So i have installed a D-130-J on my roof and my scanner now works amazingly!! However there's one frequency that is a city fire department that i am having issues with. On most nights the frequency comes in good but during the day its extremely scratchy. I am wondering if a pre-amp would help. Any suggestions?? Here are a few pictures of my new antenna install.
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Pre-amplifier
- Thread starter Colton25
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How far away is the fire dept. you are trying to hear, and on what band? Also what coaxial cable to your discone are you using?
One more question is, do you have any guy lines on that mast to help resist wind?
73,
n9zas
One more question is, do you have any guy lines on that mast to help resist wind?
73,
n9zas
The dept is about 45 miles away, it is a VHF high band, i believe i am using rg-6 with bnc connectors and yes i have 3 guy wires installed the pictures were taken before guy wires were installed also i have raised the antenna to about 40'
Depending on the radio you are listening with, then yes you may need a low noise preamp. Another option might be to install lower loss cable such as LMR400. Rg6 does have a bit of loss to it, depending on how many feet you have in line with your discone which is a wideband antenna with unity gain ( or none, as was pointed out) over its bandwidth. I would suggest the lower loss cable over the preamp however.
73,
n9zas
Depending on the radio you are listening with, then yes you may need a low noise preamp. Another option might be to install lower loss cable such as LMR400. Rg6 does have a bit of loss to it, depending on how many feet you have in line with your discone which is a wideband antenna with unity gain ( or none, as was pointed out) over its bandwidth. I would suggest the lower loss cable over the preamp however.
73,
n9zas
Im using a bct15x scanner, i was looking at these amps, do you know anything about them?
https://www.scannermaster.com/WRP_2500_Pre_Amplifier_for_Wideband_Scanners_p/28-531168.htm
https://www.scannermaster.com/LNA_2000_B_Pre_Amplifier_p/24-531042.htm
I did look at the links you provided, and while I suggest more time and money in the antennas and cable I suggest the second preamp you picked due to the fact you could mount it right at the antenna where it would do more good rather than at the scanner.
https://www.scannermaster.com/LNA_2000_B_Pre_Amplifier_p/24-531042.htm
73,
n9zas
https://www.scannermaster.com/LNA_2000_B_Pre_Amplifier_p/24-531042.htm
73,
n9zas
I did look at the links you provided, and while I suggest more time and money in the antennas and cable I suggest the second preamp you picked due to the fact you could mount it right at the antenna where it would do more good rather than at the scanner.
https://www.scannermaster.com/LNA_2000_B_Pre_Amplifier_p/24-531042.htm
73,
n9zas
Okay, now i am looking more into the yagi rout because it sounds like it would really make a difference i just want to somehow keep my discone for the local departments...
Rt169Radio
Member
Nice antenna setup,I would get some low loss coax cable and see how that works out before I would get a pre-amplifier.
Gain has nothing to do with antenna reception through a discone or any other antenna for that matter used for receiving only. But you are correct when you say a discone has zero gain, but that is on the transmission side.
Zane, how far is the city FD from you and which direction? Also what frequency are they on? It could be a matter of what is in between you and their transmitter. At night, there is less natural interference so reception near by could be better at night. By looking at the picture, it doesn't look like your antenna is being blocked by anything but if you have some tall trees and the city FD is say on 800 MHZ conventional or TRS, you'll have some reception issues due to the nature of that band.
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The FD is 45 miles north north west of me, i live in a valley with no obstructions. It is a 154 frequency
This is wrong.
Antenna gain is reciprocal, meaning it is the same whether transmitting or receiving. A gain antenna oriented in the right direction would deliver more signal to the receiver than a non-gain antenna.
Zane018, 45 miles is pretty much the limit of range on VHF hi-band. The horizon is your limiting factor. Standing on the ground with eye height of about 5.5', the horizon is going to be around 4 miles away. As you increase your eye height the distance to the horizon increases, 100' would equal around 30 miles. The signal does refract or bend around over the horizon to some extent and the transmit antenna won't be at ground level either. But you still won't get much more than 45-50 miles maximum.
prcguy
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What the H??? Somebody needs to do some reading on antenna basics.
Anyway, preamps are a touchy subject and in many cases they can degrade the overall performance due to being overloaded and generating lots of signals that interfere with reception. A really good preamp that is not so prone to this can cost more than your scanner.
As mentioned placing the preamp at the antenna is best so there is no loss before the preamp and it can make up for your cable losses. For this particular problem I would try to raise the antenna more and use a lower loss cable like LMR400 or even RG-11.
prcguy
Anyway, preamps are a touchy subject and in many cases they can degrade the overall performance due to being overloaded and generating lots of signals that interfere with reception. A really good preamp that is not so prone to this can cost more than your scanner.
