"F" connectors vs "N" Connectors

[Jerry Moody]

What is the difference between the two?

--
Jerry

[Michael Bruss]

Jerry Moody (je...@southconn.com) wrote: : What is the difference between
the two? :

F connectors are used with 75 ohm TV cable. The center conductor of the
cable protrudes through and acts as the center conductor of a male F
connector. Chances are your TV, VCR, and cable box have female F
connectors on them. The N connector is designed for 50 ohm cable and is
especially good for VHF/UHF radio work. The N is excellent for HF too,
but its performance starts to fall off compared to some other connectors
in the gigahertz ranges. The N connector is bulkier than the F connector
and has its own center conductor (in male connectors) as opposed to
having the center conductor of the cable acting as the connector center
conductor. N connectors are more expensive than F connectors.

73, Mike, KF6IMS

[Robert Lay]

On 23 Dec 1997 01:50:32 GMT, "Jerry Moody" <je...@southconn.com>
wrote:

Jerry,

I think the "F" connector was designed primarily for use with RG-59 TV
coax. The "N" connector is for much larger coax and has been around
forever. It's much more expensive and can handle relatively higher
power.

73 de Bob, W9DMK
[Change "nobody" to "w9dmk" for direct replies]

[Gary Coffman]

I'd add to this that F connectors are really really cheap, easy to install,
and can be used on the smaller 50 ohm cables (RG-58 style) too. They
aren't limited to use on 75 ohm cable. They can handle the power of
the small cables that they are intended to fit, IE about 100 watts, with
no sweat. And the impedance bump that they create is less than for
a UHF connector (often less than for a N connector installed ham
fashion).

Adapters are available from F connector to UHF, BNC, or N style
if needed. CATV uses these conectors by the zillions, so they are
very cheap, and the tooling to install them is cheap too. You can
get a bag of 1,000 of them for about what you'd pay for 10 good
quality PL-259 connectors and reducer sleeves. The female
chassis connectors are cheap too. I use them in a lot of projects.

Gary
Gary Coffman KE4ZV | You make it |mail to ke...@bellsouth.net
534 Shannon Way | We break it |
Lawrenceville, GA | Guaranteed |

[jdag...@gate.net]

On Tue, 23 Dec 1997 14:43:11 GMT, nob...@crosslink.net (Robert Lay)
wrote:

>On 23 Dec 1997 01:50:32 GMT, "Jerry Moody" <je...@southconn.com>
>wrote:
>
>Jerry,
>
>I think the "F" connector was designed primarily for use with RG-59 TV
>coax. The "N" connector is for much larger coax and has been around
>forever. It's much more expensive and can handle relatively higher
>power.
>
>

The "F" connector is designed for 75 Ohm applications The "N"
connector is a 50 OHM connector. The "N" conncetor is a guarenteed
impedance from DC to several GHz. It is a low leakage connector and
is excellant for VHF/UHF and the low end of the microwave bands. It
has better performance than the UHF conectors, PL259/SO238.

>73 de Bob, W9DMK
>[Change "nobody" to "w9dmk" for direct replies]

James

WA4BZJ

[Dave Martindale]

ke...@bellsouth.net (Gary Coffman) writes:
>And the impedance bump that they create is less than for
>a UHF connector (often less than for a N connector installed ham
>fashion).

I'm certainly no friend of "UHF" connectors - I'd prefer almost anything
else to them. But what do you mean by "N connector installed ham
fashion"? I wasn't aware that there was more than one way to install
any given N connector (or BNC or TNC or SMA, for that matter).

Dave

[Dave Martindale]

jdag...@gate.net writes:
> The "F" connector is designed for 75 Ohm applications The "N"
>connector is a 50 OHM connector. The "N" conncetor is a guarenteed
>impedance from DC to several GHz. It is a low leakage connector and
>is excellant for VHF/UHF and the low end of the microwave bands. It
>has better performance than the UHF conectors, PL259/SO238.

Actually, there are 75 ohm N connectors as well as the more common
50 ohm ones. It's important to know, because they use different diameter
pins for the center conductor, and if you try mating two of different
impedances you'll probably break one of them.

This is unlike BNC, where again both 50 and 75 ohm connectors exist,
but they *can* be mated without damage. (As well, people mostly use
50 ohm BNC connectors on 75 ohm cable - real 75 ohm connectors are
scarce).

