|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
65.19.76.104
In Reply to: RE: ATC transponders posted by rick_m on June 07, 2014 at 15:26:02
My failed unit was a "transceiver" not a "transponder". It was a 90 channel Bayside VHF unit (BEI 990-P) dating back to the 60's, with the frequencies generated by mixing the output of two banks of crystals. The Mhz knob moved a crystal turret as well as a large plate via a cam. The plate moved slugs in and out of RF coils for tuning. In addition to the poor design of the output stage the unit had all kinds of mechanical stability problems. A real piece of junk. I bought it only because it was fairly low power and ran off of batteries.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
Edits: 06/07/14Follow Ups:
Arrgh! How did I manage to morph transceiver into transponder? Sorry about that.
As I was reading your description of the radio I was struck that we made a very similar one which was an older design but still quite popular with insurgents in the banana republics. AND it's on your FCC list of unacceptable radios! I take it they have chopped the channel spacing since those days, they sure have in land mobile...
It's interesting how communications seems to make solid, monotonic progress while audio seems to go in circles. I put it down to lack of proper scoping and specifications.
Rick
There were two regulatory changes that nailed that radio. First, the FCC tightened the frequency tolerance on transmitters. Second, the FAA mandated support of additional channels.
"It's interesting how communications seems to make solid, monotonic progress while audio seems to go in circles."
I would characterize radio progress as glacial. It's definitely not following Moore's law. Almost all licensed allocations involve bandwidth assignments based on frequency division multiplexing. It's government policy that mandates 1930's technology. In a reasonable regulatory environment most spectrum allocation should go unregulated, with the exception of a tolerance on transmitted power density and a requirement that receivers are responsible for rejecting interference. Antiquated modulation schemes would be rendered unworkable, even if not illegal, per se.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
"Antiquated modulation schemes would be rendered unworkable, even if not illegal, per se."
So, you've turned against CW huh?
My point was really that what constitutes "progress" in communications seems far more readily agreed upon than it does in audio.
Rick
Post a Followup:
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: