Hello Markus, The FDTD analysis has been held up by the eclipse preparations (phase-stable VLF/LF transmitters and receivers). Back to normal tomorrow, and the FDTD diurnal should be done early next week. The dual-path data points by Stefan and yourself at 4470 Hz, and their relationship to your 3675 Hz and 8270 Hz data make me very eager for the FDTD results. 73, Jim AA5BW From: [email protected] [mailto:[email protected]] On Behalf Of Markus Vester
Sent: Monday, August 21, 2017 8:54 AM
To: [email protected]
Subject: Re: VLF: Carrier on 4470.005 Hz! - fieldstrength comparison Comparing the peaks again in 31 uHz after 9 hours of carrier accumulation, it looks like the level difference was only 7 to 8 dB, implying that the stated 2 dB propagation loss over 1/r is probably not true. The main source of error is the noise floor which is causing a significant uncertainty for amplitude measurements: Even for peak with 14 dB SNR ("five-sigma"), the standard deviation for the magnitude due to the in-phase noise component would be 1/5/sqrt(2) = 0.14, implying an uncertainty range of -3 to +2 dB at 95% confidence.
I also have some doubt now about my earlier result of +5.5 dB gain on 3675 Hz, which was based on a 8270 Hz reference, more than an octave away. The level of Stefan's peaks on 4470 and 3675 seemed to be quite similar, implying that the difference between path losses would not be more than the ~ 2 dB ERP difference.
Jim, any results yet from FDTD simulations of the 226 km W-E path?
73, Markus (DF6NM)
-----Ursprüngliche Mitteilung-----
Von: Markus Vester <[email protected]>
An: rsgb_lf_group <[email protected]>
Verschickt: So, 20. Aug 2017 21:34
Betreff: Re: VLF: Carrier on 4470.005 Hz! - fieldstrength comparison This test is going surprisingly well. producing beautiful twin peaks on 4470.005 and 4470.0025 on the DL0AO grabber. It looks like my signal is about 10 dB stronger there. Our antenna currents are similar today, but I guess the effective height and ERP are 5 to 6 dB higher at DK7FC. Thus propagation between Heidelberg and Amberg would be 13.5 - 5.5 -10 = -2 dB with reference to groundwave alone. This is somewhat surprising, given that a similar (but probably less reliable) calculation for 3675 Hz had indicated a +5.5 dB ionospheric gain.
All the best,
Markus (DF6NM)
-----Ursprüngliche Mitteilung--
Von: Markus Vester <[email protected]>
An: rsgb_lf_group <[email protected]>
Verschickt: So, 20. Aug 2017 15:37
Betreff: Re: VLF: Carrier on 4470.005 Hz! I have managed to resonate my antenna and started a carrier on 4470.0025 Hz since 13:07 UT. Antenna current is 0.16 A into 8 m effective height. Hope that it might also become visible on DL0AO, and perhaps provide an improved calibration reference for propagation from Heidelberg.
Best 73,
Markus
-----Ursprüngliche Mitteilung-----
Von: Markus Vester <[email protected]>
An: rsgb_lf_group <[email protected]>
Verschickt: So, 20. Aug 2017 11:11
Betreff: Re: VLF: Carrier on 4470.005 Hz! Hi Stefan,
this morning, an unambiguous peak has come up on the DL0AO cardioid in 31 uHz:
http://df6nm.bplaced.net/dl0ao/VLFgrabber/vlfgrabber_dl0ao_test.htm
The signal level (-140 dB) seems to be similar to that previously observed on 3675 Hz (noting that the gain of the synthetic cardioid summation has since been reduced by 6 dB to make it equal to the single antennas). We can probably hope for improved SNR during the day.
Well done again!
Best 73,
Markus (DF6NM)
-----Ursprüngliche Mitteilung-----
Von: DK7FC <[email protected]>
An: rsgb_lf_group <[email protected]>
Verschickt: Sa, 19. Aug 2017 15:01
Betreff: Re: VLF: Carrier on 4470.005 Hz! ...Rather 5 uW.
Am 19.08.2017 14:28, schrieb DK7FC: Hello VLF,
I un-wound the defective stack of the large coil which was used for 2970 Hz. It took about 4 hours to carefully unwound about 1000 turns, or about 1 km of wire. The wire will be used for new coils which are already planned.
Now, the remaining 4 stacks should hold at least 15 kV. I connected the coil to the antenna and found the resonance close to 4470 Hz.
Now i'm running (since 12 UTC) a carrier transmission on 4470.005 Hz. The antenna current is just 150 mA. That's an ERP of about 3 uW. A first signal on the 67 km band from here :-)
Let's see how long it holds until there is the next fault :-/
Reports/Spectrograms welcome...
As usual there is a monitoring of the signal in 3.5 km distance from my tree grabber: http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber2.html
73, Stefan
Am 13.08.2017 22:17, schrieb DK7FC: The repetition of yesterdays message failed. At 15:38 UTC the safety function tripped. I've just been on the roof, when re-starting the transmission i can see a spark in the center of one of the stacks. So now there is another one which has a flash over! :-(
It must be replaced, which is a lot of work. So the tranmissions on 3675 Hz will stopp for some time. At least we have some carrier detections and even EbNaut decodes.
I need to think about a different coil concept.... More current, more voltage, more power, more more more! |
|
