On 03/10/2013 06:05 PM, Michael A. Terrell wrote:
dave wrote:
On 03/10/2013 06:30 AM, Don Pearce wrote:
On Sun, 10 Mar 2013 08:15:56 -0400, "Michael A. Terrell"
Heliax for 10 KW? Ever had the filter fail on the compressor and get
water in Heliax? I had a stupid SOB for a boss 30 years ago who was too
sheap to replace filtes on schedule and ruined a piece of 3" Heliax used
at 4 GHz. Waveguide is better at high power, and better than Heliax. I
had over 1700 feet of it at one TV transmitter. It carried about 195 KW
of RF to the top of the tower. We had to maintain a set pressure of dry
nitrogen on the waveguide to keep from compressing the sync pulses.
No, not at 10kW. At 100W or so it is fine. On a long run I would
always opt for waveguide - tower dimensions permitting.
d
You can't use waveguide for digital TV transmission-something about the
joints making unsuitable anomalies. Air dielectric co-ax is what's used.
Cites? You can't use existing waveguide on a new channel. You have
to calculate the location of the nodes and they are related to the
channel frequency. I can see usinig coax for the pre-transistion phase,
but not after.
Have you ever designed a UHF broadcast plant?
Designed and built close to 2 dozen.
http://broadcastengineering.com/RF/s...smission-lines