Dave

[cj]

Jerry Moody wrote:
>
> What is the difference between the two?
>

> --
> Jerry

Well, that question could lead to a lot of different answers, such as,
SWR over different freq. ranges, usable freq. range, sizes, price, etc.
The short answer is, Type-F is what you find on most TV cable
applications, Type-N is a whole different animal, often used for
instruments and transceivers operating up to several GHz. Type-F is
generally inexpensive, Type-N can be rather costly. Type-F is 75 ohm,
Type-N is 50 ohm.

For a good look at a Type-N male and female, look at:

http://www.tmo.hp.com/tmo/datasheets/English/HP1250-1476.html
http://www.tmo.hp.com/tmo/datasheets/English/HP1250-1474.html

These are adapters to BNC, so if you're familiar with BNC you can get
an idea of sizes.

-cj

[Gary Coffman]

Well, you know the old saying about "the right way, the wrong way, and
the army way" I'm sure. To that I'd add the "ham way". I've seen lots
of N connectors (and other kinds too) installed in the most god awful
ways by hams. That's particularly true of the Amphenol wrench type
connectors, even if you're careful. OTOH, it is hard to screw up the
installation of a good King's crimp connector if you have the proper
tooling. But I've seen hams try to install them with gas pliers.

While it certainly isn't recomended, you really can get away with
installing a F connector with gas pliers. Though with the proper
crimp tools so cheap, there's no excuse for not doing it right.

[Gary Coffman]

Yeah, that's gospel. As most of us know, you can plug a N male into a
BNC female socket for temporary test purposes. But be darn sure you
are using a 50 ohm N connector and not a 75 ohm one or you'll trash
the female contacts of the BNC connector on your test equipment.
And those things are usually a pain to replace.

[Lyle Koehler]

Page 59 of the January, 1998 QST shows the results of loss measurements
in "UHF" (PL-259 type) and N connectors. Both connectors had very low
losses at frequencies up to 150 MHz. At 450 MHz, the UHF connector had a
loss of only 0.09 dB, and the N connector loss was still not measurable.

73

Lyle, K0LR

[Rich Griffiths]

George Warner wrote:
>
> jdag...@gate.net writes:
> > The "F" connector is designed for 75 Ohm applications The "N"
> >connector is a 50 OHM connector. The "N" conncetor is a guarenteed
> >impedance from DC to several GHz. It is a low leakage connector and
> >is excellant for VHF/UHF and the low end of the microwave bands. It
> >has better performance than the UHF conectors, PL259/SO238.
>

> I often see this complaint of PL259/SO238 connectors and I don't
> doubt it. Are the characterized parameters for these connectors
> available anywhere? What is their impedance? I'd like to know
> more specifically just how bad they are.
>
> Inquiring minds want to know.
>
> George Warner
> warn...@loveboat.com

Way back in the dark ages (late '60s, '70s ??) the Naval Research
Laboratory released a report on tests the Lab did on a variety of
rf connectors.

As I recall, one of the odder results was that the 'UHF'-type
connectors generated a surprising amount of spurious emissions and
leaked a surprising amount. The report was just test results --
no theorizing as to why these things happened.

If you're not shy of library research, you might look for NRL
publications related to radio to see if that report's still
available.

Rich W2RG

[Gary Coffman]

On Thu, 25 Dec 1997 03:35:53 GMT, warn...@loveboat.com (George Warner) wrote:
>jdag...@gate.net writes:
>> The "F" connector is designed for 75 Ohm applications The "N"
>>connector is a 50 OHM connector. The "N" conncetor is a guarenteed
>>impedance from DC to several GHz. It is a low leakage connector and
>>is excellant for VHF/UHF and the low end of the microwave bands. It
>>has better performance than the UHF conectors, PL259/SO238.
>
>I often see this complaint of PL259/SO238 connectors and I don't
>doubt it. Are the characterized parameters for these connectors
>available anywhere? What is their impedance? I'd like to know
>more specifically just how bad they are.

