On Saturday 2017-05-20, Paul ZS1V and Rassie ZS1YT headed to Jonaskop to investigate a problem with crackly audio on the 145.675 Jonaskop repeater and to attend to some pre-winter preventative maintenance.
The weather was sunny, but cold, with a fresh cold breeze that could be felt as soon as one was a few meters up the tower. Most of the area to the South and East of Jonaskop was under thick cloud.
Overberg under a blanket
The SWR of the VHF antenna was found to be good. On previous visits water had been found in the connection between the feedline and the 4-stack antenna, despite there being a good water seal at that point. The phasing harness has a plastic tube section and extra precautions against moisture entering the system at that point were taken.
The link controller was also attended to, and audio crackle eliminated by re-seating some of the ICs.
An adjustment was made to the repeater configuration to make it go back to the desired setting after a power interruption.
On Sunday 5 June, the team consisting of Jan ZS1VDV, Paul ZS1V, Mike ZS1TAF, David ZS1DDK and Andre ZS1AN headed to Jonaskop to attend to a number of issues at the 145.675 repeater site.
It was a sunny, but cold day at around 1C when the team arrived, but warming to a comparatively pleasant 7C by the time we left at around 5pm. A light breeze aided in keeping everybody’s hands cold.
Jan ZS1VDV selecting the correct scalpel
The following tasks were completed:
- Replacement of a faulty speech chip in the controller and re-enable temperature and voltage measurement macros
- Correction of the audio emphasis for audio from the links to the 2m repeater
- Realignment of audio talk through levels
- Installation of a second backup battery
- Reinstallation of the VHF ferrite circulator and harmonic filter after the latter was retuned
- Improve station grounding
- Install vent covers on the equipment housing
- Investigate and correct interference problem on the 2m repeater – VHF SWR was high (> 2.5)
Mike ZS1TAF and Paul ZS1V attending to the VHF SWR
At the end of the day, a light crackle in the repeater tail was traced to the audio mixer in the controller. This was also corrected.
FLTR Paul ZS1V, Jan ZS1VDV and Andre ZS1AN
Photo credit: David ZS1DDK
The team arrived home again around 19.30.
On Sunday (2016-04-17) Jan (ZS1VDV) and Paul (ZS1V) did maintenance at Jonaskop.
Left home around 06:30.
Drove to Jonaskop via Somerset West arrived on site 09:00.
It was very cold on site and windy. This made everything up to 12:00 happen slowly and with cold hands.
Paul turned the Hanskop link antenna from vertical to horizontal polarisation. Had to replace the bracket as the U-bolts broke off due to rust.
Jan resolved the power issue on site. The plastic cap on the positive terminal of the power supply was melted. The reason for this could be that it came loose due to temperature cycles. The plastic was removed and the terminal tightened with a tool.
The next step was to swap around the two GM300 link radios due to deviation differences in the models. Riversdal is 16k0F3E and Hanskop 11k0F3E. Frequencies were updated accordingly. Then the radios had to be realigned as the old Hanskop (now Riversdal) radio was off frequency by 2.8 kHz.
We started the process to change the VXR9000 audio input link from the controller to the correct pin for emphasis. This failed due to a impedance mismatch which could not be resolved on site.
The controller was also found to have speech out problems. For now only the linking macros work and all other have been deactivated till a new speech process chip can be installed.
The duplexer was re-tuned. The insertion losses were close to 2dB and the rejections were around 72dB. After re-tuning the results were: TX (1.6db insertion, 86.08db rejection) RX (1.55dB insertion loss, 81.71 dB rejection).
The circulator was removed as it was giving bad SWR (3).
Left site around 16:45 arrived home at 19:00
ZS1TAF went to Jonaskop.
He realigned the Hanskop link antenna but was not successful in re-establishing the link.
On the next attempt, it would be best to have people on both Jonaskop and Hanskop side.
ZS1TAF and ZS1VDV went to Jonaskop.
We left Stellenbosch at 06:15.
First did a quick status check on battery system, power supply and SWR on VHF repeater. All was fine, except the SWR on the VHF was a bit high (The first time I saw a VXR9000 cut back on it’s output power).
Installed small rack
Swopped out the repeater with the one aligned with link controller en link radios.
Installed new rack mount PSU.
Installed link radios.
Installed link controller.
Installed new circulator.
Replaced fly lead between duplexer and heliax (to remove a damaged barrel connector, in future we must replace the UHF t piece FMF)
Serviced the heliax to 4 stack connection. Found some water in connection. Was dried out and triple rubber taped and double isolation taped for UV protection.
Was back in Stellenbosch 14:00