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Total 133 documents matching your query.

1. Re: LF: ELF communications ? (score: 1)
Author: Dimitrios Tsifakis <>
Date: Tue, 2 Dec 2014 07:19:16 +1100
Hi Stefan, Have you done any more tests with this? I am curious to see the results. Would this idea work on VLF as well? I have come across some power toroid transformers that have a reasonablywide u
/rsgb_lf_group-archives/html/rsgb_lf_group/2014-12/msg00022.html (9,665 bytes)

2. Re: LF: ELF communications ? (score: 1)
Author: Dimitrios Tsifakis <>
Date: Tue, 2 Dec 2014 09:12:47 +1100
Hi Stefan, it's always worth giving it a try! There are people that use toroid power transformers as valve/tube output transformers. So don't disregard them for audio use! I agree that the efficiency
/rsgb_lf_group-archives/html/rsgb_lf_group/2014-12/msg00025.html (12,333 bytes)

3. LF: Japan on 475 kHz. (score: 1)
Author: Dimitrios Tsifakis <>
Date: Sun, 21 Dec 2014 10:26:15 +1100
Hello group, I have received an email from a friend in Japan informing me that Japanese amateurs gain access to 630 m from 05/Jan/2015. There are some restrictions on power and vicinity to other hous
/rsgb_lf_group-archives/html/rsgb_lf_group/2014-12/msg00188.html (9,581 bytes)

4. Re: LF: RE: Japan on 475 kHz. (score: 1)
Author: Dimitrios Tsifakis <>
Date: Mon, 22 Dec 2014 10:57:44 +1100
Hi Hideho san, Thank you for the update. I am glad to hear that even though you have all these tough restrictions, Japanese amateurs are planning portable operations in the new band! I have not heard
/rsgb_lf_group-archives/html/rsgb_lf_group/2014-12/msg00207.html (11,962 bytes)

5. Re: LF: RE: Japan on 475 kHz. (score: 1)
Author: Dimitrios Tsifakis <>
Date: Tue, 23 Dec 2014 12:58:02 +1100
Hi Hideho san, In Australia, for frequencies below 30 MHz we need to reduce our harmonics by the lesser of: 1) 43 db + 10*log(PEP) 2) 50 dB where PEP is peak power to the antenna. When I was allocate
/rsgb_lf_group-archives/html/rsgb_lf_group/2014-12/msg00226.html (12,152 bytes)

6. Re: LF: RE: Japan on 475 kHz. (score: 1)
Author: Dimitrios Tsifakis <>
Date: Tue, 23 Dec 2014 15:46:30 +1100
Hi Hideo san, On VHF and higher frequencies, the harmonics need to be -70 dBc. Conceivably, a 50 MHz transmitter harmonic could land on an FM BC station's frequency so this is the same problem as whe
/rsgb_lf_group-archives/html/rsgb_lf_group/2014-12/msg00229.html (13,547 bytes)

7. Re: LF: questions about a tx square loop fpr 470KHz (score: 1)
Author: Dimitrios Tsifakis <>
Date: Mon, 4 May 2015 13:56:48 +1000
Buongiorno Mauro, a few months ago, I build a single turn loop, 0.7 m by 0.7 m, using very thick electrical copper wire. I resonated it on 160 m using a couple of beefy silver mica capacitors in para
/rsgb_lf_group-archives/html/rsgb_lf_group/2015-05/msg00018.html (12,784 bytes)

8. Re: LF: 136kHz in VK / ZL? (score: 1)
Author: Dimitrios Tsifakis <>
Date: Mon, 11 May 2015 07:38:50 +1000
Hi Mike, we never had a 185 kHz band in OZ. From memory, many years ago, some individuals got scientific licences and did some experiments there, but it was never an open-to-everyone band. We do have
/rsgb_lf_group-archives/html/rsgb_lf_group/2015-05/msg00048.html (10,970 bytes)

9. Re: LF: MF propagation over sea water (score: 1)
Author: Dimitrios Tsifakis <>
Date: Thu, 18 Jun 2015 11:53:40 +1000
Hi Stefan, Maybe the ground-wave propagation curves in this ITU document shed some light? In this document there are curves for sea water (various salinity levels), fresh water and land (various cond
/rsgb_lf_group-archives/html/rsgb_lf_group/2015-06/msg00111.html (11,015 bytes)

10. Re: LF: 476.181 kHz from indoor loop (score: 1)
Author: Dimitrios Tsifakis <>
Date: Thu, 25 Jun 2015 11:38:45 +1000
Hi Markus, very nice experiment! I did something similar some time ago: http://people.physics.anu.edu.au/~dxt103/472/small_loop/ I would like now to make a larger loop using a 20m thick coaxial cable
/rsgb_lf_group-archives/html/rsgb_lf_group/2015-06/msg00139.html (14,893 bytes)

