Will an amplifier damage my scanner?

[TheFlyingPilot]

I bought a cheap Yagi antenna to try to help improve my 800MHz reception (link), and it came with a "high gain and low noise amplifier" that is plugged into the wall. I didn't want to try it on my new scanner (325P2), because I wasn't sure if it would damage it. So I tried it on my older scanner (BC75XLT), and it seemed to improve reception, but I stopped experimenting after the LCD screen went berserk, which it has never done before. I believe the wire leading into scanner's antenna port carries a current when the amplifier is plugged in. The 75XLT is fine now, but I'm worried about exposing my 325P2 to this. Is it safe?

<-- Amplifier

 

[ka3aaa]

depending on the strength of the incoming signal it may overload the front end of the scanner causing unwanted distoration or as you found out it may cause other problems

 

[TheFlyingPilot]

I'm not as worried about the signal strength as the electric current running into the antenna port. This antenna and amplifier is technically meant for HDTV

 

[nessnet]

My experience with amplified TV antennas is that the amplifier is actually up on the antenna. The pictured 'amplifier' is probably more like a power supply / filter. Meaning it sends current up the line to the antenna, then filters out the current so nothing is sent to the receiver (but the RF signal).

I would seriously doubt there is any current on the side going to the receiver. This would be for quality gear. Who knows with cheap stuff....

 

[RFI-EMI-GUY]

If you connect the power inserter backwards, the DC power will go toward your receiver which is never good.

Having any sort of amplifier before a receiver raises certain technical concerns.

Assuming your antenna/preamp is wideband for TV channels, your receiver will be presented with a lot of signals out of band, that might mix and cause intermod. You might try one of those variable TV attenuator between the receiver and the power inserter. This may help somewhat.

Whenever you have a mast mounted preamplifier, you seek to have a low noise preamp, with a bandpass preselector filter (difficult for wide band scanner) and just enough gain to overcome cable and splitter losses.

 

[TheFlyingPilot]

The pictured 'amplifier' is probably more like a power supply / filter. Meaning it sends current up the line to the antenna

There is a small LED that illuminates on the antenna when the "amplifier" is plugged in. You don't think it will damage the scanner though? Like I said, having the "amplifier" or whatever it is plugged in helps bring in some of the signals I am looking for better.

 

[jonwienke]

A preamp won't damage your scanner as long as it is connected properly. If you connect the power injector backwards so it feeds power to scanner antenna input instead of the amplifier, that would damage the scanner. But if you connect it correctly, the worst case is overload, intermod, or distortion from clipping and excessive gain.

 

[TheFlyingPilot]

Makes sense. Thanks!

 

[krokus]

There is a small LED that illuminates on the antenna when the "amplifier" is plugged in. You don't think it will damage the scanner though? Like I said, having the "amplifier" or whatever it is plugged in helps bring in some of the signals I am looking for better.

That LED shows that power has been supplied to the actual amplifier. The part that you showed the picture of is a power insertion device, as others have noted.

 

[wtp]

why do you feel that you need it ?
i would live with a little static, and have for years, instead of adding more signalS, the S is for all the signals it will add, and the harmonics that come with that.

 

[JoshuaHufford]

My experience with the BC75XLT when using a preamp, which was a high quality low noise narrowband unit, you get a LOT of intermod (unwanted signals) unless you are in an area with no other strong signals.

Also I'm pretty sure the BC75XLT will not receive at 800MHz, at least mine wont, so I'm curious what you were receiving?

 

[TheFlyingPilot]

Our local Wx, which is being transmitted at about the same strength and distance as the 800MHz I'm trying to pick up

 

[JoshuaHufford]

Wow, around here I can't get away from NOAA radio.

 

[Ubbe]

Scanners have band filters that stops out of band signals. Your antenna has an inbuilt amplifier so it will overcome any coax losses you have in the 800MHz band, or other bands. The amplifier are designed for television sets that would overload if the amplifier where designed badly, much more so than a scanner. So no problem in that respect to be used with a scanner. It has a noise figure of 2,5dB so it is considered low noise and very good.

Most scanners use a capacitor in line with the antenna signal so no DC voltage could damage the scanner. In some cases there are diods at the antenna port that protects from high voltage RF signals entering the electronics in the scanner. If you connect that power inserter backwards it could short circuit the power adapter and the green LED will go out until you disconnect it. But it is clearly marked "antenna" so shouldn't be a problem once you have it setup.

If you get problems with overload you can use an attenuator between that power inserter and scanner to reduce the signal, something like this:

The antenna use several front elements, directors, that are tuned to 700-900Mhz and the active folded dipole seems to be tuned to 500-600MHz and the reflector element are something like a 200MHz lenght. So not so much FM broadcast reception and also less 150MHz paging interference. You should have the antenna tilted to vertical, and not horizontal as it is in the amazon picture.

/Ubbe

 

[bob550]

I bought a cheap Yagi antenna

"Pingbingding"? Not exactly a Channel Master, is it. Try using the antenna without the amplifier and see if the results are acceptable to you. As others have said, overloading (too much signal) can be as much of a problem as too little signal. The scanner can actually become less sensitive leading to reception problems on certain frequencies. I have an amp connected to an external discone antenna primarily for 800MHz, and experience a desensitization of VHF frequencies on my PRO-163. As a result, I must selectively set attenuation for the affected frequencies.

 

[TheFlyingPilot]

I don't think overloading will be much of a problem. Without the amplifier, I got zero reception from the tower I'm trying to reach. With it, I get about 3/5

 

[bob550]

The overloading may be more prevalent on other bands such as VHF. It really depends on the scanner. Some (my PRO-163) are more prone than others (my Unidens). The amplification can be a tradeoff, but tradeoffs happen when scanning several bands.

 

[TheFlyingPilot]

I'm using my BCD325P2, and I'll be scanning ---

851.0875

851.3875

851.8875

852.3875a

853.8875c

854.6125

Pretty specific frequency range

 

[bob550]

Your antenna performance also depends on where and how high it's mounted, and the cable you're using to the scanner. 800MHz frequencies can be lossy at longer cable lengths, and so amplification can help somewhat to overcome that. Keep in mind, though, that your new antenna covers a wide swath of frequencies, and is not necessarily designed to maximize 800MHz only. There are many other directional 800MHz antennas available that may not require amplification. If 800 is all you care about, they may be a better choice.

 

[Ubbe]

The antenna seems to be perfect for scanner use. It has standard yagi elements and not any bow tie or butterfly elements to increase the frequency range down to 500MHz. All directory elements are focused at 700-800MHz and the dipole are for a lower UHF band. That long single element for 200MHz below that corner reflector can be removed if you do not need VHF reception.

I have one wideband antenna 80-700Mhz with an amplifier built into the antenna and that works great for most frequencies and doesn't need any extra filter or attenuator as it is designed to be connected directly to a tv or stereo tuner without overloading them.


/Ubbe