Joe and others, I have installed many connectors on LMR400/500/600 both
standard and U versions. I can't see any way to make a positive connection
between the connector body and the INSIDE of the foil inner shield. The foil
is just too thin and fragile to do that.
The Times instructions show cutting through the foil and inner dielectric
to install the center pin and using the braided shield for connection to the
connector body, just as in RG8/213 type cables.
If water gets inside the cable, there will be corrosion between the tinned
copper braided shield and the aluminum foil shield. When this happens, the
losses increase in a dramatic manner. I have had to replace LMR cables
having water ingress due to the elevated loss issue.
Times now offers a sealing tape that is similar to the 3M linerless
splicing tape. These tapes are the stretchy rubber types that grip the cable
tightly enough to exclude water entry. This is the only type of connector
sealant I have found that works well every time. As Martha says, "it is a good
thing".
73,
Gerald K5GW
In a message dated 7/17/2010 10:46:01 A.M. Central Daylight Time,
lists@subich.com writes:
On 7/17/2010 1:41 AM, Blake Bowers wrote:
> In my case, pretty well documented. UHF Community Repeater, and a VHF
> public safety repeater. After replacing everything else, replace the
> LMR and the recieve issues go away - no more noise introduced.
This is theoretically possible if the connectors are installed in
such a way as to separate the shields. If the connectors are
installed UNDER the inner shield, LMR cables should be no different
than any other solid shield cable.
If the body/shell of the connector is installed in such a way
that the inner shield of LMR (or any other dual foil cable) is
inside the connector body and the shield is thick enough that
skin effect prevents the RF from penetrating the shield, the
cable may not act like a coaxial cable - that is the transmission
line fields may not be confined to the area between the center
conductor and the INSIDE of the shield.
Connector installation techniques should always insure there is
an adequate RF connection between the connector body and the
INSIDE of the inner shield.
73,
... Joe, W4TV
On 7/17/2010 1:41 AM, Blake Bowers wrote:
> In my case, pretty well documented. UHF Community Repeater, and a VHF
> public safety repeater. After replacing everything else, replace the LMR
> and
> the recieve issues go away - no more noise introduced.
>
> google "lmr cable repeater" and you will see some more.
>
> Works great on base stations, just not on duplex situations.
>
>
> Don't take your organs to heaven,
> heaven knows we need them down here!
> Be an organ donor, sign your donor card today.
>
> ----- Original Message -----
> From: "Roger (K8RI)"<K8RI-on-TowerTalk@tm.net>
> To:<towertalk@contesting.com>
> Sent: Friday, July 16, 2010 7:53 PM
> Subject: Re: [TowerTalk] LMR-900
>
>
>>
>>
>> On 7/16/2010 8:08 PM, Blake Bowers wrote:
>>> There is a school of thought out there that many subscribe
>>> to, myself included, that will not use LMR cables for
>>> long runs on a repeater, due to the noise that tends to be
>>> generated.
>>>
>>
>> I've never seen it to be a problem. Is this something they are afraid
>> of, or something they have experienced and documented.
>> If some one did have a problem, was it water getting in the coax. I've
>> had that problem even with double shielded cables.
>>
>> The largest problem I ever had was with grounded EHS. Every time it'd
>> move in the thimbles the noise would over ride a 50 watt mobile just 2
>> miles out. Of course rubbing an 8" screwdriver on the guy line would do
>> the same.
>>
>> The only problems I've had with LMR cables was when the LMR-400UF rubbed
>> through the jacket on the top of the tower and when the power dividers
>> leaked water through the N-connectors into the LMR-400UF.
>>
>> Getting water in at a repeater is highly unlikely as the coax connector
>> is recessed into the bottom of the antenna and protected from the
>> elements.
>>
>> I wouldn't hesitate to use it although for repeaters we can usually find
>> 7/8" Heliax or larger for a low price or even free. In that case I'd opt
>> for the Heliax.
>>
>
> _______________________________________________
>
>
>
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