BC125AT: Noise on VHF Low

[misterpaul71]

Hi all,

I wonder can anyone help with this - I just got my hands on a UBC125XLT and I notice that when used with a telescopic antenna, or the stock one, there is quite a bit of noise across Low VHF. Enough to stop the radio scanning on many frequencies. The problem clears up when an external antenna is used but that's not much use when out and about.

I guess the noise is being internally generated, by the screen? - anyone got any ideas on perhaps lessening this.

Anyone have a similar experience with this model?

 

[popnokick]

It's not internal... mine is fine across the VHF Lo band and quite sensitive. Most likely cause is interference that is near the radio in your house/building. Suspect are: nearby computers, cable modems, Ethernet router/switch, any USB device that charges or sends data, many plasma/lcd TVs, some LED light bulbs.... and many other sources. You'll either need to get the radio away from all of those possibilities or use an external antenna.... with the latter being the best option, since it improves performance over the included "ducky" antenna.

 

[wtp]

and there is a difference ...

turned off is not off.
we got two new tvs and get plenty of interference when they are off but not unplugged.
so if you want to find the culprit unplug don't just turn them off.

 

[jonwienke]

My flatscreen TV generates a horrific amount of RFI on some VHF frequencies when she scanner is in the same room and using a ducky/whip. Switching to the attic antenna makes it go away.

 

[MotownJG]

I get the same noise when operating my scanners/ham HT's in the shack and my computer is turned on. There's RF everywhere. I sometimes have success relocating the radio in my room away from the equipment but not always.

I was told long time ago that on 450 mhz police freqs I could add 27..5(?) mhz to the frequency and sometimes avoid the interference. Something about listening to the top or bottom of the sine wave instead of the center. But I'm no engineer and i didn't write that down. Wish I had.....

Outdoor antenna is best, but don't give up indoors. Just keep moving things around. I even lay my HT flat, pointing the antenna in different directions which can "sometimes' help.

John

 

[popnokick]

An antenna that is external to the scanner does not necessarily need to be outdoors. It can be an antenna located in an attic, crawlspace, or upper level window. The BC-125AT has a removable rubber antenna mounted on a BNC connector. Remove it. Put the indoor attic/window antenna up and connect to coax cable from the antenna to the scanner with an F-to-BNC adapter. Typical attic/window indoor antennas are the OCFD (Off-Center Fed Dipole) listed in the RR Antenna Wiki, or TV antennas turned to be vertical (instead of horizontally) polarized. Any of these things can serve to get the antenna away from the noise source(s) that are near the handheld scanner. Here are two versions of the OCFD. The 2nd one (scroll down on the Wiki page when you get there) can be assembled for about $10 from home/hardware store parts and easily be hung in a window or attic: http://wiki.radioreference.com/index.php/Homebrewed_Off-Center_Fed_Dipole

 

[misterpaul71]

I'm afraid to say guys, this isnt an RFI issue. This is internal to the radio. The same thing was happening today standing on a mountain side far from electrical interference, as it was about 100 feet from my house, and inside my shack.

The problem is only at low VHF and is really annoying.

With a half decent external antenna added this is a great little radio, no doubt about it ( I sat in the shack yesterday afternoon listening with ease to a slew of 33 mhz traffic from the north eastern US) but on the rubber duck / other telescopic antenna the noise is a bit of a let down.

Again, any ideas anyone?

 

[Jim41]

I'm afraid to say guys, this isnt an RFI issue. This is internal to the radio. The same thing was happening today standing on a mountain side far from electrical interference, as it was about 100 feet from my house, and inside my shack.

The problem is only at low VHF and is really annoying.

With a half decent external antenna added this is a great little radio, no doubt about it ( I sat in the shack yesterday afternoon listening with ease to a slew of 33 mhz traffic from the north eastern US) but on the rubber duck / other telescopic antenna the noise is a bit of a let down.

Again, any ideas anyone?

Consider trying the following approaches:
1. Get a 3-foot length of coax, attach the duck antenna to one end, the radio to the other. See if the 3-foot separation significantly improves performance and reduces noise. If so, think about a lapel speaker and antenna at shoulder height and scanner on belt configuration.
2. Wrap the radio in aluminum foil and see whether this significantly improves performance and reduces noise. If so, you could explore other shielding options for the radio case.
3. Try ideas 1. and 2. together.

Jim41