Whistler TRX-1 Attenuation?

[emsflyer84]

Hey guys,

I've been working to track down a reception issue on my TRX that I'm actually using as a base public safety scanner at my house. There is something, either in my house or nearby that's causing a very noticeable decrease in reception. I am running the scanner to a roof top tuned antenna with great line of sight in all directions. Yet I get the same, if not better reception with the rubber duck on the scanner away from my house, even in low lying areas. And my house sits on a hill.

I've already cut off power to my entire house to see if the interference was coming from the house, no change. I've tried several different roof top antennas, and even tried taking the handheld on the roof and plugging it directly into the antenna, eliminating the feed line. No change.

I've been reading recently that GRE scanners can be very prone to overloading and "desensing" from strong signals. The only transmitter I have near my house is an AM transmitter tower very close to my house. But the AM transmission power is cut from 5000 watts during the day to 137 watts at night, and I don't notice a change in reception at night. The closest FM transmitter is like 10 miles away.

I've also done a full spectrum sweep on the scanner itself and found one problem frequency that sounded like pager data broadcast that was very strong. I've already got a notch filter to cut out that interference.

Can anyone shed any light on the attenuation settings in the Whistler scanners and what the settings actually do? I can't imagine they will be much help, but I'm at a loss for what else to try. I'm scanning almost all VHF high public safety range, and a little bit in the mid-400's Thanks guys!

 

[Whiskey3JMC]

Can anyone shed any light on the attenuation settings in the Whistler scanners and what the settings actually do?

From the easier to read manual:

 

[emsflyer84]

From the easier to read manual:

View attachment 97002

Thanks. I guess the language there still confuses me a bit but I’ll play with the settings. It’s mostly on the VHF high stuff (154-155) range that’s is being affected as far as I can tell. There are only a couple things I monitor in the 400’s and with the right antenna those actually come in better then expected given their distance from me.

One of the last tests I did was to actually take my rooftop antenna down (it’s a folded dipole) and connect it straight to my scanner with a 3’ coax. I then drove about a mile away, which happened to be to a lower elevation area, and just holding the antenna in my hand I was getting signals clear as day that struggled to come through when doing the same thing standing on the roof of my house.

Even just going up the road a few hundred feet from my house seems to improve reception.

 

[tvengr]

Do you have a preamp on your rooftop antenna? Inexpensive preamps are notorious for creating intermod problems which can blank a receiver.

 

[ScannerSK]

If I recall correctly on that scanner you can turn the squelch all the way down which will allow the signal strength to be visible on the display when no signal is breaking the squelch. As you drive around, the static may sound the same however most likely you will notice the signal strength indicator rise as you approach the source of the problem and decrease as you move away from the source of the interference/overload.

The PSR-600 line of scanners have a serious problem with white noise causing desense in the upper part of the VHF band originating from television towers. Driving along the highway, I could tell when a semi-truck passed me on the side the interference was originating from as the squelch would close on the PSR-600 and reopen as the semi passed. This allowed me to track down the problem on the PSR-600 in the Denver area.

From my experiments, it appeared the TRX has the exact same problem as does the PSR-600 scanner with very noticeable desense caused by white noise created inside the scanner from out of band signals; they just reworked the squelch section of the TRX so that it does not open on this interference as it did on the PSR-600. I finally sold my TRX due to this issue.

The source of the problem for me appeared to be a television station broadcasting around 190 MHz. I never could get to the bottom of why so much noise was being generated in the 170 MHz band I was attempting to monitor up to 40 miles from the towers which were the source of the problem.

173 MHz was much worse than the 154 MHz range. You might try opening the squelch and tuning to both an open channel in the 154 MHz band and another open channel in the 173 MHz band and watch the signal strength meter as you take off and put back on the antenna. Next, would be to go for a drive. Driving around a tall buidling may indicate which direction the interference is originating from, etc.

These are pesky problems some of these scanners have...

 

[emsflyer84]

Do you have a preamp on your rooftop antenna? Inexpensive preamps are notorious for creating intermod problems which can blank a receiver.

No pre-amp, just a 50’ run of new RG6 to the notch filter and the scanner.

 

[emsflyer84]

If I recall correctly on that scanner you can turn the squelch all the way down which will allow the signal strength to be visible on the display when no signal is breaking the squelch. As you drive around, the static may sound the same however most likely you will notice the signal strength indicator rise as you approach the source of the problem and decrease as you move away from the source of the interference/overload.

The PSR-600 line of scanners have a serious problem with white noise causing desense in the upper part of the VHF band originating from television towers. Driving along the highway, I could tell when a semi-truck passed me on the side the interference was originating from as the squelch would close on the PSR-600 and reopen as the semi passed. This allowed me to track down the problem on the PSR-600 in the Denver area.

From my experiments, it appeared the TRX has the exact same problem as does the PSR-600 scanner with very noticeable desense caused by white noise created inside the scanner from out of band signals; they just reworked the squelch section of the TRX so that it does not open on this interference as it did on the PSR-600. I finally sold my TRX due to this issue.

The source of the problem for me appeared to be a television station broadcasting around 190 MHz. I never could get to the bottom of why so much noise was being generated in the 170 MHz band I was attempting to monitor up to 40 miles from the towers which were the source of the problem.

173 MHz was much worse than the 154 MHz range. You might try opening the squelch and tuning to both an open channel in the 154 MHz band and another open channel in the 173 MHz band and watch the signal strength meter as you take off and put back on the antenna. Next, would be to go for a drive. Driving around a tall buidling may indicate which direction the interference is originating from, etc.

These are pesky problems some of these scanners have...

Thanks, good info. I have a second TRX-1 that behaves the same.

Just as another point of info, just as I was typing this, a signal that doesn’t usually come in came in pretty clear. Halfway through the transmission, it was like someone flipped a switch. Instantly there was lots of static and it was hard to make out the transmission. It was strange how quickly the transmission became unreadable.

 

[ScannerSK]

Just as another point of info, just as I was typing this, a signal that doesn’t usually come in came in pretty clear. Halfway through the transmission, it was like someone flipped a switch. Instantly there was lots of static and it was hard to make out the transmission. It was strange how quickly the transmission became unreadable.

Very interesting. That may rule out a TV station or FM radio station as the culprit unless there was a momentary signal outage on their end. Christmas lights, street lights, and all sorts of other unusual things can create tremendous amounts of noise. I wonder if a digital transmission which drops into analog mode to send out a brief CW identifier could explain this? If so, CW identifiers are sent out I believe once or twice per hour possibly on the same minute each hour.

Sometimes using AM mode (if available) helps bring out the interference so it is audible from the normal background static.

If you have some way to view the surrounding frequency spectrum that may reveal which signal is the culprit. I purchased a cheap $25 RTL-SDR and downloaded a copy of SDRSharp.exe which allows viewing at least a 1 MHz swath of frequencies on either side of any given frequency.

If you find the source, the next question would be whether the transmitter is throwing out unwanted noise. A professional grade receiver (Motorola, Kenwood, etc.) may be required to determine this. Most likely the problem is due to artifacts being generated inside the scanner. The only way to eliminate the problem may be to purchase a custom designed filter to reduce the offending frequency.

Shawn