{Collins} Re: "Abjuer" BUT WAIT ???

Impedance of a line (or connector since it can be viewed as a line section) is determined by the ratio of the diameter of the outer and inner conductors.
Velocity factor, and loss by the dielectric.
But I would agree that the impact of an impedance bump would be made worse by the duration or length of the change.
A long enough physical change could actually show at least two changes in impedance.
As for RCA vs SO-239/PL-259...
A friend of mine, a retired design engineer (and Collins affectionado), once told me that he looked at a "UHF" connector wth a network analyzer.
If you look at how many people install the SO-239, center conductor going straight to the center pin (good).
And the shield bundled and soldered to either a lug attached to one of the mounting screws, or soldered to one spot on the connector body.
However, installed using the tapered hood behind the connector, with the shield evenly soldered to it. There's a nicer transition of impedances.
Using RG-8 into a PL-259 gives you a decent match, but that bloody UG-175/176 adaptor for RG-58/59 really looks bad.
Once again the change of the ratio of inner and outer diameters. 
But nothings perfect, the Type N connector gives you a nice match, but will flash over quicker.
A BNC gives a nice match when it's new. But mechanically, it's not the best.
I have to ask, do we not obsess a bit much?
Below 30 Mc, and at Ham power levels (especially at the exciter power of the KWM-2), how much does it really matter?
At 5.4 KW on 910 KC, my good old Harris MW-5 transmitter exits via a brass 1/4 20 threaded stud, while the outer conductor goes to ground via a copper strap to the chassis.
And in the RF path (phasor and ATU)  there are several J plugs.
Standard Practice, and the rig has run very well into what according to this discussion shouldn't work for the last thirty years.
Robert A. Poff
Chief Engineer
Cumulus Media Partners
York, PA
Email :
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Sailing the Hunter 34 "Loon"
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----- Original Message -----
From: "Mac McCullough" <w5mc@xxxxxxxxxxxxx>
To: <w8ji@xxxxxxxx>; <johnpainter@xxxxxxxxxxx>; <COLLINS@xxxxxxxxxxxxx>
Sent: Thursday, December 14, 2006 12:03 AM
Subject: {Collins} Re: "Abjuer" BUT WAIT ???

> BUT  !!!   least we forget so soon,  The KWM-380 as well the HF-380  did
> come with the 239 matching RF connector for the NOW wildly popular PL-259
> connector .... I'm thinking I will or must change my 380 BACK to an RCA jack
> ..  it just has to be
> Located 46 miles due North of the Alamo, and 121 miles due South of the
> Western White House.   see my website at 
> ----- Original Message -----
> From: "Tom W8JI" <
> To: <
johnpainter@xxxxxxxxxxx>; <COLLINS@xxxxxxxxxxxxx>
> Sent: Wednesday, December 13, 2006 6:23 AM
> Subject: {Collins} Re: "Abjuer" ???
> > The change of impedance, going through the connector is a matter of how
> > long it is, with respect to the wavelength.>>
> >
> > Amen. People forget that.
> >
> > The rule of thumb for a modest mismatch area (say it is 2:1 SWR in the
> > mismatched area) is one electrical degree for a noticable change.  That's
> > 1.5 feet on 160 meters. and about an inch on 10 meters. But that is an
> > INCH of actual mismatch area- and it is NOT loss- it is simply a noticable
> > SWR change if we look carefully with good equipment.
> >
> > the PL-259/SO-239 connector combination, which is about 1-inch long>>
> >
> > The impedance error in the 259/239 combo is very small. The error is
> > ENTIRELY in the female except for about .1 inch of bump in the male, and
> > if the female connector is properly hooded the bump is confined to an area
> > about .5 inches long. In that .5 inch area the impedance is about 35 ohms.
> > That's a 1.42:1 mismatch for 1/2 inch. We can just start to measure that
> > at 50MHz with very good test gear.
> >
> > The loss in almost any female below a few hundred MHz is so low it is
> > virtually immeasurable outside of running  a kilowatt through the
> > connector and measuring temperature rise. Some very poorly designed long
> > barrels or Radio Shack elbows might have a heating issue, but not standard
> > connectors.
> >
> > As for power, the standard N connector actually handles LESS current and
> > voltage than the typical UHF connector. The gap distance inside an N
> > connector is almost exactly the same as in a BNC connector. As a matter of
> > fact if we remove the outer locking section of a male BNC it will fit a 50
> > ohm female N connector and make connection. I use them as quick
> > disconnects!  A typical well-installed UHF pair will high-pot to 6kV peak
> > voltage. It will handle over 10 amperes sustained current at 30 MHz. The N
> > connector falls apart at half that value by virtue of less air-gap spacing
> > and smaller pin diameter.
> >
> > The phono can't handle power, the impedance bump is a little worse, but
> > the impedance bump is actually very short. It is perfectly fine to
> > hundreds of MHz at low power.
> >
> > The entire issue at HF is one of mechanical preferences and power level.
> > If you run high power or have a high load SWR or a lot of lightning, of
> > the three the preferred connector is actually a good UHF connector. If you
> > need better weather sealing and run less power and maintain a low load
> > SWR, the N connector might be better. For indoor low power, a properly
> > installed reasonable quality phono is just as good as anything else.
> >
> > By they way, when I buy used hardline with female N connectors I actually
> > machine them into UHF style females. You won't find a single N connector
> > in my station, except on 432 MHz systems. There are hundreds of UHF
> > connectors and dozens of phono connectors in the RF system. I've found N
> > connectors to be more of a long term problem than good UHF connectors.
> >
> > 73 Tom
> >
> > Sponsored by the Collins Collectors Association
> >
> > Nets: Tues: 3.805 Mc-2000 Central / Thur: 3.875 Mc-2000 Central
> > Fri: 3.895 Mc-2000 Pacific / Sun: 14.263 Mc-2000 UTC
> > 1st Wed (of the month) AM Net 3.880 Mc-2000 local (ET, CT, MT, PT)
> > Sun AM Net: 29.050 Mc-1200 Central
> >
> >
> > --
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> > 12/12/2006 11:17 PM
> >
> Sponsored by the Collins Collectors Association
> Nets: Tues: 3.805 Mc-2000 Central / Thur: 3.875 Mc-2000 Central
> Fri: 3.895 Mc-2000 Pacific / Sun: 14.263 Mc-2000 UTC
> 1st Wed (of the month) AM Net 3.880 Mc-2000 local (ET, CT, MT, PT)
> Sun AM Net: 29.050 Mc-1200 Central

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