[Elecraft] UHF connectors [was: Array Solutions Lightning Arrestor]

[Edward R Cole]

In fact my N-connector at my in-line Bird Meter element does get warm 
enough at 1500w at 144-MHz to "barely" discern by touch.  Since room 
temp (70F) is 17c the connector may be at about 25c (nothing to write 
home about).

When I first began operation of my 2m-8877 above 1kW it did burn up a 
N-connector which probably had poor connection.  It was an old run of 
RG213 which should have been replaced for running that level.  I 
replaced the two sections of coax with a single 20-foot run of 
LMR-600 which dissipates 0.216 dB which at 1500w is 73w power 
loss).  LMR-600 at 150-MHz is rated at 1.08 dB loss/100-foot.

So I run the amp with 1400w indicated by power meter which implies 
the amp is outputing 1500w (nom.).  Most of the time I run 1300w 
which allows for 5% calib. error in the Bird indication.

In the effort to achieve best NF at 1296, I actually measured 
connector loss in an N-elbow.  It was below my measurement resolution 
of 0.02 dB.  How I measured loss was by reading thermal noise from a 
50-ohm termination with my SDR-IQ with sw set or 0.02-dB/DIV 
display.  I only began to see some loss when I connected N-elbow + 
N-relay + N/sma adapter.  That measured 0.15 dB at 
1296-MHz.  Interestingly 0.1 dB was contributed by just the N/sma adapter.

For use below 50-MHz connector loss is negligible.  Cable loss is way 
more significant but only above 50-MHz.  Of course that is for NEW 
cable.  That 25-year old run of RG8 might be loosing 2-3 dB at 
20m.  Cables do not last forever!  Hint: measure them to know.

73, Ed - KL7UW

From: Jim Brown <jim at audiosystemsgroup.com>
To: elecraft at mailman.qth.net
Subject: Re: [Elecraft] UHF connectors [was: Array Solutions Lightning
         Arrestor]

Thanks for this excellent post, Alan! IMO, "mismatch loss" is a figment
of the imagination of those who never get outside the lab. Transmission
lines was one of my favorite EE courses, and I never heard of it until I
heard it referenced in online discussions a few years ago. And the
purported losses in connectors are an urban legend with almost basis in
fact. Several years ago, W8JI poetically observed that if the 1 dB loss
falsely attributed to UHF connectors was true, each would be burning 35
W carrying a legal limit signal, and be starting fires!

Keeping track of losses in systems is, of course, a great thing. Our FD
group runs (and has won several times) FD 1A QRP Battery. Every piece of
coax in our station is low loss RG8 or RG11.

73, Jim K9YC


73, Ed - KL7UW
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