[TenTec] Connector losses actually measured

[Robert & Linda McGraw K4TAX]

> 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 at haertig.com
>