|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
50.83.134.124
In Reply to: RE: Most notably, a Spectral amp, from a private owner posted by Tony Lauck on May 18, 2014 at 09:51:27
I tend to agree with you. The special connectors required with the DNM products also are irritating.
Follow Ups:
Over the years, I've had two experiences with electronic equipment that could be damaged by load dependance. One was when I was a teenager and my uncle and I were tweaking the feedback loop of his Dynaco amplifier so that it would sound better. We got a nice square wave on the scope when connected to a dummy load, but when we connected the speaker we observed that the plates on the output tubes started to glow orange and then red. We shut if off before the output tubes were damaged, but it was close. The second was with a solid state aircraft transceiver. The manual said that the transmitter would be damaged if the output was disconnected. They didn't say that this would happen instantly or that connectors could be intermittent. The company that made this piece of junk later went out of business after their factory burned down. Go figure.
In my opinion, reviewers should do everything possible to see if equipment is going to be reliable. This is even more important than their description of how the equipment sounds, because a potential customer can listen for himself in a brief audition, but this won't tell him whether or not the equipment is likely to continue working.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
Hi Tony,
Just happened across this post. Having actually designed a transponder in the mid 70's I may have a warped view, but I don't recall any special VSWR requirements. In those days the outputs were integrated tube/cavity assemblies from GE or RCA and you just had to ground the cathode to squirt out a pulse.
Since the install has to be done by qualified people and since the transponder only emits pulses when interrogated it's hard to see a likely scenario where damage would occur since a broken aerial likely won't hear the interrogation.
That being said and sans any requirements I never tried it. Of course the only thing at risk was the cavity/oscillator assembly and they were easy to replace and not very spendy.
Just another viewpoint from the dim past...
Rick
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: 06/07/14
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: