DIAMOND CP 6 ANTENNA REPAIR
by Rob Stokes ZL1RJS
Diamond CP6 Antenna Instruction Sheet
I have added the instructions sheet if needed. Just click on the link
below to download a copy.
Download Diamond CP6 Instruction pdf file to PC.
Photo 1. Diamond CP6S Vertical Antenna
My diamond antenna must be about 10 years old now and has been
performing very well. The antenna covers the 6, 10, 15, 20, 40 and 80
meter bands. A great antenna if you are pushed for tight spaces.
Of late I was experiencing some strange behaviour from this antenna
and it seemed it was happening only when it rained. I had a high SWR,
which went up and down then came right again.
This has been going on for months and it seemed every time we had a
storm it affected the performance. We had some very high winds one
night and the next morning I went into the shack and my antenna would
not load up on any of the bands.
Upon further investigation I took out my VNA and did a sweep across
the antenna which revealed something was definitely wrong.
I tilted the antenna over and removed the whole antenna off the mast.
I suspected the first vertical trap from the base was faulty as this
being the trap that is common to all the bands, and logic to me says
to suspect this trap as it was not loading up anymore on any of the
bands.
If it had been just one band or a couple of bands, then I would have
looked at another trap. A quick measurement using an ohm meter
revealed that there was an open circuit on the 1st trap.
No continuity was measured between the two ends or to the case of the
trap. Continuity was between the case and the top end of the trap
indicating the break was on the bottom end of the trap.
Dismantle of the Antenna
If you have installed these antennas before, you will know that the
vertical section is made in 3 parts. I decided to dismantle the whole
antenna to check it all over.
You could just remove the top two sections to get to the first trap,
without removing any of the trap radials.
I did not take any photos at this point but now the antenna has been
completely dismantled almost as if it was just unboxed.
I did find that some of the screws were already loose and a couple of
them were almost about to fall out where the antenna joins each
section, so when you come to reassemble check and re-tighten.
Seeing this I may put some electrical tape over the screws to prevent
it happening. With the electrical tape, I will only use the brand
"Nitto" as I totally recommend this tape.
Using this electrical tape, I have found that it is the only tape
that will not undo with heat and sticks to itself. (Good for wiring
looms in cars also with high tempertures from the sun.)
As with most other electrical brand tapes I have tried, they are not
as good and will undo and eventually the tape will come un-done over
a very short time.
I did actually end up using cable-ties, fitted over the screw heads
and not electrical tape. I will see over time if this works.
The cable ties will go brittle over time with the sun and may break
off, but as this is not taking any stress, they should not break and
be good to stop the screw head from working loose and coming out.
Photo 2. 1st vertical Trap (Lower Trap of 3 verticals)
1st Vertical Trap
Upon inspection, all three of these traps have been center punched 16
times for each of the traps.
You have no way of opening these traps up, so each punched dot or
dimples needs to drilled out so you can slide the casing off.
To drill each of these dimples, I first used a 2.5mm drill as I tried
not to create a burr once you drilled a hole as I was a bit worried
by drilling the hole would create a burr on the inside and stop the
casing from coming off.
I then used a 3mm drill and drilled through each of the 2.5mm holes.
This worked out very well. I was also worried by drilling too big a
hole of the 16 punched dots, I would not get a screw to fit.
This of course now made the outer casing almost easy to come off but
with a bit of very careful persuasion it came off.
Photo 3. Trap Opened.
Inspection
It revealed the 1st trap was definitely broken at the bottom end of
the trap. I did some homework online to see if other Hams have had
the same problem or similar and to see how they fixed the problem.
I found and watched a video on YouTube and thanks to Stan PA8C, for a
good video. It was all recorded in Dutch, but I got the idea on what
he had done.
Diamond did not think it through when they designed this antenna and
the quality control was certainly lacking, in fact, I would say a
very poor design or cheaply made.
It appears that by only having one rivet on each side has caused the
issue that once the wind blows it was rocking back and forth until
finally, it snapped the connection. I will show the extra rivets
added in the photos on what I did. (See Photo 9)
Modification
After the repair of the coil, I also made improvements on the
mechanical construction and modified the trap by adding 2 more rivets
on each end of the trap to make it stronger.
After reinforcing was done by adding these extra rivets, it has
indeed made it very strong and shows no movement.
I also reinforced by soldering up each side of the screw that
connects to the center of the coils, which acts as a capacitor.
I saw that in the video that his had broken off completely and
although mine had not broken yet, I soldered up on each side to
reinforce anyway just to be safe. (See Photo 7 and 8 from a different
angle.)
I drilled out the broken lug and added and pop riveted in a new
terminal lug and used a 4mm drill to add the lug. I then soldered the
connection terminal and it is now better than before.
Photo 4. Close-up of broken trap.
When the coils connection broke off, it shows the coil wire out of
sight as the wire is not sitting in the groves of the plastic former.
Photo 5. Trap with rivet drilled out.
This shows the wire waiting for the new lug and rivet.
Photo 6. Close-up of drilled out rivet.
Photo 7. Capacitance nut, side view (Soldered)
Photo 8. Capacitance nut, other angle
Photo 9. Extra rivets added.
Photo 10. Trap repaired with riveted lug.
Reassembly of the Trap
As I have now drilled out those pressed center punched dimples to
gain access to the trap to repair, I found some self-tapping screws
just the right size making sure not to go all the way through and
short out the trap.
The outer casing of the trap can only go on one way as the outer
middle screw on the trap makes sure it aligns up exactly the same.
Once I fitted the case back over the trap, I fitted the screw back
into the trap and then used a 2.5mm drill just to pre drill the
plastic former on each hole to allow for the new 16 self-tapping
screws to fit.
I would recommend that you use stainless steel screws as not to rust.
Photo 11. Finished Trap all re-assembled.
Photo 12.Showing the coax connection circuit board.
Coax Connection
In photo 12, it shows the PCB at the coax connector it has a little
PCB board. On one side, it has one 240pf capacitor and a coil with 5
turns.
Photo 13. Shows the other side which has two wound coils round a
ferrite core. The coils have 16 turns and 21 turns. It has a large
capacitor of 60pf and a smaller capacitor of 33pf.
Photo 14.Shows a side view of connection board.
Photo 15.Showing it has a slot on the pin's end.
Conclusion
As the first vertical trap was found to be the problem, I did not
open the other traps but measured for continuity on all the traps. It
is easy to lower or tilt over my antenna to service, if necessary,
but all the rest of the traps will be built in the same way so if you
want to reinforce the rest, then make sure you have enough screws.
My motto is" If it ain't broke, then Don't fix it."
I added the coax connector information at the bottom as I saw this
online and did not know it had this inside. Again, I did not open
that, but to show you it exists.
I hope you enjoyed the read and that it helps you to repair your
antenna.
73 de Rob
© 2024 ~ ZL1RJS