[Antennas] COAX Connector insertion losses
A10382
[email protected]
Tue, 23 Apr 2002 20:57:20 -0400
Here's the numbers from Amphenol engineering. Their BNC & N connector
number is in line with three other manufacturers,
----start from Amphenol Engineering----
We don't have a readily available insertion loss chart at this time. We are
working on updating our web site to have product family pages (BNC, TNC, N,
etc.) that will contain this info. For now, here is quick overview. I hope
this answers your question:
BNC 0.2 dB maximum at 3 GHz
N 0.15 dB maximum at 10 GHz
UHF Insertion loss for this connector series is inconsequential to the
performance of the UHF connector since it is such a low-performing connector
(DC-300 MHz)
--end from Amphenol Engineering---
The only addition I have at this time is about BNC. Every time I need a
barrel or cable end connector in a hurry, I go fishing in my junk first.
BNC comes, currently, in 75 and 50 ohm. There is still a lot of junk at
swaps that is really old 91 ohm pre-Ethernet networking BNC. I found quite
a few 91 ohm terminators and barrels in my stuff. I believe the difference
is in the ratio of conductor to shield diameter and the dialectric material,
I wonder what the effect are of mixing the 91 and 50 ohm stuff to cobble up
a quick connection to test someone's field day tower ?
<<--- END OF MESSAGE --->>
----- Original Message -----
From: "A10382" <[email protected]>
To: "Antenna reflector list" <[email protected]>
Sent: Monday, April 22, 2002 3:32 PM
Subject: [Antennas] COAX Connector insertion losses
> 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.
> 2) The losses per connector are very small, but you may have 8 or more
connectors
> between your rig and the antenna feed point (rig(1), SWR meter(2),
antenna tuner (2),
> antenna switch (2), and antenna feed (1) total eight. You might
want to consider the
> soldered points on your antenna and any traps in the line as
additional 'connectors'.
> A well soldered connection with no corrosion would just about a
0db loss.
> 2) There is less conductivity between the two surfaces of the connector
than then the
> skin-effect on a continuos run. This is exacerbated by as
increase in frequency
> 3) A barrel connector is really two connectors. An inserted 'box' (a
preamp or converter)
> 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
> dissipated in the antenna. It's possible for a really bad
transmission system to have
> a very low SWR reading.
> 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
> the antenna switch is on the tower.
> 8) Very few connectors are airtight. All require some sealant when used
outdoors
> (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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