Antenna booster needed

[darticus]

Is there something I can purchase to go in the line to increase the signal on my police scanner. I was looking on Ebay but not sure what to get. Using a RS Discone antenna. Thanks Ron

 

[Blackswan73]

How far are you trying to receive? That discone should be good for 30+ miles for VHF and UHF, depending on height. Normal VHF communications are usually not intended for more than 50 miles.

 

[darticus]

How far are you trying to receive? That discone should be good for 30+ miles for VHF and UHF, depending on height. Normal VHF communications are usually not intended for more than 50 miles.

Thanks for getting back. I live in a mountainous area and I think mountains block me. I'm only trying to go about 20 miles but just shy on the meter from getting the distant station. Thanks Ron

 

[teufler]

There are preamps that you can get. Uniden made one, BC004. Mine gets about 2 bars more, when used with a 780xlt or a 396xt. Some people don't like them, as they say they increase noise. I used it mobile for years and it made a difference in reception. Both the signal and the audio came up when turned on. GRE makes one, Uniden saeems to have stopped making one.
http://www.amazon.com/GRE-Amplifier...9hUfXeL&dpSrc=sims&preST=_AC_UL160_SR160,160_

 

[ka3jjz]

'Boosters' (preamps, really) can cause more problems that they're worth. They can increase your noise levels and overload issues...however in your neck of the woods, that might be less of a problem (I'm from the Paramus area originally).

However before you go that route, what coax are you using? If you're using some cheap RG-58 or 59, think about improving that first.

Really it's difficult to get over a mountain on VHF (even more so on UHF) without adding height to the equation...

Mike

 

[trentbob]

... agree with the RG-58 coax... if you are not using low loss coax like RG-8 or LMR 400 on UHF or 800 it will make all the difference in the world if you upgrade... night and day... I use a GRE super amp 3001 every day on one of my 3 rooftop ground planes... it's about 20 years old but works great if you can find a used one...

 

[darticus]

'Boosters' (preamps, really) can cause more problems that they're worth. They can increase your noise levels and overload issues...however in your neck of the woods, that might be less of a problem (I'm from the Paramus area originally).

However before you go that route, what coax are you using? If you're using some cheap RG-58 or 59, think about improving that first.

Really it's difficult to get over a mountain on VHF (even more so on UHF) without adding height to the equation...

Mike

I don't want to get killed climbing up 50 feet or paying someone to do it if different cable is not going to help. You may be right as this is RS cable and some say its OK and others say terrible terrible while test say its about the same when tested on site. Meaning changing the cable for 100 dollars for a 1db gain is not worth it. If a booster can be used efficiently at a reasonable priced than I'll give it a try. I personally think the mountains are causing the problem. I connected my Diamond X-510 antenna and it gives me 2-3 lines receive out of 4 With great cable. When I was only getting one line from the RS Discone. Thanks Ron

 

[prcguy]

I agree with everything said about a preamp causing more problems than it can fix. In your case the preamp should be at the antenna before the long run of coax to be beneficial, otherwise your feeding the preamp a weak signal and it can't invent a signal that's not there.

Upgrading coax is usually the first step and in some cases a preamp can help like making up for losses from splitting to multiple scanners, but if you are near any repeater sites, FM/TV broadcast or cell phone towers a preamp can ruin your day.
prcguy

I don't want to get killed climbing up 50 feet or paying someone to do it if different cable is not going to help. You may be right as this is RS cable and some say its OK and others say terrible terrible while test say its about the same when tested on site. Meaning changing the cable for 100 dollars for a 1db gain is not worth it. If a booster can be used efficiently at a reasonable priced than I'll give it a try. I personally think the mountains are causing the problem. I connected my Diamond X-510 antenna and it gives me 2-3 lines receive out of 4 With great cable. When I was only getting one line from the RS Discone. Thanks Ron

 

[darticus]

I agree with everything said about a preamp causing more problems than it can fix. In your case the preamp should be at the antenna before the long run of coax to be beneficial, otherwise your feeding the preamp a weak signal and it can't invent a signal that's not there.

