[TowerTalk] 50:75 ohm transformation

[Eric Gustafson]

>Date: Thu, 11 Feb 1999 09:42:01 -0700
>From: Eric Gustafson <n7cl@mmsi.com>

SNIP...

OOPS!  I mistyped a number.  The change is not significant to the
discusion but I'm sure there are those who will worry about it.
The following insert from the previous message has the corrected
numbers.  Of course it would also be easy to shorten the jumper a
few feet to restore the original analysis...

Mea Culpa, Eric

>The matched loss at 30 MHz for 25 feet of RG-213 is 0.31 dB.
>The 2:1 mismatched loss for this jumper is 0.38 dB.  So the
>increased loss due to mismatch is 0.07 dB for the jumper.
>
>And the total additional loss for both cables due to the mismatch
>from not using UNUNs is 0.12 dB.  This is not a 10% efficiency
>decrease it is a 1.2% efficiency decrease.
>
>The difference is actually smaller than this since I don't think
>anyone can buy or build lossless UNUNs.  I don't know what the
>losses in a typical UNUN are.  But I bet they are comparable to
>the 0.06 dB they would need to be in order not to make the system
>worse rather than better.  Anyone have some real world measured
>loss numbers for this component?
>
>73, Eric  N7CL


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