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RE: ULF: A short summer experiment on the 191 km band

To: <[email protected]>
Subject: RE: ULF: A short summer experiment on the 191 km band
From: <[email protected]>
Date: Tue, 5 Jun 2018 12:44:24 -0400
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Hello Stefan,

 

Compliments on finding a good 11.8km location and extracting the signal from sferics and other noise, and very good SNR at 3.8 mHz at 11.8 km, 1570 Hz.

 

In your Thursday (June 2nd) early-morning message you mentioned that noise was higher on the H-field receiver, and that (SNR_E / SNR_H) was ~ 15 dB.

 

Do you perhaps remember roughly how much higher measured H noise was (how much higher than measured E noise)?

 

The reason for the question is: an experimental estimate of (signal_E/signal_H) would be quite interesting at this frequency and range; it could be a helpful indicator of propagation effects.

If your H noise was ~ 14 dB above your E noise (early-morning of June 2nd), that would seem to agree with a standard algebraic approximation of: 11.8 km 1570 Hz non-radial signal_E/signal_H = 29.3 dB (excluding radial component)

 

If so that would be interesting, because I would not expect (signal_E/signal_H) to be very close to the theoretical value at 11.8 km 1570 Hz, but this could be good news if it indicates that some aspects of propagation are not too far from normal.

 

Do you recall roughly how high H noise was, compared to E noise?

 

73,

 

Jim AA5BW

 

 

 

 

From: [email protected] [mailto:[email protected]] On Behalf Of DK7FC
Sent: Monday, June 4, 2018 6:47 PM
To: [email protected]
Subject: Re: ULF: A short summer experiment on the 191 km band

 

...and here are some more images, showing spectrograms from the 2 hour long carrier transmission. A spectrogram is more common in the LF world maybe.
Amazing, the carrier reaches 25 dB in 424 uHz. Even in 3.8 mHz ('DFCW-600') it is still 'O copy'. The wideband spectrogram shows how vlfrx tools' filter curves look and how the hum and sferics are removed.

I calculated that the far field begins at just 30.4 km distance on that band. I'm not so far away...

73, Stefan


Am 02.06.2018 12:41, schrieb DK7FC:

Hello dear friends of the Ultra Low Frequencies,

I want to report about a short experiment i've done on thursday morning.

Early in the morning i placed my RX loop antenna (0.8m diameter, 84 turns, preamp) and an active E field antenna (now using a J310) in JN49KK03HQ . That's a distance of 11.8 km to the TX antenna, about 3x farer than the best distance crossed on that frequency so far, but still well into the near field.
For about two hours i transmitted a carrier on 1570.01 Hz followed by an EbNaut message (3 chars, 16K21A, CRC20, 6 sec/symbol). The ERP was just 90 nW.
This time the E field antenna was not sourrounded by trees. Although it was mounted just 2...3 m above the ground, reception in the E field was excellent. A spectrum peak integrating two hours of carrier transmission reaches > 30 dB SNR in 134 uHz, see attachment.

Unfortunately there was a bad contact on the BNC connector of the H field (problems of portable equipment which is built up and down several times | headless recorder, i.e. no chance to check if all works well) , but at least during a part of the EbNaut message it was working, so a comparison of the E and H performance is possible: The E-field SNR is about 15 dB higher than the H-field SNR. This is expected when using an E-field antenna in the near field to receive a signal radiated from an E-field antenna.
But it is not only propagation, it is also the lower hum components in the E field.

Another attachment shows the extraction, filtering and sferic blanking out of the recorded signal as well as the 3 character message decode, E field only.

This experiment was done just for fun, to check the equipment and to spend some hours in the nature :-)
Another one will be done very soon (today?), but then in the far field!

73, Stefan

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