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: [email protected]
>[mailto:[email protected]] On Behalf Of DK1IS
>Sent: Thursday, April 18, 2019 7:31 PM
>To: [email protected]; [email protected]
>Subject: Re: LF: NEW VLF antenna
>
>Am 18.04.2019 um 16:11 schrieb [email protected]:
>
>
> 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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