On 04/24/18 17:03 PM, Grant Saviers wrote:
Andrew published some research that shows the PIM (passive intermod)
differences between braid and solid copper shields for coax. I couldn't
find that pdf on the web, but it shows how braid generates more IM
products than solid Cu tubing. I think its pretty insignificant for HF
ham radio.
Mostly true. For HF it's insignificant. For UHF and above it's
insignificant for receive only or simplex. For UHF duplex (repeaters) I
*think* it can be significant. LMR style cables have very poor PIM
performance (like 25 dB worse or more) compared to Heliax/hardline style
cables. I've measured PIM on LMR400 & LMR600 at 700 MHz and above, and
it's horrendous by cell service LTE standards (which is -143 dBc using
two 20 watt carriers).
Kinda surprising given that the *RF* foil shield is solid for all (or
most) practical purposes.
-Steve K8LX
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|