A UHF male connector has a characteristic impedance on the order of 30 ohms.
But the connector is such a tiny fraction of a wavelength long at the frequencies
where it is commonly used that this impedance bump doesn't have any practical
effect for most applications. The same applies to normal female versions of the
connector (though the internal impedance of the female connector can vary depending
on the type of dielectric used in its construction). There are long F-F couplers that
can have a noticable impedance transformation effect at the upper end of the usable
frequency range.

A N connector is constructed to have a constant 50 ohm or 75 ohm impedance
internally (N connectors are available for both impedances, don't mix them, the
center pin is a different diameter). But the care, or lack of same, with which it is
installed can change this enough to make it a moot point for most applications.
Again, it is short enough that there is very little impedance transformation across
it at the frequencies where a UHF connector might also be commonly used. Long
F-F couplers are available in either 50 ohm or 75 ohm characteristic impedances.
Using the wrong one, besides wrecking the center pin female receptacle, can cause
a noticable impedance transformation at the upper end of the frequency range, but
using the correct one should have little effect.

The F male connector can be viewed as just an extension of the cable on which
it is installed. In theory, it offers no impedance bump at all. But in practice, the
care with which it is installed will make that moot. The F connector is the shortest
of the three connectors, so its ability to act as a transmission line transformer is
the least of the three. The same can be said for normal female F connectors.
There are long F-F couplers available for it too, and they are internally 75 ohms.
This can have an impedance transformer effect at the upper end of the frequency
range where F connectors are usable, if used in a 50 ohm system. For 75 ohm
systems, there's no effect.

In regard to power handling, the UHF connector has the highest power handling
ability of the three, due to the larger contacts and greater contact spacing. The
50 ohm N connector shares the same pin diameter and spacing as a BNC, and
thus the same power handling (lots of people don't seem to realize this). Those
two, and the F connector, have lesser contact spacing and lesser contact area
than the UHF connector, and thus lesser power handling ability. But the care
with which they are installed has a large effect on this. It is easy to get a poor
shield bond to a UHF connector or Amphenol style N connector, and that can
reduce its power handling ability sharply. Crimp styles, applied with the proper
tooling, are much better.

[Jeff Anderson]

In article <34a2fc2d....@news.atl.bellsouth.net>,
ke...@bellsouth.net (Gary Coffman) wrote:

>In regard to power handling, the UHF connector has the highest power handling
>ability of the three, due to the larger contacts and greater contact spacing. The
>50 ohm N connector shares the same pin diameter and spacing as a BNC, and
>thus the same power handling (lots of people don't seem to realize this). Those
>two, and the F connector, have lesser contact spacing and lesser contact area
>than the UHF connector, and thus lesser power handling ability.

What *is* the powering handling abilities of UHF, BNC, and N connectors?

Thanks,

- Jeff, WA6AHL

[Gary Coffman]

It depends. If the line is mismatched, there will be current and voltage nodes
along the line. If the connector is at a current node, contact resistance
dominates, at a voltage node flashover holdoff dominates. Etc. Frequency
is also a factor since it affects skin resistance. For a matched line, a N or
BNC connector can easily handle a couple of kilowatts continous at 200 MHz,
more peak. A F connector is basically limited to the power handling capacity
of the cable, since it is just an extension of the cable. That's a small cable,
RG-58 or RG-59 size, so the continous power rating is only a couple hundred
watts at 200 MHz, again a bit more peak.

I can't get more precise than that without examining the particular case and
particular connector construction. I have seen N connectors used to carry
5 kW when part of a flexible cable to rigid line transition. It would be carrying
10 amps at 500 volts in that case. That's pushing things. The center pin is
approaching its maximum safe current carrying capacity and runs pretty
warm. Teflon insulation was used.

If the line had been mismatched at that power level, there would have been
hot spots sufficient to melt cable insulation in places, and the possiblity of
arcing over would have been real at other places. If the connector happened
to be at one of those places, it would fail.

Because of the wider pin spacing of the UHF connector, and because of
the larger contact area, it will tolerate power levels higher than the other
connectors. But that isn't the whole story. It depends on how the braid is
bonded to the connector. For UHF connectors, that's usually the weak
point, and the braid will literally unsolder itself from the connector under
high power if it is of the solder on type. A Kings crimp UHF connector
can handle more current. (In general, good quality crimp connectors,
installed with the proper tooling, are better in every respect than soldered
on connectors.)