Goodluck Buy Antenna Warning! Bluetooth Micro Build - Help Needed

Well I guess they call themselves, 'Goodluck Buy', for a reason. Unfortunately I was out of luck, I bought two 433mhz antennas in the hope they would improve my range/rssi. Infact, they smoked my air module. 

The lengths appear all wrong, and the resistance is far to low (20 ohms). Is it possible to solder more wire onto the active element to tune them or is it better to throw them? 

The good news, is that my micro radio bridge works superbly and supports both USB and Bluetooth modes through the side switch. 

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How did you measured "resistance"?

You shouldn't smoke module even if you'll connect simple piece of wire (of course if it not shorts antenna pin to ground)...

Hi Marcin, I measured the outer brass case to the center element. Any ideas why my RSSI is so low?

1. In RF we're talking about impedance, not resistance.

2. You can't measure it this way.

3. I'm afraid you should have around infinity during this kind of measurement for this type of antenna.

4. There's short inside this antenna (fancy why it's 20 ohms, not around zero).

My advice: put it into bin...

Ok thanks, back to the drawing board!

Just a note on the Goodluck buy guys on ebay.  They run under several names in fact. And yeah, their stuff and their service or shipping is hit or miss. I have dealt with them a few times. I am with Marcin Karawczyk on this one.

Hi Sen, any idea what the lengths for this antenna ( the long wire) should be? I want to try and fix them rather than buy another set.

Cheers, Chris

I suggest you to investigate why you have only 20ohms between contacts in SMA plug. This can damage your radio. Then you should google for monopole antenna calculator.

Take a look at http://blog.solidremote.com/post/rf-module-external-antenna-design....

Chris,

I'm making my antennas from pieces of coax cable salvaged from dillapidated laptops. The ones running to the WiFi antennas on the top lid above the screen.

I'm running my telemetry in 868MHz, and my quarter wavelength is 82mm. So I just cut a 167mm length of said cable, strip 3 mm from both outer and inner conductor to solder on the radio module (less connectors that can rip in a crash) and from the remaining 164mm I strip the outer insulation and shield on 82mm. Then I add some heatshrink over it to straighten and harden it, and let it dangle from the craft.

It works really well. I've had a radio-loss RTL from behind a line of trees once, but telemetry was still solid.

Your working with 433MHz will double all the sizes and will yeld a pretty long antenna, but it's doable, and unless it hinders some 360-deg pan camera it won't feel like a PITA.

Cheers para, ill have a look for some micro coax, it looks like 34cm in length for 433mhz, that sound about right?

Ill first try and add about 24cm of wire to this one, check out the rssi and if that fails, build your design.

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