Where to get an amp for a scanner
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ka3jjz
Wiki Admin Emeritus
Have you improved your coax/antenna situation first? You might get more bang for your buck that way.
We've got a few listed under 'Preamps/Splitters' on the Military Monitoring Wiki 73s Mike
We've got a few listed under 'Preamps/Splitters' on the Military Monitoring Wiki 73s Mike
Thanks for the link!
Preamplifier Found
I found this on the http://www.strongsignals.net web stie. The url is http://www.strongsignals.net/access/content/new_user.html
Hear is what the the article read:
I found this on the http://www.strongsignals.net web stie. The url is http://www.strongsignals.net/access/content/new_user.html
Hear is what the the article read:
Do I Need An Amplifier?
You've undoubtedly heard about signal amplifiers or preamplifiers which are used to increase reception range by boosting the strength of weak signals. It sounds like a truly wonderful device that every hobbyist should have in their monitoring arsenal, right?
The problem is that most people tend to oversimplify the problem of weak signal reception and how it can best be solved. While adding a preamplifier will boost weak signals so that they can be heard easier, this device also boosts ambient noise as well as already strong signals.
The biggest problem here is that by increasing the strength of already strong signals, you are bombarding your receiver with a large amount of radio frequency energy it might not be able to handle. The result is more and stronger images, as well as increased intermodulation interference. And boosting the ambient noise is no joy either. Like they say, you don't get something for nothing!
So while you MIGHT be able to pick up a few more distant frequencies, you'll probably find that trying to monitor your local signals make for a nightmarish experience as your receiver now "barfs up" all kinds of interference signals that weren't there before.
In short, if you live in the "sticks" and far from most man-made radio frequency energy, you will probably be able to get some benefit from using a preamplifier to boost those far away signals.
If you live in or near an urband area, chances are that adding such a device will create more harm than good. If you want to increase your reception distance then think about adding an external antenna and using good quality co-ax cable. If you have an external antenna, think about putting it up higher, upgrading to a more efficient design (usually larger in size), using a tuned antenna for a certain frequency range, or a beam antenna to focus your listening into one geographic area of your choosing.
Current manufacturers of such devices are Radio Shack (made by GRE), JiM, Grove and Watson. Radio Shack was offering both handheld and base model versions. While cheaper than the rest, they are not as flexible in their design. The Watson line is available from most larger dealers in the UK and Europe.
There are two models by JiM (M-51 & M-75) available in North America from Durham Radio (Canada) and Scanners Unlimited (US). Both are quite nice since they offer selectable bandpass filters and variable attenuation. Just expect to pay a pretty penny for them.
The Grove PRE-5A is available from Grove Electronics in the US. This model has variable attenuation but uses co-ax F-type connectors. If you use BNC or PL-259 you'll have to buy adapters.
Copyright © 2003 by Richard J. Wells
You've undoubtedly heard about signal amplifiers or preamplifiers which are used to increase reception range by boosting the strength of weak signals. It sounds like a truly wonderful device that every hobbyist should have in their monitoring arsenal, right?
The problem is that most people tend to oversimplify the problem of weak signal reception and how it can best be solved. While adding a preamplifier will boost weak signals so that they can be heard easier, this device also boosts ambient noise as well as already strong signals.
The biggest problem here is that by increasing the strength of already strong signals, you are bombarding your receiver with a large amount of radio frequency energy it might not be able to handle. The result is more and stronger images, as well as increased intermodulation interference. And boosting the ambient noise is no joy either. Like they say, you don't get something for nothing!
So while you MIGHT be able to pick up a few more distant frequencies, you'll probably find that trying to monitor your local signals make for a nightmarish experience as your receiver now "barfs up" all kinds of interference signals that weren't there before.
In short, if you live in the "sticks" and far from most man-made radio frequency energy, you will probably be able to get some benefit from using a preamplifier to boost those far away signals.
If you live in or near an urband area, chances are that adding such a device will create more harm than good. If you want to increase your reception distance then think about adding an external antenna and using good quality co-ax cable. If you have an external antenna, think about putting it up higher, upgrading to a more efficient design (usually larger in size), using a tuned antenna for a certain frequency range, or a beam antenna to focus your listening into one geographic area of your choosing.
Current manufacturers of such devices are Radio Shack (made by GRE), JiM, Grove and Watson. Radio Shack was offering both handheld and base model versions. While cheaper than the rest, they are not as flexible in their design. The Watson line is available from most larger dealers in the UK and Europe.
There are two models by JiM (M-51 & M-75) available in North America from Durham Radio (Canada) and Scanners Unlimited (US). Both are quite nice since they offer selectable bandpass filters and variable attenuation. Just expect to pay a pretty penny for them.
The Grove PRE-5A is available from Grove Electronics in the US. This model has variable attenuation but uses co-ax F-type connectors. If you use BNC or PL-259 you'll have to buy adapters.
Copyright © 2003 by Richard J. Wells
Last edited:
Randall
Member
rf preamps are simple to build, just look in a radio amateur handbook for some plans.
Randall
Member
you can also use a video amplifier, the kind made for cable tvKE5EHI said:
Okay, I guess the question is do I need one? The main issue I'm having is that there's some area's around town (mainly intersections) that I get intermittent signals and a lot of interference. Some of them are in 'valleys' where all roads from the intersection are uphill, and some other areas just get bad reception. Would an amp help fix this or is there something else I should try first (antenna, coax, etc...). Also, when it's really cold out, I get some interference in the signals, but I think part of that problem is with the cities system. I'm using a ProAm PMM3B antenna and it works great most places, so I didn't know if maybe I just need a larger antenna/cable. I've use another taller antenna I have with larger coax and got about the same results.
