Help, Need Diagnosis

[cassidy1190]

Well guys I can’t believe I am back but here I am...

As it turns out I have compound issues with my setup. I fixed the short in my connectors finally today, and I though for sure I would have solved the reception problem. I am getting a signal now, but it is simply not the quality at all I would expect with a top rated antenna 50 ft in the air. Instead of performing worse than my 1/4 wave in the attic, It performs almost just as well.

I think my new problem is an FM radio station which broadcasts from my town. I am located not even a mile from the tower. I have noticed, even with my first stock antenna in fact, that it often sounds like the radio is playing in the background of the pilot transmissions, and I know they don’t have FM radio from NJ being blasted in the cockpit. If I turn the squelch down all the way on just about any airband VHF frequency I can hear an extremely distorted version of what sounds like an FM broadcast. I never thought of this before, but now that I have eliminated so many variables (height, antenna type, coax, the list goes on) I feel like this is the last thing that could stand in the way.

Is there any way to better confirm if that is my issue? If it is, what are some recommendations on an FM type filter?

If this is truly my problem I think I might give this a try: http://www.universal-radio.com/catalog/filters/0098.html

 

[737mech]

FM Trap

Well guys I can’t believe I am back but here I am...

As it turns out I have compound issues with my setup. I fixed the short in my connectors finally today, and I though for sure I would have solved the reception problem. I am getting a signal now, but it is simply not the quality at all I would expect with a top rated antenna 50 ft in the air. Instead of performing worse than my 1/4 wave in the attic, It performs almost just as well.

I think my new problem is an FM radio station which broadcasts from my town. I am located not even a mile from the tower. I have noticed, even with my first stock antenna in fact, that it often sounds like the radio is playing in the background of the pilot transmissions, and I know they don’t have FM radio from NJ being blasted in the cockpit. If I turn the squelch down all the way on just about any airband VHF frequency I can hear an extremely distorted version of what sounds like an FM broadcast. I never thought of this before, but now that I have eliminated so many variables (height, antenna type, coax, the list goes on) I feel like this is the last thing that could stand in the way.

Is there any way to better confirm if that is my issue? If it is, what are some recommendations on an FM type filter?

If this is truly my problem I think I might give this a try: PAR FM Broadcast Filter

You could try a cheap FM Trap from Radioshack first to see if that improves things. I had good results with it. I ordered the PAR as well, should be here this week. I'm hoping to solve the same problem.
Belmar huh? I grew up in Point Boro. You probably get great Marine traffic on the scanner?

 

[cassidy1190]

Well I am hoping I will once I get my discone to work properly. But yeah i hear alot of the closer to shore comms, pretty good stuff, especially the helo ops.

I'll have to take a ride to radio shack and see what they have.

 

[737mech]

fm trap

Well I am hoping I will once I get my discone to work properly. But yeah i hear alot of the closer to shore comms, pretty good stuff, especially the helo ops.

I'll have to take a ride to radio shack and see what they have.

RadioShack.com
Get one of these and adaptors if needed f to bnc.

 

[cassidy1190]

I put the FM trap on. Had to go to two different stores to get the right adapters as I figured haha. There is definitely a difference, still not what I was expecting at all though. I can just barely hear the approach controllers now every once in a while, but it still seems they are being overpowered. Also, the FM trap is 75 ohm. That along with the 3 adapters probably isn't helping (f-bnc + f-bnc + bnc-uhf).

What about interference from other sources, like pagers for example. I know I will sometimes get a loud burst of that digital sounding pager noise for a moment on certain vhf frequencies at random. Are there filters for them as well?

Also, is there a filter that filters out everything BUT the airband. Its the only thing I am really trying hard to pull in, and I could just put a switch in the system and use the filter only when I am monitoring aviation.

 

[n5ims]

I put the FM trap on. Had to go to two different stores to get the right adapters as I figured haha. There is definitely a difference, still not what I was expecting at all though. I can just barely hear the approach controllers now every once in a while, but it still seems they are being overpowered. Also, the FM trap is 75 ohm. That along with the 3 adapters probably isn't helping (f-bnc + f-bnc + bnc-uhf).

