP that comes in Fairly strong where I'm at just on the handheld scanner and the whip on the back of the desktop unit.

I'm an ex-cop and I know the difference between simplex and being on dispatch. At LAPD we have the station frequency and actually used it on Simplex all the time. I can't hear that from where I'm at and honestly I don't want to. Lol. I heard it for 30 years and that was long enough. But with all the fires around me I think it just makes sense to listen so I have mainly a head start. Plus when I go hiking I'm learning where to tune so if I'm in an area and need to get the hell out of there I have a chance to do that as well.
 

prcguy

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What area did you work at LAPD?

Thank you for your reply. We don't have any police or fire on 700 / 800 megahertz here. Actually we do but they are encrypted on the police side and fire is provided by Cal Fire and they are on 151 megahertz. From the hill I live on I can hear San Bernardino County Fire where I enjoy hiking and of course I can hear Cleveland National Forest right next to me. San Bernardino National Forest is also right next to me since they seem to have an outcropping if you will that's not connected to the main mountain range. But they're on 170 megahertz. Their air tankers are at 169 megahertz so I have no problem hearing them. It's just there's a difference between hearing the tactical versus the repeaters. I've been using this site to figure out the tacticals and they seem to have an awful lot to choose from between County, state, and federal. You guys really get into this I don't know how you remember all this stuff. I don't imagine I'll listen much during the winter although I do listen to CHP that comes in Fairly strong where I'm at just on the handheld scanner and the whip on the back of the desktop unit.

I'm an ex-cop and I know the difference between simplex and being on dispatch. At LAPD we have the station frequency and actually used it on Simplex all the time. I can't hear that from where I'm at and honestly I don't want to. Lol. I heard it for 30 years and that was long enough. But with all the fires around me I think it just makes sense to listen so I have mainly a head start. Plus when I go hiking I'm learning where to tune so if I'm in an area and need to get the hell out of there I have a chance to do that as well.
 

Ubbe

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I wanted best possible antenna for VHF marine band 156Mhz and bought a Diamond F23 antenna that comes with a cutting diagram to fine tune it to different VHF frequencies. It receives VHF airband better than a 5/8 GP gain antenna specifically tuned for airband and receives 170Mhz better than the 5/8 GP tuned to that frequency. It will do much better than a discone and also some low-vhf works good and uhf as well but not the whole band as a discone can do.

I can really recommend the big Diamond F23 antenna if you only focus on best possible VHF reception.

/Ubbe
 
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I wanted best possible antenna for VHF marine band 156Mhz and bought a Diamond F23 antenna that comes with a cutting diagram to fine tune it to different VHF frequencies. It receives VHF airband better than a 5/8 GP gain antenna specifically tuned for airband and receives 170Mhz better than the 5/8 GP tuned to that frequency. It will do much better than a discone and also some low-vhf works good and uhf as well but not the whole band as a discone can do.

I can really recommend the big Diamond F23 antenna if you only focus on best possible VHF reception.

/Ubbe
What frequency did you cut the antenna for? I was noticing that the forest service is roughly 166 to 173. Cal Fire though is roughly 151 to 160. They have tac channels with most of the tacs at 159. So I'm thinking the midpoint which is 154. My ham radio friend helped me figure that out.

But the one thing he told me when looking at the F23 that you recommend is that it has high gain. 7.8 something or another. He said that is like a flashlight. You can have a flood light or you can have a spotlight. The 7.8 is more like a spotlight and he said it won't get down into the canyons as well. That's why I picked up a discone. It does really well on aircraft but not so well on San Bernardino County Fire. It does fantastic really on the Forest Service and Cal Fire but you are saying I can do better? I've already got two scanners and I don't expect that I'll be buying a third. I noticed that the aircraft it's view the retardant are at 169 but the helicopters are way down at 122 and they're the ones that I want to listen to. I'm afraid though I'm turning into a scanner geek. LOL. I can't tease friends of mine that are firemen anymore. When I was on the job we used to drive by their stations at night time and blare our siren as we went by. They would make sure to drop off a box of donuts every now and then.

So like do I need that high of a gain antenna? He told me I need something like 3db and I haven't got a clue what that even means. He says that 3db is more like a flood light than a 7.8db spotlight. He also told me I can get the antenna at half the price just by buying I think he called it a Tram. He says it's the same antenna. Now he wants me to study for my damn ham radio license. I didn't sign up to get all excited and spend lots of money. I don't really stay glued to the radio. It's just when there's fires burning around me. If you've ever driven down Interstate 15 in the Menifee and looked up at the newer houses at the top that's where I'm at. We got to be careful with the fires though because it's all yellow grass around us. My wife wants horses now and I got the swimming pool. The grandkids now have a place to come play.
 