Al42
Member
It depends on how bad the signals are. An amp won't help if there's no signal - it'll just amplify the noise.KE5EHI said:
If you're talking about going from a 3" antenna (on 850 MHz) to a 4 or 5 foot antenna, you should notice a significant difference. If you're talking about going from a 12" scanner antenna to a 15" scanner antenna, you won't notice the difference.
Al42 said:
There's signal there, it just cuts out and gets some noise along side of it.
I'm using a 13" ProAm PMM3B antenna with a Radio Shack Pro-2053. I haven't had any issues with it while storm chasing and it works great around town (except the given areas it breaks up).
soupster
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check this out
I will be getting this soon trying to do exactly what you are in need of. I will make a review soon.
http://www.advancedreceiver.com/page47.html
I will be getting this soon trying to do exactly what you are in need of. I will make a review soon.
http://www.advancedreceiver.com/page47.html
soupster said:
That looks pretty sweet. After talking to a buddy of mine with an actual city radio (emergency manager), he suggested maybe a dedicated 800MHz antenna instead of wideband, but said he even hits dead spots (most of those areas are either directly below a tower, or they have other radio interference in the area.
I still think I'm going to opt for an amp for storm chasing and see if it helps my scanner in-town issue. If not, I'll add an 800MHz antenna. Thanks for the link! Let us know how it works for ya.
Hi all,
"you can also use a video amplifier, the kind made for cable tv"
Be VERY CAREFUL with this one! While a TV mast head amplifier will work in this application a CATV distribution amp (DA) will fry your scanner for sure. Having typically 53dB gain they're intended as line distribution amps and the line drops are attenuated accordingly.
Frankly I try to discourage the use of wide band preamps for two reasons. First they do little to nothing for FM except raise the overall signal plus noise level which is later attenuated by the receiver's IF limiters, the net result is no improvement in the signal to noise ratio. Second they themselves are prone to overload producing intermodulation (mixer products) which show up on oddball frequencies and can jam signals you want to listen to. They also tend to produce mixing products by overloading the receiver's front end with the same results. Some lucky fellows may dispute this but they're the exception to the rule.
Since a good scanner has a VHF sensitivity of .1uV and a UHF sensitivity of .25uV you realy can't get better than that. My suggestion and that of knowlegable hams and other enthusiasts is that you remember 80% of your station is on the roof, 2% in your "shack" and the remaing 18% is what's in between.
"I still think I'm going to opt for an amp for storm chasing and see if it helps my scanner in-town issue."
Perhaps you won't get >TOO much< intermod out in the wide open spaces but "in town" being an RF rich invironment you're flirting with disaster. Save yourself the heartache, read on.
"If not, I'll add an 800MHz antenna."
An 800MHz 5dB gain trunk lip mount cell phone antenna worked for me. I use a plain old CATV signal splitter hooked up backward as a combiner with the same performance results as a passive splitter made for scanners at more than 10 times the price. Yup, the Rat Shack Special has the same little ferrite thingamajig inside so I went for the cheap and dirty option.
"you can also use a video amplifier, the kind made for cable tv"
Be VERY CAREFUL with this one! While a TV mast head amplifier will work in this application a CATV distribution amp (DA) will fry your scanner for sure. Having typically 53dB gain they're intended as line distribution amps and the line drops are attenuated accordingly.
Frankly I try to discourage the use of wide band preamps for two reasons. First they do little to nothing for FM except raise the overall signal plus noise level which is later attenuated by the receiver's IF limiters, the net result is no improvement in the signal to noise ratio. Second they themselves are prone to overload producing intermodulation (mixer products) which show up on oddball frequencies and can jam signals you want to listen to. They also tend to produce mixing products by overloading the receiver's front end with the same results. Some lucky fellows may dispute this but they're the exception to the rule.
Since a good scanner has a VHF sensitivity of .1uV and a UHF sensitivity of .25uV you realy can't get better than that. My suggestion and that of knowlegable hams and other enthusiasts is that you remember 80% of your station is on the roof, 2% in your "shack" and the remaing 18% is what's in between.
"I still think I'm going to opt for an amp for storm chasing and see if it helps my scanner in-town issue."
Perhaps you won't get >TOO much< intermod out in the wide open spaces but "in town" being an RF rich invironment you're flirting with disaster. Save yourself the heartache, read on.
"If not, I'll add an 800MHz antenna."
An 800MHz 5dB gain trunk lip mount cell phone antenna worked for me. I use a plain old CATV signal splitter hooked up backward as a combiner with the same performance results as a passive splitter made for scanners at more than 10 times the price. Yup, the Rat Shack Special has the same little ferrite thingamajig inside so I went for the cheap and dirty option.
Al42
Member
Again - if it cuts completely out (no signal there at all) an amp won't have anything but noise to amplify.KE5EHI said:
Which direction is "along side of"? If all that's there is noise an amplifier won't help, since there's nothing but noise to amplify. If the signal gets a little noisy, most scanner amps will overload (or produce intermod) from that much signal fed into an amplifier.
Due to the design of scanners (specifically the capture ratio), there will be noise on signals at times - but the signals will be too strong for most amplifiers to handle without causing problems. What you want is a single stage of not much more than unity gain (no "amplification" really) but lower noise figure than the scanner's first stage. Since low noise is easy (and cheap) to achieve these days, even at 800 MHz, it's difficult to find an amp that will give you a better noise figure and no (or little - no more than about 3db) amplification. What you usually find is an amplifier that gives you a lot of gain (10db or more), but with a worse noise figure than the scanner's front end, or the same noise figure. If the noise figure of the amp is the same as the noise figure of the scanner there won;t be much improvement in what you hear, and there may even bedegredation, due to intermod, overload, etc.
Depending on the band we're talking about, you may be able to do a bit better in the antenna, but that won't do much for spots in which you receive nothing.
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