What about interference from other sources, like pagers for example. I know I will sometimes get a loud burst of that digital sounding pager noise for a moment on certain vhf frequencies at random. Are there filters for them as well?

Also, is there a filter that filters out everything BUT the airband. Its the only thing I am really trying hard to pull in, and I could just put a switch in the system and use the filter only when I am monitoring aviation.

The 75 ohm change really isn't a factor. It's probably reducing things only about .1%. While it's important when you transmit, for wide-band receivers, the 50 ohm spec is only for a few sets of frequencies (only the designer know what they are) and others are probably closer to 75 ohm while others are probably closer to 25 ohms.

Interference could be from many sources, NOAA Weather Radio transmitters, FM broadcast transmitters, paging transmitters, TV broadcast transmitters, etc. They transmit continuously or often enough they might just as well be continuous and very high power. They can override your scanner's front end easily causing issues like what you're seeing. There are filters you can chain to reduce them as well if you wish, but you must be careful that they don't also filter out (or reduce) the frequencies you're interested in as well. Aircraft band is just above the FM and between TV channels 6 & 7 which makes it hard to filter cleanly.

They do make bandpass filters that allow aircraft band frequencies while reducing everything else (BPF-AIR Air Band Band Pass Filter is one example). Be sure to check the specs to make sure the filter pattern will reduce what is causing you interference (the FM station is probably easy to find, others may take some scanning to find) and passing with minimal loss the frequencies you're listening to.

A 100% job may not be possible though. For example, if the FM station is on 107.7 and your local airport is on 108.3 you'll either cut off some of the airport as the filter recovers or not fully reduce the FM station. Filters all slope on both sides as they transition from what they pass and what they filter. There are some (often the more expensive ones) that you can either adjust or special order that move this slope up or down to help you fine tune where they work. If your FM station is on the low part of that band and your airport is also on the low part of that band, you may order one that instead of doing 88 - 108, it does 80 - 100 and will do a good job of knocking out that 98.3 station while allowing you to hear your 108.3 airport.

 

[cassidy1190]

My only problem is I am on a budget, so like you said, I am really going to have to do some scanning and find out EXACTLY what I need. FM is a no brainer for sure, and luckly the station is 95.9 which is far from any vhf air I monitor which are almost all above 120 MHz. Ill probably just keep the chinsky radio shack thing on there if the impedance match is not a factor.

What I did find while searching through 150-153, is some extremely loud paging station on 151.125 I think it was...and I mean LOUD. It was that same noise I hear blare through my other vhf frequencies from time to time. I think what I will do is pick up the Par VHFSYM152HT (PAR VHFSYM152HT Scanner Intermod Filter).

I am aware of the NOAA band, but these don't seem to be giving me too much trouble. In fact, they barely come in due to interference haha...What are some other bands I should look over?

 

[737mech]

FM Trap

I put the FM trap on. Had to go to two different stores to get the right adapters as I figured haha. There is definitely a difference, still not what I was expecting at all though. I can just barely hear the approach controllers now every once in a while, but it still seems they are being overpowered. Also, the FM trap is 75 ohm. That along with the 3 adapters probably isn't helping (f-bnc + f-bnc + bnc-uhf).

What about interference from other sources, like pagers for example. I know I will sometimes get a loud burst of that digital sounding pager noise for a moment on certain vhf frequencies at random. Are there filters for them as well?

Also, is there a filter that filters out everything BUT the airband. Its the only thing I am really trying hard to pull in, and I could just put a switch in the system and use the filter only when I am monitoring aviation.

Did you try any other antennas with the trap? Disconne antennas as described in this forum are good but it has been discussed many times over how other designs are far better in some areas. I tried the RS disconne and couldn't hear anything on it. I have the DPD 118-1000 LP. Like I said I have ordered the PAR FM broadcast filter and will let you know if that is a better improvement over the RS trap. What model scanner are you using?

 

[cassidy1190]

I wish I could, but the only other antennas I have are in the attic and get terrible reception as it is. going up on the roof to switch one out isn't really an option right now unfortunately.

Please do let me know how it works out for you. I am having trouble making a decission on how to go about filtering my signal, an really cannot tell what exactly is overloading my reciever.

