rf distance measurement (2023 Update)

The company was Martin Communications, who did a wide range of interesting projects, including sat-phones (too many projects, perhaps, not enough focus to get any one of them to go big-time). Very reputable crowd.

You are welcome to speak with Bruce, who can describe the system in detail - he wrote the DSP code for it (on Blackfin chips, I believe). Email me privately and I'll give you his phone#.

If I recall correctly the transducers were in the 60-80Khz range. The huge dish gave them massive gain, or it wouldn't have worked. The system was extensively tested out at Tullamarine Airport, but never sold commercially.

Clifford Heath

You are still top-posting. Try to compose your responses so that your text follows the text you are responding to, so that somebody reading the text has read what you are responding to before they start reading your response.

It shouldn't. The wavelength of a 5GHz electromagnetic wave in air is about 6 cm, a bit over two inches. The device has to work by measuring phase shift, and you can do that pretty precisely if you are careful. 1/16 inch is 2.6% of the wavelength at 5GHz, but 0.26% of the wavelength at 500MHz, and 0.05% at 100MHz, all of which are attainable.

Processing 5GHz signals is an expensive pain. Lower frequency signal are easier to cope with.

On a sunny day (Sat, 10 Sep 2022 10:13:56 -0700) it happened snipped-for-privacy@highlandsniptechnology.com wrote in snipped-for-privacy@4ax.com:

Right, and I could even hear if the 15625 Hz was in sync, Same loss of very high frequencies here, tried it a few month ago with the signal generator and Sennheiser headphones, But then I played "jojo left his home in Tucson Arizona" at eehh "reasobale" volume here few days ago and the percussion came out really well on the 200 W stage amplifier and piezos for the high frequency part. So that was cool. Was a Beatle fan ,,

The use of an active reflector (with a.g.c) is nice, since the received signal is proportional to the inverse of 2nd power of distance. With passive reflections, the Rx power is proportional to inverse 4th power of distance, making long distances impractical.

How about a 10 GHz GunPlexer used in door openers ?

These are Doppler devices with a difference in the audio range for slow movement. If you frequency modulate the Tx with a linear ramp, the received signal frequency offset is directly proportional to distance.

The laser range finder from Harbor Freight (Ames Laser Distance Meter, 100ft) has a STM8L052 8 bit microcontroller, a dual 10mc op amp and MS5351M clock generator with a 200mc max output. The clock generator seems to fit the device into the frequency modulation method you mention.

Hul

snipped-for-privacy@downunder.com wrote:

Clifford Heath wrote: ================ >>

** But YOU are not. ** Absorption about 2dB per METER in dry air. ** 2.5m is tiny.

** You have no clue if or how.

And you did not answer point, at all. I do not believe in fairy tales. ======================

Le 09/09/2022 à 00:39, Hul Tytus a écrit :

Look at the design of radio altimeters. Use of directional aerials on the source or/and the target can improve performances a lot.