Hi Al,
Yes, but don't forget that the connector "loss" is a mismatch loss, not
absorptive power loss. In other words, it affects the SWR slightly but
does not actually absorb any power.
If you are using any kind of antenna tuner and tuning for 1:1 SWR,
mismatch "losses" have no effect. Even if you aren't doing that, the
antenna is probably not a perfect 50-ohm resistive load anyway, so the
connectors' mismatches are about as likely to make the SWR better as
worse, depending on the phase and magnitude.
But the general point is sound. Power loss is even more important for
QRP than for QRO even though the number of watts of loss is less. When
the other station can barely hear you, every dB counts!
Alan
On 02/11/2018 11:49 AM, Al Lorona wrote:
Excellent. Thank you, Alan. Data for this particular measurement are very
difficult to find on the web -- of course it took an ex-HP guy to do it!
Times Microwave (a manufacturer of coaxial cable) says 0.01 dB per UHF
connector pair (PL-259-to-SO-239) at HF; I have seen other private measurements
that estimate 0.02 dB; and now this data from N1AL. I usually take the greater
of these, 0.02 dB, as a worst-case number. But Alan's measurements pretty much
show that the loss at HF is almost too small to measure-- even if he had
performed a full two-port cal.
Even so, you might be surprised to see how quickly it can add up. Beginning at
the transmitter output (or receiver input) it is not uncommon to find 20 or
more UHF connections in the path to the antenna. Using the 0.02 dB worst-case
figure, that's at least 0.4 dB, or 9% of your power. I wouldn't worry about
that but I know there are folks on here that would be bothered by that.
This, of course, is not counting loss in cables, filters, lightning arrestors,
power meters, bulkheads, switches, antenna tuners, baluns, amplifier
through-paths, transmission lines, etc. These can add another dB or more to the
total and far outweigh any loss in UHF connectors. If you want to minimize
losses, UHF connectors are the last thing you should worry about.
I encourage you to do an analysis to determine your system efficiency. I
recently did so and discovered that I have a worst-case loss (to the feedpoint
up at the antenna) of 1 dB, which is 21% of my power. Gone. Forever. Whoosh!
Al W6LX
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