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"F" plugs, Good or Tat?

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"F" plugs, Good or Tat?

Post by Boater Sam » Tue Aug 25, 2015 2:53 pm

Is it just me or are F plugs a load of junk compared with coax plugs?
They are never secure on the coax cable, the centre core is just pushed into a poor fitting hole, and the water resistance is pants. The life before the water gets in and ruins the cable is in my opinion only days.
How did we ever get into these?

 
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Re: "F" plugs, Good or Tat?

Post by CTV » Tue Aug 25, 2015 3:05 pm

When I install any external F connectors ( sat dishes) they are sealed in self amalgamating tape. In over 12 years of doing that for friends and family, I've not had one single failure resulting from water ingress. I accept your point though, they are my least favourite too, I much prefer coax plugs, then again I prefer CRT TV's so what do I know. I even put an adapter on my Aurora to change it from F to coax.

 
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Re: "F" plugs, Good or Tat?

Post by sideband » Tue Aug 25, 2015 3:39 pm

Boater Sam wrote:They are never secure on the coax cable

They come with different bores and should always be a tight fit. I use them with CT100 cable....tight, solid, never give a problem. Even if they are used with standard 75 ohm, the smaller bore should be a tight screw- fit over the cable.

Boater Sam wrote:and the water resistance is pants.


I'm not aware that the standard ones were ever for outdoor use. Neither are ordinary coax plugs as far as I am aware. There may be IP rated types available. I'm fairly sure that when the aerial guys' came to fit the new aerials at Philips, they used weather-proof rubber boots over the plugs. Must admit I've only ever used them indoors.

 
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Re: "F" plugs, Good or Tat?

Post by rob t » Tue Aug 25, 2015 3:45 pm

I prefer the crimp on f connectors to the screw on ones .
on an LMB i always use self amalgamating tape (better than rubber boot)
Rob T

 
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Re: "F" plugs, Good or Tat?

Post by marc » Tue Aug 25, 2015 4:35 pm

CrustyTV wrote: I even put an adapter on my Aurora to change it from F to coax.

Snap, so did I :)
I also think it helps the Aurora's cooling too by adding a bit more heatsink area to it :aal

Marc.

 
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Re: "F" plugs, Good or Tat?

Post by Cathovisor » Tue Aug 25, 2015 4:46 pm

The F connector, properly made off, is a very good connector - far better than the traditional coax connector to be honest.

 
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Re: "F" plugs, Good or Tat?

Post by turretslug » Tue Aug 25, 2015 6:07 pm

I very much like the design as an "installation" connector- minimum number of metallic connection transitions, potentially very good loss and impedance characteristics, and very compact. It does need precisely the right connector for the coax diameter, though, and it's not suited for repeated cycling, hence the remark about it being for installation use, definitely indoors.

Naturally, as it's also very cheap, it's appeared on everything nowadays, even when less than appropriate. The "traditional" type really shouldn't have been used above about Band I, but the company accountants would have jibbed at anything half-decent like the BNC or TNC.

 
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Re: "F" plugs, Good or Tat?

Post by sideband » Tue Aug 25, 2015 6:10 pm

Cathovisor wrote:The F connector, properly made off, is a very good connector - far better than the traditional coax connector to be honest.


Absolutely. They were essential in the very early days of digital TV. Properly made F connectors will never give noisy connections like some standard coax plugs will. I've used them exclusively on the distribution system and never had a problem. The crimp-on type are probably better although I have never personally used them. You need the proper crimping tool to make a really professional job.

turretslug wrote:It does need precisely the right connector for the coax diameter, though,


^^^This definitely!

 
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Re: "F" plugs, Good or Tat?

Post by GlowingAnode » Tue Aug 25, 2015 10:02 pm

When I was installing CTV 20 odd years ago, we used connectors similar to these for external connections; http://www.markertek.com/product/sns1ps ... lue-sleeve
The collar is pressed in with a special tool, providing a hermetic seal.


Rob.

 
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Re: "F" plugs, Good or Tat?

Post by Boater Sam » Tue Aug 25, 2015 10:30 pm

I can accept that f plugs that are crimped on and sealed with Self Amalgamating tape will probably work. My gripe is with the ones supplied with external aerials with a rubber boot as water protection.
To have a connector outside that is made of steel rather than brass or aluminium and that is screwed onto a steel socket which is welded onto the aerial seems a cheap and poor idea. The rubber boot is inadequate.
I have just had to remove the last 4 feet of coax lead and re-terminate because the cable was rotten due to water ingress. Everything is rusty and it is only 3 months old.
Give me a good old plastic junction box and a tube of sealant any day.

