[Moon-net] LMR 400UF

[Edward Cole]

Interesting topic.

I have used a ten foot jumper of LMR-400UF to get around my az-el 
rotation for about 8-years with no SWR change noted.  However, I 
guess I will find out if there is any problems once I achieve 1/2QRO 
or QRO.  Perhaps running only a 125w thru the jumper is not affected 
as much?  Substituting 8214 would likely increase my system noise 
figure about 0.1 dB.

I only use the UF cable where flexibility is needed.  I run either 
LMR-400 or hardline for the long runs.

BTW I am still looking for L7NF connectors for my old-style 1-5/8 
inch Heliax.  This is the old spiral corrogation vs. the newer 
annular ring style.  I will use it for 1296 and if enough is left 
over I may exchange it for the 103-foot run of 7/8 inch hardline that 
is currently used for 144-eme.  Thwe difference might add 100w at QRO 
at the antenna.

73 Ed - KL7UW


At 09:00 AM 6/6/2008, LANCE COLLISTER wrote:

>Hello Bob,
>
>I had a similar problem with LMR-600 UltraFlex on 6m, and I 
>understand there have
>been other similar situations.  Apparently, the coax is very soft, 
>and it will deform
>if taped too tightly to a tower, or kinked or left in a permanent 
>tight loop.  When
>it deforms from a true circular cross section or becomes pinched, 
>the impedance
>changes and the loss goes up seriously.  I don't know what to 
>suggest except be aware
>that it is very delicate and do your best to relieve any strain on 
>it and prevent it
>from any sharp bends or kinking.  GL and VY 73, Lance
>
>
>Bob Baker wrote:
> > Dear Moon-net,
> >
> > I am again in need of your wise, collective advice.
> >
> > I just had a failure of a piece of LMR400 UF coax. It was only 
> about 2 years
> > old. It is clearly blown, SWR terrible, and you can see a small 
> piece of the
> > white dielectric sticking  through the black outer insulator.
> >
> > I have a 2 yagi system, the other coax and antenna are working fine. Same
> > coax, same age. swr perfect, looks almost new.
> >
> > At the time of failure I was running 1500W jt65 144mhz. Measured at the
> > antenna, the swr was about 1.3 to 1.4. The most power I could have had in
> > the failed coax was 700W and it is rated at 1500W for 150MHZ. But 
> my SWR was
> > not perfect in the antenna with the failed coax.
> >
> > Obviously I need to buy more coax. Has anyone had similar problems with LMR
> > 400 UF? Was the cable defective or did I just push it a little 
> too hard? Any
> > recommendations? LMR 600UF?
> >
> > Thanks in advance,
> >
> > 73,
> >
> > Bob
> > KD3UY
> >
> >
> >
> > _______________________________________________
> > Moon-Net posting and subscription instructions are at 
> http://www.nlsa.com/nets/moon-net-help.html
> >
> >
>
>
>--
>Lance Collister, W7GJ (ex: WN3GPL, WA3GPL, WA1JXN, WA1JXN/C6A, ZF2OC/ZF8)
>P.O. Box 73
>Frenchtown, MT  59834  USA
>QTH: DN27UB
>TEL: (406) 626-5728
>URL: http://www.bigskyspaces.com/w7gj
>2m DXCC #11/6m DXCC #815
>
>_______________________________________________
>Moon-Net posting and subscription instructions are at 
>http://www.nlsa.com/nets/moon-net-help.html