October 18, 2018 - Trip to the VE7EGO Site on the Commonage for Fault Finding
Summary:
Technical committee volunteers went to the VE7EGO repeater site to investigate why the UHF DR-2X repeater's output was so weak. What we found was an out-of-tune duplexer. We tested the repeater and it is functioning properly. We also tested the VHF DR-2X repeater to ensure all was good and it is. Mike VE7KPZ took the duplexer down from the site to get it retuned while the UHF DR-2X repeater stays offline.
Attendees:
Terry VE7TRZ
Ted VE7UIH
Keith VA7TEE
Mike VE7KPZ
David VA7SZ (remote tester in Vernon)
Access:
The usual route was taken to access the VE7EGO Commonage site. The road was a good challenge.
Just before heading up to the site, Mike telephoned Kevin at 250-744-0732 who is in charge of exploding/disposing of WW2 munitions still in the hillsides. Upon departure from the site, Mike texted Kevin to notify him of our departure. Kevin likes to know both the ins and outs of our visits to the site.
Tasks Undertaken:
The team started the visit by inspecting the UHF DR-2X repeater and related feed lines, duplexer and antenna. We had thought the reason for the weak output might likely be the antenna, but it turned out that it was the duplexer out of tune.
A scan of the feedline and antenna showed very low VSWR at TX and RX frequencies - good.
An output test of the repeater into a dummy load showed exactly the power output expected - good.
A scan of the duplexer showed the notches off frequency - bad.
A final RF output test of the repeater confirmed again that the repeater was in good order and it was all the fault of the duplexer - good. Thanks David VA7SZ for being our remote tester for the output test.
Now, let's flash back a year or so when the duplexer was installed and placed into service. Shortly after that day, we were informed by the tuner of the duplexer, Ralph VA7NU, that the rod nuts on the duplexer may not have been tightened after the recent tune. We hadn't touched the duplexer rods, and scans showed the notches in the right places at installation time, so we left it in service.
Flash forward to a couple of weeks ago and the likely expansion and contraction of the duplexer due to heating and cooling cycles from our ever changing weather patterns likely moved the rods.
With the issue sorted, Keith VA7TEE, a first-time visitor to the VE7EGO site, continued to prime the seasonal system checks on the VHF DR-2X repeater. Keith utilized Terry VE7TRZ's power/VSWR/frequency counter meter, Mike VE7KPZ's power/VSWR/frequency counter meter, and Mike's RigExpert AA-230 Zoom antenna analyzer to inspect the system under the careful supervision of Terry, Mike and Ted VE7UIH. All checked out well with the VHF DR-2X repeater, its duplexer, feed line and antenna.
Next Steps:
Mike VE7KPZ will get the duplexer re-tuned, the rod nuts securely tightened and then return the duplexer to the site for reinstallation with Terry VE7TRZ and any other club members who want to join us.
FYI and 73,
Mike
VE7KPZ
NORAC Vice President