[TowerTalk] Beverage on Ground: 50 ohm or 75 ohm system?

Jim Brown jim at audiosystemsgroup.com
Wed Jan 24 12:57:40 EST 2018

On 1/24/2018 4:47 AM, Richard Thorne wrote:
> I don't have room for traditional beverages.  Ground mounted receive 
> loops like the K9AY array will not be a good solution as I have a 
> large deer population that would end up tearing it down.  We had an 8 
> point buck with xmas lights hanging off his antlers so I don't think 
> loops would survive

Over the years, we have had a lot of deer running around (although fewer 
now with growth of the mountain lion and coyote populations). My 
Beverages have been up for 11 years, with no apparent damage from deer. 
The only issues are limbs (and even a tree) falling on them, which 
typically pulls the wires out of the termination or feed boxes.

> As I go through the design I'm trying to determine if I should use a 
> 75 ohm system (the most common due to cheap rg-6 coax I suppose) or a 
> 50 ohm system. 

The difference doesn't matter for RX systems for the low bands. The only 
effect would be a fraction of a dB greater loss, and the loss would 
attenuate both signal and noise picked up on the antenna. We use RX 
antennas to separate desired signals from other noise picked up on the 
antenna, NOT from circuit noise in the receiver.

Most commercially built RX antenna products use F-connectors because 
both the connectors and the coax designed for CATV systems are 
inexpensive, and a particular variety of CATV coax designed for direct 
burial is commonly used because it's "flooded" with a sticky substance 
that self seals any breaks in the jacket, and because "varmints" tend 
not to like the taste of it.

73, Jim K9YC

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