Weak Scanner Reception

[philyumpshus]

I have a Uniden Bearcat scanner in my truck that I use to monitor our dispatch channel 46.3800. The scanner has always worked awesome with various antennas, including the one that's on it now (NMO mount low-band radio antenna). Recently, our county changed the direction of one of the output antennas so it points in a less favorable direction for me in regard to receiving. Now my scanner doesn't pick up half the traffic it used to. I know that the transmitting antenna being moved has a lot to do with this, but is there a way to increase my receiving power or something? All of the radios in our trucks/POVs don't have any problem receiving or transmitting, it's only the scanner. Should I just buy a radio?

 

[GaryErrol]

Is your scanner antenna the same type as your mobile radio antenna? If not and since you have no problems receiving on your mobile, using the same antenna for your scanner should give you the same great reception.

 

[philyumpshus]

I don't have a mobile but it is the same antenna; it was an extra one that my FD had. It is tuned for that frequency and was used with a mobile until I put it on my truck. That's why I don't understand why it doesn't work as well as a mobile.

 

[NPS Ranger]

Look in the specs for your scanner under VHF-lowband sensitivity, and compare it to published specs for a comparable lowband mobile. You may find that the scanner which is designed to do low, high, UHF etc has a worse sensitivity than you thought. Unless you get a higher gain antenna, you may be stuck with buying a lowband mobile radio.

 

[PC Comms]

The receiver in a scanner and in an actual two way radio are like night and day. MUCH tighter tolerances. As already said, try a gain antenna and if that doesn' work, get a cheap mobile like a Maxtrac. I have a couple of 2 channel units around here for $75 or so, shipped.

 

[tnems7]

I was going to reply with advice similar to NPS ranger. I had the same problem with a 47.50 MHz channel. Even with a tuned antenna, the reception was weak. I had the scanner specially tuned ($ for radio tech and shop time), and then bought a signal amplifier specific for than bandwidth (more $$).


In the end, it would have been more cost effective to do as suggested by PC Comms. Or, if you have more than a couple of lowband frequencies to monitor, try finding a scanner than has better low band sensitivity.

 

[philyumpshus]

Thanks for the help guys, I thought it had something to do with the antenna. I think I will try to find a cheap radio and just take the mic off so people don't bitch.

 

[Steve0625]

There are more and more two-ways showing up on Ebay and other places, probably because many agencies are using the narrowband thing to move to other technologies and/or frequency ranges.


If you are only monitoring one channel, most any decent mobile will work. If you need to monitor 2 or more channels, find a good, programmable mobile that has the scan feature.


Some mobiles need a jumper if you remove the mic. If you go with a Motorola rig, batlabs.com has tons of reference info for just this kind of thing.

 

[philyumpshus]

I think I'm going to try to fix the antenna problem first because it will be cheaper and easier. I found the specs for the scanner and the antenna I'm looking at (Antenex C40 by Laird). The antenna is supposedly "high gain" but I want to make sure it will improve the scanner's performance. Here are the specs:


(Scanner)


Sensitivity: 12 dB SINAD.


(Nominal)


0.5mV 29.000 - 54.000MHz


(Antenna)


Model # C40


Product Description 40-47 MHz DC Gnd Base Load


Frequency (MHz) 40-47


Product Narrative DC grounded base-loaded antenna. Higher power handling and less ground plane required than standard base loaded antennas. Internal and external contacts are gold plated for best conductivity.


Gain (dB) Unity


Maximum Power (Watts) 500


Your help is appreciated. Thanks!

 

[SlickTop Solutions]

(Antenna)


Model # C40


Product Description 40-47 MHz DC Gnd Base Load


Frequency (MHz) 40-47


Product Narrative DC grounded base-loaded antenna. Higher power handling and less ground plane required than standard base loaded antennas. Internal and external contacts are gold plated for best conductivity.


Gain (dB) Unity


Maximum Power (Watts) 500


Your help is appreciated. Thanks!

