LNA-WIDE-O Pre-Amplifier Yes? No?

[HappilyRetired]

I was reading that using the discone antenna that if I added a pre-amplifier it would amplify the signals coming in. I was also warned that I would be amplifying noise coming in as well. Something like you can't get something for nothing. Since the antenna that I have has no gain and its main selling point is that it's able to hear the different channel ranges, is a pre-amplifier like this a good choice? I already know my wife won't let me buy a separate radio and antenna for two different bands. I have been listening to the Orange County Fire Authority as well as Cal Fire and the Forest Service. The main thing I've read and my ham radio helper is telling me is that you really cannot replace the proper antenna design to do the job. He really thinks that a 3 DB gain VHF antenna is what I need without a pre-amplifier. Something about lobes or nodes or something that drop below horizontal and can hear below the antenna. I was also warned that by adding a pre-amplifier I might start hearing bleeps and bloops from paging systems. I already hear some and imagined they would get worse. So then he tells me I would have to get a paging filter and I'm thinking am I biting off really more than I can chew since I don't really know how this stuff works to start off with? I just want to be able to hear the stuff being said when they're not on the repeater.

 

[iMONITOR]

Application and Technical Information (Stridsberg)

Tech Information

www.stridsbergeng.com

 

[HappilyRetired]

Application and Technical Information (Stridsberg)

Tech Information

www.stridsbergeng.com

Thank you but I'm not technically inclined. I'm new at this and that seems to be about multi couplers and not preamplifiers.

 

[iMONITOR]

Thank you but I'm not technically inclined. I'm new at this and that seems to be about multi couplers and not preamplifiers.

There is still a lot of information you can look over and give you a basic understanding on what these devices do and how they work. Skip the stuff that's too technical for now.

Tell us more of what you're trying to accomplish and what problems you're having, then we can give some advice.

 

[HappilyRetired]

There is still a lot of information you can look over and give you a basic understanding on what these devices do and how they work. Skip the stuff that's too technical for now.

Tell us more of what you're trying to accomplish and what problems you're having, then we can give some advice.

I don't want to appear obtuse but what you provided is about multi couplers and I asked about preamplifiers. Specifically about bleeps and bloops that I'm told I should expect if I put a pre-amplifier on a discone. Then I'm told I would need to put a filter in line that blocks out the pager noise. These don't have anything to do with a multicoupler right? Does the spending money ever end? LOL.

 

[iMONITOR]

I don't want to appear obtuse but what you provided is about multi couplers and I asked about preamplifiers. Specifically about bleeps and bloops that I'm told I should expect if I put a pre-amplifier on a discone. Then I'm told I would need to put a filter in line that blocks out the pager noise. These don't have anything to do with a multicoupler right? Does the spending money ever end? LOL.

I think you should be aware of what a multicoupler does and why you might need/want one in the future. In the case of Stridsberg, their 4-port multicoupler w/preamp is the same price (or close) to what just a preamp cost alone. It allows you to connect up to four radios to one antenna, a cost saver down the road most likely. Again we need more information from you if you expect a precises recommendation. Depending on your needs a discone might not be the best choice. The need of a notch filter has not been established yet and no one can predict you will need one.

Once again, "Tell us more of what you're trying to accomplish and what problems you're having, then we can give some advice".

 

[WB9YBM]

I was reading that using the discone antenna that if I added a pre-amplifier it would amplify the signals coming in. I was also warned that I would be amplifying noise coming in as well.

Yeah, amps aren't "smart" enough to differentiate between an actual signal and most noise plus all active components (receivers, pre-amps, etc.) have at least a small amount of internal electrical noise which is why the good ones will use Field Effect Transistors (GETs) instead of more standard transistors (FETS have a lower internal noise figure).

That being said, the amount of noise that gets amplified can be reduced if the amp's installed near the antenna end of the coax, BEFORE incoming signals get reduced in strength by coax losses (and--especially in the case of weak signals).

 

[K5MPH]

Have you tried to put your antenna more higher you should try that first instead of spending money you dont need to be spending......

 

[mmckenna]

If CalFire and USFS is of interest, you may do better to get a dedicated VHF base antenna with some gain. Discone antennas suck equally well across the band, even worse out on the fringes.