Upgrading coax is usually the first step and in some cases a preamp can help like making up for losses from splitting to multiple scanners, but if you are near any repeater sites, FM/TV broadcast or cell phone towers a preamp can ruin your day.
prcguy

Are you saying the preamp can't be down at the radio in the house? Thanks Ron

 

[prcguy]

You can put it anywhere you want, but if you expect it to provide the best performance you put it right at the antenna. This way it will make up for your cable loss and lower the noise figure of your entire system. That is assuming the preamp does not get overloaded by nearby strong signals and create IMD which raises the noise floor, or its got a noise figure so high it introduces excessive noise into your system and the signal to noise ratio is not improved even though the signal level is higher.

This is typical with cable TV amps which are designed to amplify a known group of signals and not to be connected to an antenna with unknown levels that are way outside its design range. The key to everything is improving your signal to noise ratio and not necessarily the signal levels.

Problem is most people live in areas with enough strong signals around that it will run a low cost or average wide band cable TV preamp into saturation or to a level where they create IMD. A really good wide band preamp that will survive in a high RF environment is very expensive and of the dozens of preamps I've tested at my house, only one is useable on a Discone antenna without a preselector filter and it was real expensive new. Many preamps will work fine for a narrow band of frequencies if you put a specific band pass filter in front of them, but most people are looking for a wide band solution and you won't know if it will work in your area until you try it.
prcguy

Are you saying the preamp can't be down at the radio in the house? Thanks Ron

 

[darticus]

You can put it anywhere you want, but it you expect it to provide the best performance you put it right at the antenna. This way it will make up for your cable loss and lower the noise figure of your entire system. That is assuming the preamp does not get overloaded by nearby strong signals and create IMD which raises the noise floor, or its got a noise figure so high it introduces excessive noise into your system and the signal to noise ratio is not improved even though the signal level is higher.

This is typical with cable TV amps which are designed to amplify a known group of signals and not to be connected to an antenna with unknown levels that are way outside its design range. The key to everything is improving your signal to noise ratio and not necessarily the signal levels.

Problem is most people live in areas with enough strong signals around that it will run a low cost or average wide band cable TV preamp into saturation or to a level where they create IMD. A really good wide band preamp that will survive in a high RF environment is very expensive and of the dozens of preamps I've tested at my house, only one is useable on a Discone antenna without a preselector filter and it was real expensive new. Many preamps will work fine for a narrow band of frequencies if you put a specific band pass filter in front of them, but most people are looking for a wide band solution and you won't know if it will work in your area until you try it.
prcguy

Thanks, Great info.
Maybe my best way it to receive the week channels on Broadcastifiy and the others on my scanner. Thanks Ron

 

[wtp]

maybe...

just might be time to go directional, if you want just one site.

 

[trentbob]

... as much trouble as it would be it's a no brainer if you really are using RG-58 coax... that IS your problem... you might as well use a back of the set antenna... we still don't know what coax you are using but if it's RG 58 then that IS your problem... however you do it, you need to replace it with RG 8 or LMR 400... I learned that lesson 45 years ago when I replaced 20 feet of RG58 with RG8 on my first rooftop... if someone told you it doesn't make a difference on UHF or 800 they don't know what they are talking about... RG 58 is for 11 meter CB band where there is no signal loss... you will love the performance of RG 8 and will not need a preamp... no preamp will ever make up for the loss of signal through RG 58 coax... it really is a fact of life...

 

[KT4HX]

Agree with the others, if you are using RG-58, that is an issue. I would not use RG-58 for anything over a few feet, such as in a mobile situation for VHF, UHF and 800 (especially). For example, using the calculator at Times Microwave, even at the frequency of 150 MHz, using a cable run of 50 ft as an example, RG-58 shows an attenuation of 2.8db, at 450 MHz that goes up to 5.0db and at 800 MHz that goes to 6.8db. Running the calculator for the same run using RG-8 gives you 1.2db attenuation at 150 MHz, 450 MHz is 2.2db while at 800 MHz the attenuation goes up to 3.1db. Now if you try putting in LMR-400, then your attenuation drops to 0.8db at 150 MHz, at 450 MHz 1.4db and finally at 800 MHz it would be 1.8db.

