Attention: Mike, WA6ILQ, Gary, K2UQ, and Randy, W0AVV
Hello All:
We finally took the 220 antenna apart, and it was an education. I would
like to share our experiences with you.
First, depending on the vintage of the antenna production, these
antennas may be assembled and disassembled differently. I have looked
at some other Stationmaster type antennas, and there are some
construction variations, however my pictures and comments only concern
this particular model.
This antenna as I previously mentioned had been up on a tower for a
considerable time, and it was broken (and repaired poorly) about a foot
and a half from the top earlier in its' life. This repair job probably
resulted in the eventual failure and extreme difficulty taking it apart
for trouble shooting and repair.
Mike, if I could Email the Jpeg pictures to you and make them available
elsewhere, then others can easily see the construction and problems that
can occur with this type antenna.
In the photo of the antenna tip, there is one allen screw holding the
last antenna element in place. This allen screw goes through the brass
tip which is epoxyed to the fiberglass tube and pinches against the top
element. This allen screw has to come out in order for the whole
element assembly to come out FROM THE BOTTOM of the aluminum antenna
base. There was no heat necessary.
There are three countersunk screws at the top of the aluminum tube base
where the fiberglass tube meets the aluminum tube. They need to come
out. These screws hold the circular brass doughnut connected to the
internal brass tube part of the internal antenna. Please note that
epoxy covers these screws, so you need to scrape the epoxy away very
well to get at the allen head, and be careful not to strip the head with
the allen wrench! Using WD-40 around each of the three screw rims
carefully helped in removing them. Also, the fiberglass is never
separated from the aluminum base tube.
Next is a killer. This is the doughnut sandwich where the SO-239 UHF
connector is mounted. The way this connector assembly is held in place
is by tightening the three 1/4 inch bolts and compressing the two
circular (inside the aluminum base tube) plates together with a rubber
bushing or doughnut inside. This rubber bushing expends, and prevents
the the inside guts or antenna stacking assembly from sliding out.
What made it so difficult sliding this assembly out of the tube bottom
was the two plates were rusted and corroded very badly. One of the
three bolts broke because the inside end was frozen. We sprayed WD-40
around the inside perimeter so it would slide out easily, but it fought
us all the way. We had to make up a plate with holes to place at the
antenna base tube, and use the two remaining bolts holes to mechanically
screw out the assembly.
The pictures show the center conductor break in the bottom element. The
center conductor of this element needs to be replaced. Also, the two
sandwich plates are extremely corroded and need to be replaced. One of
the pictures displays the foam spacers used to hold the elements in
place throughout the fiberglass tube. We also noted there was no bees
wax in the tube, only the foam spacers.
We have investigated the Polane T Plus epoxy for the fiberglas repair,
and the index needs to be updated. The prices are out of sight as well
as the minimum quantity. There are other solutions, but this is a
separate story.
I assume there are lots of these antennas out in the field, and they
could be modified and/or repaired for amateur radio repeater use. This
above information might help you make a decision to buy a new one or
modify or fix a free bee.
Have fun. Ciao, Tony, K3WX
Tony Faiola wrote:
>
> [EMAIL PROTECTED] wrote:
> >
> > The epoxy sealing the three recessed screws on 120 deg centers near the
> > aluminum mounting tube meets the fiberglass must be removed.
>
> I have removed these three allen head screws, however the epoxy is
> wedged between the aluminum and the fiberglass. Will heating the
> aluminum near the fiberglass loosen the physical connection?
>
> The set screw at top
> > must be removed and the tip heated with heat gun. Cap will come off. Don't
> > overheat fiberglass. The complete antenna then can be removed from the
> > fiberglass
> > tube.
>
> I did remove the allen head screw from the top metal tip. With a little
> WD-40 on the tip (no heat necessary) the one foot of broken fiberglass
> pulled out of the tip and exposed the one foot of copper element. It is
> important to note that the metal tip separates into two pieces. After
> the allen screw is taken out, the center of the tip separates from the
> collar portion of the tip. This collar portion of the tip is fastened
> by epoxy to the fiberglass tube at the antenna top.
>
> Suggest you place complete antenna on a flat board at least 4 inches
> > wide prior to pulling fiberglass tube off.
>
> I can see where we have to lay it flat on the ground or a board. It
> looks very fragile.
>
> It gets very floppy and the board
> > will keep things straight for you. My problem was the first radiating
> > section
> > where it connected from one outside tube to the next center conductor. It
> > flexes
> > and the center conductor becomes work hardened and eventually forms a fine
> > hairline crack. Could not see it with eye, touched it with a finger and it
> > broke. Soldering the joint with lead/tin is a temporary fix. I used low temp
> > silversolder. Made a sleeve from brass tubing purchased at hobby shop. The
> > spacers
> > for the center conductor will melt if you apply too much heat. Adjust
> > nothing
> > in bottom of antenna near the coax connector.
>
> We did take out the three bolts as mentioned, but I would assume this
> whole assembly should slide out of the bottom...or the top of the
> aluminum tube?
>
> Painted antenna with similar
> > color fiberglass Sherwin-Williams Co paint from boat store. Worked fine.
> > Don't
> > use a dark color. Have more info from CellWave if you want, contact me
> > directly.
> > Gary K2UQ
> > [EMAIL PROTECTED]
>
> One question is the antenna base. There are three brass bolts, 7/16ths,
> in the base around the UHF connector. We took these screws out, however
> nothing came loose.
>
> I realize what you are saying about the top of the aluminum base support
> tube, and it has to be separated from the larger diameter fiberglass
> tube...but what about the connector portion of the antenna coming out.
> Does it slide out with the towards the antenna top or come out of the
> bottom of the base aluminum tube.
>
> Incidentally, for this PD-200 antenna for 220, the top element has the
> bandwidth inscribed on the copper with the two operating frequencies.
>
> Thanks for your first response. I did take digital pictures of the
> various sections and parts, but the big picture will come after
> separation of the base parts.
>
> 73, Tony, K3WX
Yahoo! Groups Links
<*> To visit your group on the web, go to:
http://groups.yahoo.com/group/Repeater-Builder/
<*> To unsubscribe from this group, send an email to:
[EMAIL PROTECTED]
<*> Your use of Yahoo! Groups is subject to:
http://docs.yahoo.com/info/terms/