Adding a pre-amp will, as you said, amplify everything, even the stuff you don't want to hear, like paging, strong cellular base stations, etc. All those things can easily overwhelm your scanner and cause issues. If you are already hearing interference from paging systems, adding an amplifier isn't going to make it better.

As for the Orange County system, you should be able to pick that up easily with the stock antenna, and I'd be willing to bet you a cold beer that it would probably come in just fine on the VHF antenna.

Better antennas and coaxial cable, as well as getting the antenna up as high as you safely can, is always a better investment. Using a preamp to compensate for a mediocre antenna system isn't going to lead to happiness.

 

[HappilyRetired]

I think you should be aware of what a multicoupler does and why you might need/want one in the future. In the case of Stridsberg, their 4-port multicoupler w/preamp is the same price (or close) to what just a preamp cost alone. It allows you to connect up to four radios to one antenna, a cost saver down the road most likely. Again we need more information from you if you expect a precises recommendation. Depending on your needs a discone might not be the best choice. The need of a notch filter has not been established yet and no one can predict you will need one.

Once again, "Tell us more of what you're trying to accomplish and what problems you're having, then we can give some advice".

I think my first post was pretty clear about what I need. I'm sorry I don't speak the same language you do yet but a multicoupler I can figure out and it's not what I need and not what I'm asking about. You say I may need one later. The poster above yours seems to have understood my needs but I sincerely thank you for trying to help me. If I have a need for a multicoupler you'll be the first one I come to. I bookmarked the page on Multi couplers.

 

[dlwtrunked]

I was reading that using the discone antenna that if I added a pre-amplifier it would amplify the signals coming in. I was also warned that I would be amplifying noise coming in as well. Something like you can't get something for nothing. Since the antenna that I have has no gain and its main selling point is that it's able to hear the different channel ranges, is a pre-amplifier like this a good choice? I already know my wife won't let me buy a separate radio and antenna for two different bands. I have been listening to the Orange County Fire Authority as well as Cal Fire and the Forest Service. The main thing I've read and my ham radio helper is telling me is that you really cannot replace the proper antenna design to do the job. He really thinks that a 3 DB gain VHF antenna is what I need without a pre-amplifier. Something about lobes or nodes or something that drop below horizontal and can hear below the antenna. I was also warned that by adding a pre-amplifier I might start hearing bleeps and bloops from paging systems. I already hear some and imagined they would get worse. So then he tells me I would have to get a paging filter and I'm thinking am I biting off really more than I can chew since I don't really know how this stuff works to start off with? I just want to be able to hear the stuff being said when they're not on the repeater.

This has been asked many times here. There is no general answer as it depends on how close you are to other strong transmitters and what pre-amplifier you use. And then there is the possibility of using filters to block out nearby problems. The only general answer is that one has to experiment. Other answers are someone's experience at their location.

That being said, using an FM broadcast band block is always a good idea. Many think they need to amplify a signal when their receiver is being desensed by a local FM broadcast station (and they do not know it because you do NOT hear the station that is desensing your receiver when it does so). Sometime adding such will allow hearing stations not heard before. And since you already mention pager problems, they would almost certainly worsen and you should tackle them first by determining their frequency and blocking them.

 

[prcguy]

Can you describe your antenna setup a little more, like how high is the Discone, how many feet of cable to it and what kind of cable? Looks like most of the stuff your listening to is in the VHF band, can you comment on any other frequency ranges you need?

 

[prcguy]

Can you describe your antenna setup a little more, like how high is the Discone, how many feet of cable to it and what kind of cable? Looks like most of the stuff your listening to is in the VHF band, can you comment on any other frequency ranges you need? Who is your ham friend, I might know him.

 

[HappilyRetired]

This has been asked many times here. There is no general answer as it depends on how close you are to other strong transmitters and what pre-amplifier you use. And then there is the possibility of using filters to block out nearby problems. The only general answer is that one has to experiment. Other answers are someone's experience at their location... And since you already mention pager problems, they would almost certainly worsen and you should tackle them first by determining their frequency and blocking them.

I did look for an answer to this question before posting the question myself. I didn't find it. This is what I read on the site where I was going to make the purchase. Even they suggested that paging filters might be required if using this device. But specifically they state that one can turn a discone antenna into a powerful receiving antenna.

