UHF and propogation conditions - weird experience last night.

[SvenMarbles]

So my 2 year old son woke up in the middle of the night last night (after 2am), which caused me to be awake and not be able to fall back asleep.

I decided to just head down to my radio desk for a little while. I switched the radio on and hit the scan button, not actually expecting to actually hear much at that hour. Within one cycle of scan it lands on Channel 15 and it's a full quieting conversation between two guys (about radio stuff). Channel 15 is .550 and we also have a very prominent repeater on Repeater .550. So I automatically think, "this is the Joliet .550". I tune over to where I actually have Joliet .550 with the appropriate tones and shift in case I might want to chime in. It's not there.. Signal bars are full scale, but it's not tone-opening the audio... Now I could tell that this conversation was being had via a repeater by the way the transmissions were tailing out. Well that makes no sense... I'm aware of all of the repeaters in my region, and there isn't another .550 repeater in range, and frankly it wouldn't be wise to put a new one there in this area because the existing one there is a monster. 

Long story short, I listened for a while trying to identify a call but within a few more minutes it started just sort of fading out like you might hear some shortwave or AM radio station from far away do.

It was some sort of propagation anomaly, and I was hearing a very distant .550 repeater. I didn't know that this was possible at the UHF level!! No joke, at one point it sounded like my local machine, and then it faded away into nothing..

Has anyone else had this happen?

[SteveShannon]

3 minutes ago, SvenMarbles said:

So my 2 year old son woke up in the middle of the night last night (after 2am), which caused me to be awake and not be able to fall back asleep.

I decided to just head down to my radio desk for a little while. I switched the radio on and hit the scan button, not actually expecting to actually hear much at that hour. Within one cycle of scan it lands on Channel 15 and it's a full quieting conversation between two guys (about radio stuff). Channel 15 is .550 and we also have a very prominent repeater on Repeater .550. So I automatically think, "this is the Joliet .550". I tune over to where I actually have Joliet .550 with the appropriate tones and shift in case I might want to chime in. It's not there.. Signal bars are full scale, but it's not tone-opening the audio... Now I could tell that this conversation was being had via a repeater by the way the transmissions were tailing out. Well that makes no sense... I'm aware of all of the repeaters in my region, and there isn't another .550 repeater in range, and frankly it wouldn't be wise to put a new one there in this area because the existing one there is a monster. 

Long story short, I listened for a while trying to identify a call but within a few more minutes it started just sort of fading out like you might hear some shortwave or AM radio station from far away do.

It was some sort of propagation anomaly, and I was hearing a very distant .550 repeater. I didn't know that this was possible at the UHF level!! No joke, at one point it sounded like my local machine, and then it faded away into nothing..

Has anyone else had this happen?

Tropospheric ducting. 

 

[SvenMarbles]

2 minutes ago, SteveShannon said:

Tropospheric ducting. 

 

Yeah I'd heard of tropo before but never developed an great understanding of how it works or what causes it. But I guess I just had a first hand experience with it...

[kidphc]

Tropospheric ducting. 
 

But in the middle of the night? It occurs due to temperature inversion. Maybe it was ducting caused by an incomming storm, maybe?

Sent from my SM-S901U using Tapatalk

[WRUE951]

I live in the upper Mojave Desert (Indian Wells Valley)  every once in a while as it nears evening hours i can hear a popular repeater  out of the San Bernadine Mountains.  The communication doesn't last long and fades weak to very strong.  As Steve Shannon points out, it is a phenonium caused by elevated ducting caused  by cooling Air.  Although 'listening' would be common, i think it would be a very rare instance where you could actually communicate with that distant repeater  during these conditions.  

