Hearing myself respond to my Call

Thats the ultimate in long path. I used to experence that years ago as a kid in Jr. High school Radio club on 20 m. quite a kick.....

73 de Bill

 

This is a very interesting topic. One technique would be to have a friend some diatance way with the side of his beam on you, in contact on a phone patch and feed audio from another station back on the same frequency with the least delay loud an clear probably quicker than backscatter or going around the world. He also could record and with various tape loops for delay feed to another station this audio for replay. This could be very impressive.
I know of a case back about 30 years ago where an AM diehard refused to go on SSB. He was received on AM calling CQ, the audio fed to another station to his rear and side and suffieicent distance so when he retransmitted this audio on SSB on the orginal AM carrier without QRM to the receive station. It would detect with just a short delay on the original AM signal. So a SSB signal was superimposed on top of the original carrier reinforcing it. It had quite a sound.
Then another technique was to retransmit it about 100 KHz higher in the SSB protion where he had never been heard before and had never been on SSB. Some would call him there but he didn't hear them being 100 KHz lower on AM. Some told him later that they heard him on SSB which he of course denied.
I have another theory of what would cause a legitmate delay. It's based on the concept of how 2 wet and smooth surfaces can adhere to another. Would you believe this can occur when the bottom of the Ionosphere varies to a very smooth surface with low solar winds for starters. Then a LSB signal is transmitted and the smooth side off the signal (USB) hits the bottom of the Ionophere and sticks like 2 wet plates. Depending on the power it tends to evaporate the adhering medium and releases this signal at various times later. When it sticks it RF Freezes the signal and it holds its amplitute. When the RF Glue release, away it goes back to earth confusing all that hear it. You can talk to yourself and as some have mentioned you can request a QSL etc.
Now that's an absolutely true possibility--I just made it up.
The time delay of bouncing off the moom of 2.5 seconds always happens with all signals but they are often just too weak to hear. This is proven by those who moon bounce and the antenna gains they need to do it. Mars--totally impossible. Storage and frozen on the bottom surface of the Ionsphere keeps it very close for minimun attenuation up and back. Ahem!
I plan to build an W8JK on say 20M of 4 dB gain both ways. I will use it for band opening tests. I'll send dits and if the band is open all the way around the earth (now that's really WIDE open), it will come in the back of a beam with 4 db gain also (instead of say 25 dB F/B attenuation). By the time of delay you can distinguish between the first hop signal echo coming right back (backscatter) and/or a signal from around the world. k7gco

 

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (kf5jq @ Oct. 22 2002,11:25)</td></tr><tr><td id="QUOTE"></span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (ke0vh @ Oct. 20 2002,23:27)</td></tr><tr><td id="QUOTE">Last Saturday, while calling a friend on a schedule on 20 meters, I was surprised to hear my own voice coming back to me making the same call.  It sounded like someone recorded my calling my friend and played it back on the air without any further identification or anything.  I have not had an incident like this before in 26 years of ham operation.  Nor have I heard it on the bands before.  Has anyone else had this experience?  
Any comments would be appreciated.  73' KE0VH[/QUOTE]<span id='postcolor'>
You hearing yourself via long path. Your signaly has bounced around the globe and your receiver has piske dit up again. Pretty neat huh! . [/QUOTE]<span id='postcolor'>
That is impossible!  There is no known propagation effect or situation that will allow one to here one's own voice (whole words) after transmission except via the moon or other planets.

The only way you will hear an echo of your own signal is very short duration 150ms delays of a cw signal going around the planet long path.  I have heard my own cw signals coming back to me via this path.  I recorded this event and washed the recording through a computer, eliminated my own local signal and was left with a reasonable facsimile of my cw echo.

You may here echo sometimes on other voice signals indicating this effect but not on your own.

K2WH

 

de don/kf4cup;

there is nothing strange about it, guys have nown to hear their own
transmissions in the fashion described

you are hearing your own transmission longpath, given the proper
atmospheric conditions, after you have un-keyed the mike..................


73
don/kf4cup

 

I have noticed a significant increase in lid activity over the last decade or so.  Couple that with the digital voice keyers that are commonly available and I would question any other explanation.  Remember that the moon is only about 1.22 light seconds away, making a round trip 2.44 seconds.  This means that your signal, assuming it was delayed by 10 seconds, must have travelled 4 times the distance to the moon and back.  That is really efficient reflection by the ground and the ionosphere, an alien spacecraft beaming the signal back from beyond the moon, or a voice keyer.  Which do you think is more plausable?