 
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Re: "F" plugs, Good or Tat?

Post by Terrykc » Tue Aug 25, 2015 11:33 pm

"The humble F connector costs us 8 cents plus $50 for every truck roll ..." read the headline of an article in a US magazine I read about 25 years ago. F connectors have been consumed in the millions by the CATV industry over the years and the article highlighted how such a cheap connector could turn out to be very expensive if not correctly fitted in the first place.

In those days all F connectors used for CATV were crimp connectors and cable preparation was done manually, usually using a craft knife - it being vitally important to get this part correct. Later variations in connector design allowed this to be done with cheap cable preparation tools and, more recently, crimp connectors tend to have been superseded by a type which relies on lengthwise compression, using a special tool.

However it is fitted, when correctly done, the resultant termination is capable of many years of trouble free service.

If a rubber boot is used for weatherproofing it is important to fill it with silicone grease or a similar water repellant - don't just rely on the boot alone! Self amalgamating tape, as has been said, is an excellent way of doing the job, although it takes a little longer ...

Some modern compression fittings provide a high degree of water proofing.

The correct connector to fit the cable must be used, as has been said. The problem is that it is not always easy to find a suitable connector for a specific cable. The professional user will, of course, have no problems - the connector manufacturer will offer a wide variety to suit any cable which the user will buy in bulk. Not much use for someone wanting one or two, though!

For a start it is vital ensure that you use a good quality cable and ensure that the connector, no matter how it is designed to be fitted, is the correct size to match the cable. Then you must ensure that the cable is correctly prepared to suit the connector before assembling it. If you don't do all of this, your efforts are doomed ...

 
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Re: "F" plugs, Good or Tat?

Post by Hartley118 » Tue Sep 15, 2015 7:26 pm

I reckon the F plug is a good example of cheap US design that happens to work rather well. Yes the centre conductor is unplated copper wire but the socket typically applies enough contact pressure to bite through oxide and contaminants.

When we're comparing a 'coax connector' with an F plug, I guess we mean the venerable Belling Lee connector design. Originally they were intended to have the centre conductor tip-soldered (along with the hazard of melting the polythene insulator), but how often is that the case with the average domestic TV installation? Usually the coax centre conductor just kind of hangs around inside the connector male centre contact, with its electrical connection a rather chancy random affair!

In an effort to overcome this problem, I recently spent an afternoon trying to connect a number of coax plugs with grubscrews to attach the centre conductor. Waste of time! The grubscrews shorted to the outer earth conductor!

F connectors work better.

Martin

 
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Re: "F" plugs, Good or Tat?

Post by Terrykc » Wed Sep 16, 2015 7:43 pm

To fit any of type of crimp connector it is vital to use the correct tooling but it should be possible to make a tool to suit the compression connectors that Rob mentioned.

The basic idea is as shown below. I,m assuming it would be made from scraps of U angled mild steel of a hefty gauge of ali alloy.

The piece of tube must be small enough to fit inside the threaded portion of an F connector but as the centre pin or conductor is never any bigger than about 1.5mm, any tube will do. The open end must be cut square whilst a suitable sized bolt or screw is fitted in the other end.

I haven't shown them but I envisage blocks of wood will be fitted in the main channels to turn them into comfortable handles.

In use, the cable is stripped and the connector fitted. Then the connector is placed between the front plate - with the cable passing through the slot and the handles squeezed slightly so that the tube enters the other end of the connector. Now just squeeze the handles tightly together to compress the connector fully.

Obviously you will have to design the tool to open up sufficiently to accept the plug and compress it sufficiently to correctly terminate the plug.
F Compression Tool.png

I have the correct tool for the LRC Snap'n'Seal connectors - similar to those in Rob's link but haven't seen the connectors themselves for several years - I think they priced themselves out of the market - and with other types I've come across - PPC springs to mind - the uncompressed connector is too long to fit in the slot of the tool!

Here's the PPC compression tool, by the way.

 
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Re: "F" plugs, Good or Tat?

Post by Rally Coordinator » Sat Oct 03, 2015 3:49 pm

Hartley118 wrote:In an effort to overcome this problem, I recently spent an afternoon trying to connect a number of coax plugs with grubscrews to attach the centre conductor. Waste of time! The grubscrews shorted to the outer earth conductor!


I have experienced similar problems with coax connectors in the past and if I don’t feel inclined to shorten the centre screw, I now terminate coax using an F type in conjunction with a coax socket/plug adaptor, which also overcomes the problem of repeated connections/disconnections.

Mike


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