From: "Clemens Paul" <cpaul@gmx.net>
To: <rsgb_lf_group@blacksheep.org>
References: <5CADE53C.30201@posteo.de> <e0ba3e0c-ea1e-4858-1291-c88dbd0d69f4@aeritel.com> <b94b2f43-2d07-1128-3066-3be4c72cbf62@kabelmail.de>
In-Reply-To: <b94b2f43-2d07-1128-3066-3be4c72cbf62@kabelmail.de>
Date: Fri, 19 Apr 2019 17:28:05 +0200
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Subject: RE: LF: NEW VLF antenna
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Hi Tom,

interesting experiment!
Do you think it is possible for a more true comparison to compare the quartz resonated wire antenna 
against he same wire resonated conventionally by an inductor regarding field strength and 3dB BW?

73
Clemens
DL4RAJ 

>-----Original Message-----
>From: owner-rsgb_lf_group@blacksheep.org 
>[mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of DK1IS
>Sent: Thursday, April 18, 2019 7:31 PM
>To: rsgb_lf_group@blacksheep.org; rsgb-lf-group@groups.io
>Subject: Re: LF: NEW VLF antenna
>
>Am 18.04.2019 um 16:11 schrieb info@aeritel.com:
>
>
>	Hallo,
>	
>
>	
>https://incompliancemag.com/creating-a-novel-compact-antenna-th
>at-can-go-where-radios-cant/
>
>	Friends are there any news? Home made new antenna??
>
>	
>	
>
>	'73 from Richard - IK7FMO
>	
>
>	
>	
>
>Hi group,
>
>
>a little bit OT, but the public interest seems to rise ;-)! At 
>April 15, Roman, RW3ADB, pointed out here a similar article 
>leading to a more detailled link: 
>
>https://www.nature.com/articles/s41467-019-09680-2 
><https://www.nature.com/articles/s41467-019-09680-2> . 
>
>The paper describes a kind of matching a low source impedance 
>to a very high load impedance by using a piezoelectric 
>resonator. Thus it is possible to feed an extremely short 
>antenna with a very high voltage in resonance without using 
>lossy L-C-circuits, resulting in a relatively "high" antenna 
>current. Of course such a system has a very small bandwidth 
>and is frequency-wise very sensitive to stray capacitances at 
>the high-impedance side. The authors turn this to an advantage 
>with regard to a fast capacitve re-tuning when using it in DAM 
>systems (Direct Antenna Modulation). A second problem is that 
>the crystal has to stand voltages in the 100 kV range which is 
>impossible for commercially available quartz resonators. 
>Therefore the authors use a special lithium niobat crystal at 
>about 35 kHz with 94 mm length which is mounted in a chamber 
>filled with hexafluoroethane gas - not so easy for a normal ham ...
>
>
>Anyway, the idea is fascinating. Having no VLF crystals up to 
>now, I made some preliminary tests with a randomly available 
>HC-6-U quartz, QRG 2434 kHz, wavelength 123 m. And yes, it works!
>
>
>*	TX: Sythesizer Schomandl MG100M, 300 Hz ... 100 MHz, 
>smallest step 0.1 Hz, Ri = 50 Ohms, P = 10 dBm, output tied to 
>first leg of quartz, alternatively direct to the antenna wire
>	
>*	RX: Perseus SDR with an active rod antenna on my 
>garage, fed by a solar system, no external wire connections, 
>air-line distance 100 m to my shack
>*	Antena wire: 2 m or 4 m, laid out in the shack, tied to 
>second leg of quartz, alternatively direct to the TX output 
>	
>
>Results with 2 m antenna wire:
>
>*	with quartz resonator: fres = 2,433,908.8 Hz, RX level 
>at resonance = - 63,1 dBm, - 3dB-bandwidth = 48.3 Hz resulting 
>in Q = 50391
>*	without quartz resonator: RX level = - 85,4 dBm 
>resulting in a gain of 22.3 dB with quartz
>*	comparision: my 13 m T-Marconi with top load 4 x 33 m, 
>tuned to 2434 kHz and fed by the synthesizer with 10 dBm 
>results in a RX level of - 32.1 dBm ;-)
>
>Results with 4 m antenna wire:
>
>*	with Quartz resonator: fres = 2,433,773.6 Hz, RX level 
>at resonance = - 59 dBm. - 3 dB-bandwidth = 49.4 Hz resulting 
>in Q = 49376
>*	without quartz resonator: RX level = - 75.4 dBm 
>resulting in a gain of 16.4 dB with quartz
>
>So it seems the best effects can really be achieved with very 
>short antenna wires. The long range performance is in no way 
>comparable with more fullsized antennas but for special 
>applicatios the features could be interesting. For instance 
>realising some capacitive feedback from the vicinity of the 
>antenna rod could result in a small low power beacon with 
>integrated matching - it even could be used as a presence 
>detector with direkt frequency read out ... 
>
>
>- But yes, Rik, I`ll certainly will keep my Marconi - making 
>QSOs on VLF costs enough efforts even when using a big 
>antenna. But I´ve alredy orderd some VLF crystals on the bay ...
>
>73 es Happy Easter!
>
>Tom, DK1IS
>
>
>
> 
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