 

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (K8AG @ Oct. 24 2002,08:17)</td></tr><tr><td id="QUOTE">I have noticed a significant increase in lid activity over the last decade or so.  Couple that with the digital voice keyers that are commonly available and I would question any other explanation.  Remember that the moon is only about 1.22 light seconds away, making a round trip 2.44 seconds.  This means that your signal, assuming it was delayed by 10 seconds, must have travelled 4 times the distance to the moon and back.  That is really efficient reflection by the ground and the ionosphere, an alien spacecraft beaming the signal back from beyond the moon, or a voice keyer.  Which do you think is more plausable?[/QUOTE]<span id='postcolor'>
That's a novel approach. But LDEs were around decades before voice keyers, and are not a ham-radio only phenomena. Almost all of my own experience with them occurred on international government and maritime frequencies. Standford University was investigating them in the early-mid 1960s, and perhaps before.

For K2WH - I have never personally heard a voice LDE. But they were documented plenty of times through the research at Stanford. If 8 seconds of a CW signal can be ducted back, entirely, with no distortion other than local QRN, then it would be hard to accept that other types of signals could not be as well. In constant-carrier modes, such as RTTY and AM, unless the carrier is cut, the transmitting station is never going to hear his LDE anyway. And heard at a different geographical point the listener would not know for sure if it was LDE or if the transmitting station had simply transmitted again, briefly. I would guess that during the time I heard CW LDEs, if there had been a way to do it, I would have heard far more RTTY LDEs, but we could not be transmitting RTTY and listening on the same frequency at the same time, so no way to hear it even if it did occur.

Presumably it also happens on SW stations, but then they aren't cutting their carrier and listening to themselves either! Therefore the most likely place to hear it is with station operating in the 10-20 MHZ range, (that's a guess&#33 in intermittent types of transmission.

Nope, it isn't a space ship!

73
Ed

 

Does a QSO with yourself via LP count as a valid contact? WAM (worked all ME).

 

I heard a net on 14.336 the other day, and there was some idiot with a tape recorder playing games with the guys on there. It's hard to believe there are actually idiots out there who spend their money on ham radio equipment just to do stuff like that. A person like that needs some serious mental help. N5MFA Dan

 

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (KV4BL @ Oct. 23 2002,14:41)</td></tr><tr><td id="QUOTE"></span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (ke0vh @ Oct. 21 2002,05:27)</td></tr><tr><td id="QUOTE">Last Saturday, while calling a friend on a schedule on 20 meters, I was surprised to hear my own voice coming back to me making the same call.  It sounded like someone recorded my calling my friend and played it back on the air without any further identification or anything.  I have not had an incident like this before in 26 years of ham operation.  Nor have I heard it on the bands before.  Has anyone else had this experience?  
Any comments would be appreciated.  73' KE0VH[/QUOTE]<span id='postcolor'>
This is an interesting phenomena to say the least.  I remember about nine or ten years ago, when I was a Public Safety Officer with SC Dept of Mental Health, we had an old VHF radio system on 155.160 MHz which consisted of an old GE base station on top of a 5 story building on the State Hospital grounds and a two bay-pole antenna for that band.    The base was hooked to a GE MASTR control head in the Central District Public Safety Headquarters dispatch room.   While the base encoded a 94.8Hz PL tone, it had an open (carrier squelch) receiver to accomodate some of the older radios used that had no PL capability.  The 5 story building, by the way, was actually situated in a rather low place so  coverage was not normally really great on our system.  On a regular basis, especially at night and early in the morning, it was not usnuual to hear dispatchers for ambulance crews and rescue squads out 100-150 miles.  this was something we just learned to tolerate.  One night when I was off, the officer that was dispatching for the department that night and his sergeant stated that for about three hours, EVERY time he would transmit on the base station, they would hear what he said repeated within a second or two of his unkeying the mic.  They said the signal was kind of weak and that they could not hear it on the mobiles or portables from anywhere on the grounds.  I quizzed them as to whether there were any tell tale signs that somwone may have been taping and replaying his transmissions such as change in sound of his voice, mis-cued replays with parts of the transmission cut off of the beginning and / or end, or other parts of other transmissons coming in and they said that there wasn't anything like that noted.  As I was one of the resident radio geeks working there at the time, they pressed me for answers and I had none that were likely, other than someone with taping gear that knew what he was doing!  We all pondered the possibility of the signal bouncing off of something WAY OUT THERE, and that still intrugues me to this day.  One other thing that makes me tend to doubt the tape and replay theory is that this had never been reported prior to that night and no one heard of it again, even though that story made its rounds at the department.  One would think that if it was a prankster, they would have continued to have fun with their pastime.
        73,
           Ray  KV4BL[/QUOTE]<span id='postcolor'>
Hmmm.


A radio at a state mental hospital?

Ken N4VSD

 

I've seen a great many theories here about this. One extremely creative theory that I kind of enjoyed talked about two smooth surfaces sticking to each other. My hat's off to you OM for coming up with that one, and it may be possible, but I don't see it likely...

Also, as far as a 20m signal bouncing off of a terrestrial body, well, about the lowest frequency that you could get out of the atmosphere with any reliability is about 50MHz or so. The signal can go either way there, but up at around 108MHz or so, you loose most of the atmospheric path distortion (with the exception of tropospheric E propogation...)

Therefore, I do not really see an HF signal getting out of the atmosphere. Sure, it could come back in (hence H/V mode satelite communications), but it'd have a heck of a time getting out.

I'd say it's quite possible that someone somewhere who has never managed to grow up has a great deal too much time on his hands, and is possibly someone who resents ham's because we could pass the test and he couldn't (just a thought)...

Just my observations...

73's
John KB5SXH

 

LDE (Long Delayed Echo) is nothing new, and has been covered from time to time in QST.  One very good article can be found in the February 1970 issue, page 30.  It's even written in plain language, so you don't need a  list of letters after your name to understand it (hi,hi).  But I have read others as far back as 1958.

For those of you who keep believe it's a jerk with digital recorder, I doubt you would have found one of those in common use back then.

For the math hounds, measuring the path does not give you anything usefull unless you include an extensive number of factors: layering, reduction of the signal velocity, changing positions between the source and reflecting body, topography of both surfaces, etc.....  No easy feat, even with a computer.  This is not a+b=c!

While it could indeed be some jerk with a digital recorder in some instances, the fact is that LDE is a well documented, long known, fact of life.  

While still not fully understood, it is, one of the things that make the whole concept of radio communications such a fascinating (dare I say magical?) thing!

Enjoy the mystery....it's all part of what got you into this hobby in the first place.  The days of magic are not over....!!

73,

Jim/K7UNZ

 

After spending a bit of time here reading all this stuff, I decided to contact a friend at Lawernce Livermore Labs, whom worked at Stanford in the 60s and 70s. When i brought this article to him he chuckled at first, and then went into such detail as to how and why, he lost me! However I did get the information I was looking for. It comes down to LDE has been around longer than the radio, and wasnt noticed until the radio, so it is not man made, but rather natural. as was pointed out before the chances of hearing your signal on the same ant. as transmitted is unlikely but not imposs.there r several factors to this phenominon. power, location, angle of radiation, weather (big factor), and of course orintation of ant. because of the characteristics of our atmosphere, it is impossable to predict how a signal will truly act once it leaves the antenna, sometimes they die before they leave the back yard and sometimes they dont. to say that the signal would be greatly attenuated between layers before it was returned, doesnt always aply. in ideal conditions a siganl may be accelerated, and decelerated, or compressed and stretched. of course most are familiar with the latter, making it a watery sound. ( what sound is that by the way, i didnt think water had a sound). but in an unobstructed path, it would return as sent, musch as a wave guide does in microwave comms.
the chances are very small but none the less do exist and as noted severla times around the world do happen.
73's
KF6NFW

 

I got my Novice (WN4ZOH) in 1972 and my Elmer (WB4WWL) was in the shack when I experienced a LDE on 15 meters just at the band was closing. WB4WWL confirmed the event and related that as a radio intercept operator in the service he had experienced several LDEs.

For a new operator it was a surprise to hear your callsign come back faintly. I still have the log page somewhere signed by both of us.

 

I was working at the ham station at the Franklin Inst. in Phila (W3TKQ aka W3AA). I was talking to a station in Japan. When I heard my voice comming back to me??? It was a long path echo delayed about 1.5 sec. I friend and more experenced ham was also in the shack. He explain the long/short path theory to me.
This was (so far) a one time event, realy a net event.

 

Hey folks, IT is a LID ... couple of comments.

I've heard this person several times recording not only my calls, but also others.  They will record you, and then play it back on another frequency causing deliberate interference.  I've noticed it several occassion, and yes the long path echo and such are valid, but this is NOT the echo your so describe, its obviously the following:

An individual is using a computer/soundcard recording feature to record your audio via his computer, then they feed it back to the audio input of their rig just like you would a RTTY input, or Packet input, nothing special.

However, I've noticed on 3 occasion they have recorded someone's CQ, and then played it back several times on that one frequency, then they slide up and down the band causing QRM to others using the same recording of YOUR CQ.

This is an obvious LID performing this, and sooner or later someone will catch them.  As typical, new technology comes, and someone has to find a way to abuse it.

One more reason to ensure you maintain a LOG, not only of your QSO's but also your CQ's.  They are the only defense you have for yourself to ensure a record is maintained of how and when you operate your station.  Yes the FCC no longer requires a log, but believe me when I say, I've had to use mine in defense of my station and how it is operated in the past, and it was useful in troubleshooting RFI issues, when dealing with the City of Wyoming, Michigan and the Touch Lamp issues.

My 2, or 3 cents worth.

73 - W8YRB
Rob