new active antenna with bootstrapping of the SFET to minimize the input capacitance

At v(out)? Change R9 to 1 meg and it will be even less!

A 50 ohm source driving a jfet follower makes for poor power transfer. People tune antenna front ends to get better s/n, although atmospheric noise usually swamps everything else.

--

John Larkin      Highland Technology, Inc 

The best designs are necessarily accidental.

Am 27.12.2020 um 17:16 schrieb snipped-for-privacy@highlandsniptechnology.com:

You are kidding.

I guess You don't know the theory of active antenna. Active antenne will be designed by noise-matching ...

Theory of active Antenna:

... sorry, I have no translation of it ...

:)

Am 27.12.20 um 17:16 schrieb snipped-for-privacy@highlandsniptechnology.com:

This has been in de.sci.elctronics already ad nauseam. The context is _short_ groundplane antennas, optionally w/o ground plane.

The fault is first, that everything in the world can be explained by LTspice.

2nd, measurements don't count and are superfluous, and 3rd, getting models that resemble reality is not needed.

One such assumption is that 15 cm of wire over a ground plane is broadband like 50 Ohms in series with 18 pF. Nothing could be more wrong, esp. over the simulated frequency range.

Just imagine the noise of the 2Meg at the gate. It would need to be shorted through a low impedance antenna or determine the noise.

18 pF against the universe won't do that.

Enough from that.

Is here anybody who understands the HP8970B noise figure meter? I feel quite lost and the handbook cares more about special cases like plotting F(f) on a xy scope for a frequency-converting DUT. I just want F at 432 MHz.

Gerhard

regards

:)

Not at all. The bigger R9, the lower the output noise. It even reduces the atmospheric noise.

--

John Larkin      Highland Technology, Inc 

The best designs are necessarily accidental.

Easier to just turn power off.

This should read 2.7 GHz

You do not care about power transfer. You care about S/N ratio.

With a 50 ohm source, you can use a step-up transformer at the input to improve S/N.

Atmospheric noise dies out around 20 - 30MHz. See

It has little effect on 6 meters (50MHz) and almost none on the FM bands.

You are really interested in low noise on the FM and cellular frequencies.

Quote:

The actual frequencies used by smartphones varies by country and by carrier. In the United States, there are the four major frequency bands in use:

698-806 MHz (700 MHz Band) 806-849/851-896 MHz (800 MHz Band) 1850-1910/1930-1990 MHz (PCS Band)

The wide bandwidth of the circuit is useful for instrumentation but makes it susceptable to low frequency atmospheric noise for reception. However the use of small SMD antennas makes the low input noise desirable.

--
The best designs occur in the theta state. - sw

Which seems like an e-field probe to me. The antenna might look like

18 pF. But as you say, not 18 pF in series with 50 ohms.

This looks like a good place for paralleled jfets or phemts, then a step-up transformer.

--

John Larkin      Highland Technology, Inc 

The best designs are necessarily accidental.

Am 27.12.2020 um 18:33 schrieb snipped-for-privacy@highlandsniptechnology.com:

R9=39.8 Ohm is the correct additional resistor for power-matching to the

50 Ohm-receiver-input or coax-cable.

Am 27.12.2020 um 09:12 schrieb Leo Baumann:

This active antenne in combination with a very short ground-plane shall work between 10 kHz and 30..100 MHz

The passive antenna is matched to the 1.73 nV/sqrt(Hz) of the electronic. The gain is -6 dB, but it is regardless of which, about -6 to +6 dB.

regards

It throws away half the signal. If the coax is end terminated, why source terminate too?

--

John Larkin      Highland Technology, Inc 

The best designs are necessarily accidental.

Am 27.12.2020 um 21:32 schrieb snipped-for-privacy@highlandsniptechnology.com:

Maybe the coax-cable is long, so it is necessary.

regards

regards

Makes no sense. There will be no reflection from an end termination, no matter how long the cable.

At the source end, an end-terminated coax looks like a 50 ohm resistor.

--

John Larkin      Highland Technology, Inc 

The best designs are necessarily accidental.

Is that a non-metallic roof? Noise from house wiring will be big, and those dinky radials won't help much.

--

John Larkin      Highland Technology, Inc 

The best designs are necessarily accidental.

Am 27.12.2020 um 21:56 schrieb snipped-for-privacy@highlandsniptechnology.com:

If You don't match to the coax-cable at the source, the crazy source-impedanz will be transformed to the end of the cable and then You have a totally wrong match at the end.

:)

Am 27.12.2020 um 21:59 schrieb snipped-for-privacy@highlandsniptechnology.com:

Well, Who has a metallic roof?

The radials stabilize the antenna-characteristic.

:)

One can get a usable English translation by pointing Google Translate at .

It may be useful to used Google Chrome for this, but Firefox also works. (MSIE and MS Edge not tried.) Go to Google Translate and point it at the pdf on your computer.

Joe Gwinn

Am 27.12.2020 um 23:07 schrieb Joe Gwinn:

I tried this, but the translation is bad with this pdf-file.

We do in Truckee. It won't rot or burn, and the snow slides right off.

At HF frequencies, probably not. They just reduce the e-field that you want.

--

John Larkin      Highland Technology, Inc 

The best designs are necessarily accidental.