| Home |
| Search |
| Today's Posts |
|
#4
November 9th 03, 06:12 PM
|
|||
|
|||
In article , Dr. Anton Squeegee
writes: In article , says... John Walton wrote: with what would appear to be a plethora of devices using SMA connectors, why are they still so expensive? Precision machining. The tolerances are tighter than most connectors. Some of the newer RF connectors are even worse. They have to be machine assembled and ordered made to length, or with a single connector. Regrettably true. The SMA/SMB series are the last ones I know of that still have big enough individual pieces (barely) to be hand- assemble capable. Those tiny center pins are a real pain, though... The basic SMA design came about almost 30 years ago as a small coaxial connector that would work on up to X-band (8 to 12 GHz). In order to even approach that frequency ALL the mating surface tolerances have to be precise in order to avoid discontinuities that raise the VSWR. Tighter tolerances mean greater cost to produce. The old "UHF" connectors (SO-, PL- numbers) common on amateur HF and low-VHF equipment were obsolete for new designs a half century ago. Those are cheap because there isn't much QC on them and the tolerances are sloppy in comparison. SMAs used with semi-rigid coax are quite easy to make once you get the hang of it and are incredibly durable physically and in all kinds of environments. The solid center conductor of the semi-rigid becomes the "pin" just as in the TV set F connector used with RG-59 75 Ohm semi-flexible. F connectors are good to 1 GHz (with some higher VSWR than others) so don't anyone knock the method. SMAs are dandy to use with stripline in aluminum hog- out enclosures. SMBs are on the SMA basic plan but are push-on, pull-off mating for quick connect/disconnect. Okay for limited testing in systems and prototyping. Note that BNC males with the outer bayonet connecting sleeve removed will mate with N females for quick testing too (no remarks about miscegenation, please...). You can spot a pro in microwave RF work by the extra 3/8" across the flats wrench within easy reach. An open-end, closed-end combo 3/8" wrench is only about 3 1/2" long (Craftsman). I used to carry mine on the business keychain in my pants pocket...:-) Len Anderson retired (from regular hours) electronic engineer person |
| Thread Tools | Search this Thread |
| Display Modes | |
|
|
Similar Threads
|
||||
| Thread | Forum | |||
| Expensive SX28A for sale on B/A classifieds.... | Boatanchors | |||
Threaded Mode
