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Author Topic: Propagation effects on CW  (Read 2666 times)
N3QE
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Posts: 2285




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« on: November 07, 2011, 08:08:44 AM »

I've been a ham long enough that I can listen to a CW signal and know from its sound where it might be coming from. e.g. the burbly/warbly sound that near-local signals often have on 15M vs the clear as a bell sound on signals from the other coast. Or the way VK and ZL sound in grey path on 40M in the morning.

But last night in CW SS the I was stymied by one 40M station that was nearby (him in zone 2, me in zone 3). He was really loud (at least 20 over 9) but not the loudest. And try as I might I could not separate out his dits from his dahs from his spaces. It was not too dissimilar from two stations zero-beating on the same frequency with similar strength and sending simultaneously - but at least there they will eventually stop stepping on each other. I had to tell the guy NIL and move on to the next signal because despite at least 4 or 5 attempts I was unable to copy him; I was a little embarrassed.

It honestly felt like there was some kind of delayed echo and his dits were being replicated in the inter-dit silences. He would've been about 25WPM so if this delay concept is right... it would have been like a 50 millisecond delay. If he could've QRS'ed maybe I could've copied him but we didn't get that far. While I think I've heard echoes like this before, I've never heard them so loud and to such an extent that I couldn't copy a nearby station. Any thoughts? Is there a propagation forum here on eham or elsewhere?
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WB2WIK
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« Reply #1 on: November 08, 2011, 09:26:00 AM »

Sure it wasn't just "backwave?"

Used to be a really common problem with some old boat anchors.  Any idea what he was using for a transmitter?
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AA4PB
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« Reply #2 on: November 08, 2011, 10:25:28 AM »

With people using sound card generated audio tones to create the CW there can be all sorts of "new and unusual" sounds.  Roll Eyes
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K3STX
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« Reply #3 on: November 08, 2011, 10:59:09 AM »

zone 2 = aurora?? We had some minor storms this weekend.

paul
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PA0BLAH
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« Reply #4 on: November 09, 2011, 03:17:15 PM »

I experienced the same effect with a contact.

After some trials reporting QLF and QSD  the QSO partner came back with another transmitter, and it turns out he was working (trying to) with a Flex5000.

Splendid radio, fantastic receiver but don't use it for CW.

Bob
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AE4RV
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« Reply #5 on: November 10, 2011, 07:54:40 AM »

I experienced the same effect with a contact.

After some trials reporting QLF and QSD  the QSO partner came back with another transmitter, and it turns out he was working (trying to) with a Flex5000.

Splendid radio, fantastic receiver but don't use it for CW.

Bob

I know it's unofficial but someone should add QLF to this list: http://en.wikipedia.org/wiki/Q_code


About a week ago I heard a Chinese station on 20 or 15 (my log isn't here) and it was the most fluttering signal I have ever heard. I attributed this to atmospherics, not his transmitter, but the point is it was very difficult to read. He didn't have a pileup but I thought about not trying for him because I could barely understand his keying through the flutter. I waited a bit and tried anyway. He stopped sending while I called and seemed like he could hear me. After a few ???s I sent my call three times, and he sent it back - I couldn't be very sure but it really sounded like he got it right so I sent 599 TU and he sent TU 73 and 24 hours later it was confirmed via LotW. Awesome.


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VE3XDB
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« Reply #6 on: November 10, 2011, 09:22:07 AM »

With people using sound card generated audio tones to create the CW there can be all sorts of "new and unusual" sounds.  Roll Eyes


I wondered about that, too.  Will the CW tone generated by a sound card and fed through an interface to the rig "sound the same" at the receiving end?  I have tried it for a few qso's, just for fun, and when monitoring my own transmission, it sounds fine.  But I am wondering if there are any implications at the receiving end?  Interesting thought. 

I will stick to my old keyer and Bencher paddle for generating cw.  I do find the sound card decoder useful for zero beating and logging, but my ears do a much, much better job of copying cw. 

Remember, any cw is better than no cw.