Ubbe

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If you live at that hill top at 2000 feet and everything is lower to you, then the F23 are no good. If you have any obstructing hills in between you and the transmitters you will have to receive the signal from those hill tops, as the radiosignals cannot penetrate rock, it has to go over those hills.
The F23 vertical pattern looks like this:


And a more no gain antenna like a discone looks like this:


Remember that radiosignals have to go over any hill tops and ridges and that 7,8dB compared to probably 2dB from a discone are 6dB, or a 4 times, stronger receive signal, if the radiosignal are inside that spotlight beam. Sunlight and radiosignals behave exactly the same when it comes to shade, obstructions and reflections.

/Ubbe
 

Ubbe

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I can't really pinpoint your position. Every hill I see are at max 1000 ft. It's east of interstate 15 and near lake Elsinore?
Play a little with this line of site map and see what kind of obstructions you have from your exact GPS position and to the areas where the transmission are coming from and compare the obstructions highest point with the beam angle from the F23 coverage diagram.

/Ubbe
 
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If you live at that hill top at 2000 feet and everything is lower to you, then the F23 are no good. If you have any obstructing hills in between you and the transmitters you will have to receive the signal from those hill tops, as the radiosignals cannot penetrate rock, it has to go over those hills.
The F23 vertical pattern looks like this:


And a more no gain antenna like a discone looks like this:


Remember that radiosignals have to go over any hill tops and ridges and that 7,8dB compared to probably 2dB from a discone are 6dB, or a 4 times, stronger receive signal, if the radiosignal are inside that spotlight beam. Sunlight and radiosignals behave exactly the same when it comes to shade, obstructions and reflections.

/Ubbe
These are the maps that my amateur radio friend showed me. That's how he described it was the top one was like a spotlight and the bottom one was like a flood light. That's why he suggested the discone was probably the better choice because of my modest altitude if I used the top antenna style I would basically be shooting into like Elsinore Peak when actually what I want is to be able to hear things coming in from down below Santiago Peak or the many Canyons around me as well as in the Cleveland National Forest. I've hiked in all of those so I know where they're at.

If you live at that hill top at 2000 feet and everything is lower to you, then the F23 are no good. If you have any obstructing hills in between you and the transmitters you will have to receive the signal from those hill tops, as the radiosignals cannot penetrate rock, it has to go over those hills.
The F23 vertical pattern looks like this:


And a more no gain antenna like a discone looks like this:


Remember that radiosignals have to go over any hill tops and ridges and that 7,8dB compared to probably 2dB from a discone are 6dB, or a 4 times, stronger receive signal, if the radiosignal are inside that spotlight beam. Sunlight and radiosignals behave exactly the same when it comes to shade, obstructions and reflections.

/Ubbe
 

Ubbe

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It's difficult to get signals over the top of hills and then dive down into valleys. According to the map you are surrounded by hills.
I live with hills almost all around me and have no clear sight to any transmitters and I have tried 1/4 wave GP's, 5/8 GP with a little more gain and the F23 with the most gain and it's a big difference in reception with F23 that picks up much more than any other VHF antenna I have, even as the beam seems to point directly into most hills. When a use a high gain yagi antenna it almost receives the same whatever direction I point it, so I probably only receive reflections of the original signal.

You could assume that the diagram with the F23 coverage has it's beam generating a 4 times stronger signal than the flood light diagram. That could compensate for the narrower beam by the much higher gain. It all depends of where those radiosignals are coming from and how they could bounce of any other hills, if any. Aircrafts will be flying at a higher altitude and should be no problem hearing. Rangers in the woods in the valleys using portable radios are the problematic ones if they only use simplex frequencies. The ranger station and firebrigades probably have their receivers at the top of the highest mountains so they will hear everything.

/Ubbe
 
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It's difficult to get signals over the top of hills and then dive down into valleys. According to the map you are surrounded by hills.
I live with hills almost all around me and have no clear sight to any transmitters and I have tried 1/4 wave GP's, 5/8 GP with a little more gain and the F23 with the most gain and it's a big difference in reception with F23 that picks up much more than any other VHF antenna I have, even as the beam seems to point directly into most hills. When a use a high gain yagi antenna it almost receives the same whatever direction I point it, so I probably only receive reflections of the original signal.

