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House de Kris
04-14-2006, 11:30 AM
Recently an AK member (DKak) sent me a few digital audio cables to measure. This time I grabbed a 1.5 foot Canare LV-61S cable with BNC/BNC terminations. I have no idea about the cost of this cable, or the claims made by the manufacturer, or if it was even homemade. Attached are a couple pictures of the network analyzer measurements. The cable came supplied with a directional arrow on it, and I respected this for the measurement.

RESULTS
Two pictures are presented, first one with raw data, then followed by a smoothed picture. The center screen reference is at -3dB with 3dB/div. Marker (1) is at the -3dB point, marker (3) was going to be set to the -10dB point, but there isn't that much loss even at the top frequency that I chose to use which is 15GHz. Marker (2) was just randomly placed at 11GHz for no good reason. In the future I will make it a point to put markers at the -1dB, -3dB, and -10dB points since these are common loss points when considering bandwidth. If we define bandwidth as the -3dB point, then this is easily a 7.5GHz cable.

This is the first DKak cable I've measured with the network analyzer, and it is a screamer. He's got some other cables on loan to me that appear, from the external construction details, to be able to beat this cable. Can't wait to get around to measuring them. My TDRs are still being fixed, when they are returned, I will add time domain measurements to these frequency domain measurements.

More to come later.

DKak
04-14-2006, 12:08 PM
This cable was inexpensive. LV-61S is a Canare-made RG-59 type and this cable has Canare's 75-ohm BNC connectors.

IIRC, I believe this one was made up my Markertek.

www.canare.com
LV-61S link:
http://www.canare.com/index.cfm?objectid=0D01B44F-3048-7098-AF1C088D26068A8A

www.markertek.com
Search LV-61S to find the cables that use this wire with different types of connectors.

Dave

House de Kris
04-17-2006, 07:23 PM
I was able to make some TDR measurements of this cable. Attached is the picture.

The yellow trace is the TDR trace, and the cable length is the 'rise' section of the trace. Note, it is exceptionally flat and right at 75ohms. This is a freshly repaired and calibrated TDR module, so I trust these measurements more than my previous ones. The yellow trace is 25ohms/div with the center of the screen being 50ohms. Yikes, I just noticed I didn't have my graticle value up high enough to be able to see the divisions, danggit! The TDT (green trace) says this cable is 2ns long.