A very high low noise antenna

Useful information regarding antennas for SDR products.
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ernestyn
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Joined: Mon Jul 22, 2019 1:40 pm

A very high low noise antenna

Post by ernestyn » Mon Jul 22, 2019 2:41 pm

I have been following this forum for some time because I am interested in noise and antenna noise reduction technical and have found many interesting articles here. Especially the miniwhip and the special low noise whip described here are very interesting because they give good performance in small size so big antennas requiring a lot of space are not required any more. This is important because with sdr or other pencil type receivers it is possible to have miniature systems that can go anywhere. I think that all the posts here do not consider capacitance tap antennas that have been researched intensively in the last times. Yes, the conventional PA0rdt can be conceived like a capacitive tap capturing the electric field of the free space, but following the recent works of many scientists I have found it is possible to capture signals with general capacitive coupling, see for example the works of prof. Y.Zrhforooshand A.Siahcheshm of Azad University, Iran: one of the articles is: ULTRA WIDEBAND MONOPOLE ANTENNA BY A CAPACJTIVE COUPLING FEED WITH DOUBLE BAND NOTCH FUNCTION.

Here we have the concepts of small size, low noise, ULTRA wide bandwidth all obtained by the novel idea of the capacitive coupling conception. In fact it is very strange that, since the invention of the radio, attention was always concentrated on very big antennas, therefore mostly inductive, and little or no attention was concentrated on its analogue, or capacitive. As far as I know, only a German Scientist, during the second world war, Dr. Von Blumenthal (see "directory of deported German scientific personnel" - Springer & Verlach - Berlin - 1981) was pioneering this novel concept. He was an assistant, in early years, of distinguished Russian Dr. Popoff, by many believed to be the real inventor of radio. I could now mention Tesla, the genius, but we would digress too far.

I now wish to describe here my experiments and results with integrated Capacitive coupling in the course of next articles, but I invite others to share they experience if they also read and thought about novel antenna tecnics.
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ernestyn
Posts: 14
Joined: Mon Jul 22, 2019 1:40 pm

Re: A very high low noise antenna

Post by ernestyn » Tue Jul 23, 2019 7:25 pm

I wanted to correct my post, but I am not able to do it, so I correct here as the names of the Scientist are : Dr. Zehforoosh Y. And Dr. Siahcheshm. Sorry for that. I also wish to exchange information with Mr. Mike2459 and hope he replies, as his smallest antenna he wrote data e.g. special old transistors, but I do not see any more. Next I wish to explain capacitive sensors, as for body interaction
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ernestyn
Posts: 14
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Re: A very high low noise antenna

Post by ernestyn » Sat Aug 03, 2019 1:00 pm

What is capacitive sensor ?

it is sensor that measure changes in capacitance between a sensor antenna and its surrounding. It has 3 mode Loading Mode, Transmit Mode, Shunt Mode.

https://ichickii.wordpress.com/2014/02/ ... teraction/
I didn't design a miniwhip, I've built two, one based on PA0RDT's design the second from a design used by PA3WFM at the University of Twente. I used a vintage Motorola 2N5160 UHF transistor in place of the BFQ149 and a SMD type J310 as the input FET. (I couldn't find any BFQ149's.)
The performance of both antennas are about the same. The purpose of building the 2nd was to achieve better IMD performance, it does pretty well in that respect as long as the supply voltage can be maintained at 12 volts at the antenna.
In the antenna described in the post by Mike2459 and modified by him we see an example of a simplest capacitor antenna which couples to the aethereal electric field of space. This was obtained using vintage UHF transistor and these properties perhaps cannot be reproduced. However, by changing the form of the the capacitor theory ensures it is possible to better couple to gain more electricity good without getting electricity bad which noise is. And this can be obtained by devising an omopolar surface suspended on space. I am studying special omopolar forms as suggested by Dr. Y. Zehforoosh in his article "CALCULATING OMOPOLAR SURFACES FOR FIELD CAPTURE ENHANCEMENT" and will propose a new antenna type.
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ernestyn
Posts: 14
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Re: A very high low noise antenna

Post by ernestyn » Sat Aug 10, 2019 5:08 pm

The design principles of a capacitor antenna are based on the capacitor equation in free space where the capture cell is immersed in the static electric field. When the field is perturbed by radio waves the cell charges with an instantaneous variable voltage which then must go to the receiver. In the first approximation the most larger the cell the higher the voltage and the higher the sensitivity, but by the discovery of prof. Y. Zehforoosh and others the shape and electrical profile of the cell determine the noise rejection of the device. I am experimenting on different mathematical shapes to get the besf performance in noise. Also the wideband can be obtained by using more sensors with calculated distances and complementary omopolar shapes. I will sbow some results soon, now that has been explained the stylus antenna in the other post cannot work
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