Two Stations On The Same Freq. ?

[BOBRR]

Hello,

Probably a silly question, but thought I'd ask anyway:

Let's say there are two (or more) am or fm stations broadcasting on the exact same freq.
Both have the same power, distance, etc.

If one of them didn't exist, either one, the other would come in loud and clear.

Is there any parameter, or technique, that could be utilized in separating them, such that
one or the either would be "listenable" to ?

Thanks,
Bob

 

[a417]

directional antenna

 

[vagrant]

A directional antenna.

 

[hill]

For AM stations you could use a portable radio with a directional loop antenna. By rotating the radio you can null out one station if they broadcast from different locations in different directions.

With the FM capture effect the stronger one will be received. Like the AM one if they both are located different directions might be able to use a broadcast FM directional antenna to only receive one.

 

[GB46]

Oops; a couple of people with good replies beat me to it!

Hello,

Probably a silly question, but thought I'd ask anyway:

Let's say there are two (or more) am or fm stations broadcasting on the exact same freq.
Both have the same power, distance, etc.

If one of them didn't exist, either one, the other would come in loud and clear.

Is there any parameter, or technique, that could be utilized in separating them, such that
one or the either would be "listenable" to ?

Thanks,
Bob

I would think that the direction each signal is coming from might make it easier to separate them, provided you have a very directional antenna, such as a loop, etc.

Also, the same power and distance doesn't always guarantee the same signal strength on the listener's end. There could be other variables, such as the elevation of the transmitter sites, etc., so perhaps one of them could be stronger than the other. On the AM band in the evening you can often hear two or more stations on the same frequency, causing harmonics, which result in loud whistles. Under those conditions, you may be able to make out one of the signals if the others fade out.

 

[BOBRR]

Hi,

Thanks.
Good suggestions with the directional ant.

Stay well,
Bob

 

[jwt873]

As a side note of interest (just to give credit to the directional antenna advice).

I have a three element SteppIR Yagi that can be physically tuned to any frequency between 14 and 52 Mhz. It makes a great antenna for both ham and SWL use.

On 15 Mhz, I occasionally receive the WWV signals from Colorado and Hawaii at the same time with equal strength.

Even though HF Yagis aren't as sharp as VHF/UHF Yagis, I can still separate the stations quite well. When I point to Hawaii, the female voice is loud and the male voice from Colrado is just audible in the background. When I point to Colorado, the male voice is strongest with a hint of he female voice in the background.

Edit.. Just slipped up to 15 Mhz to check conditions.. 14:43 UTC.. I can just make out Hawaii in the noise. Can't hear Colorado at all..

 

[ka3jjz]

We have many BCB/AM capable loops in our wiki, and you can easily build them if you can find the parts

Loops - The RadioReference Wiki

wiki.radioreference.com

Mike

 

[Boombox]

On FM, you move your whip antenna, either axially or angle it differently. Generally it will select one station over the other. I have done this when receiving two separate fringe FM signals before.

 

[ka3jjz]

If you are using a SDR (i.e. Airspy) and SDR#, this is for you...

Ivan demonstrates the incredible SDR# Co-Channel Canceller

Many thanks to SWLing Post contributor, Ivan (NO2CW), who shares the following short demo of the new SDR# Co-Channel interference canceller tool: That is simply amazing! Readers note: this powerful…

swling.com

Mike

 

[devicelab]

Let's say there are two (or more) am or fm stations broadcasting on the exact same freq -- and both have the same power, distance, etc. Is there any parameter, or technique, that could be utilized in separating them, such that one or the either would be listenable?

To quote the great Colonel Mertz von Quirnheim: Any problem on Earth can be solved with the careful application of high explosives.

 

[Patch42]

The dipole wire antennas that used to be included with most tabletop FM radios are directional if you spread them out with the arms in a rigid tee. I once built a simple tee stand using PVC pipe and strung a dipole from that. Hooked it up to a Sony HD radio and did a band scan. By rotating the antenna I was able to differentiate two or three FM stations on a number of frequencies where there was no station within the local reception area. (A local station will usually overpower the null region of the antenna and make it nearly impossible to get anything else on that frequency.)

Most MW/AM antennas are directional, so rotating the antenna, or the whole radio if the antenna is internal, can help when there are multiple stations on a frequency. Most antennas will have a null reception region. The better the antenna, usually the sharper and deeper this null will be. The most effective approach is usually to rotate the antenna until one of the stations fades away rather than trying to peak one station. The radio will have an AGC that can usually compensate for lower signal strength on the non-nulled station. Get one station in the null region and as long as the other is out of the null you'll likely be able to hear it.

In both cases, AM and FM, if you draw a line from the location of each transmitter through your location and well out to the other side, the closer to perpendicular those two lines are, the easier it will be to null one station while getting a good signal on the other. The closer to each other the lines are, the more difficult it will be to separate the two stations. If the lines are very close you'll need an antenna with an extremely sharp null and a very steady hand to null one without nulling the other.

 

[BOBRR]

Hi,

Interesting and very informative write-up.
Thanks.

Happy Holidays,
Stay well,
Bob