I use a RS pro-2052 for vhf and uhf air, and a pro-2096 for just about everything else.

 

[737mech]

What airport?

I wish I could, but the only other antennas I have are in the attic and get terrible reception as it is. going up on the roof to switch one out isn't really an option right now unfortunately.

Please do let me know how it works out for you. I am having trouble making a decission on how to go about filtering my signal, an really cannot tell what exactly is overloading my reciever.

I use a RS pro-2052 for vhf and uhf air, and a pro-2096 for just about everything else.

What airports are you trying to monitor?

 

[smason]

I would guess that the RS FM trap is probably attenuating some of the aircraft band as well, since it is so close to FB broadcast.

There are better filters out there, but they do cost more. I use a cheap RS trap myself, but the radio that is it on I don't use for air, the radio I use for air doesn't care about the nearby FM station at all.
As mentoned, Par filters are very good. I just put an AM BC filter on my SW receiver and it made a huge difference. I'm very close to an AM station and it was killing anything under 9 mhz.

 

[737mech]

RS Trap

I would guess that the RS FM trap is probably attenuating some of the aircraft band as well, since it is so close to FB broadcast.

There are better filters out there, but they do cost more. I use a cheap RS trap myself, but the radio that is it on I don't use for air, the radio I use for air doesn't care about the nearby FM station at all.
As mentoned, Par filters are very good. I just put an AM BC filter on my SW receiver and it made a huge difference. I'm very close to an AM station and it was killing anything under 9 mhz.

I don't think it notches in the air band? The trap graph I've seen is basically a narrow notch centered on 98mhtz and only 6-10 db deep. That's the best info I've found online about the FM Trap. It did however have a positive result on my scanners front end overload, before I couldn't even hear ATC tower comms and now they are clear. That little bit of IM removed allowed my scanners to perform better on air-band. That is why I'm hoping the PAR filter improves things even more. I expect it will based on other's opinions I've read.

 

[cassidy1190]

I am most of all trying to monitor McGuire Approach on 124.15 MHz. I do notice an improvement with the FM filter on some nearby RCAGS but I still think I have a bigger problem than just FM. Like I said, the intermod from pagers in my area is definitely there. I am so torn between getting just an air band pass filter which blocks out everything but air band. I feel like otherwise Ill keep adding filters, and finding a different interfering signal each time until there is nothing else I can do. At the same time, I enjoy monitoring other bands as well, which is why I went with the discone.

I should definitely be able to recieve McGuire from my location right? I mean with this this type of setup I am blown away that I am not getting it even at all...

 

[737mech]

Kwri

I am most of all trying to monitor McGuire Approach on 124.15 MHz. I do notice an improvement with the FM filter on some nearby RCAGS but I still think I have a bigger problem than just FM. Like I said, the intermod from pagers in my area is definitely there. I am so torn between getting just an air band pass filter which blocks out everything but air band. I feel like otherwise Ill keep adding filters, and finding a different interfering signal each time until there is nothing else I can do. At the same time, I enjoy monitoring other bands as well, which is why I went with the discone.

I should definitely be able to recieve McGuire from my location right? I mean with this this type of setup I am blown away that I am not getting it even at all...

Yes you should be getting McGuire, I assume you have all the freqs? http://www.airnav.com/airport/KWRI
Do you hear anything on the UHF freqs from McGuire?

 

[737mech]

You can also try this method Radio Shack FM Trap 75 ohm Product Reviews I'm giving it a try right now because I have four of the fm traps I figure why not try? So far after doing this mod airband is very clear and freescan is logging the rssi hits with average 700 plus strength. The best hits were above 1000 on the rssi. I've never had that happen before. Mind you the airport is not far from my house so this is not surprising. Having said that I cannot hear anything from the tower or aircraft on the ground without using the trap. I can actually see the tower while standing on my roof. The tower comms are clear as day, planes on the ground and in the air. Nellis afb is 17 miles away and I can hear that just as well. I'm not sure if this mod hurts other bands though? That will take some time to figure out. I also scan just about everything 118-900 mhtz. The Par Filter should be here friday. I'll let you know how that works. I wish I had a friend with an analyzer to test these filters. Oh well? Maybe a RRDB reader will try this and post results???

