How to build external megasized horn ???

[teeto]

I'd like to see if an supersized radar horn will have any effect on performance. I'd assume it would but I'd like to goof around and find out.

Does a horn have to be made out of any certain metal??

Is the purpose of a horn to collect and condense the signal into the tip?


If I extended the factory horn on the same vector(s) and made the "new" horn to be a shoe box sized opening will it work ?

[teeto]

Similar to the Spectre 4 but MUCH LARGER.

[MetalFlame]

You don't need to build mega size horn extension to gain dB's.
You can use metal,inox or carbon fibre to build one.But don't expect 25db gain,because each horn extension must be calculated for the exact type/brand of RD.In EU this extensions cost around 80 to 100€
Here is horn extension for Bel975r with 25dB gain.It is only 8cm long,7cm wide and 5cm tall.I posted this link just to show you a picture,but if you are serious about building one yourself,then translate the page to learn more about this.

http://todoradares.com/web2007/conos/hdr.php

BTW,check www.Flitsservice.nl for more info about this.Two of the Flitsservice guys (Enerby and Dr.Q) have sucesfully build GREAT horn extensions and RDD filters for Target966EVO;Bel915 and Bel975r
RadarRoy tested theirs RDD filter see results: http://www.radarbusters.com/rddfiltersarticle.cfm
and http://www.flitsservice.nl/cm_php/main_repo.php?id=2354

[MEM-TEK]

Yes, it would work.

The easiest material to work with is thin sheet aluminum. Most hardware stores sell aluminum flashing or rolls of thin sheet aluminum for flashing on roofs. Aluminum duct tape works quite well for taping together your giant radar horn.

For the new horn's side walls, use the same angles as the side walls of the RD's horn -- usually 15 degrees. For the top and bottom walls, make sure that the difference in their angles is no greater than 20 degrees. For example, if the top wall has an angle of +5 degrees and the bottom wall has an angle of -15 degrees, the difference between the two is 20 degrees.

Design your horn such that its rear exit is approximately 1/4 inch larger than the front dimensions of the original RD horn. This way you can easily position the RD behind the horn extension and know that all of the RD's horn is definitely within the exit aperture of the giant horn extension. Alternatively, you can design the horn extension such that it perfectly mates with the front of the RD's horn and is taped in place using aluminum duct tape.

I tried the same idea around 20 years ago, and it definitely works!

--Michael

[MetalFlame]

MEM-TEK,I didn't say it can't be done.I did build one for my RX-65.
I did it just for kicks,I wasn't going for 20dB or more,when I build mine.
I just wanted to see if it would work and
I used the same "philosophy" as you described,to match RX-65 horn angles.

BUT,this isn't so simple as it looks.To get 25dB,it must be precisely calculated and built.For Bel975r there are 2 different horn extension.Why?Because Beltronics made some minor changes in Bel975r circuits.They didn't change horn design or improve performance or some major tweaks.They just made Bel975r according to RoSH standard.Now there's two horn extensions for 975r.One for non-RoSH and another for RoSH 975r.

Here take a look at "cloned" horn extension.Same dimensions like original,but you won't see 20 or more dB's with that.
http://todoradares.com/web2007/conos/imitaciones.php

[MEM-TEK]

MEM-TEK,I didn't say it can't be done.I did build one for my RX-65.
I did it just for kicks,I wasn't going for 20dB or more,when I build mine.
I just wanted to see if it would work and
I used the same "philosophy" as you described,to match RX-65 horn angles.

BUT,this isn't so simple as it looks.To get 25dB,it must be precisely calculated and built.For Bel975r there are 2 different horn extension.Why?Because Beltronics made some minor changes in Bel975r circuits.They didn't change horn design or improve performance or some major tweaks.They just made Bel975r according to RoSH standard.Now there's two horn extensions for 975r.One for non-RoSH and another for RoSH 975r.

Here take a look at "cloned" horn extension.Same dimensions like original,but you won't see 20 or more dB's with that.
http://todoradares.com/web2007/conos/imitaciones.php

Hi MetalFlame,

If the horn design didn't change at all between the non-RoHS and RoHS 975R models, then there was no need to change the horn extension design at all -- unless it was discovered that the newer horn extension design produced a higher gain. Since both the non-RoHS and RoHS 975R models share the same FCC ID, this means that the actual horn and LO board/microstrip antenna design didn't change at all.

Once you use a horn extension which extends past twice the length of the original horn's wave guide, then there really is nothing all that critical about the horn extension design except possibly for matching the horizontal width of the horn to be a multiple of the wavelength for whichever radar frequency on which you desire the most gain. Even that isn't really critical once the horn extension's width exceeds twice the 1.1 inch wavelength of X band radar since K and Ka radar are on much shorter wavelengths.

A crude calculation of the horn extension's gain, based on the area of its entrance aperture compared to the area of the RD horn's entrance aperture, will be within 3dBm of the theoretical gain -- assuming that you fairly closely match the angles of the RD's horn and that the length of the horn extension is at least twice the length of the waveguide(s) within the RD's horn.

It is not rocket science. I built several horn extensions for various radar detectors around 20 years ago, and all were very effective with gains which closely matched my calculations. Yet the companies producing these horn extensions would have you believe that the design of the horn extension is very critical. It isn't as long as the horn extension's length is at least twice the length of the waveguide(s) within the RD's horn, as long as the difference in the angles of the extension's side walls do not exceed 30 degrees, and as long as the difference in the extension's top and bottom walls do not exceed 20 degrees. Note that I am assuming that the RD's horn is horizontally polarized with vertical wave guide(s).

[MetalFlame]

MEM-TEK,if you have a lot experiences with building horn extensions,then it would be a very good idea to build one for specific RD and send to MikeB. for laboratory testing to see how much -dB you'd get.I am pretty sure,that if you make a good one,a lot of people would like to have it.So this is your chance to contribute to our community and make some $$$ on the way.I think this is by far better idea,then yours was...you know.. trying to buy RDs from Canadian police and sell it on E-Bay :wink: J/k
Anyways,that's how it should look

http://www.flitsservice.nl/shop/images/Qplus1.jpg

[MEM-TEK]

...I think this is by far better idea,then yours was...you know.. trying to buy RDs from Canadian police and sell it on E-Bay :wink: J/k ...

Yep, building a radar horn extension is definitely a better idea than that "other" idea I had a few months back!

[Harold]

you mean like this:



and yes, it works.

[mimo]

anyone want to sell one?