I'm still focusing on the coax. May be a hole somewhere away from the
antenna that he didn't spray water on.
Chuck W5PR
On Sat, Apr 2, 2016 at 9:54 AM, Kelly Taylor <ve4xt@mymts.net> wrote:
> The stumper here, however, is when he said a five-minute deluge from his
> garden hose produces zero change. It’s only rain that changes it.
>
> Would acidic rain be more conductive than tap water? But then, why
> wouldn’t the rain affect the other?
>
> Must be some difference between the antennas Gary can’t identify, hairline
> cracks, or something, in an insulator.
>
> 73, kelly, ve4xt,
>
>
>
>
>
> > On Apr 2, 2016, at 9:51 AM, Grant Saviers <grants2@pacbell.net> wrote:
> >
> > I'd bet with Joe, maybe the DE insulator is cracked or holding water.
> One "used" antenna I own had ABS pipe as the insulator. ABS pipe is foam
> core can hold water and worse has a lot of creep with age so the U-bolts
> loosen. I replaced the ABS with custom UV resistant nylon split clamps.
> >
> > Grant KZ1W
> >
> > On 4/2/2016 6:14 AM, Joe Subich, W4TV wrote:
> >>
> >> How is the driven element constructed/insulated and matched?
> >>
> >> The downward shift indicates increased capacitance across the feed
> >> point when the antenna is wet. Look for moisture to be trapped in
> >> the DE insulator ... for example, if you are using split PVC is the
> >> split *UP* in one antenna and *DOWN* in the other? If you have a
> >> rod of some kind in the element to stabilize the feedpoint is it
> >> completely sealed to moisture? Are the balun feed points completely
> >> sealed? If there is a support for the beta match (if one exists)
> >> is it designed so it will not absorb water/allow water to stand on
> >> it? If there is a coil across the feed point, does the construction
> >> allow water to accumulate on supports, etc.? If the antenna is an
> >> OWA design, check the insulator of the *FIRST DIRECTOR* as well as
> >> that element has a significant impact on antenna tuning.
> >>
> >> It only takes a very few picofarad change in shunt capacitance to
> >> move the "resonant point" quite a bit.
> >>
> >> 73,
> >>
> >> ... Joe, W4TV
> >>
> >>
> >> On 4/2/2016 8:21 AM, StellarCAT wrote:
> >>> I’m testing a yagi... I can raise it to ~37’ for testing and lower it
> >>> to about 8’ for adjustment ... it was made as a duplicate to another
> >>> one and testing showed it to be just that – a duplicate. Until it
> >>> rained! The SWR shifted downward. At 21425 it was ~1.35:1 ... and it
> >>> would go over 2:1. I’m at a loss as to what is causing this. It is a
> >>> used antenna reassembled... but I find it very difficult to believe
> >>> that water could get in to the mechanical joints and cause this kind
> >>> of a problem. The balun doesn’t appear to be taking on water – there
> >>> wasn’t a drain hole in the bottom – there is now – I went out early
> >>> this morning just after it rained – SWR up high – and there was
> >>> nothing coming out of the drain hole. I have checked all connections
> >>> – they’re tight. Oh – and the strange thing – it goes back to normal
> >>> after only about 4 – 5 hours without rain. It has done this 3 times
> >>> now. It is now – 45 minutes after checking it this morning where it
> >>> was at 2.33:1, its now down to 1.8:1 and continuing its decent. And
> >>> further note the SWR seems to be about the same – its just shifted
> >>> downward when wet. Also I hosed it down – the balun/coax connection,
> >>> hairpin for a good 5 minutes – no change. I hosed down the elements
> >>> at their joints – no change. It rains: changes! The fact that it
> >>> shifts seems to be independent of height – it does this if at 37’ or
> >>> at 8’.
> >>>
> >>> Also: is Noalox the same as penatrox? It is the No AL OX sold by HD
> >>> ... it says it is for increased conductivity as well as anti-seize...
> >>> perhaps IT is the problem at the joints ... unless someone knows it
> >>> to be fine (or KNOWS it to be bad).
> >>>
> >>> thanks – I’m hoping someone has personally seen such a thing and has
> >>> an idea. Its holding up the testing of the other antennas.
> >>>
> >>> Gary
> >>>
> >>> ps: the first one had no problems when it was rained on.
> >>> _______________________________________________
> >>>
> >>>
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