Carroll County - FM Interference?

[emsflyer84]

Hey guys, just a question for anyone who happens to be using a base scanner in Carroll County. I’m in Wolfeboro and seem to have strong interference when an antenna is placed on my roof. Basically I have better performance with the same scanner / antenna setup when the antenna is at ground level basically anywhere in town then when I have it on my roof. Reception seems to drop significantly as soon as the antenna is 35’ AGL. I live only about .25 miles from an AM transmit site for WGIR radio here in Wolfeboro. The tower sits down in the valley and my house is on a hill. When I’m on the roof I’m about level with the top of that tower. I can see the tower from my roof. Not from the ground. The same station also transmits on FM but I think the transmitter is in Wakefield.
I’m curious if anyone else in the area experiences scanner de-sense from FM or AM, or other strong transmissions. I’ve got an FM notch filter on the way based on recommendations. Thanks guys.

 

[tvengr]

You failed to mention which scanner you are using. Are you using an antenna preamp? Preamps can be overloaded and cause intermod problems.

 

[vagrant]

Why a new thread about the same problem of which you have a filter on the way?

There are two FM stations in Wolfeboro. One has 250 watts another puts out 620 watts. Go to the Radio Locator website and enter your Zip Code. It will pull up a list of AM & FM stations near you. Radio-Locator.com

 

[emsflyer84]

You failed to mention which scanner you are using. Are you using an antenna preamp? Preamps can be overloaded and cause intermod problems.

Using a Whistler TRX-2 and a tuned folded dipole antenna, tuned for high vhf. Also have a Larsen tri-band on a ground plane kit that works well also.

Both Antenna’s hooked directly to the scanner and ground level work well. Hooking both antennas directly to my TRX-1 handheld scanner, they both work very well also, even when the antennas are just laying in my car. Also tried hand-holding the antennas at different locations around town, lower elevations then my house. Excellent reception.

Both antennas mounted on the roof, not good reception. In fact, the handheld scanner with the stock rubber duck antenna works as good if not better at ground level then running the other antennas on the roof.

 

[iMONITOR]

Why a new thread about the same problem of which you have a filter on the way?

There are two FM stations in Wolfeboro. One has 250 watts another puts out 620 watts. Go to the Radio Locator website and enter your Zip Code. It will pull up a list of AM & FM stations near you. Radio-Locator.com

There's a FM broadcast station (WBCT) in Grand Rapids, Michigan that has an ERP of 320,000 watts! The antenna height is 800 feet!

 

[emsflyer84]

Why a new thread about the same problem of which you have a filter on the way?

There are two FM stations in Wolfeboro. One has 250 watts another puts out 620 watts. Go to the Radio Locator website and enter your Zip Code. It will pull up a list of AM & FM stations near you. Radio-Locator.com

I was mostly just looking for other people local in my area that might be experiencing the same thing.

 

[W1KNE]

There's a FM broadcast station (WBCT) in Grand Rapids, Michigan that has an ERP of 320,000 watts! The antenna height is 800 feet!

The antenna is 800 feet above ground. It's got 12 elements (an ERI SHPX-12BC6), so the actual RF at ground level isn't much more than a station 1/10th the power.

emsflyer84. WGIR (AM) doesn't transmit from Wolfesboro. Their transmitter is off of Stark Lane just north of Manchester. Not sure where you saw that it was a 1/4 mile from your home.

 

[W1KNE]

Regarding your question, de-sense from FMs can happen but you're more likely to just hear straight up interference. (Hearing the FM modulation peaks over analog signals). An AM station could de-sense your radio, but you'd have to be literally right next to the tower to see any real effects from it, unless it was a high powered AM, which you were in the major lobe of. Which won't be your case in Wolfesboro. You say you have better reception with your antenna lower down. Using the same cable? Remember that higher on your roof means a longer cable run, which could attribute to more loss. Or you have a connector issue on the longer cable you don't on the shorter one. There are a lot of elements at play into why one antenna location doesn't perform as well as another.

 

[emsflyer84]

The antenna is 800 feet above ground. It's got 12 elements (an ERI SHPX-12BC6), so the actual RF at ground level isn't much more than a station 1/10th the power.

emsflyer84. WGIR (AM) doesn't transmit from Wolfesboro. Their transmitter is off of Stark Lane just north of Manchester. Not sure where you saw that it was a 1/4 mile from your home.

Sorry, I meant WASR....