"The combination of the wideband LNA and a discone, Ferret, air-band, or other high-quality antenna will result in an excellent active receive antenna system which has very few rivals. Mounting the pre-amp outdoor at the antenna site is by far the best way to boost signal without boosting extraneous signal received via the coax line. This is one of the most recommended ways to listen to distant stations."

I can see now how this hobby turns into a money sucker. The more you have the more you want better. 🤣

 

[Ubbe]

If you are only monitoring UHF frequencies and below, <450Mhz, then a discone will probably more or less equal a 1/4 GP or Dipole antenna but the discone have a much wider frequency span and works at everything from 90-450MHz and are prefered.

The coax at those frequencies have hardly any loss if it is of a relative short lenght and of good quailty, not a RG 58 type for the 400MHz band.

When you reach 700Mhz and upwards the discone begins to be less usefull than a GP or dipole type of antenna as the discone have some 10dB loss or more at those frequencies.

All scanners will have something like a 3-5dB noise figure and there are 0,5dB low noise amplifiers at the $30 range that will make the scanners noise a non factor. The difference in noise factor, 3-4dB can be considered as pure antenna gain. A standard low noise amp will have something like a 20dB gain that will overload any scanner. You will have to attenuate it down to a 3-6dB gain. Best is to use a variable $20 attenuator that can be set to any value between 0-20dB and have that at the scanner and adjust until you have no overload issues, the bleeps and bloops.
If you can have the amplifier at the antenna it will also make any coax loss obsolite and you'll gain another 1-2dB, equal to pure antenna gain.

So instead of buying a 5dB gain antenna, that will only work in a narrow frequency range, you can keep your discone and still have that 5dB increase, if you do not monitor the 700-800Mhz band.

A discone antenna works best at VHF, in the broadcast band, so add a $20 low loss FM trap filter between antenna and amplifier as it is usually the sum of FM broadcast and pager signals that makes the scanner overload. Getting rid of either will help but FM broadcast filters are less expensive as they doesn't need to be so narrow in frequency and are so much more available compared to specially made $75 pager filters that only one or two makes at those reasonable costs. Modern amplifiers usually withstand huge signal levels so try first with a filter between amplifier and scanner as you then do not add the 1dB loss that most filters has at the frequencies they are not notching out. Try everything out at the scanner, where to put the filter and the attenuation level, and then, if yoy wish, you can move the amp up to the antenna, but then you probably also need to power the amp from the coax and need an additional $20 bias-T, or make one yourself for a dollar.

/Ubbe

 

[HappilyRetired]

If you are only monitoring UHF frequencies and below, <450Mhz, then a discone will probably more or less equal a 1/4 GP or Dipole antenna but the discone have a much wider frequency span and works at everything from 90-450MHz and are prefered.

...

/Ubbe

Your reply squares with my Elmer who told me I can't really amplify something that isn't there to begin with. He does disagree slightly on a discone working on 700/800 but only because I'm close to the transmitters. Because of my altitude at 2 100 feet I can hear the San Bernardino County Fire system in the mountains just fine. They are on Strawberry Peak. The area that I was hiking and has all burned out now so that hardly doesn't matter at the moment. I'll start hiking the Cleveland again.

Now that I'm retired I don't want to be a couch potato. I'm thinking of joining the search and rescue team. Most of them are ham radio operators as well and I'm about to get my technician license. I'm in good shape, I am an EMT as well, and I think I could still do good for mankind as corny as that sounds. My whole life shouldn't be about chasing bad guys. The people I appreciated working for where the good people and they were many.

He recommended that I use a cable TV amplifier "bullet" that mounts at the antenna and has a wall wart at the other end of the cable. He said they are about 5-7 DB and enough to overcome cable loss with a little extra. He also told me I can take a cable TV attenuator with the proper adapters (they have F connectors on them) and it basically has a variable resistor in the middle. He said that when there's no signal present look at how many bars are on the scanner and rotate the variable attenuator until there are zero bars. He said that will be my noise floor without all the crap. He finished with telling me that the 996P2 has a 20 DB attenuator per channel and if I have a particular repeater I'm listening to the get some bleeps and bloops I can try turning that on. Otherwise he said I would need a paging transmitter filter. Does that make sense?