Regards,

Doug VE3XDB/VE3IID
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PA0WV
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Posts: 137




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« Reply #7 on: November 10, 2011, 10:39:19 AM »

With people using sound card generated audio tones to create the CW there can be all sorts of "new and unusual" sounds.  Roll Eyes


I wondered about that, too.  Will the CW tone generated by a sound card and fed through an interface to the rig "sound the same" at the receiving end?  


You never know what happens when HF enters the soundcard. But normally any sound from that card is accurate, it is a 16 bit signal so the quantisation distortion will be around 1/300 of one percent.

In order to experiment with a Morse decoder, I made some wav files, using math, with a test signal in noise, duration about 7 second, when you play it, set the player on repeat mode, then the signal is very useful for testing performance, dependent on different parameters (of a Morse decoder) http://pa0wv.home.xs4all.nl/TIMorsedecoder/TIMosedecoder.html presents the links to the audio files.

Interesting story of AE4RV, about difficulties to copy the signal of the Chinese ham, but anybody able to explain me why you are classified as LID when you give a honest report, in this case 199?

May be in the heat of a contest, but even then: We are allowed to use radio frequency space in order to experiment. Contest can be classified with a lot of goodwill as experiment, but hardly so when the reports are default 5nn.

Actually QLF is recorded in wikipedia: I copy:

There are also a few unofficial and humorous codes in use, such as QLF ("try sending with your LEFT foot") and QSC ("send cigarettes", not the official meaning of "this is a cargo vessel"). In the question form, QNB?, is supposed to mean "How many buttons does your radio have?" A reply of the form QNB 45/15 means "45, and I know what 15 of them do." QSJ is sometimes used to refer to the cost of something - "I would like an FT9000 but it is too much QSJ". (QSJ actually means "What is the charge to be collected to ... including your internal charge?").

Wim PA0WV
« Last Edit: November 10, 2011, 10:55:09 AM by PA0WV » Logged

Using an appliance without CW is just CB
WX7G
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Posts: 6131




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« Reply #8 on: November 10, 2011, 01:23:13 PM »

If the problem was the transmitter he would know it; no QSOs .

But if he was making contacts you were likely earing a long delayed echo or simply short and long path.  I've heard both phenomena with short/long path being fairly common. It can make copying CW very difficult.
« Last Edit: November 10, 2011, 02:53:39 PM by WX7G » Logged
AE4RV
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« Reply #9 on: November 10, 2011, 01:32:43 PM »

If the problem was the transmitter he would know it; no QSOs .

But if he was making contacts you were likely earing a long delayed echo. I've heard them before.

I hadn't considered echos, I figured the flutter was from his signal going over the pole through some aurora activity. I don't really know.

When I last called him with my call three times, I slowed my keyer down a bit to help compensate for any flutter that may have been on MY signal. I sure was happy to get China - usually I can't hear them at all.
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STAYVERTICAL
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Posts: 875




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« Reply #10 on: November 14, 2011, 02:23:18 PM »

The last few weeks activity on the higher bands has been pretty good for me with intercontinental CW qso's on 10 and 12m
very consistently being made.
But the burbles and burps which the ionosphere has been making is a hoot, sort of like listening to ones stomach after
a spicy meal.
I have learned when the band is open on 12 and 10m by simply watching the noise level and listening for the "burps".
I guess the noise level is distant thunderstorms or cities propagating via the ionosphere.
The burps are probably caused by aurora effects.
Once, I heard a signal like that described, but I suspect it was the equipment not the ionosphere which was involved.
On psk31 multipath reception on close by stations is not new, and can make psk31 unreadable, but with DX, on the higher bands,
so far, I have not observed this effect, except due to station malfunction.

I would not discount long delayed echo's however, since there are many strange effects associated with our local planetary waveguide.
Scientists have only recently discovered, for example, that cosmic rays are also produced in our own atmosphere by some effect,
probably thunderstorms but who knows.

The more we look, the more we learn.

73s
« Last Edit: November 14, 2011, 02:25:27 PM by STAYVERTICAL » Logged
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