• Effective immediately we will be deleting, without notice, any negative threads or posts that deal with the use of encryption and streaming of scanner audio.

    We've noticed a huge increase in rants and negative posts that revolve around agencies going to encryption due to the broadcasting of scanner audio on the internet. It's now worn out and continues to be the same recycled rants. These rants hijack the threads and derail the conversation. They no longer have a place anywhere on this forum other than in the designated threads in the Rants forum in the Tavern.

    If you violate these guidelines your post will be deleted without notice and an infraction will be issued. We are not against discussion of this issue. You just need to do it in the right place. For example:
    https://forums.radioreference.com/rants/224104-official-thread-live-audio-feeds-scanners-wait-encryption.html

AM Broadcast interference on SW

Status
Not open for further replies.
Joined
Feb 24, 2006
Messages
152
#1
I've been working with the rtl-sdr v3 for a few weeks now. I am receiving interference from a local AM broadcast virtually everywhere I tune across the sw bands. The station transmitter is about 2 miles from me and transmits with low power, especially at night on 1450. I have coax going out of the house to a wire that connects to a down spout about three stories tall running up to the gutters across the eaves of the house. The gutter runs more or less north-south and the 1450 transmitter is to the east. Any ideas how I can eliminate this problem?
 

ka3jjz

Wiki Admin Emeritus
Joined
Jul 22, 2002
Messages
21,675
Location
Bowie, Md.
#3
A good AM broadcast filter will take this out very easily. These el-cheapo dongles have next to no front end filtering, and is a very common issue. I would also check your gain settings - sometimes running them too high will overdrive it, at least from what I've read.

Mike
 
Last edited:
Joined
Feb 24, 2006
Messages
152
#4
Can't change the antenna orientation since its the gutter on my house but I will probably try setting up another antenna with a different orientation or try to get creative and DIY a vertical to experiment with. Any ideas for the AM broadcast filter? I've done a quick look this morning and the couple that I've found cost three times what I paid for the dongle. Just thinking...I have an old Radio Shack SW amplifier/band pre-selector. I might dust that off and give it a try as well. Thanks for the input!
 
Joined
Dec 22, 2013
Messages
2,937
#5
The broadcast reject filter is a must. Also a gutter is a poor antenna due to 1) it is unbalanced and you probably have common mode current from the broadcaster getting into your system, 2) the junctions can create noise and intermodulation. You should install a balanced fed 1/2 wave dipole antenna or a G5RV. Also a good RF ground.
 

ka3jjz

Wiki Admin Emeritus
Joined
Jul 22, 2002
Messages
21,675
Location
Bowie, Md.
#6
Joined
Feb 18, 2015
Messages
291
Location
where they make the cheese
#7
im in the process of building the BCB notch filter from this article
https://goo.gl/bUFxs8
when i switched to the SV1AFN upconverter i found that its response is very flat across the bands
and yes i could hear things better(much quieter upconverter)
if i got the dongle gain to high i got images everywhere
the upconverter has a very nice 20db preamp built in but i cant use it at all till i get the local BCB filtered out
i chose the notch filter over a simple high pass as i like to snoop about below 500Kc
will report!
but keeping your dongle gain down is easiest short term
on my system when below 5mhz i have to keep the dongle gain to 5db or less
 
Joined
Sep 13, 2005
Messages
381
#8
The AM broadcast is vertically polarized. Use a horizontal antenna for SW listening and orientate it such that the AM station is off one end and not broadside. That should at least drop the signal strength of the local AM station at your feed and make filtering more effective.
 
Joined
Jul 25, 2004
Messages
3,669
#9
I had a similar issue at a previous address where the local AM station's transmitter was less than a mile away and their signal swamped nearly everything that wasn't properly terminated or had any corrosion at all. Start by ditching the gutter as an antenna. There are just too many unbounded joints for it to work for you. Each joint will sooner or later start to corrode (not necessary leak, but make a poor electrical connection) and act as an RF detector and cause the issues you now have. Fix one and another will take its place quickly.

Other issues I had to correct were, the signal being heard on my landline, both by me and the other party; the station being heard over my stereo speakers when the stereo was off; a florescent light glowing to the station's signal, just to name a few. Some were fixed by using chokes on the wires while others had no permanent resolution, but were reduced to only happening at times, such as when the phone line was out (not really an issue then) or when the weather was bad. The florescent light had to be replaced by an normal light.
 
Joined
Feb 24, 2006
Messages
152
#10
Thanks for all the responses. Its fall here in Connecticut so I'm spending way more time than I want to raking leaves but I will find time in the next couple of weeks, before the cold weather sets in, to try some of the various antenna suggestions as well as settings within the software itself. Thanks again all !
 
Joined
Feb 23, 2014
Messages
582
#11
That station runs 1000 watts day and night and looking at the contour map it looks like signal strength 2 miles from the transmitter would be at least 100mV/m. That's a pretty strong signal and all those gutter joints, rivets, screws act as excellent detectors. Forget about the gutter antenna.

btw, that PAR EF-SWL mentioned in response #6 is an excellent antenna
 
Status
Not open for further replies.
Top