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

[Pete Smith N4ZR]

Very interesting, Jim - I have been using Ideal connectors from Home 
Depot, and they have no color band at all (nor do they have decent 
instructions for installing).  I will try to find some of the 
black-banded ones (I have red-banded ones for RG-59).

73, Pete N4ZR
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On 5/4/2013 11:13 PM, Jim Garland wrote:
> I'm sure most of you know this already, but there are different compression
> F-connectors for ordinary RG6 and for quad-shield RG6.  I use "Ideal" brand
> connectors with matching compression tool, and there is a color-coded band
> for the two types of cables (blue for RG6 and black for quad-shield). It is
> not always easy to find the installation instructions, but for quad shield
> especially, it is very important to follow the directions so as to make sure
> the multiple aluminum foil and braided shields make appropriate contact at
> the connector, just as Tom cautions.
> 73,
> Jim W8ZR
>
>> -----Original Message-----
>> From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of Tom
> W8JI
>> Sent: Saturday, May 04, 2013 6:08 PM
>> To: Topband at contesting.com
>> Subject: Re: Topband: Problem with compression F connectors on Quad RG-6
>>
>>> I'm having a repeated weird problem with compression F connectors on
>>> quad-shield RG6.  When I connect a short length (say 4 feet) of cable to
>>> my MFJ-259B, I would expect R>650.  Instead, when I wiggle the coax,
>>> occasionally I see the display change to R=0 and X= several hundred ohms
>>> at 1.8 MHz.  This makes no sense to me - the R implies ashort, but
> where's
>>> all the X coming from?
>> R doesn't come from a short, it comes from no loss resistance, or more
>> correctly very low loss resistance.
>>
>> It sounds like the connector you have is not contacting all the shields.
>> This is typical for mismatched connectors and cable,  or improperly
>> manufactured cables. It could be somewhere else also, but I've seen this
>> before with quad shield. That's why I avoid it.
>>
>>
>>   The problem seems to vary with the same
>>> connector and different PL-259 to F adapters, which makes me wonder what
>>> might be happening inside the adapters, but I can't imagine anything
>>> producing this result.  I have also been unsuccessful in detecting a
> short
>>> using a simple DC multimeter.
>>>
>> Remember how RF current flows. It flows on the outside of cables, unless
> it
>> has a connection path to the inner shield. If you have cable with Mylar on
>> the inside of one or more shield layers, and a connector that only
> contacts
>> the outside of the outer shield, the inner shields that carry nearly all
> of
>> the desired transmission line currents will be insulated and isolated from
>> the shield at the connector.  Every shield has to be contacted at the
>> connector, or at least the inner shield does.
>>
>> This might not be it, but it is a common issue with quad shield. Dual
> shield
>> is much more forgiving of connectors.  You'll never detect the leakage in
>> dual shield in outside runs. If you have nasty common mode problems, a
>> thicker shield will help. It is also just as simple to add a few dozen or
>> few hundred ohms of common mode choking to regular dual shield cables and
>> knock down CM ingress to levels that cannot be noticed.
>>
>>> I;'m wondering if I should go through my RX antennas and replace all the
> F
>>> connectors and particularly the F to 259 adapters with something else,
> but
>>> what?  BNCs?
>> BNC's are worse yet, as a general rule. They rely on spring pressure for
> the
>> shield path. Look into a type match error between the cable you have and
> the
>> connectors, or a connector installation error.
>>
>> 73 Tom
>>
>> All good topband ops know fine whiskey is a daylight beverage.
>> _________________
>> Topband Reflector
> All good topband ops know fine whiskey is a daylight beverage.
> _________________
> Topband Reflector
>