I’ve been using the WRL-00705 from Sparkfun with great success. Range is far more than I need for my application (I need about 100 - 200’, indoor, line of sight).
But, if I could get away without a whip antenna, that would be even nicer. Currently, the SMA connector protrudes from a 24" x 2.5" x 2.5" acrylic box. If I could keep the antenna inside the box, I could eliminate the possibility of damage to the connector if the box gets dropped, etc. Not to mention user’s loose the antenna + extra cost of SMA connector and external antenna can be eliminated.
So, I bought the SRL-00691. Not sure how much range I’ll loose with the chip antenna, and I really can’t find a place to mount it in the box that isn’t “shadowed” by a 20" x 3/4" x 1/8" aluminum strip. So, I want to try using a wire antenna, mounting on an inside corner of the acrylic box.
Can I just remove the chip antenna and solder a wire for an antenna? How long should the wire be? Can I expect range comparable to the whip antenna, if I use the same length? Will the acrylic box antenuate the signal significantly?
Try a 1/4 wavelength. It won’t be very well matched to the output, but it should work. 5/8 would be best, as it’s matched by the bottom 1/4 wave section. The box won’t have much effect on the signal. The wire needs to be straight, of course.
leon_heller:
5/8 would be best, as it’s matched by the bottom 1/4 wave section. The box won’t have much effect on the signal. The wire needs to be straight, of course.
I don’t understand this part, are you saying using 5/8 wavelength would be better than 1/4 wavelength? What do you mean by “as it’s matched by the bottom 1/4 wave section”? Are you saying leave the chip antenna on the WRL-00705 and solder the wire to the end of that?
If my math is right, full wavelength at 2.4 Ghz is 12.5 cm. So, there is no constraint on length, up to 20" or more.
Will close proximity to the acrylic change the velocity and length I should use?
You have to remove the chip antenna if you want to attach a wire one, of course.
The 5/8 wavelength antenna can be thought of as a 1/2 wavelength antenna fed by a 1/4 wavelength section. The 1/4 wavelength section matches the top part to the transmitter output. They are popular for mobile radio as they don’t need a ground plane and movement doesn’t cause detuning.
Vertical polarization (tip points up). Long dimension of the 24" x 2.5" x 2.5" acrylic box is up.
Works great, way more range that I need. Now I have four of these:
00691
Figuring I could loose the external antenna. But, I can’t really mount the card where it won’t be blocked by the 3/4" x 24" piece of aluminum running down the center of the acrylic box. And, reading more, I’m worried the range with the chip antenna would be far less than what I need.
So, the Subject line of my original post SHOULD have said “Wire antenna for 00691” (sorry!)
So, now I want to add a simple wire to 00691 that is in the front of the acrylic box so it’s not shadowed by the aluminum strip.
I was planning to run the antenna wire in the front corner of the acrylic box, up to (almost) 24" long would be no issue, but I do need to run about 2.5" from the back of the box (where the transceiver is ) to the front of the box.
if you’ve got a pair of your boxes handy, just try mounting the radio to the interior end panel (something temporary, double side foam tape etc.) 1/2 way between the metal support and the adjacent plastic wall using the the antenna’s built in elbow to fold it’s direction so it’s parallel with the metal plate. you may be pleasantly surprised. I once worked on a fully enclosed metal “shoe box” (emi gaskets on covers, ferrite on the power cord, 1" strap gnd to a 8 ft. copper stake in wet earth etc.) for a job that wanted to test production line FCC part 15 1.2/2.4 Ghz telemetry chirpers in a factory that also used the same chirpers to pass info around the factory. What a nightmare. The best I could do was to drop the range from 300+ ft. to ~ 50 ft. ( they also had NO RF test equipment. Very annoying, I couldn’t even tell them whether one or both freqs. was leaking out and corrupting the data in the factory. There’s frugal and then there’s penny-wise pound foolish.)
It’s a no cost thing you can try quickly, that can’t hurt.
Ok, I’ll give it a try. Of course if a simple wire gets close to same range, I’d rather loose the rubber ducky altogether.
of course.
I’d try a just stiff 1/4 wave wire without a 50 to 377 ohm match first myself. I get great reception my spec. an. 50 ohm input connector with just a paperclip in the female center conductor. You can make a LOT of microwave antenna from a spool of radioshack magnet wire for $6.99. To bad the reverse SMA is a male center conductor, if it were female or you could just stick a piece of wire in it.
So, I’ll just solder a wire to the land instead of the chip antenna. (I’d rather loose the connectors two–the card itself is pluggable, so the antenna wire can be permanently attached to the wire.
Looks just like what I built, except I just soldered to the transceiver card instead of using the connector (antenna will be permanently installed inside the acrylic box).
Found the design from an old “Mr RCCAM” post (learned a lot from that guy!)