[TowerTalk] CAT6 Broadside Beverage combiner video

[Jim Brown]

On 1/5/2026 11:51 AM, VE6WZ_Steve wrote:
> I have been expanding my RX system to include more Beverages fed with CAT6 rather than RG-6.

One thing we learned in the world of pro audio is that twisted pair can 
be more effective than shielding, especially if the shielding is not 
done poorly. And I'm talking about VHF, not audio frequencies, where 
interference from high power broadcast transmitters can be problematic.

Cable shields do not work if they are not continuous, which requires 
termination to the shielding enclosure at the point of entry. Failure to 
make that connection also excites "The Pin One Problem."

The effectiveness of cable shields is also strongly dependent on their 
resistance AT THE FREQUENCY OF INTEREST, as well as their 
quality/uniformity/density. It is quantified by the "transfer impedance" 
of the shield, which is the differential voltage induced inside the 
cable by current on the cable shield. The lower limit is its resistance 
at the frequency of interest. This is a shortcoming of the cables 
manufactured for CATV. One of the advantages of the quad-shielded cables 
is their added conductivity. And for all practical purposes, the foil 
isn't there at lower frequencies, thanks to its resistance. In the world 
of pro audio, I published experimental work evaluating more than a dozen 
cable types that showed that the most effective shields were those which 
were those constructed from high quality, dense copper braid, and 
Belden's best was the cream of the crop, and by a fairly wide margin.

That AES Paper is on my website. Scroll way down.

73, Jim K9YC