[BC] Digital Radio Express

[Tom Bosscher]

khcs at juno.com wrote:
> Since we're on the subject of IBOC here -- I seem to have misplaced my info on calculating power levels for high-level combining.  Combiner loss and all that.  Does somebody have a source?  Thanks.

	Glenn, for regular high level combining, you need to increase your 
analog TPO by 10%. Your Ibiquity tx will run 10% of your new tpo. That 
signal will be knocked down by 10 db on the combiner.

	Ex: existing station with 20KW TPO.

	Analog now needs to run 22KW TPO

	Your new digital TX will run 2.2 KW

	The combiner and reject load will have to dissipate the additional 2 KW 
of the analog TX, and just under 2kw of the digital transmitter. So you 
will have the heat of the new digital tx, plus about 2 kw on the reject 
load, plus the 2 kw from the analog, plus the added heat from the analog 
tx making the additional 2 kw, say another 500 watts worth of heat.

	If your tower can handle it, if you have an omni pattern, a separate 
antenna is very nice. With a typical Class B running 50 KW erp,  putting 
up a single bay (gain of .95), and moderate feedline losses, you can now 
keep you analog tx the same, and only run about 700 watts or so on the 
digital TX.

	tom bosscher