Hi Jeff, > "Jeff DePolo" <[EMAIL PROTECTED]> wrote: > > There's good reason a "hot air" alarm probably went off for many > > of you when reading the article.
I went back and read the article through... even though it was tough to bite that bologna sandwich. One of the Authors is reported to be a PE? > I'm trying to figure out what his closing paragraph is trying > to say. I had to turn on the AC because the hot-air was so bad. > However, should you hear a slow oscillation of the transmitter > when it turns on and off (a rate of about 1-2 Hz rate on weak > signals), then you do have duplexer desensitization." > > What is this 1-2 Hz oscillation he's talking about? You're right... Doesn't make sense... > His use of "quasi-simulcast" is what we used to call "sloppycast". I'm laughing... "sloppycast", I'm going to steal that from you and use it to describe a few things. > Basically the transmitters are not time-aligned as far as the > launch time of the audio from each site. > Furthermore, the transmitters may or not be locked to a high > stability reference (UHSO TCXO/OCXO, GPS, Rubidium, etc.), > so there may be carrier frequency errors as well resulting in > audible beat products. Regarding the frequency stability... you can often sync the transmitters easy enough. The fly in the soup is how well they stay in sync over time and/or when they do drift... where and how far. > Several of my co-channel ham repeaters are sloppycasted, but with > accurate carrier frequency matching (using Rubidium reference > oscillators). As long as the frequency stays put... you're not forced to use high dollar standards. Sometimes you have to burn your fingers on heated channel element assemblies. > There is some minor distortion in areas where the signal levels > from two transmitters are comparable due to the lack of AF > time-alignment, but none of the users have ever commented on it. Most don't know what it is... a usable signal is butta' than no usable signal. The human brain has one real good audio dsp filter software built right in. > Still bugs ME though - will have to do something about > that eventually... Another example of a "round tu-it" Jeff? > I question whether or not the Icom radios they used for "links" > are certificated for use as fixed station equipment. We've had > local instances of field agents from the Commission shutting down > Part 22 and Part 90 base/repeater stations operating using mobile > radios. Almost never happens except when there is a problem, which might bring the Evil Fire-Eye of Sauron looking up from Mordor. > In one case, a Mitrek had such bad LO leakage that it was getting > into another receiver several miles away, which is what prompted > the FCC interference investigation. > --- Jeff Someone not paying attention to the details turns the Eye of Fire toward them. He will send Orcs to visit you. cheers, skipp
