What Do I Need To Block Out Everything On The Specturm Except VHF And UHF?

[AngWay]

I am so confused on this so i'm gonna ask you guys and see if i can get pointed in the right direction.

I want something to block out all other signals on the spectrum except what i listen to which is 150-160mhz and 450-460mhz which is VHF and UHF everything else on the spectrum i'd like to just block out because i dont' listen to any of it. i have looked at all these nooelec devices like the sawbird Here they are but i just don't understand what is what from my understanding they are a LNA plus a filter but i don't know if any of those would even do what i need it to do.

So has any of you already figured it out? when you are using your scanners to listen to police and ems do you just have a straight coax from the antenna to the reciever or do you have filters and LNA's as well? To me it just makes sense if i could block out everything else on the spectrum and only amplify the part of the spectrum i need, i just don't know what setup i would need to do that my knowledge is lacking in that department. Thanks

 

[dlwtrunked]

There is no reason to block a frequency unless it is strong enough to cause a problem (like Fm broadcasters or other nearby strong signals). And blocking something else, you are likely to block something I guarantee others are going to want to hear, or a change of frequency allocations, or your interests will make you want to hear (for example, you left out the two popular ham radio VHF and UHF bands). Many of us do not do just listen to just fire polices--heck, I even drove from Fredericksburg, VA several hours to your location (Buchanan, VA) to get close to and record and analyze the CARSR radar on the Blue Ridge Parkway on Apple Orchard Mtn. There is also and experimental 70 MHz beacn up there (currently off the air and some other amateur radio stuff)> And "no" there is not is customizable consumer filter device to select just frequency bands that particular people might want. There are mostly ones to block certain bands/signals but often they will sacrice sentivity on nearby freqyencies you might want so one must be careful. Note if you block what you said, beiseds blocking the amateur ham bands, you also blocked aircraft communitons--and unclest they are a problem, why do you want to do that? You might later want to tune these frequencies. You really only want to block signals that are a broblem. Your reciever already is trying to tune only what you told it to.

 

[kc2asb]

So has any of you already figured it out? when you are using your scanners to listen to police and ems do you just have a straight coax from the antenna to the reciever or do you have filters and LNA's as well?

Just a straight run of coax to the radio. I live in a very dense RF environment (NYC area) and have had no need to filter/block frequency ranges I do not want to hear. Best to keep it simple, unless you are overwhelmed by interference from a particular band (say FM broadcast)

The best thing you can do, after choosing a radio, is to choose an antenna(s) that closely matches the frequency bands you want to listen to. (150-160, 450-460 MHz)

 

[AngWay]

There is no reason to block a frequency unless it is strong enough to cause a problem (like Fm broadcasters or other nearby strong signals). And blocking something else, you are likely to block something I guarantee others are going to want to hear, or a change of frequency allocations, or your interests will make you want to hear (for example, you left out the two popular ham radio VHF and UHF bands). Many of us do not do just listen to just fire polices--heck, I even drove from Fredericksburg, VA several hours to your location (Buchanan, VA) to get close to and record and analyze the CARSR radar on the Blue Ridge Parkway on Apple Orchard Mtn. There is also and experimental 70 MHz beacn up there (currently off the air and some other amateur radio stuff)> And "no" there is not is customizable consumer filter device to select just frequency bands that particular people might want. There are mostly ones to block certain bands/signals but often they will sacrice sentivity on nearby freqyencies you might want so one must be careful. Note if you block what you said, beiseds blocking the amateur ham bands, you also blocked aircraft communitons--and unclest they are a problem, why do you want to do that? You might later want to tune these frequencies. You really only want to block signals that are a broblem. Your reciever already is trying to tune only what you told it to.

Well i don't have no desire to listen to amatuer or air traffic i'm only concerned about the police ems and fire in my area.. i do have a overload problem that i have had since i began it only happens between 150 and 156mhz i think it may be one frequency that is strong but i can go to any other frequency in the spectrum that is stronger than the one in the 150mhz and the overload does not happen on that one and it's stronger. I really don't know what that is, I can show u a video here of DSDplus showing when the overload happens. Alot of the frequencies if not most of them that i listen to are in that part of the spectrum that overloads so it really messes with my listening on my scanner when all of a sudden the traffic gets garbled.

I have not heard of the CARSR radar i'll have to look into that. here is the DSDPlus Overload Video

 

[Whiskey3JMC]

Well i don't have no desire to listen to amatuer or air traffic i'm only concerned about the police ems and fire in my area..

Then simply don't listen to those bands. Blocking out segments of spectrum isn't going to help you bring in the bands you're interested in monitoring. Get a dual band VHF & UHF antenna if you're only interested in listening to those bands

 

[vagrant]

1. Get an antenna tuned for each of the frequency ranges you want. That will attenuate other signals to some degree.

2. Get a bandpass filter for each band from DCI for the ranges you want and connect them to their respective antenna.

DCI Digital Communications

3. Get a diplexer and combine both antennas to one feedline, or keep them separate to different scanners/receivers/SDR’s.

4. The overload between 150-156 may be a local paging system. I have a problem with a system around 152 MHz. I use two notch filters inline to reduce the interference. They are made by Dale Parfitt. Find the offending frequency and have him tune the notch filter before sending it to you. You may need two. PAR Electronics | Filters for the commercial 2 way market, MATV, FM broadcast, laboratory, marine industry, amateur radio, scanner and short wave listening enthusiasts

* You may not need 1, 2, and 3. Number 4 may solve your noise. Unfortunately your video had zero audio to help discern the “noise”. You really need to identify the offending frequency first. An SDR with a wide waterfall view will help see/identify it. Also, if this noise is heard more frequently between 8-5 PM and much less after 9 PM, there is a good chance it is a paging system, or a digital signal that may or may not be encrypted. Find the frequency first.

 

[ecps92]

Well i don't have no desire to listen to amatuer or air traffic i'm only concerned about the police ems and fire in my area.. i do have a overload problem that i have had since i began it only happens between 150 and 156mhz i think it may be one frequency that is strong but i can go to any other frequency in the spectrum that is stronger than the one in the 150mhz and the overload does not happen on that one and it's stronger. I really don't know what that is, I can show u a video here of DSDplus showing when the overload happens. Alot of the frequencies if not most of them that i listen to are in that part of the spectrum that overloads so it really messes with my listening on my scanner when all of a sudden the traffic gets garbled.

I have not heard of the CARSR radar i'll have to look into that. here is the DSDPlus Overload Video

you need to ID the offending frequency first

 

[dlwtrunked]

you need to ID the offending frequency first

I do not think he has an offending frequency. His post makes it sound like any frequency he does not wish to listen to is one he wishes to block from his receiver.

 

[kc2asb]

I do not think he has an offending frequency. His post makes it sound like any frequency he does not wish to listen to is one he wishes to block from his receiver.

That was my take as well, but the OP later stated he is experiencing overload in the VHF-high band. It's almost certainly a paging station in the 152.xxx or 158.xxx ranges.

 

[dlwtrunked]

That was my take as well, but the OP later stated he is experiencing overload in the VHF-high band. It's almost certainly a paging station in the 152.xxx or 158.xxx ranges.

I have now seen that video. As you and others have noted, he needs to find the offending frequency (since he is using an SDR, using another program, not DSD+, could easily do that. I suspect a pager in the 152-153 MHz range as those in the 158 MHz have mostly disappeared in Va. Also, I *suspect*, it may help if he turns down the gain on his SDR (unfortunately, I suspect a cheap NOOELEC dongle prone to overload). If it is a 152 MHz pager and turning down his gain does not work, of course he could try one of Stridsburg blocking filters for that but that company is sometimes slow in responding due to the death of the original owner and if the station is to weak and on a nearby frequency, of course, he may not help things as the filter skirts may also weaken it. In that case, may be a better SDR ($) might help. But if I were him, I would start by trying less gain on the SDR (just enough to see his signals) and also finding the frequency causing the overload/intermod using a different program like HDSDR.

 

[Napalm]

OPs radios front end is the issue here. It's probably an RTL-SDR. They need all the filtering help they can get.