 

[cassidy1190]

I am sure I have all the correct frequencies. I have a private license and fly out of a nearby field, so I know what I should be listening too and what to listen for...maybe that’s why it’s so frustrating haha.

I have not really tried the UHF frequencies yet. That may prove interesting. The FM signal that is giving me a problem must be extremely strong though, because I have noticed that without the trap the 800 MHz NJSP TRS control channel signal drops to about 70%. I can get 100% with the trap. Same goes for another Motorola system in the 500 MHz band. I am surprised it can affect frequencies over 8 times itself.

That E ham review was interesting. I suppose I wouldn't mind screwing up a cheap little thing like that. I assume it was a pretty simple mod.

 

[737mech]

UHF aircraft freqs

I am sure I have all the correct frequencies. I have a private license and fly out of a nearby field, so I know what I should be listening too and what to listen for...maybe that’s why it’s so frustrating haha.

I have not really tried the UHF frequencies yet. That may prove interesting. The FM signal that is giving me a problem must be extremely strong though, because I have noticed that without the trap the 800 MHz NJSP TRS control channel signal drops to about 70%. I can get 100% with the trap. Same goes for another Motorola system in the 500 MHz band. I am surprised it can affect frequencies over 8 times itself.

That E ham review was interesting. I suppose I wouldn't mind screwing up a cheap little thing like that. I assume it was a pretty simple mod.

Most of the flights out of Nellis AFB use UHF, I can hear Creech AFB (KINS) north of here and sometimes I can hear places north of that. I figured you had the freqs correct as you are a pilot. No doubt you know how to get the information you need for airports near you.
The mod was easy if you have the required supplies. I'm guessing the PAR filter will blow it away. My bct15 can still tune FM radio, even with the trap. I wouldn't have expected that?

 

[cassidy1190]

I made a new coil with 6 turns for my FM trap, and attatched it to the input terminal. I didn't have any 24 awg wire so I just used a center conductor from some rg-6 I had laying around, seems to be about the same gauge. Still don't really notice a difference. I plan to stop by radio shack again today to pick up a second one and do the same thing. Maybe once they are coupled I can clear out the FM interference I am getting. I am noticing more and more though that I am getting allot of interference from pagers and even the weather band which I thought wouldn't be an issue. I might have to settle for the air bandpass filter and just get rid of everything but the airband in order to pull in what I want to hear.

Hey this cought my eye today: http://www.universal-radio.com/catalog/filters/2978.html

It seems to take care of all my offenders, but will I still be able to monitor UHF, and higher 800MHz frequencies?

 

[737mech]

PAR filter

I made a new coil with 6 turns for my FM trap, and attatched it to the input terminal. I didn't have any 24 awg wire so I just used a center conductor from some rg-6 I had laying around, seems to be about the same gauge. Still don't really notice a difference. I plan to stop by radio shack again today to pick up a second one and do the same thing. Maybe once they are coupled I can clear out the FM interference I am getting. I am noticing more and more though that I am getting allot of interference from pagers and even the weather band which I thought wouldn't be an issue. I might have to settle for the air bandpass filter and just get rid of everything but the airband in order to pull in what I want to hear.

Hey this cought my eye today: PAR VHFBP Aero Band Pass Filter

It seems to take care of all my offenders, but will I still be able to monitor UHF, and higher 800MHz frequencies?

That looks like an excellent choice for a filter, I would email Dale at PARelectronics.com if I were you. He can help you find the best filter for you, he can set it up for a specific problem freq, and you can buy it from him for very close to the same money. Check the policy at that website, they order/drop ship. They may or may not stock these filters? Again, I will receive my PAR filter this week and let you know.
Did you try UHF freqs from Mcguire?

 

[cassidy1190]

I did send dale an email, and explained to him that I need attenuation on the FM broadcast bands, but also one or two NOAA frequencies and a loud pager on 152.125 MHz. Im not sure if its possible to design a filter specific to all three needs, but its worth it to ask i suppose.

I have been listening to UHF from McGuire, but haven't heard much yet. Since its only very active at certain times of the day, Ill just need to spend more time listening to know for sure.