 

[emsflyer84]

Regarding your question, de-sense from FMs can happen but you're more likely to just hear straight up interference. (Hearing the FM modulation peaks over analog signals). An AM station could de-sense your radio, but you'd have to be literally right next to the tower to see any real effects from it, unless it was a high powered AM, which you were in the major lobe of. Which won't be your case in Wolfesboro. You say you have better reception with your antenna lower down. Using the same cable? Remember that higher on your roof means a longer cable run, which could attribute to more loss. Or you have a connector issue on the longer cable you don't on the shorter one. There are a lot of elements at play into why one antenna location doesn't perform as well as another.

I took my handheld and a 3’ cable up to the roof and the reception got worse. It was basically the same as using the 75’ run of cable that I normally use. I tried both the dipole and the tri-band and both had the same bad performance on the roof with the 3’ cable direct to the handheld scanner. Then I took the same cable and antennas to the ground and they worked better. Then I drive about a mile away with the same setup, again at ground level and lower elevation, and I was hearing normally very weak signals coming in clear as day. And I heard signals I had never heard before with the roof mounted antennas. Based on my testing, it really seems like there is something about my rooftop location that is causing poor reception. Even though it’s a fairly high elevation with clear line of sight for several miles in all directions.

Regarding the AM interference... there is an AM transmitter about .25 miles from my house and the top of the tower is about the same elevation as my roof. WASR Wolfeboro.

 

[W1KNE]

1/4 Mile from your house? Here's how you can tell if WASR is your issue. They transmit 5,000 watts day, which at 1/4 mile is quite a bit of signal. Potentially enough to cause overload. However (if they are running legally, which let's just assume they are), they have to drop down to 140 watts at night. 140 watts at 1.42MHz, at 1/4 mile won't even be a blip on your radio.
So try your experiment again, but after 6pm. See if you have the same issue. If you don't, then WASR is your culprit, and you'll need to filter them out. (not hard to do). If you do still have the issue, then it's not WASR and something else causing you grief.
If it hasn't been asked yet, do you have a metal roof or an asphalt roof.
(Also to your comment, the top of an AM tower means nothing. The entire piece of steel is a radiator, and in some cases, there are long cables strung down the side as the radiator. AM in close field relies on Ground-wave radiation, and your going to get more RF the lower you are, but at your distance, it would be not measurable.)

 

[emsflyer84]

1/4 Mile from your house? Here's how you can tell if WASR is your issue. They transmit 5,000 watts day, which at 1/4 mile is quite a bit of signal. Potentially enough to cause overload. However (if they are running legally, which let's just assume they are), they have to drop down to 140 watts at night. 140 watts at 1.42MHz, at 1/4 mile won't even be a blip on your radio.
So try your experiment again, but after 6pm. See if you have the same issue. If you don't, then WASR is your culprit, and you'll need to filter them out. (not hard to do). If you do still have the issue, then it's not WASR and something else causing you grief.
If it hasn't been asked yet, do you have a metal roof or an asphalt roof.
(Also to your comment, the top of an AM tower means nothing. The entire piece of steel is a radiator, and in some cases, there are long cables strung down the side as the radiator. AM in close field relies on Ground-wave radiation, and your going to get more RF the lower you are, but at your distance, it would be not measurable.)

Thanks. I actually saw on their tower info that the power drops off at night. I am getting the same issues 24/7, but I havn't run the test with the 3' cable direct from the antenna to the scanner at night yet. I'll give that a shot, but you're right, I think it's likely something else that's causing my issue. It's an asphalt shingle roof.

 

[DannyM86]

Check NOAA Wx channels and Part 22 VHF paging channels also..

 

[AJ1L]

If I remember right, when I worked for UCOM Paging, now American Messaging, I think we put a transmitter on Huggins Hospital in Wolfeboro. Check to see if a strong signal at 152.600 could be giving you issues. If so, there are filters out there you can get that will notch out a specific frequency or the whole paging band.

 

[emsflyer84]

If I remember right, when I worked for UCOM Paging, now American Messaging, I think we put a transmitter on Huggins Hospital in Wolfeboro. Check to see if a strong signal at 152.600 could be giving you issues. If so, there are filters out there you can get that will notch out a specific frequency or the whole paging band.

Funny you say that. I actually had a notch filter made for 152.600 because the pager noise was overpowering weak signals on other frequencies. It works well, but on very weak signals I can still hear some pager noise in the background. I was wondering what the source of it was. I figured it might be the hospital. I only live about 1.5 miles from the hospital, if that.

 

[vagrant]

The points about the pager transmitter are quite valid. That was resolved several threads ago. Unfortunate that different people are kindly offering or answering the same points again...that were already resolved in several other threads...about the same issues.