Some days I receive from 300km's, all others only ~30 ?

[AlexandrosKord]

I have frequencies X, Y, Z stored and always scanning them. They're in use 24/7. I have verified myself that they actually work and that they are used, indeed , for what I believe they're used for.

So here's the weird thing. Most of the days (98% of the month) my scanner only receives frequencies within a ~30-50km range, and very, very few days of the month, I can receive Frequencies X, Y, Z, that are 300km's away. How's that happening? Why's that happening? (The "tests" were conducted on the exact same location/spot with the exact same scanner/antenna)


I thought that the recent C.M.E.'s might impact this, but I don't believe they do...
What's causing that? Can I do something?

Thank you.

 

[trentbob]

There are a lot of factors lately that are affecting fluctuating reception results including tropospheric ducting and sunspots. Be more specific regarding the frequencies you are trying to pick up, your location, your radio, your antenna and any other environmental factors.

 

[AlexandrosKord]

There are a lot of factors lately that are affecting fluctuating reception results including tropospheric ducting and sunspots. Be more specific regarding the frequencies you are trying to pick up, your location, your radio, your antenna and any other environmental factors.

Thanks.

Location is Greece, freqs. are 100-300MHz, UBC125XLT, stock antenna, nothing special.

 

[trentbob]

Well I'm from the northeast coast of the United States in the Philadelphia PA area. I live along the Delaware River and we get what's called tropospheric ducting on VHF frequencies, approximately the same range that you are listening to. In 10 or 11 meters we are enjoying periods of skip from the ionosphere due to a sunspot cycle that is just begun and will peak in the future.

Not to say that atmospheric conditions and weather can also affect signals, also you will find foliage on trees increasing or decreasing can change reception results.

I'm really not able to help you any more than that as we are in 2 Worlds LOL. I'm sure you'll get many responses to your post.

 

[AlexandrosKord]

Well I'm from the northeast coast of the United States in the Philadelphia PA area. I live along the Delaware River and we get what's called tropospheric ducting on VHF frequencies, approximately the same range that you are listening to. In 10 or 11 meters we are enjoying periods of skip from the ionosphere due to a sunspot cycle that is just begun and will peak in the future.

Not to say that atmospheric conditions and weather can also affect signals, also you will find foliage on trees increasing or decreasing can change reception results.

I'm really not able to help you any more than that as we are in 2 Worlds LOL. I'm sure you'll get many responses to your post.

That's some great info. You really did help me a lot! Thank you!

 

[HavenBTS]

I am reading the OP post as saying that he believes that the ~300km reception distance is the norm and the ~30-50km reception is unusual. The opposite is true. But that is just the way I am interpreting his question.

 

[mmckenna]

Thanks.

Location is Greece, freqs. are 100-300MHz, UBC125XLT, stock antenna, nothing special.

Tropospheric ducting will cause that.
One thing you can try is compare your experience with what the predictions are on this website:

https://dxinfocentre.com/tropo_eur.html

When atmospheric conditions are right, RF signals can get bounced along between some levels of atmosphere and the ground, resulting in traffic from a long ways off arriving at your radio.

I have an AIS (ship tracking) receiver at one of my radio sites. AIS uses VHF frequencies in the Marine VHF band to send location data out to other ships and shore stations. I've received ships 750 miles out at sea when conditions are correct. The periods of long range reception match up with the info on the website linked to above.

 

[AlexandrosKord]

N

I am reading the OP post as saying that he believes that the ~300km reception distance is the norm and the ~30-50km reception is unusual. The opposite is true. But that is just the way I am interpreting his question.

Nope. Bad wording on my part but I didn’t mean that. I’m just saying, since I can receive a frequency from 300km away, why not receive it all the time? 😅
I understand it’s not the norm.

 

[AlexandrosKord]

Tropospheric ducting will cause that.
One thing you can try is compare your experience with what the predictions are on this website:

https://dxinfocentre.com/tropo_eur.html

When atmospheric conditions are right, RF signals can get bounced along between some levels of atmosphere and the ground, resulting in traffic from a long ways off arriving at your radio.

I have an AIS (ship tracking) receiver at one of my radio sites. AIS uses VHF frequencies in the Marine VHF band to send location data out to other ships and shore stations. I've received ships 750 miles out at sea when conditions are correct. The periods of long range reception match up with the info on the website linked to above.

That’s awesome. Thank you!

 

[HavenBTS]

N

Nope. Bad wording on my part but I didn’t mean that. I’m just saying, since I can receive a frequency from 300km away, why not receive it all the time? 😅
I understand it’s not the norm.

It is my fault for reading it in my illogical way!

 

[n6hgg]

My wife caught me listening to frequencies X, Y, and Z and I got in trouble. Proceed with caution.

 

[merlin]

First you have to consider, RF is some really strange stuff. Many things can affect propagation, Most noted is the CME effect and tropospheric ducting. Many cases up to 300 Mhz.
Near a freeway after a rain, ground conductivity increases, that has greatly increased reception from MF up to UHF.
Also funny is a semi goes by and signals take a dip. this is related to reflections.
You move your antenna more than a wavelength, this can increase or decrease signals for phase difference from reflections.(ghosting) Directional antennas take advantage of this for gain.
There is a lot more to antennas and propagation than I mentioned here.
Even in my case, sunlight even has effect in many Ghz.

 

[AlexandrosKord]

First you have to consider, RF is some really strange stuff. Many things can affect propagation, Most noted is the CME effect and tropospheric ducting. Many cases up to 300 Mhz.
Near a freeway after a rain, ground conductivity increases, that has greatly increased reception from MF up to UHF.
Also funny is a semi goes by and signals take a dip. this is related to reflections.
You move your antenna more than a wavelength, this can increase or decrease signals for phase difference from reflections.(ghosting) Directional antennas take advantage of this for gain.
There is a lot more to antennas and propagation than I mentioned here.
Even in my case, sunlight even has effect in many Ghz.

That’s some awesome info! That’s all I needed to learn.
Thank you so much!