On 5/30/2011 3:29 PM, Jim Brown wrote:
> On 5/30/2011 11:59 AM, Jim W7RY wrote:
>> How about something as simple as a bad coaxial cable from the station move?
> YES. Someone else mentioned that, and I meant to reinforce it. Two
> common problems -- coax with a crummy, lightweight shield, and a poorly
> soldered (or crimped) connector. NEVER NEVER NEVER use the light-weight
> foil-shielded stuff designed for cable TV and home antenna wiring --
> it's very difficult to get a good shield connection, and the shield is
> FAR too lightweight for HF, especially for HF transmitting. Also, make
> sure that all coax connections are screwed down really tight. I use
> nothing but soldered connectors myself, and am serious about soldering
> them.
I've gone completely to crimp as I find them more mechanically secure,
faster, and reliable. BUT I have several crimping and stripping tools.
I also solder the center conductor on all connections. OTOH I have found
that they do not work well on CNT240 which has a very fragile braid, but
work very well on RG-8X and 8X with foil plus braid.
With the number of connectors in the SO2R system, I'd spend all of my
time soldering connectors and I find them impractical when working at
100 feet.
I avoid solder connections any where there is motion, for the same
reason they are prohibited in aircraft wiring. A spade lug soldered on a
wire if fine if not subjected to any movement, but if moved or subjected
to vibration they are likely to live short lives compared to crimped
connectors. For example the coax feeds to my sloping dipoles are always
crimped and reinforced with flooded heat-shrink. Although I prefer the
smaller cable due to lower wind resistance and weight, I have gone to
Davis BuryFlex(TM) as it's much more rugged and does not flop around in
the wind like 8X or the other smaller LMR and CNT 240 cables. There is
so much flexing that it breaks the tiny, solid center conductors and
fragile braid. Rotator loops are another place i avoid solder
connectors although it's not near the problem there as it is at the
sloping dipole feed points.
> Some are happy with crimps -- if you DO use crimps, make sure
> that you're using quality connectors and crimp tool that matches them
> (EXACTLY), and that the connector matches the coax you're putting it on.
> EXACTLY.
>
> And a JUNK coax connector or adapter. The crap you buy at hamfests and
> even at many online vendors is cheap JUNK.
When purchasing on-line you need to specify what you want! Most
suppliers have both the good stuff and junk. Many hams purchase based
only on price and they need to cater to that clientele, but stock the
"good stuff" as well.
I have to agree that "most hams are cheap", but often by necessity. I
call on the phone and ask for what I want.
> Look for crummy coax
> splicers (barrels), Tees, elbows (right angles), and adapters (PL259 to
> BNC and/or N, etc.). If it doesn't say Amphenol on it, 99% odds are
> that it's junk.
I've purchased those "recognized name brand" parts that came apart, were
not threaded, and failed electrically at far less than the rated
voltage. IOW some one slipped up in QC, but I've found that although I
*may* improve my odds by purchasing specific brands, many of those
brands including coax and vacuum relays are now produced "off shore".
Check the labels to see where they were produced.
I don't care who made them, IF and I emphasize the IF they pass *MY*
inspection as to materials and quality,
I have to often purchase imported connectors to get what I want and
those get a careful inspection. (White PVC looks a lot like Teflon...to
the point of being difficult to detect only by appearance.)
73
Roger (K8RI)
> An exception are the old unbranded mil-type connectors
> with numbers stamped into them.
>
> 73, Jim K9YC
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