Unity Gain usually means 0 Gain.

 

[philyumpshus]

So does that mean that basically the antenna isn't pulling in any reception; it's up to the scanner?

 

[tnems7]

No, it is providing a signal to the receiver and the height on the vehicle (antenna placement) can affect reception.


Usually, additional windings in the base of an antenna incrementally increase the length to supply a stronger signal.


(5/8 wave and 1/2 wave length antenna are the most popular for VHF Highband to increase ERP -effective radiated power.)


However, low band radios originally used a unity whip antenna (like Broderick Crawford's car as seen in Highway Patrol.) Tennessee Highway Patrol still uses many of these, mounted on the left rear fender. These antenna are over 100 inches in length, so antenna manufacturers like Antenna Specialists made a base load unity antenna that was shorter (around 47 inches).


Look in antenna catalogs (or on-line, likeTessco) to see if 5/8 wave low band antenna may be available (usually that would increase "transmit power" , but because it is longer, reception also increases. While it is costly for its benefit a powered signal amplifier or "booster" can be acquired to pull in communications, but this also induces more signal "squelch noise" or static in the received signal.


Another trick accomplished in Tennessee is that some low-band remote transmitters have a control frequency in high band or UHF, and you can monitor that frequency in certain areas to hear dispatch activities.


And, in some areas where newer frequencies were added, the dispatch consoles are set to "Simulcast" and transmit the frequency on several emergency service frequencies.


Good luck in finding a solution.

 

[PC Comms]

Thanks for the help guys, I thought it had something to do with the antenna. I think I will try to find a cheap radio and just take the mic off so people don't bitch.

Radios can be programmed with "receive only" channels basically which means that there aren't any transmit frequencies programmed into them. No need to worry about pissing anyone off and you can use you scanner antenna with it since you won't be transmitting on it.

 

[rick h.]

you might also try a Radio Shack dual band magnetic scanner antenna for around 34.00 .I live out in the country and get really good reception with mine on all bands .

 

[SlickTop Solutions]

No, it is providing a signal to the receiver and the height on the vehicle (antenna placement) can affect reception.
Usually, additional windings in the base of an antenna incrementally increase the length to supply a stronger signal.


(5/8 wave and 1/2 wave length antenna are the most popular for VHF Highband to increase ERP -effective radiated power.)


However, low band radios originally used a unity whip antenna (like Broderick Crawford's car as seen in Highway Patrol.) Tennessee Highway Patrol still uses many of these, mounted on the left rear fender. These antenna are over 100 inches in length, so antenna manufacturers like Antenna Specialists made a base load unity antenna that was shorter (around 47 inches).


Look in antenna catalogs (or on-line, likeTessco) to see if 5/8 wave low band antenna may be available (usually that would increase "transmit power" , but because it is longer, reception also increases. While it is costly for its benefit a powered signal amplifier or "booster" can be acquired to pull in communications, but this also induces more signal "squelch noise" or static in the received signal.


Good luck in finding a solution.

I looked at Tessco and was going to post a link if there was anything that had some sort of gain other than Unity. Search came up blank. (while I was originally looking at 2-way antennas, I did find the following under Monitor antennas: http://www.tessco.com/products/displayProductInfo.do?sku=338283&eventPage=1).


Gain is mainly for transmit and stated above, but can have some effect on receive. Unity = 0Db gain so what the antenna "sees" is what the scanner gets. The 3 DBi gain antenna linked above will increase the receive signal (as well as any noise and interference) to the scanner.

 

[SlickTop Solutions]

You also might try a preamp between the antenna and scanner.


http://www.advancedreceiver.com/page3.html

 

[philyumpshus]

Thanks for the link Dan! That looks like it will be my best cost/PITA alternative.

 

[philyumpshus]

I ordered a preamp from Advanced Receiver like Dan suggested; it should come Monday. We'll see what happens!