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Author Topic: "E" on 21.929MHz CW, not Russian Naval, so what is it?  (Read 2565 times)

Offline Looking-Glass

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I have regular reception of the letter "E" being sent in CW on 21.929.35MHz, 21.938.25MHz & 21.950.50MHz, with the latter not always on air.  These are received during daylight hours 2.00pm local time which suggests to me that they are located in the Asia Pacific region.  They are not time signal pips either.

A search of my Russian Naval frequencies single letter beacon stations show that the letter "E" is not used.

The latter "E" on 21.950.50MHz is not always on air, or maybe is at a different location and out of skip range?

Of note is that the transmitters for "E" key in three power stages, low/medium/high and have a whooshing noise always in the background.  Been monitoring this trio for around two weeks now, curious as to what they are about and where they are located, any help or suggestions?  Google has given nothing. ???
Condobolin, NSW.

Grid Square:  QF37ub

Yaesu FT-1000D, Yaesu FT-2000D, ICOM IC-736 HF/50MHz, ICOM IC R75 & Tecsun S-2000 to 450 feet of wire, 27MHz 1/2 wave CB antenna converted to 21MHz & a multi band vertical of dubious reliability.

Offline Token

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Re: "E" on 21.929MHz CW, not Russian Naval, so what is it?
« Reply #1 on: May 06, 2016, 0155 UTC »
As mentioned in the stickied message in this forum, a recording would help, or a screen shot.  Fortunately, I can take a good guess as to what this is, because other listeners have made the same mistake of thinking this is CW.  Without a recording or a screen shot, or both, I can not be 100% sure, but I would bet a sizable amount I am right.  Assuming I am, the following applies:

This is not the letter E, nor is it CW.  Everything that goes beep and boop is not CW or Morse code ;)

Many digital modes have a pilot tone.  A pilot tone can be intermittent or it can be on the full time the digital mode is on the air.  When they are intermittent they typically occur at the beginning of the transmission.  That is what you have here, a pilot tone at the beginning of a digital transmission, in this case HFDL (High Frequency Data Link), also called HF ACARS.

HFDL is a data link used by commercial aircraft to report various information to ground stations.  It consist of a short pilot tone of 250 msec (0.25 second) sent on 1440 Hz (when properly tuned in USB) followed by a 295 msec 2PSK preamble and then 1.8 or 4.2 seconds of 2PSK data.

The 1440 Hz pilot tone makes what you are hearing as the letter E and the PSK data is the whooshing noise you hear.  The multiple power stages or levels you are hearing are the different received strengths of the aircraft reporting.

The frequencies you report are close, but no cigar.  Try USB mode, and then try 21928 kHz, 21937 kHz, and 21949 kHz.  This should result in the pilot tone, what you are taking as the Morse letter E, at about 1440 Hz audio freq, followed by the data.

There are several possibilities for who the sources are.  Both 21928 and 21937  kHz is used by Molokai, Hawaii, and Barrow, Alaska and aircraft reporting to those stations.  21949 kHz is used by Auckland New Zealand, Hat Yai, Thailand, and Johannesburg, South Africa, and aircraft reporting to those stations.

Later I will try to put up a recording of HFDL on my Youtube channel, so you can compare it to what you are hearing.  It may not happen for a couple days though.

T!
« Last Edit: May 06, 2016, 0305 UTC by Token »
T!
Mojave Desert, California USA

Offline Looking-Glass

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Re: "E" on 21.929MHz CW, not Russian Naval, so what is it?
« Reply #2 on: May 06, 2016, 0519 UTC »
You have it right Token, I had a friend, John VK4FNQ, tune them this afternoon and he said there was a digital style data burst at the end of each "E" which matches what you have said.  Sorry, I am not equiped to post things heard on the net via You Tube or whatever as I have a very poor net connection (wireless) as out in the bush, it drops in and out all the time or doesn't work at all!

Also radio gear is down stairs and computer is up stairs, computer doesn't work down stairs as net signal drops right out.  Thanks for the additional data and "E" mystery case book now closed...Jack
Condobolin, NSW.

Grid Square:  QF37ub

Yaesu FT-1000D, Yaesu FT-2000D, ICOM IC-736 HF/50MHz, ICOM IC R75 & Tecsun S-2000 to 450 feet of wire, 27MHz 1/2 wave CB antenna converted to 21MHz & a multi band vertical of dubious reliability.

 

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