[TenTec] Repeatability of Tuner Settings

[patents@dx0man.prestel.co.uk]

In my experience it is not wise to keep anything vulnerable to the
elements in a garage ... unless you have air con. I prefer to keep my
TT 253 ATU indoors where I can get at it and it is warm and dry. I
have used remote motor-driven tuning at the base of a vertical. But
the capacitor visibly deteriorated over a period of time, despite
attempts to seal the plastics box.

Anything out-of-doors, or in an uncontrolled atmosphere is vulnerable
to temperature, humidity, condensation. Even the ground under our feet
gets a good soaking every once in a while. (Well, it certainly does
here). It would be amazing if things stayed exactly the same. If you
try to seal the box, you get condensation. If you don't seal it, you
take a chance on humidity changes. Or the bugs/roaches crawl in there
to get warm and have a snack before they get roasted. 

I gave up on total weatherproofing a long time ago. Its an illusion.
Just look at an aluminum antenna that has been out there for a
while. 

One useful thing to do is locate a good silicone based wax as used
to underseal car bodies (we have stuff called WAXOIL) and use it
liberally to coat anything you might need to unfasten in a few years'
time. Another useful thing is to use self-amalgamating rubber tape on
coax connectors because thats one area where you absolutely need to
exclude water - there's nothing worse than finding water dripping
from the coax where it enters the rig. This problem is very common
here where most folk have outside TV aerials ... the cap comes off
the antenna junction box or the installer forgets to fix it properly.
You find out when the water drips from the TV cabinet and the coax
braid turns green/black.

Some (inexpensive) TV repairmen puts a drip loop in the cable outside
the home, and cut away the outer jacket at the bottom of the loop, to
let the water escape. My daughter just unplugs the video and drops the
cable end in a bucket if it rains .... she must take after me.

Anyway whats wrong with checking the ATU/SWR before transmitting ??
Are you sure you are on the right antenna ?? (Or even on the right
band !!)

It costs less to check the settings than it costs to buy/repair a
rig/amplifier. Remember that transistors tend to crispy critter
quietly. There's no warning bright red glow and sparks like you get
from a stack of 811As. But then I've been successfully crispy
crittering things for 45 years now, long before those darned three
legged fuses were around to confuse me.

73 John G3JAG

On 23-Jan-99 K & H Darwin wrote:
> 
> I'm not sure the lack of repeatability in tuner settings is the
> fault of
> the tuner.  Let me explain.
> 
> My antenna is a 32' ground mounted vertical.  30 Feet of RG-8 coax
> run from
> the base to my garage.  Just inside the garage, I have an MFJ
> tuner.  From
> there I run another 40 feet of RG-8x to my rig in the basement.  I
> use the
> tuner on 80/75, 30 & 17 to get an impedence match.
> 
> Since the tuner is in the garage, I use the presets.  I ran some
> tests with
> my rig in the garage to get the initial settings, the moved the rig
> into
> the basement.  For over a month I was able to cruise into the
> garage, dial
> in the settings and have a perfect match for the radio.  Then, as
> the
> weather here in VT began to change, some of my settings quit
> working.  When
> I rechecked them the MFJ Ant analizer, they had shifted quite a
> bit.  I saw
> these problems on 80 where the settings are very touchy as well as
> on 30
> where they are not.  I expected this on 80 but on 30 I sure didn't.
> During
> this whole time the SWR on 40 remained largely unchanged.  I set
> the tuner
> to bypass for 40 m operation.
> 
> My conclusion is that the antenna system itself changed enough to
> throw the
> settings off.  I've also checked impedence of my 20 M dipole and
> have seen
> it shift around a bit as weather conditions change.
> 
> Keith Darwin
> KD1E
> Ferrisburg, VT
> 
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E-Mail: patents@dx0man.prestel.co.uk
Date: 23-Jan-99
Time: 11:08:44
John Crux
Consultant in product forgery - Asia and
Africa

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