You could assume that the diagram with the F23 coverage has it's beam generating a 4 times stronger signal than the flood light diagram. That could compensate for the narrower beam by the much higher gain. It all depends of where those radiosignals are coming from and how they could bounce of any other hills, if any. Aircrafts will be flying at a higher altitude and should be no problem hearing. Rangers in the woods in the valleys using portable radios are the problematic ones if they only use simplex frequencies. The ranger station and firebrigades probably have their receivers at the top of the highest mountains so they will hear everything.

/Ubbe
I think a clarification of what I want to listen to is in order. I'm not interested in listening to distant dispatch centers. I'm interested in listening to tactical communications throughout the general area and down in the canyons around me, as well as up in the Cleveland, the San Bernardino's and San Jac Wilderness Area. I live right in the middle of these different systems if that's what they're called.

I had an opportunity yesterday to talk with a Forest Service Communications Tech and he was answering my questions about antennas. The way they are set up is by zones. They have mountaintops where dispatch communications come from and they generally use low gain base station antennas. He told me next time I'm in the National Forest near one of the lookouts to look for an antenna that looks like a loop going up vertically and then radials coming out from the sides. He told me the characteristics of this type of antenna are more likely to get down into the canyons as opposed to talking to vehicles on the highways.

He also told me they have white fiberglass antennas that are about 6 ft tall that are low gain as well. He said they can be electronically tuned so that they are able to hear better down below them instead of out and away from them. He went on to say that the channels that they have tend to work well down in the canyons and actually come up the canyon walls and spillover the top. Looking at a list of the different mountain tops used in the Cleveland National Forest helps me visualize what he's talking about.

The specific reason is that the higher gain antennas that you speak of are great when talking from one mountain top to another but terrible when talking down into the canyons. They're the ones that I'm not able to hear but using Cal Fire as an example I am able to hear them much better when they're on their tactical channels. Listening to a repeater is easy. He also told me that the Forest Service mobiles don't usually go through the repeater. They normally use talk around (?) as he called it through what I know as direct. I'm used to station fall back channels that we could use in repeater mode or direct for short-range communications. It just depends on the nature of their radio traffic.

So I guess it comes down to what I want to hear versus what you want to hear. With me discone antenna I can hear CHP just fine and even occasionally some car-to-car traffic as well as Cal Fire and the Forest Service. I can even hear the Game Wardens but they don't talk very often. I can even hear the aircraft in the aviation band quite well. This small antenna seems to fit my casual needs. The antenna that came with the radio is crap. My main interest isn't actually the tactical stuff but the aircraft communications that are really intense especially at the beginning of a fire. I need to be able to listen down at 122 and up at 169. Unless it's Cal Fire which is what's mostly around here and then it's 159. I guess they don't make an antenna that covers this large span other than a discone and says I can even use on the ham bands.

It sounds to me like you want to listen to the distant stations and so the spotlight type antenna works better for you whereas I want to hear the local stuff down below me and the airplanes above me which means the flood light or the two round circles back to back works better for me.

My needs may change in the near future. He talked me into taking my ham radio test a week from Saturday. The questions are pretty easy. I bought a baofeng radio which he laughed at but told me it's a good start. He said from my elevated location I should do quite well from up here. He told me I can listen to Cal Fire and the Forest Service on the baofeng as well.

I'm retired now. I don't really want to hear the cop talk after decades of listening to it. But when it comes to fires burning up hillsides around my home it becomes a little more personal. My god do they move fast!
 

Ubbe

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Ok, so you have your house on a hill top and every transmission you want to hear are right below you and no hills and mountains are obstructing the radio signals. I live with my hills so close as 500ft and then it's 2 miles with more hills in between then it dips quickly down to waterlevel where all ships go to and from Stockholm where I want to receive their 156MHz transmissions and also helicopters that are at a 1000ft hight around greater Stockholm that hide behind the hill tops I have. The F23 are the absolut best antenna for me.

But you have clear sight down into the valleys surrounding you so you are correct, you need an antenna that points the beam downwards as you do not need to try and receive any signals that go over any hill tops. I've seen antennas that have the groundplane radials that point outwards being installed upsidedown so that the beam points down. Not knowing exactly where you live and looking at the topograf map I though you had lots of hills that obscructed the radiosignals but I guess I was wrong.

/Ubbe
 
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Ok, so you have your house on a hill top and every transmission you want to hear are right below you and no hills and mountains are obstructing the radio signals. I live with my hills so close as 500ft and then it's 2 miles with more hills in between then it dips quickly down to waterlevel where all ships go to and from Stockholm where I want to receive their 156MHz transmissions and also helicopters that are at a 1000ft hight around greater Stockholm that hide behind the hill tops I have. The F23 are the absolut best antenna for me.