If the run is even longer, then the attenuation figures only go up. The type of cable certainly does make a major difference, particularly as your frequency rises. RG-58 is very good for HF applications, but as you get into the VHF range its performance starts to drop off quickly. Now I cannot vouch for the nth degree accuracy of the calculator, but it does present a picture I am quite familiar with and have personally experienced over the years with numerous installations. For a base station installation with an outside antenna I will always recommend one use the best cable they can afford. You simply can't go wrong with that mindset.

 

[n5ims]

Another issue could be the discone itself. While that may be a good choice if you actually NEED to cover a wide frequency range. Just because your scanner will receive over that wide range, if you just listen to the many 700/800 MHz trunking systems, an antenna that covers just this range will way outperform any discone or other wide frequency range antenna.

I also agree with others that the coax used will also make a great deal of difference on the amount of signal reaching the radio. More length = less signal. Higher frequency = less signal. Higher frequency + more length = WAY less signal.

Also coax type is important here. In the amount of signal loss by coax type (least signal to most signal):
* RG-174 - Very thin, very lossy. Used on several mag-mount antennas.
* RG-58 - Thin. OK for low frequencies (below 50 MHz) or VERY short runs (like a mobile at 15' or less).
* RG-8X [8 Mini, etc.] - Thin and flexible. Good for low frequencies (below 50 MHz).
* RG-6 - Thin, cheap, and easy to work with. Made for TV use, but also works on scanners or other receive-only situations. Short to moderate runs (under 100').
* RG-8 - Moderately thick (1/2") - Good for most uses, receive-only or transmit/receive.
* LMR-400 - Moderately thick (1/2"), moderate price, rather stiff - Same size as RG-8, but more difficult to work with due to stiffness. Lower loss (more signal) than those above. Not for repeater use.

 

[teufler]

Coax Loss Calculator
coax loss calculator

 

[cbehr91]

I recently "upgraded" from a 20' run of RG-58/U to RG-8X and even with that short of a run I've noticed better "reception" (i.e. less loss) across all the popular scanner bands, even with that short of a run.

I won't say don't use a preamp, but your mileage may vary with one. However I would recommend an upgrade to .400 diameter coax (RG-213/U or LMR-400). Theoretically you will have a mismatch using RG-6, but people have used them with scanners for years with good results.

 

[KT4HX]

Theoretically you will have a mismatch using RG-6, but people have used them with scanners for years with good results.

Agree, I use RG-6 quad-shield buriable cable (about 75 ft) to feed my Drake receivers for shortwave, with about 50 feet buried. For reception I have never found the mismatch presented by the 75[FONT=&quot]Ω cable [/FONT]at the 50[FONT=&quot]Ω antenna feedpoint and [/FONT][FONT=&quot]input at the receivers to negatively impact reception. However, if I were transmitting, I would use cable that matches the antenna/transmitter system[FONT=&quot], u[/FONT]sually RG-8 or RG-213.[/FONT]

 

[darticus]

Agree, I use RG-6 quad-shield buriable cable (about 75 ft) to feed my Drake receivers for shortwave, with about 50 feet buried. For reception I have never found the mismatch presented by the 75[FONT=&quot]Ω cable [/FONT]at the 50[FONT=&quot]Ω antenna feedpoint and [/FONT][FONT=&quot]input at the receivers to negatively impact reception. However, if I were transmitting, I would use cable that matches the antenna/transmitter system[FONT=&quot], u[/FONT]sually RG-8 or RG-213.[/FONT]

Which is Better RG-8 OR RG-213 OR LMR-400 with the best price. Thanks Ron

 

[ka3jjz]

'Better' - in terms of what? If you want loss figures, use the link Teufler gave you in this thread (message 16)

It's much too general a question to answer properly - more specifics, please...Mike