> You may have wondered as I have, about the so called UHF type of connector
and
> how robust it really is with regard to its RF power handling abilities.
> Here is some dialogue and test results that seemed to be of interest. Oh,
> sorry, I didn't mention Tentec, but for those of you running a Titan or
> Centurion, this may be of interest.
> 73
> Bob, K4TAX
>
> **********************************************************
> Regarding PL-259 loss, here is a prior post from K7FR who actually
measured
> it.
>
>
> Back in senior year at Washington State U (W7YH, Go Cougs!) we had to do
a
> measurement project in Measurements Lab. Since there were two hams in the
> Lab we decided to measure losses in coax connectors (the Prof was a ham
> too).
>
> We set up a calorimeter and measured I**2R losses from DC to 2 GHz for a
> PL259/SO239 combo (did it for BNC and N too...hey it was a senior
project).
> Here are some of the results from my Lab Notes:
>
> Input power = 1,000 watts (100V, 10A @ DC, homebrew 4-1000 .1-30 MHz,
> borrowed USAF signal source 30-2,000 MHz (black box from Fairchild AFB),
> Bird dummy load) (We used a kW because neither of us had ever run more
than
> 100 watts...power trip!)
>
> f (MHz) Loss (W) dB
> 0.1 1 -0.00435
> 1 1.2 -0.00521
> 10 1.3 -0.00565
> 20 1.5 -0.00652
> 30 1.8 -0.00782
> 50 2.2 -0.00957
> 100 2.6 -0.01131
> 200 3.5 -0.01523
> 300 5 -0.02177
> 400 7 -0.03051
> 500 10 -0.04365
> 1000 15 -0.06564
> 1250 18 -0.07889
> 1500 28 -0.12334
> 1750 39 -0.17277**
> 2000 100 -0.45757**
> ** Connector failed before calorimeter stabilized.
>
> We attributed the steep upswing after 100MHz to the finish on the
connector,
> not the connector design. Nickel plating seems to exhibit non-linearity
> above 100MHz. The N and BNC runs were much better. BNC went flakey above
> 600MHZ (RG-58 size, RG-8 BNC went to 1000 MHz). We were able to isolate
> cable loss from connector loss by building a teflon box around the
connector
> body and only "viewing" the inside of the box with the sensor. The
> Department Chair was not at all happy that this teflon box cost $750 to
> build (teflon was rare in 1977). As you can see from the table we
> experienced two failures. Both were due to
> the solder melting in the probe part of the connector. The 1250 and 1500
> watt runs showed discoloration but no melting. The values for 1750 and
2000
> MHz were the calculated values at the time of failure. Each run took 1
> hour, these two failed 28 and 17 minutes into the test.
>
> We experienced a failure of an N connector at 2000MHz. We ran the
output
> up in 100 watt steps until we observed a sharp up turn in losses. We were
> able to boil the water in the calorimeter at 15000 watts and at 17100
watts
> the fingers inside the connector relaxed and started arcing.
>
> Before this experiment I was paranoid about my connectors. Since then I
> have only been concerned with the quality of the assembly and water
ingress.
> My take on it.......
>
> > > > >> 73 Gary K7FR
> > > > >
> > > > >
> > > > >Good job!
> > > > >
> > > > >Experience has always told me that .5 db per connector was silly,
> > > > >especially at anything below UHF. I think the figure arose from
the
> > > > >folks in the high UHF and microwave business, where connector loss
> > > > >becomes something more than virtually immeasurable. I suspect the
> > > > >relatively high loss at you measured at >1 gHz is not all that much
> > more
> > > > >than the loss in an equivalent piece of line.
> > > > >
> > > > >The non-linearity of nickel plating is well established. In high
> > > > >quality land mobile instalations where there are high power
> > transmitters
> > > > >and very sensitive receivers sharing a common site, it is common to
> > find
> > > > >nickel plated connectors banned. The non-linearity aparently
arises
> > > > >from the fact that nickel is somewhat ferromagnetic. Our old
friend
> > the
> > > > >hysteresis curve.
> > > > >
> > > > >I still use the ,5 db figure when I work out microwave link
budgets.
> > > > >It's always better to predict a little more loss than is actually
> > > > >there.
> > > > >
> > > > >Gray
> > > > >
> > > > >
> > > > >--
> > > > >Telecommunications Engineering
> > > > >Gray Frierson Haertig & Assoc.
> > > > >820 North River Street, Suite 100
> > > > >Portland, Oregon 97227
> > > > >503-282-2989
> > > > >503-282-3181 FAX
> > > > >gfh@haertig.com
>
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