[Antennas] COAX Connector insertion losses

[A10382]

A number of you have emailed me about the insertion loss of typical coax =
connectors.

Manufacturers usually provide this in their OEM specs (sent to =
manufacturers and integrators), but typically exclude it form consumer =
specs.  It's usually application dependent (frequency and power) and is =
a lab spec with no corrosion, moisture, pure carrier, and always done in =
a anacholic chamber - not a real world spec but usually 'close enough =
for gov't work'.

I've looked at quite a few for L band and above.  All the specs seem to =
be at .15-.20db or less for S band and above.  Doesn't sound like much, =
but when you add up all the connections (rig, SWR meter, Tuner, Switch, =
barrels, band converters, preamps, antenna components, etc, and try to =
work a satellite for data when it's just above the horizon, with 10W on =
5GHz, the losses can be VERY noticeable.  Loss specs for  HF, VHF, and =
UHF for these same connectors should be lower.  DC would be just about =
0db (actually something like 1x10-9 db), HF would be about half or less =
than the 2GHz db loss.  The higher the frequency, the greater the loss - =
typically....

A few things to remember (I'm sure many of the group can add many more) =
are:
1) Any connector will be slightly less efficient than a continuous =
transmission line.=20
2) The losses per connector are very small, but you may have 8 or more =
connectors=20
        between your rig and the antenna feed point (rig(1), SWR =
meter(2), antenna tuner (2),=20
        antenna switch (2), and antenna feed (1) total eight. You might =
want to consider the=20
        soldered points on your antenna and any traps in the line as =
additional 'connectors'.=20
        A well soldered connection with no corrosion would just about a =
0db loss.=20
2) There is less conductivity between the two surfaces of the connector =
than then the=20
        skin-effect on a continuos run.  This is exacerbated by as =
increase in frequency =20
3) A barrel connector is really two connectors. An inserted 'box' (a =
preamp or converter)=20
        is really two connectors.
4) Every connector is another opportunity for corrosion and moisture to =
enter
5) SWR can be misleading.  Just because it's low doesn't mean all the =
power is being=20
        dissipated in the antenna.  It's possible for a really bad =
transmission system to have
         a very low SWR reading.=20
6) connector halves from different manufacturers can have slightly =
different metals, plating, etc.
7) What works well on 40M may barely work on 6 or 2M.  This is =
especially true when=20
        the antenna switch is on the tower.
8) Very few connectors are airtight.  All require some sealant when used =
outdoors=20
        (and indoors in exposed areas like you attic).
-----------------
I'm looking for a general HF/VHF/UHF/SHF insertion loss chart for =
commonly used connectors (UHF, BNC, N, etc) for multiple bands.  I've =
asked AMP.  If I find or get one in an electronic form, I will send it =
the group.  I did have one years ago from work, but if I use it, I'll be =
facing a military firing squad.
---------------
On the more pragmatic side:  I agree wholeheartedly with some of the =
responses about it being very easy to get wrapped up in specs and the =
quest for that last nth degree of efficiency.   Use connectors =
appropriate for the frequency, seal them well, clean and inspect them =
from time to time (every time you're up the tower or on the roof).  If =
you're having good RST half way around the world on 40M using 50 or 100W =
than you're probably OK from key to antenna end!

73
Frank

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