[Cydrome Leader]

In sci.electronics.misc Michael A. Terrell wrote:

T wrote:

In article ,
says...

wrote:

On Sun, 10 Mar 2013 02:43:08 +0000 (UTC), Cydrome Leader
wrote:

Not many folks making hard coax runs anymore.

this stuff was pretty darn old.

are there power levels where they stil use wavegides and the like?

In countries still using analog TV, the UHF final amplifier is often
implemented with klystron in the 100 kW range. The waveguide is quite
large, due to the low frequency.

DVB-T digital TV transmitters typically operate with only 1-10 kW,
consisting of multiple redundant solid state modules, so there is not
much need for waveguides any more.


How do you get that to the antenna without waveguide? Coax losses are
much higher than waveguide, and is less likely to have problems since
there is no dielectric to break down.

Hardline! In essence it's a solid shield with a center conductor. That's
enough for RF into the 900MHz and 1.2GHz range.


There are many types of hardline, and more in use by CATV systems
than anything else. I engineered in that field for four years and
designed extensions and upgrades. I also designed community loop
systems.


Specify a brand, type length, frequency and power level. There is a
reason they have so damn many trunk amplifiers in a system.


I found a link to some 5.5" heilical air dielectric that doesn't look
too bad, but the specs stop before a GHz. look at the power handling
spec at .5 MHz, and at 894 MHz. It drops from 1890 KW to 43 KW. The
insetion loss goes from .0045 dB to .215 dB over that range.

http://www.rfsworld.com/dataxpress/D.../?q=HCA550-50J

how does one terminate such cables? What sort of wiring goes on inside a
giant transmitter or the antenna end of such a monster?