Menu

Two coax as substitute for open line

Search this Thread

Prev

Previous Post

Next Post

Next

#2

Report Post

Old

February 24th 10, 07:28 PM posted to rec.radio.amateur.antenna

Owen Duffy Owen Duffy is offline

Owen Duffy is offline

external usenet poster

First recorded activity by RadioBanter: Dec 2006

Posts: 1,169

Default

Two coax as substitute for open line

ve2pid wrote in news:cd290c79-c0c7-4308-af41-
:

Let's suppose that we use to identical length of coax, and on each
one, we connect the shield to the inner conductor at each of its ends.
If we use these two independant (?) sections as a substitute for an
open-wire line, could we use the usual formula Z=276*log(2S/D) to
compute the impedance of that line?

In that case, the characteristic impedance Zo of the coax could be
neglected. And what about the matched losses in dB/100' of the
resultant line? Twice the one of the coax?

Pierre,

The formula you give is an approximation which is not good for low Zo,
and it ignores the effect of the dielectric (coax jacket).

I have seen discussion of this recently in another place.

Yes, you can fabricate a two wire open line like this. You need to find a
way to bind the two cables for consistent physical spacing, if the jacket
is PVC you are using a lossy dielectric, the braided conductor is lossier
at RF than an equivalent solid copper tube. So an expensive low Zo line,
not a low as you might think, with poor performance.

Why would you do this?

Owen

Reply With Quote

Reply With Quote

Thread Tools	Search this Thread
Show Printable Version	Search this Thread: Advanced Search
Display Modes
Switch to Linear Mode Switch to Hybrid Mode Threaded Mode

Posting Rules
Smilies are On [IMG] code is On HTML code is Off Trackbacks are On Pingbacks are On Refbacks are On

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Zo of two wire open line	Owen Duffy	Antenna	11	February 10th 08 09:11 PM
WEWN {EWTN} - Open-Line on 5850 kHz @ 10:10 UTC	Michael Black	Shortwave	2	September 11th 07 11:04 PM
Open ladder line question	S.Fritts	Antenna	11	August 9th 05 05:17 AM
OPEN WIRE LINE	me	Antenna	16	February 17th 05 07:40 PM
WTB: 2" spreaders for open wire line	K9SQG	Antenna	2	September 29th 03 02:30 AM

All times are GMT +1. The time now is 05:08 AM.

About Us

"It's about Radio"

Contact Us RadioBanter forum home Privacy Statement

Copyright © 2017