[SvenMarbles]

9 minutes ago, WRUE951 said:

I live in the upper Mojave Desert (Indian Wells Valley)  every once in a while as it nears evening hours i can hear a popular repeater  out of the San Bernadine Mountains.  The communication doesn't last long and fades weak to very strong.  As Steve Shannon points out, it is a phenonium caused by elevated ducting caused  by cooling Air.  Although 'listening' would be common, i think it would be a very rare instance where you could actually communicate with that distant repeater  during these conditions.  

Would my signal not inversely travel the duct just as it were traveling to me?

[SteveShannon]

10 minutes ago, SvenMarbles said:

Would my signal not inversely travel the duct just as it were traveling to me?

It might, but it might not. It’s  possible that it could because of the temperature inversion. There’s a website that predicts the possibility. I’ll try to find a link. 

[Socalgmrs]

Yup. I’ve experienced this many times.  Especially in the fall and spring. 

[WRUE951]

1 hour ago, SvenMarbles said:

Would my signal not inversely travel the duct just as it were traveling to me?

Every instance i've heard off, ducting in the upper UHF Band seems to probagate on receiving signals more than it does allowing two way communications over the same distance..   I've heard a lot of stories where people can listen to a very distant station but none where two stations actually commucated over that distance..  Would it be possible  YES,  but conditions would have to be near perfect..    I would like to hear from someone if they ever made a two way contact under ducting conditions.   Haven't yet.   

[SteveShannon]

2 hours ago, SteveShannon said:

There’s a website that predicts the possibility. I’ll try to find a link. 

https://www.dxinfocentre.com/tropo.html

[SteveShannon]

3 hours ago, kidphc said:

But in the middle of the night? It occurs due to temperature inversion. Maybe it was ducting caused by an incomming storm, maybe?

Sent from my SM-S901U using Tapatalk
 

From weather.gov:

(3) The most common inversion is the radiational inversion. The earth is cooled at night by longwave radiation emission to space. This is maximized on clear nights with light wind and dry air. Air in the lower PBL will cool much more rapidly than air at the top of the PBL at night. This will cause an inversion that at times can be quite impressive. These inversions generally erode rapidly once daytime heating warms the lower PBL.

[AdmiralCochrane]

9 hours ago, WRUE951 said:

Every instance i've heard off, ducting in the upper UHF Band seems to probagate on receiving signals more than it does allowing two way communications over the same distance..   I've heard a lot of stories where people can listen to a very distant station but none where two stations actually commucated over that distance..  Would it be possible  YES,  but conditions would have to be near perfect..    I would like to hear from someone if they ever made a two way contact under ducting conditions.   Haven't yet.   

I have not had 2 way UHF transmissions via ducting, but have had 2 way ducting VHF transmissions between Long Island and central Maryland

[WRXB215]

56 minutes ago, AdmiralCochrane said:

but have had 2 way ducting VHF transmissions between Long Island and central Maryland

I talked from Houston to Beaumont one morning on 2M. So far that has been my longest on 2M.

[LeoG]

1 hour ago, AdmiralCochrane said:

I have not had 2 way UHF transmissions via ducting, but have had 2 way ducting VHF transmissions between Long Island and central Maryland

I have talked with people by tropospheric ducting.  Windsor Locks to LI NY.  Only issue is that I have a 700+ foot mountain directly in the way between us.  There should be no possibility of me talking with them.  There was one night I was able to use my 5 watt TD-H3 talkie to have a full quieting conversation with them.

[WRYZ926]

We have been picking up another repeater here lately when the band opens up between 8 and 10 in the morning. The signal is weaker at about a S4. I've only heard that other repeater during that time period.

One morning last week I ws talking on a repeater 55 miles west of me to a guy in Springfield Ill. He is about 168 miles from the repeater. Once the band closed around 10-10:30 he was gone.

[LeoG]

I'm able to contact the LI repeater tonight.  Was walking around and I heard it's half hour blerb about what it is, where it is and how to join by going to their website.  I was able to hit it with my 5watt talkie along with my 25watt base.  No one answered my radio checks from the talkie and I didn't do a radio check from the base.