On Mon, 2008-04-07 at 21:30 -0400, Gene Heskett wrote: > On Monday 07 April 2008, Da Rock wrote: > [...] > >Ok, if I may go OT a little- what's your opinion of digital? Is it hard > >to maintain, because its certainly appears worth it? > > The problems will be different problems because the only place it is analog is > actually on the air. The transmitter linearity requirements will probably > mean we run bigger stuff in relation to the actual power output just to have > the headroom to maintain that linearity so its at least a correctable error. > > OTOH, we can run with less ERP, by a factor of around 10 (so they are telling > us anyway) To compare, our current analog transmitter is making 26.7 kw at > synch tip peak, which is derived from the average reading, often based on an > actual heat measurement, and is multiplied by 1.68 when the transmitter is > sitting in black without any setup and showing 16.xx kw on the power meters. > That, multiplied by the gain of our antenna makes it equal to a 100 kw signal > in terms of field strength. > > Now, we have been told we will have the same coverage in digital, with only a > 10 kw *average* signal, one whose peaks are not over 6db above that 99.99% of > the time. That translates, using the same hardware and math, to an average > power output from the transmitter itself, of 2.76 kw, or an absolute peak > somewhere in the 12kw area. I have 3 amplifiers on site now that can easily > make that power level as one is rated at 35kw but may not have enough gain, > and the other 2 are rated at 18kw and surely have sufficient gain when driven > with the 200 watt average power starter transmitter we already have on the > air on channel 6, but which will be retuned to channel 5 next February. > > Our biggest problem ATM is that by staying in the low vhf band due to our > proximity to the Green Bank Observatory, we are a very small minority of two, > and we cannot find a vendor to construct the required channel 5 mask filter > for us. Inquiries are out to several makers of UHF sized such devices, so > the math to calculate what it takes is at least moderately well known by now. > > Heck, I'm not allergic to making it, my chopsaw cuts transmission line to > whatever lengths I'd need quite handily, IF I can somehow become privy to the > required math functions. Right now, it seems to me that it is being treated > as proprietary info by most. We're obviously going to be held hostage unless > we can get a waiver from the commission until such time as the conversion is > largely done, and the coppersmiths suddenly find they have bodies standing > around doing nothing. That unforch, may put us in a bind till then. > > More than you asked, and less, but its what I know ATM. Stay tuned as they > say. > Sure, I'm happy with all the info I can get- always room to learn more I say. > >Also what is the difference in equipment for digital? > > Whole new ballgame in the house. A converter box will get a signal to your > existing analog tv, with a good clean pix but no sharper that you are getting > now. New receivers will of course get you a pix as sharp as we are > broadcasting, and some have chosen to effectively run more stations at the > old sharpness because we can stuff 4 of those pictures into the same > bandwidth. But I think the public will smarten up, and demand the better > picture once all the dust is beginning to settle. > Are you talking about the diff between SD and HD here? > The Nextel re-arrangement of our studio-transmitter linkage facilities in the > 7GHZ band will also effect this, and despite all the commissions grand plans, > and the public pronouncements to us by Nextel, the reality is that they are > dragging their feet, leaving quite deep trenches in the land from their heels > because its turning into a project of about 10x the cost of their estimates. > We can't get an answer from them either as to when it will be done in our > market if ever, and its about a $100k question for us. If we have to do it > because of this conversion deadline, and then do it twice when the band > re-assignment actually takes effect, Nextel is gonna need a whole army of > lawyers I'd guess. > > Sometimes I wonder why I didn't just learn to dig ditches or something, but it > has been an interesting ride so far. :) > > -- > Cheers, Gene > "There are four boxes to be used in defense of liberty: > soap, ballot, jury, and ammo. Please use in that order." > -Ed Howdershelt (Author) > Breadth-first search is the bulldozer of science. > -- Randy Goebel >
