[TowerTalk] PL259 Insertion Loss?

[Dan Zimmerman N3OX]

> I've always assumed that UHF connectors had negligible insertion loss
> below 30MHz, but I recently spotted a couple of quotes on the web that
> put losses between 0.3 and 0.5db @ 30Mhz. If that were the case, the
> cumulative effect of a typical installation with 6 to 8 connectors would
> not be so negligible, especially on 10 and 12 meters.

If a PL-259 had 0.3dB loss on 10m, that would mean it would dissipate
100W out of 1500W legal limit inside the connector.  At 0.5dB that
number is over 160W.   Even with a low duty cycle, the average
dissipation might be 10W or  20W or 30W, probably mostly on the center
pin.  It would not take long for the connector to de-solder itself and
start melting dielectric and braid.  People with high power stations
would at least occasionally be unable to un-mate PL-259/SO-239 pairs
because the center pin would have soldered itself to the socket.

I think people just like to make up "small" numbers for dB losses for
connectors without thinking about the implications or testing.

Steve beat me to posting my picture :)
(http://n3ox.net/files/23_adapters_28400kHz.jpg just so it's in this
message for later)

Losses per connector were 0.004dB if they were distributed evenly;
probably the RCA from a Radio Shack wall plate is lossier than the
high quality silver plated type N and UHF connectors, but it would be
difficult to measure losses as small as those from individual
connectors even by heating, at least without a legal limit or higher
amp here.  A full-bore RTTY op might feel connector warmth at 0.004dB
loss per connector.

By the way, I think it's worth pointing out that a foot (about the
length of all those adapters)  of RG-58 has about 0.03dB loss, so the
adapters are only 0.05dB worse than that.

73,
Dan