Luke

Thanks! ~Luke

Just did some searches, didn't come up with anything? Have a link, perchance? ~Luke

Besides being delicate, are there any complications involved in soldering an antenna directly to the RF output? (SWR issues, tuning etc.) I'm looking to cut the weight down on a Lawmate 500mw TX, and I'd like to remove the (heavy) SMA connectors, if possible. ~Luke

Thanks, that's just what I was after! ~Luke

Thanks, fixed the link. The half-wave dipole seems to work well, sans plastic housing, so I'm sticking with that for now. By the way, how does polystyrene foam rate for (lacking the proper term) 'microwave transparency', relative to say, Teflon or (dry) wood? ~Luke

Ok, thanks! On a slightly different topic, how sensitive are these video links to less-than-perfect SWR? I'm thinking of trying a DIY GP antenna (see here: http://www.yb2normal.com/antenna3.html) but I definitely don't want to fry the Tx, and since I don't have a SWR meter, I can only assume that since other people have built/used it, it must have a 'safe' SWR... ~Luke

Oh, also tried a Dimension Engineering (I think) switching regulator which I had for another project... Unfortunately, it introduced a lot of noise. ~Luke

Ok, I was looking though the datasheet, and it indicated a range of acceptable ESR values, ranging from 0.05 Ohm to 1 Ohm. I was shooting for the middle of the range, so about 0.5 Ohm. (Many of the caps I looked at had too low an ESR, according to the datasheet.) In any case, I did end up ordering some electrolytic caps, with ESR values at the low end of the acceptable range, so I guess I made the right call there. Thanks again for all the assistance! ~Luke

Ok... Maybe I'm just doing this all wrong, but... I can't find any KEMET C322C ceramics in the 22uF range..? Digikey and Mouser both list the largest value as 0.47uF. The ESR range that the datasheet for the LM2940 gives is driving me crazy. Can I just use "any" suitable capacitor, and drop a small resistor in series...? (Sorry for being such a newbie...) ~Luke

Going back to the plastic housing question... I'm guessing that decasing a 2.4 GHz half-dipole (removing the plastic shell) is a bad idea, in terms of tuning? Also, (complete RF neophyte) exactly what equipment is required to tune an antenna? I'm assuming it's appallingly expensive? ~Luke

That's what I thought. Thanks for the cap. recommendation, that makes things a lot easier! ~Luke

By the way, are switching regulators any good in this application? I imagine they could produce some pretty nasty interference..? ~Luke

Gotcha. Yep, I noticed the dropout behavior at around 6.75-7V, but just "used" it to keep from overdischarging the LiPoly... (The CMOS camera would develop dark lines in the feed about 5-10 minutes before the regulator would drop out... Really professional, no? ) I assume I should also heatsink the LDO? Also (just being lazy) you wouldn't happen to have some capacitor part numbers I could 'borrow'? Thanks for the info! ~Luke

Regulator: I've got an L7805 linear regulator on a wiring harness; it powers both the camera and the Tx, off a separate battery. I've got a 0.1uF capacitor across the output. See attached. (Finally got a picture!) I was wrong about the max. current, it's rated at 1A. Mounting: I'll look into the Tx mounting, try securing it better, and run some tests. Voltages: 2s LiPoly for the supply, 5V output. I think I have a little aluminum heatsink in my collection of parts, I'll try attaching it to the regulator, and see if it helps. Of course, I could also just switch to a better (more efficient) regulator......... ~Luke

Well, here are dimensionally-accurate CAD renders, all the same. (5 minutes wasted, oh well.) The only thing missing is the purple rubberband, wrapped around the external mount.... Two things occured to me, though: First, the Tx was unsupported, except by the antenna mount, and second, the linear regulator would have been REALLY hot inside the closed canopy. Even exposed, it runs quite hot, but has never seemed to cause any problems. (1.5A rating; the camera and Tx draw about 0.45A.) ~Luke