As mentioned placing the preamp at the antenna is best so there is no loss before the preamp and it can make up for your cable losses. For this particular problem I would try to raise the antenna more and use a lower loss cable like LMR400 or even RG-11.
prcguy
gunmasternd
Member
My vote is for a better antenna a discone is just a fancy rubber duck antenna a yagi/preamp your just throwing money at your hobby you could be spending on another scanner.
a yagi/preamp your just throwing money at your hobby you could be spending on another scanner.
Boatanchor
Member
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I run a low noise, FM band-reject, home brew preamp on my D130J and 996XT setup and it does improve the Signal to noise ratio a lot on VHF hi band (on most days). However, I live in a semi-rural setting, which is relatively 'RF Quiet'.
The 'BUT' in all of this is that you need to live in a 'quiet' (RF noise) location to obtain any real benefit from a preamp.
If the signal you are listening to gets 'noisy' during the day and quieter at night, it is likely caused by local noise rather than a fading signal.
Localized noise on the VHF band is commonly caused by plasma TV's, inverter air conditioners, anything with a switch mode power supply, power line interference etc etc etc.. All of which tend to get worse during daylight hours due to higher use/loads.
If you have a relatively high noise floor on VHF to start off with, a preamp will only increase the noise by the same level as the signal you are trying to listen to and, you will end up no better off! You will see an extra one or two bars of signal strength which may make you feel warm and fuzzy about spending the $'s on the amp, but the signal won't be any clearer and could actually be worse.
If you have very strong LMR or FM broadcast transmitters within 5 miles of your home, adding a preamp can cause significant additional interference on many frequencies too.
First thing to try is get hold of a handheld scanner. Go to an VHF frequency near to where you want to listen to and select AM mode. This is very important. You must have the handheld on AM, not FM. If your scanner wont go to AM mode on 153Mhz, go down to the AM aircraft band (108-136Mhz). Turn the mute/squelch off and the volume up until you hear background noise. Now go for a wander around your home and see what appliances are generating noise on VHF. You will find that holding the scanner near to your TV, computer, air-con and many other appliances causes the noise level to increase on the scanner. If you are lucky, the main noise source will be in your home somewhere and you will be able to switch it off or fit ferrite 'clip-on' suppressors to the power lead to reduce the radiated noise (can be quite affective).
The D130J is a fantastic scanner antenna, but it does have some downsides.
Firstly, the top elements are not grounded. Which means that the antenna can be susceptible to static build up (causing noise).
Secondly, its vertical radiation pattern is very broad, meaning that it will pick up signals from your house and your neighbors houses (signals and noise you don't want) almost as well as signals coming from the horizon (the signals you do want). Consequentially, localized RF noise radiated below the level of the antenna is also received quite effectively.. If you changed the discone for a high gain VHF vertical or yagi antenna, you would find that the noise level drops and the wanted signal level increases, however, this comes at the price of very narrow operating bandwidth.
Good luck..
Rick
The 'BUT' in all of this is that you need to live in a 'quiet' (RF noise) location to obtain any real benefit from a preamp.
If the signal you are listening to gets 'noisy' during the day and quieter at night, it is likely caused by local noise rather than a fading signal.
Localized noise on the VHF band is commonly caused by plasma TV's, inverter air conditioners, anything with a switch mode power supply, power line interference etc etc etc.. All of which tend to get worse during daylight hours due to higher use/loads.
If you have a relatively high noise floor on VHF to start off with, a preamp will only increase the noise by the same level as the signal you are trying to listen to and, you will end up no better off! You will see an extra one or two bars of signal strength which may make you feel warm and fuzzy about spending the $'s on the amp, but the signal won't be any clearer and could actually be worse.
If you have very strong LMR or FM broadcast transmitters within 5 miles of your home, adding a preamp can cause significant additional interference on many frequencies too.
First thing to try is get hold of a handheld scanner. Go to an VHF frequency near to where you want to listen to and select AM mode. This is very important. You must have the handheld on AM, not FM. If your scanner wont go to AM mode on 153Mhz, go down to the AM aircraft band (108-136Mhz). Turn the mute/squelch off and the volume up until you hear background noise. Now go for a wander around your home and see what appliances are generating noise on VHF. You will find that holding the scanner near to your TV, computer, air-con and many other appliances causes the noise level to increase on the scanner. If you are lucky, the main noise source will be in your home somewhere and you will be able to switch it off or fit ferrite 'clip-on' suppressors to the power lead to reduce the radiated noise (can be quite affective).
The D130J is a fantastic scanner antenna, but it does have some downsides.
Firstly, the top elements are not grounded. Which means that the antenna can be susceptible to static build up (causing noise).
Secondly, its vertical radiation pattern is very broad, meaning that it will pick up signals from your house and your neighbors houses (signals and noise you don't want) almost as well as signals coming from the horizon (the signals you do want). Consequentially, localized RF noise radiated below the level of the antenna is also received quite effectively.. If you changed the discone for a high gain VHF vertical or yagi antenna, you would find that the noise level drops and the wanted signal level increases, however, this comes at the price of very narrow operating bandwidth.
Good luck..
Rick
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