Monthly Archives: Jun 2019

Jonaskop maintenance 2019-06-29

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On 26 June it was reported that the repeater is not functioning and constant keying.

From the detailed fault report it was concluded that a power supply is the most likely problem. However with power problems, there could also have been big equipment failure.

Paul ZS1V and Peter ZS1PDE assisted with the ordering and pickup of a replacement PSU for the site.

Jan ZS1VDV packed for all scenarios on Friday evening. This included making controller link cables for the spare repeater.

All equipment ready and packed

Saturday started very early with Sybrand ZS1SJ meeting up with Paul to collect keys and replacement PSU in Somerset West.

    Sybrand next was picked up Jan ZS1VDV and loading all equipment in Stellenbosch at around 07:20.

    Sybrand driving 330km for the day

    A route via Worcester to Jonaskop the best option, as the Franschhoek pass was closed and the round via Grabouw to Villiersdorp was reported on Thursday to have loads of sand after the winter storms,

    Arrived on site, it was very clear that this was going to be a very cold and windy visit. Around -2.5 C and very strong gusts of wind.

    Sybrand hiding from wind

    As soon as the repeater hut was opened, it was found that the repeater was on backup power (measured to be 12.8V). This was very strange as the repeater never went to backup power during the week. Next the PSU and 220V was tested all over the site, and found the no 220V was available. With out more information, it was decided to swop the PSU.

    Isolator after lighting strike

    On the way down, Eskom was found working on the line. At this stage it was clear why the repeater was on backup power. In the process of driving up, Eskom switched of the 11 KV line to work on it. The 11KV line was hit by lightning and an isolator needed to be replaced. With the one line on the delta 11 KV line down, the transformer would have converted to 220V star 3 phase, but the 220V would not have been stable. After about 1.5 hours the repair was concluded. They had to use a gas flame to shrink the heat shrink on the lug.

    Eskom replacing isolator

    Returned to site, checked that all power was up and running. It was found the that controller configuration was corrupted and needed to be updated. The main and battery sense DTMF codes was also swopped as listed on the TODO list for the site.

    Jan using repeater hut door to hide from wind to configure controller

    The link radio the Hanskop audio levels could not be realigned as it was just to cold and wind to strong.

    The tower guy lines was giving a quick inspection and found that they will need service on next visit.

    Unpacked in Stellenbosch around 14:00.

    Sybrand last stop at home around 14:30 for a total round trip of 330km.

    Sutherland Repeater maintenance 2019-06-11

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    Transmitter:

    Output power:                  21.6W
    Frequency error:              -315Hz
    Deviation:                          1.49kHz

    Receiver:

    Sensitivity:                          0.683uV for 12.2dB SINAD (NOT CCITT weighted)
                                                 @1.5 kHz deviation AT 1kHz
    Squelch                              Could not be measured. Comms test set only goes down to 0.350uV

    TX Filter unit:

    RF power before filter:   42.63dBm (18.3W)
    Return loss:                       3.4dB  !!!!!!(VSWR 1:5.23)
    RF Power after filter:      34.3dBm (2.7W)
    Antenna Return loss:      15.7dB (VSWR 1:1.39)

    After tuning the filter unit, I got the following results:

    RF power before filter:   42.85dBm (20.1W)
    Return loss:                       23.2dB (VSWR 1:15)
    RF Power after filter:      40.34dBm (10.3W)
    Antenna Return loss:      15.7dB (VSWR 1:1.39)

    RX Filter unit:

    Measured loss at intended frequency:     20.6dB
    Isolation at plus 600kHz                               Around 50dB

    After tuning the filter unit, I got the following results:

    Measured loss at intended frequency:     2.4dB
    Isolation at plus 600kHz                               Around 50dB

    Repeater without filters at high input RF level; 20uV 88.5Hz CTCSS @400Hz and 1.5kHz deviation @1kHz tone

    Repeater without filters at low RF level; 0.683uV 88.5Hz CTCSS @400Hz and 1.5kHz deviation @1kHz tone

    RF power going into the filters. Note poor return loss.

    After tuning the filter. Note marker on 145.000MHz. Reference at the -10dB mark.

    Results after tuning the TX filters.

    Receiver filters before tuning: Reference is at the -10dB mark (-22.6dBm) indicating filter loss at 20dB.and off frequency.

    Receiver filter after tuning. 2.4dB loss and on frequency. +600kHz isolation of around 51dBm

    Repeater performance through both TX and RX filters after tuning filters.

    The Site: Gentle reminder not to tamper……..

    Conclusion:
    I could probably get better results tuning the filters if I had the directional coupler with me. Maybe next time. I would have also preferred to have the manufacturers specifications to test against but did not have at the time. In my experience the repeater performs well according to what I measured. I tested the repeater from the town using a 5W hand held radio and got full quieting from the repeater with good quality audio. I there is someone who can test from the N1, some feedback would be great.

    Report compiled by Neville Gleeson (ZS1NEV)

    Site tested by: Neville Gleeson (ZS1NEV) and Deon Lamprecht (ZS1AFU)

    Hawequa maintenance 2019-06-09

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    On Sunday a team of four consisting of David ZS1DDK, Mike ZS1TAF, Markus ZS1MTB and Rassie ZS1YT left home at 7h00 to meet at the site gate at 8h00. The purpose of the visit was to replace the 3 cable stays on the tower with new Stainless Steel cables, clamps and turn buckles.

    Stay replacement

    A 6m dipole was also fitted to the tower for future linking of a 6m simplex radio onto the repeater system.

    Although quite a strong wind was experienced, the temperature on top of the mountain was a very cool 18o C.  Work started immediately with Mike and Markus climbing the tower and David and Rassie fixing the cable stays on the bottom anchor points. The team returned home by about 12h30.

    6m antenna

    The 6m Webb-antenna and Stainless Steel cable was donated by Rassie ZS1YT

    The antenna clamps, cable ties and other hardware was donated by Mike ZS1TAF

    Travelling to the site by ZS1TAF, ZS1MTB and ZS1YT was also donated.