11. Re: LF: QRSS/DFCW transmission with a Raspberry Pi (score: 1)
Author: Dimitrios Tsifakis <>
Date: Fri, 9 Oct 2015 11:24:08 +1100
Hi Stefan, if there is nothing else out there, I would be happy to write a simple c program to do this... 73, Dimitris VK2COW
/rsgb_lf_group-archives/html/rsgb_lf_group/2015-10/msg00075.html (11,305 bytes)

12. Re: LF: QRSS/DFCW transmission with a Raspberry Pi (score: 1)
Author: Dimitrios Tsifakis <>
Date: Sat, 10 Oct 2015 11:21:16 +1100
Hi Stefan, new callsign and new QTH indeed. I am now outside the city, the nearest house is about 300m away from mine. I also have some space, about 20 hectares, so expect more traffic on LF/MF :-) O
/rsgb_lf_group-archives/html/rsgb_lf_group/2015-10/msg00085.html (13,414 bytes)

13. Re: LF: QRSS/DFCW transmission with a Raspberry Pi (score: 1)
Author: Dimitrios Tsifakis <>
Date: Sun, 11 Oct 2015 07:58:48 +1100
Hi Stefan, all your good suggestions noted! Hmm, that's about 2 km of wire, my place is not big enough, but the people around me seem to be quite friendly, so I guess it's possible. What sort of wire
/rsgb_lf_group-archives/html/rsgb_lf_group/2015-10/msg00091.html (13,188 bytes)

14. Re: LF: QRSS/DFCW transmission with a Raspberry Pi (score: 1)
Author: Dimitrios Tsifakis <>
Date: Sun, 11 Oct 2015 16:46:50 +1100
Hi Stefan, By chance, and after I picker the COW callsign, I discovered that the QTH locator is the appropriate QF44ox :-) There is a lot to consider. I am still unpacking boxes here, so I have been
/rsgb_lf_group-archives/html/rsgb_lf_group/2015-10/msg00095.html (13,404 bytes)

15. Re: LF: Beverage on LF/MF (score: 1)
Author: Dimitrios Tsifakis <>
Date: Mon, 12 Oct 2015 16:06:14 +1100
Hi Alex, very interesting, thanks for your information. The challenges in my case would be keeping the kangaroos, wallabies and wombats away from the wires, but at least the temperatures are a bit mo
/rsgb_lf_group-archives/html/rsgb_lf_group/2015-10/msg00116.html (11,212 bytes)

16. Re: LF: Valve LF amps and tank coil size / voltage rating? (score: 1)
Author: Dimitrios Tsifakis <>
Date: Mon, 16 Nov 2015 09:22:14 +1100
If this is of any use to anyone, I have made a simple online calculator: http://people.physics.anu.edu.au/~dxt103/calculators/toroid.php 73, Dimitris VK2COW
/rsgb_lf_group-archives/html/rsgb_lf_group/2015-11/msg00352.html (13,320 bytes)

17. Re: LF: VLF in VO (score: 1)
Author: Dimitrios Tsifakis <>
Date: Mon, 21 Dec 2015 09:21:03 +1100
Hi Joe, thanks for sharing your experiment details. I have been doing similar tests on VLF, using about 120 m of wire, about 10 m of the ground. I have used initially much less power, so signals disa
/rsgb_lf_group-archives/html/rsgb_lf_group/2015-12/msg00362.html (12,584 bytes)

18. LF: a lot of ferrite (score: 1)
Author: Dimitrios Tsifakis <>
Date: Sat, 12 Jan 2019 14:48:40 +1100
Hi LF group, I have managed to acquire a few very large ferrite rods (36 cm x 10 cm x 2 cm). The material is unknown but I managed to form a square 'toroid' with four of them (they are heavy so gravi
/rsgb_lf_group-archives/html/rsgb_lf_group/2019-01/msg00098.html (9,052 bytes)

19. LF: Re: a lot of ferrite (score: 1)
Author: Dimitrios Tsifakis <>
Date: Sat, 12 Jan 2019 15:03:13 +1100
Minor correction, the calculated relative permeability should be about 500, I made a mistake in the initial calculation. I just discover why they call it initial permeability (bad joke) :-) 73, Dimit
/rsgb_lf_group-archives/html/rsgb_lf_group/2019-01/msg00099.html (10,235 bytes)

20. Re: LF: RE: Re: a lot of ferrite (score: 1)
Author: Dimitrios Tsifakis <>
Date: Sun, 13 Jan 2019 06:55:10 +1100
Hi Clemens, the mistake I made the first time was that I incorrectly set the ID/OD difference of the equivalent ring to be 2 cm instead of 4... 73, Dimitris VK2COW
/rsgb_lf_group-archives/html/rsgb_lf_group/2019-01/msg00117.html (13,298 bytes)


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