Signal Amplifer

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popnokick

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They do indeed work but you're not going to be able to use it easily with the stock antenna on the radio. You'll need an antenna like this (scroll down the Wiki page and look at the "wire only" version) -
Homebrewed Off-Center Fed Dipole - The RadioReference Wiki
I use an amp like that to feed three scanners in my house via 75 ohm RG6... works very well. BE AWARE however that if you are in a high RF "noise" environment or close to FM broadcast transmitters you will also amplify that noise, with the net effect being undesirable. Fortunately this antenna and the amplifier you linked to are not expensive.... so try it and see what happens, but if you get a noise / FM interference problem you may need to add an FM trap.
 

svankrev

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Thank you so much for the reply. As you were typing I was just perusing that very page about the home-brew dipole and rummaging through my junk looking for an old balum.
 

jim202

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As has been mentioned the use of an amplifier can help reception. But it also can cause undue problems depending on your location and what towers may be within several miles from you.

Not only will TV and FM broadcast signals cause problems, but being close to cellular towers and public safety towers will also cause issues with intermod of signals. Towers with paging transmitters is like a death to scanners. The extent of the issues will depend on the individual amplifier. Some are really bad to overload and generation of intermods in your scanner.

Most scanners don't do well with strong signals. This can also cause problems inside the scanner with false signals showing up in places they really don't exist.

You can't tell how an in line signal amp will perform and cause or not cause problems based strictly on cost. Some lower cost amps work well in a high level signal environment. Some of the high cost amps really blow. The results are based on the design and the type of components used.

The best way to select an amp is to rely on the feedback of users that have already used them. I know this is not a really good way to select an amp quickly, but other than word of mouth, it is not easy.
 

popnokick

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Simple and inexpensive way to test for "what's best" for your setup:
- Connect the wire version of the Homebrew Off-Center Fed Dipole into your radio. You may need an adapter to go from the 75 ohm coax F-female to your 996-P2. Hang the antenna in the highest window in your house or attic. You may have to move it around away from large metal objects, metallic glass, or other metal objects.
- Don't connect the amplifier yet. Listen to the scanner long enough to observe how it is doing with what you want to hear. Good place to check on VHF is all the NOAA weather frequencies... see how far away the stations are you pick up. Listen for signs of interference, paging transmitters, broadcast towers, etc.
- NOW connect the amplifier and see if it's better, worse, or the same for what you want to listen to.
 

svankrev

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Thanks for all the input. I will have to digest a bit. I am in a low noise area away from the city. Closest towers are 3 to 4 miles out. One thing I am experiencing out of the box is voice transmissions that sound clear (emergency dispatch, etc.) seem to cut in and out. Sort of like a bad mic. But many of them do it. Do you think this could be caused by a weak signal. (I am seeing 4 bars many of the times this is occurring) Or did I get a dud unit with issues? I have been combing the settings using "Freescan" and dont see anything jumping out at me. I am monitoring AnokaCounty Simulcast (MP25). Could a better antenna alleviate this do you think?
 
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jonwienke

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Signal strength isn't your problem, it's simulcast distortion. You have multiple towers broadcasting on the same frequency (simulcast), and the signals are interfering with each other.

Your best bet is to get a directional antenna like a Yagi or LPDA, and aim it at one of the towers so you only get signal from a single tower. An amplifier would just make things worse.
 

prcguy

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I would positively identify the reason for your problem before buying a new antenna or doing anything radical. The problem may be simulcast distortion, it may be signal overload from a nearby frequency or it could be something else.

Try turning on the attenuator in your scanner and see what that does. If its overload then having the attenuator on will usually improve reception. You haven't mentioned the frequency range of your problem and a Yagi for 800MHz can be cheap but one for VHF is usually expensive.
prcguy


Any recommendations would be greatly appreciated. I see some Yagi antennas that are fairly inexpensive.
 

737mech

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Traps / rotators / directionals

Please try the cheap stuff first. Go find a radio shack fm trap and adaptors (F to BNC) and try inline with that first. If that works upgrade to a better FM trap. Let us know if you have improvement. Then think outside antenna. Not a fan of the ocfd for trunking 800/900 systems. Those antennas tend to radiate upward cone pattern not a horizon wide pattern. LPDA directionals are far better. Yagi for freq range would be best. Maybe figure a way to have a rotator to move it around from your listening desk? At least point toward the source? Lots of things to consider I'd try cheapest first.
 

Ubbe

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It's pretty much impossible to get a good result using only a signal amplifier. You must also use a variable attenuator and often also a FM trap filter. Connecting just an antenna amplifier with a fixed gain between scanner and antenna will in most cases result in a disaster.

Each situation has it own unique solution and one guys praise over an amplifier and antenna setup means very little to the next guy.