But you have clear sight down into the valleys surrounding you so you are correct, you need an antenna that points the beam downwards as you do not need to try and receive any signals that go over any hill tops. I've seen antennas that have the groundplane radials that point outwards being installed upsidedown so that the beam points down. Not knowing exactly where you live and looking at the topograf map I though you had lots of hills that obscructed the radiosignals but I guess I was wrong.

/Ubbe
PRCGUY - You've asked me where I live and you even asked me what stations I worked out of. I'm not going to reveal exactly where I live or which stations I've worked out of for personal and professional reasons. PII - personally identifiable information. I'm sure you understand.

UBBE - Look right along the east side of the 215 freeway and you will see hilltop's ranging from 1600 feet to 2,700 feet with homes on top of them. Make sure the software you're using reads out in feet and not meters. A meter is just over three feet. So you can take the hilltops you see that may read like 792 and just multiply times 3 and come up with about 2,600 feet. I only know this because of the hiking I do in the maps that I read. I have a software app on my cell phone that lets me choose. I have given you the box that I am in that includes Lake Mathews, Chino Hills State Park, San Jacinto State Park, Cleveland National Forest, and Lake Elsinore. Put it somewhere in the middle near the 215 freeway. Nuevo and Mapes east of the 215. I don't know how to insert an image so I can't show you myself. You will find a mountain peak or hilltop or whatever you call it at 2662 feet in what is called the Lakeview Mountains.

I didn't say I only had one hill that I wanted to hear down below. But I'm not trying to hear distant dispatch stations. I looked up the diamond f23 and it's actually a 5.6 dbd gain antenna. My Forest Service Radio Tech friend tells me that's more realistic than 7.8 dbi. He says it's a game manufacturers play by giving two ways to measure an antenna. It's pretty Greek to me. Advertising. I forgot to ask him where a damn db is. LOL.

At any rate, it sounds like you like listening to stations at a distance. I just need to hear the stuff in closed because that's the stuff that burns. Near me anyway. They burn hot and fast. That yellow grass just goes up in an instant and you can watch it as it just gobbles it up. I've got good clearance around my house. I need an antenna to covers 39.88 for CHP and then 122 something for the helicopters. The Cal Fire tacticals are up at 159 but their airplanes are down at 151. Then there's the forest service that's up at 166 to 172. The Diamond DJ 130 discone seems like the best choice for me.

While reading my amateur radio books I was reading about VHF and how the range goes out based on the height of the antenna towards the horizon and if there's a hill in the way it goes to the hill and then drops over about 20%. I know that I don't have the most perfect setup but I don't think I'm in the same category of listeners as you guys. I think once winter comes the thing will be turned off most of time. I've listened to radio calls for decades and I don't really need to hear CHP. But it is pretty cool watching the Cal Fire airplanes parked at Lake Elsinore suck up the water as they take off and then pull up in the air. I think that's pretty damn cool. That's the next item on my bucket list. I want to learn how to fly. I'm not that old in my eyesight still pretty damn good. I've got a donut ass and I don't know if I'd sit in the cockpit well. It might lean to one side. Lol.

Thanks for your help on the antennas. It's going to take me awhile to catch up.
 

Ubbe

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My monitoring range max out at 10-15 US miles due to all those darn hills. The F23 are three 5/8 wavelenght antennas stacked on top of each other. One 5/8 might have up to 2dB gain over a standard 1/4 wave GP antenna, so max 6dB gain for a F23 and then some loss due to the coupling circuits between the antenna elements.

Buy that D130 discone that has a top element for the 35MHz band and try to monitor holding it up in your hand or using a temporary fix to something using tie wraps or similar. If it doesn't work out you can sell it as new, only tested, and get back almost all you money.

/Ubbe
 

mmckenna

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I see some concern about the frequency spread between CalFire and Federal users (BLM, USFS, etc)

Remember that all these agencies have each others frequencies programmed into their radios for interoperability. They use one antenna for those. If you look on top of some CalFire Type 3 engines, you may see two whip antennas about 18" long. This is for two separate radios. The antennas are a quarter wave VHF whip. The nice thing about quarter wave antennas is that they are very broad banded. You can cut them for the middle of the VHF band and they will work well across it. It's no problem to use them with a radio that may be transmitting/receiving at 151MHz, as well as up around the 170 range.
I use them on top of my personal and work truck, and they operate just fine. I have the test equipment to properly tune them, and they show more than acceptable performance across the entire VHF spectrum from the bottom of the 2 meter amateur band up past 170MHz.


