Topband: Problem with compression F connectors on Quad RG-6

[ZR]

Im another who has been using the RF Industries tool for well over 20 years 
for both 50 Ohm and mostly CATV or Belden RG-11 foam. No failures or funny 
things happening.

Carl
KM1H


Mike,
>
> Here's a link to an article on crimp UHF connectors with suppliers. It's 
> from 2008 so the prices may have changed:
>
> http://www.eham.net/articles/19257
>
> Today, you can get a crimp tool from a number of suppliers ranging from 
> the low $30s and up.
> I have been using RF Industries UHF Crimp connectors with RG213 and LMR400 
> for years with excellent results.
> Make sure you have the correct connector for the coax you are using.
> I always solder the center conductor in the connector rather than crimping 
> it.
> No more connector problems, no shorts or melted dielectric, etc. and much 
> faster and easier to get it right.
>
> W3LPL and others have mentioned many times that the extra cost of the 
> connectors is small compared to the cost of the entire installation and is 
> worth it to reduce or eliminate a common point of failure.
>
> Les W2LK
>
>
>
> On 5/8/2013 6:16 PM, Michael Tope wrote:
>> On 5/7/2013 7:55 PM, Tom W8JI wrote:
>>>
>>> LMR400 or any cable, in sensitive applications, requires a solid bond to 
>>> the shield that carries the vast majority of return current. In the case 
>>> of almost all cables on HF and higher, that is the innermost foil. Of 
>>> course it is different at audio or lower frequencies.
>>>
>>> One common connector problem comes from not forcing the woven shield 
>>> tight against the foil at the connector, or having the foil or woven 
>>> shield tarnish or corrode. The path to the inside of the foil is out on 
>>> the braid to an eventual contact point, then back on the outside of the 
>>> foil to the foil edge. At the edge current can go inside.  This is like 
>>> adding 2X the length of the path to the connection point in overall 
>>> shield connection path length.
>>>
>>> (Current can also "get in" across the edge of a longitudinal seam, if 
>>> the seam's overlap is insulated. The problem with that is the seam can 
>>> kill UHF performance.)
>>>
>>>
>>> If you solder to the shield of LMR400, and put it on a network analyzer 
>>> and measure the "stub" characteristics, many times (not always) it will 
>>> move around as the cable is flexed. This is because the soldering heat 
>>> contracts the dielectric, releasing pressure between the braid overlay 
>>> and the foil. Now you have a crummy connection that changes electrical 
>>> length of the connection to the "real" shield.
>>>
>>> Even if you do things right, once the foil and braid develop an oxide 
>>> layer the connection goes away. This can work its way out for several 
>>> feet of cable length, really messing up a cable. This will not show with 
>>> a single shield.
>>>
>>> Cables with foil have to be installed and treated correctly. The more 
>>> layers you add, the more careful we must be. Since the extra layers are 
>>> pretty much meaningless, the best practice is to avoid them. Use a good 
>>> shield against the center and connect to it at the connector.
>>>
>>
>> Tom,
>>
>> I'll have to admit that I haven't given this much thought, but what you 
>> are saying about the foil to braid contact makes perfect sense. I do 
>> recall one friend who is a rabid VHF/UHF repeater builder complaining 
>> that LMR-400 has issues with IMD. Perhaps this is why. Can you recommend 
>> a source for a good LMR-400 crimp connectors and the corresponding 
>> installation tools? To date I've been soldering PL-259s on all the 
>> LMR-400 I've used as if it were regular single shield RG8. I haven't had 
>> any hard failures, but clearly there is some risk to doing this depending 
>> on the application. In fact I do recall some phantom inter-station QRM 
>> that would come and go when we had an SO2R setup running at W6UE some 
>> years back. Some of the coax used in that setup was LMR-400 with soldered 
>> PL-259s.
>>
>> 73, Mike W4EF.................
>>
>> All good topband ops know how to put up a beverage at night.
>> _________________
>> Topband Reflector
>>
>>
>
> All good topband ops know how to put up a beverage at night.
> _________________
> Topband Reflector
>
>
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