/Ubbe
 

popnokick

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Agree completely with the other posters... your problem is NOT related to weak signals from what you want to hear. More likely P25 simulcast distortion due to signals from many towers at your location. You may want to post a question in the Minnesota Radio Discussion Forum here on RR. There are many posts re: Anoka there and you may find info regarding whether others are experiencing this and what they've done about it. Here's a link -
https://forums.radioreference.com/minnesota-radio-discussion-forum/
 

svankrev

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Good morning all, thank you for all the great insight and advise. Already nixed the signal amp. I have one on the attic TV antenna feeding 4 sets in the house and it works great. But that antenna is aimed directly at the towers some 30 miles out. The situation with the scanner is quite different as I am learning. The tower(s) are closer and in different directions. I am a network IT guy and test engineer by trade but I have a great deal to learn about RF world.

I do have a question about the FM trap. I doubt that there is sufficient signal strength from TV or FM radio in this area to be interfering. Is there something I am missing and/or are there other reasons for trying that? After this I will move over to the MN forum you listed above. Thanks again all!

(I did try turning on the 20dB attenuation and I basically got less of the same..:) I was trying to find if I could try it to a lesser degree but did not see the option. It was getting late....)
 
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krazybob

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They do indeed work but you're not going to be able to use it easily with the stock antenna on the radio. You'll need an antenna like this (scroll down the Wiki page and look at the "wire only" version) -
Homebrewed Off-Center Fed Dipole - The RadioReference Wiki
I use an amp like that to feed three scanners in my house via 75 ohm RG6... works very well. BE AWARE however that if you are in a high RF "noise" environment or close to FM broadcast transmitters you will also amplify that noise, with the net effect being undesirable. Fortunately this antenna and the amplifier you linked to are not expensive.... so try it and see what happens, but if you get a noise / FM interference problem you may need to add an FM trap.
I have used them for years on outdoor antennas. They are not very effective in metropolitan areas because they are very broad banded and can easily put your scanner into a mixture overload situation where the mixture becomes nonlinear and creates its own intermod for my experience you don't want to run an amplifier greater than what you actually need. You essentially just want to cover line losses with maybe a little bit extra bump on 800. I have an 8 tap version multicoupler fed with a 30dB amplifier. After the amplifier and before the coupler I insert an intermod filter and if necessary an FM radio station filter.

Sent from my SM-N920V using Tapatalk
 

prcguy

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Filters always go before the amp because its usually the amp that gets blitzed from strong FM or cell phone towers.
prcguy

I have used them for years on outdoor antennas. They are not very effective in metropolitan areas because they are very broad banded and can easily put your scanner into a mixture overload situation where the mixture becomes nonlinear and creates its own intermod for my experience you don't want to run an amplifier greater than what you actually need. You essentially just want to cover line losses with maybe a little bit extra bump on 800. I have an 8 tap version multicoupler fed with a 30dB amplifier. After the amplifier and before the coupler I insert an intermod filter and if necessary an FM radio station filter.

Sent from my SM-N920V using Tapatalk
 

Sirzep66

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scaanner Amplifier

Hi all, I am new to the scanner world. I was wondering if and in-line signal amplifier like one used for TV and FM would work on my Uniden BCD996P2 scanner with the stock antenna. One like this:

https://www.amazon.com/gp/product/B001FY0B90/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1
I have been selling some on eBay for awhile now.. different antenna inputs.. this one is BNC on each end.. Here is a link below..

Crosswinds Scanner Amplifier
https://www.ebay.com/itm/263391486366?ssPageName=STRK:MESELX:IT&_trksid=p3984.m1558.l2649
 

Ubbe

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I good amplifier with a high dynamic spec don't neccesarily need the filter to be put between antenna and amp, which will usually reduce the signal 2dB before it arrives at the amplifier. (The FM filters from GPIO labs only attenuate 0.2dB)

Try some of the $25 amps from this ebay seller: http://stores.ebay.com/GPIO-Labs
I suggest looking at the PGA-103+ types with 0,5dB noise figures. Don't forget to acuire a variable attenuator from another source.

/Ubbe
 

krazybob

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On average and depending on whether or not you live in a rural area or metro area are good or bad. If you live in a metro area like Los Angeles as soon as you use an external antenna you are at risk of an increase in "intermod." It isn't real intermod. It is self-generated and is caused by overloading the front-end and causing the mixer to go non-linear. Adding an amplifier will increase the beeps and bloops many times over. Been there, done that. You will end up adding 20dB attenuation but may still come out slightly ahead. I use a PAR Electronics intermod filter in front of an amplifier that knocks out the paging transmitters. If feeding more than one scanner I use cable TV combiners that have 3dB loss per port because it keeps the intermod at bay. Scanners just cannot handle high RF environments and external amps magnify the problem much of the time. A TV broadband amplifier with a 2dB noise figure is not a good choice. What you want is an inline "bullet" that mounts at the antenna and has a Bias-T inside your home that powers it over the coax. I use the 10dB version with a 1dB noise figure. It is just strong enough to overcome the line loss in the coax.

Selecting the proper coax is your FIRST choice in better signal reception. Below 700MHz you can use RG6Q and do well. LMR400 is even better and works up to 800MHz. But once again too much gain on the front-end creates self-generated intermod when the mixer goes non-linear.
 
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