That's pretty geeky stuff, but let me explain:
Usually in the 2 way radio industry, anything below 2.0:1 SWR is considered acceptable. This plot shows that the 1/4 wave antenna provides an SWR of 2.0:1 or less from 138MHz all the way to 170MHz. For receiving, SWR isn't much of an issue, so reception of the air band, 108MHz to 137MHz is going to be fine.
These are the same antennas that CalFire is using for their vehicles.

What has been talked about above with getting signals in/out of steep canyons is right on. You don't want a high gain/long/tall antenna in those applications. That's why CalFire is using these. With all the money CalFire has, all their radio guys, all their experience, this is what they have chosen.

Most of the stuff you want to hear is going to be simplex, and fairly low power. The hand held radios only run 5 watts or so. Aircraft radios are often running no more than 10 watts. The mobile radios are running 50. Having a good antenna connected to your scanner is going to help.

In your original post, you talked about being a "perfectionist that wants the best". Then you talk about Tram antennas. That similar to a car enthusiast buying a Yugo. I mean, it'll probably get you from point A to point B (eventually/maybe) but you'll ultimately be disappointed. Tram antennas are bottom of the barrel Chinese knock off antennas. Ham radio operators tend to love them because most hams are cheapskates by default, and they'll gravitate towards the cheapest antennas they can lay their hands on. That's fine if your budget is really tight and you don't mind replacing your antenna periodically. If budget is not a concern (and it sounds like it isn't) you can -easily- do better than Tram. Installing cheap Chinese antennas is not a good investment.

So, what I was showing above was that the simple quarter wave mobile antennas work better in most of the situations you describe. It'll cover the frequencies you want just fine. But, sounds like you want a base antenna. There's a couple of good options that are from reputable companies that make quality antennas, as opposed to cheap Chinese crap knock off antennas:

You can also use a "base adapter" and a mobile antenna and make a low profile setup:

If your tolerance for something that stands out a bit more is higher, and your budget doesn't get in the way:
I'm using several UHF versions of this same antenna for a few repeaters up along the Big Sur coastline. They solved some coverage issues that were created by some higher gain antennas. They cover well down into deep canyons (2,000 feet below the antenna). They are also ridiculously durable.

If you want to listen to other radio traffic outside the VHF band, the discone antenna might be a good option. But again, skip the Cheap Chinese crap antennas. High quality commercial discone antennas are really expensive, in the 2-3 thousand dollar range, and overkill for what you need. While not my favorite antenna brand, Diamond D-130 discone is a good option. It'll let you hear some stuff from the UHF, 700 and 800MHz bands, if that ever interests you. If VHF is all you want to listen to, then stick with one of the others.

CHP can be tricky to receive. Often it requires band specific antennas to work well. If you are close enough to one of their sites, then the antenna that you are currently using sounds like it'll work well. You might see some reduced performance if you switch to a different type of antenna.

Don't overlook the rest of the install. You can have the 'best' antenna in the world, but if you connect it to your radio with cheap coaxial cable, you've wasted your investment. You want some decent cable to get it all to work right. The exact type depends on the individual install, how long the run is, etc.
You also need to consider mounting, lightning protection and proper grounding, but that's a different discussion.

Don't put all this effort into this project and buy cheap hobby grade antennas. You'll put some labor, time and money into installing this correctly, and using cheap materials will often require frequent replacement and maintenance. Better to do it right the first time...
 

mmckenna

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I'll also add this about the aircraft band:
The aircraft use the lower end of the VHF spectrum, 108-137 MHz, they also use AM modulation. While your scanner will handle that just fine, it's probably not what you'll want to listen to for most of what you want. Yes, the helicopters, tankers, spotters, etc. will use the AM aircraft band, they also use the FM portion of the band where CalFire and USFS, etc. talk. Usually the guys on the ground are not carrying VHF AM aircraft portables, the aircraft talk to the guys on the ground on the higher VHF frequencies.

Having the ability to listen in on the AM aircraft band would be useful, and the antennas I linked to above will work, but don't get too hung up on that, most of what you want will be on the higher frequencies.
 

Ubbe

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Usually in the 2 way radio industry, anything below 2.0:1 SWR is considered acceptable. This plot shows that the 1/4 wave antenna provides an SWR of 2.0:1 or less from 138MHz all the way to 170MHz.
You probably have some special antenna there for the upper part of VHF where it flattens out that doesn't show a balance to the lower part. When I sweep a 1/4 VHF GP antenna I get a 2:1 SWR range of 140-160MHz.


/Ubbe
 
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