 

[dlwtrunked]

I did look for an answer to this question before posting the question myself. I didn't find it. This is what I read on the site where I was going to make the purchase. Even they suggested that paging filters might be required if using this device. But specifically they state that one can turn a discone antenna into a powerful receiving antenna.

"The combination of the wideband LNA and a discone, Ferret, air-band, or other high-quality antenna will result in an excellent active receive antenna system which has very few rivals. Mounting the pre-amp outdoor at the antenna site is by far the best way to boost signal without boosting extraneous signal received via the coax line. This is one of the most recommended ways to listen to distant stations."

I can see now how this hobby turns into a money sucker. The more you have the more you want better. 🤣

Put "pre-amp" into the RadioReference "Search" that is probably in the top right corner of the page you are on now and look through the results for appropreate ones. And yes, if you want to press things to the limit, it does take money. And also, remember that lowering the noise figure rather than adding gain is your main goal.

 

[HappilyRetired]

Put "pre-amp" into the RadioReference "Search" that is probably in the top right corner of the page you are on now and look through the results for appropreate ones. And yes, if you want to press things to the limit, it does take money. And also, remember that lowering the noise figure rather than adding gain is your main goal.

Thank you. When you're brand-new at scanning you don't really know what to put in the search engine to find answers. The same is true when I ask of how someone lowers the noise figure? According to my ham radio Elmer the noise figure is a combination of your location and the fact that the radio you have creates noise within itself. Neither of these I can change right? It would seem the only way to lower part of this would be to buy a used fire department radio made by like Motorola or someone, right? I see them on eBay but have no idea what I would do with one.

 

[Ubbe]

If you have external noise on the exact frequency that you are trying to monitor then nothing you do will help if it is some kind of noise in the atmosphere. If it comes from only one direction then it could be possible to cansel it out with a signal in the opposite phase, a noise canceller device that uses two antennas where the signal from one antenna are fully out of phase with the interfering noise signal.

Electronic components have internal noise that generates when atoms move. You can slow down the atoms by cooling them with liquid hydrogen and will then produce less noise. If components get hot they produce more noise.

The amplifiers in scanners usually has a lot of internal noise, they use the cheapest components they possible can use when building scanners. The internal noise will work as a treshold that the actual radiosignal has to overcome to be heard. If you amplify the signal before the scanner it will make the signal level be higher than the internal noise and you will hear that signal that earlier was buried in the noise. Also if the signal are weak from the antenna then the loss in the coax might make the signal be lost in the noise and and it will be too late to try and retrieve it by amplification at the scanner and needs to be amplified right at the antenna.

Amplifiers start to increase its internal noise level when the input signal are too strong and filtering those out will usually help to reduce the noise level.

/Ubbe

 

[ArloG]

I'm compelled to reply that for the little bit it costs, try it. I'm using a nooelec lana with my SDR radio.
I live in the boonies. 1 strong FM broadcast station at 100 MHz. 1 very strong pager frequency on 152. The local NOAA weather at 162.
The usual cell frequencies where they are, Pa-Starnet and few others around 800-900 MHz.

Yes. If it's not there, you cant snag it (signals). I'm using a Diamod discone. And as incorrect as it may be the LNA is at the radio antenna in.
It's just a pita to go put the amp at the antenna right now.
It works very well. Do I get imaging? A little. But it's not as overwhelming as many would have you believe.

In the past using a mast mounted antenna amplifier it let me get those FM stations in that I couldn't even barely hear.
Being a transistorized amp of the 80's, when in stereo mode those stronger stations also had a high level of MPX hiss. So to listen to them it was necessary to switch over to mono. Today I can put the same lna I use on the SDR on my stereo and FM stereo comes in quite well.

As for public service FM and such the amp does quite well. It would do much better mounted at the antenna and even much better with a directional antenna. I don't even want to get into theory. Just grab an lna, a bag of correct fittings to adapt your cabling to it. And because your scanner doesn't have bias-t you might have to dig up an old 5 vdc micro USB phone charger to power it.

Oh, FYI. I also use the LNA on my IC-R8600 with a DC block from amp>radio. Ham satellites, pirates on 250 MHZ, APT sats on 137, Many trunked and normal public svc. freqs. come in where they didn't before. It's a bit of a trade off maybe. A little noise for a lot of gain.