Punch cards

[Da Rock]

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
>