On Saturday 30 May, John ZS1EQ, Paul ZS1V and Jan ZS1VDV visited the Bottelaryberg highsite that hosts the 145.575 DSTAR and 438.300 multimode digital repeaters. While both repeaters were operating correctly, the internet link to the site had been down for several months, limitting the utility of these repeaters.
The internet link was re-established and a general health check of the site was performed. The gateway unit for the VHF DSTAR repeater was found to be faulty and removed from the site. As a consequence the UHF multimode repeater is now fully functional, but the DSTAR repeater is not linked to the internet.
A battery switch over and low voltage cutout unit on the backup batteries was installed.
On Saturday 9 May, Jan ZS1VDV and Ralf ZS1RK visitted the Jonaskop 145.675 repeater site. High wind conditions prevented close up inspection of the antenna connections on the tower, but the SWR of all the antennas were checked and found to be good.
The VHF repeater squelch was adjusted. The audio levels were re-aligned and one coax connector was seated correctly.
On Saturday 25 April, ZS1VDV, ZS1V and ZS1RK visited the Hawequa site, home of the 145.650 repeater and 438.800 link repeater between Piketberg and CPUT. The 4 x 200AH backup batteries donated for the purpose were installed with their fusebox and charger.
In addition the Vertex/Motorola repeater system swapped out for a pair of Kenwoods, a TKR750 VHF and a TKR850 UHF.
Kenwood TKR-750 and TKR-850
The waterproofing of the antenna connectors was also inspected and found to be in good order for the coming winter.
Connected a test repeater direct to duplexer (By passed all filters and pre amp except duplexer). Repeater was set at 0.22uV to open. Received ZS1GVW with lots of rain on signal (ZS1GVW running 20w) Received ZS1GVW clear (ZS1GVW running 60w) Did receive some interference on RX. Tested if CTCSS was a good enough filter (Confirmed).
Local RF noise suspected to be around 0.3uV
Removed 1 can from Celwave cavity set and retuned for 145.750 (-0.58dB insertion loss) Replaced VHF Engineering Bandpass filter with Celwave cavity (Insertion loss moved from -2.7dB to -.58 dB) Bypassed one of the two cavity bandpass filters in RX side (left -0.97dB)
Reconnected the installed PYE repeater.
Power after duplexer up by 60% +_ 15W output now.
UHF repeater:
Checked all cables. Fixed N-male connector on RG214 between duplexer and repeater in RX path) Retuned duplexer (434.625 -0.79 dB / 433.025 -1.38 dB / 102 dB isolation) Placed duplexer back.
Connector needed to be refitted correctly
Measured power and SWR: Repeater output 30W SWR 1 After circulator 27W SWR 1 After duplexer 22W SWR 1 (With dummy load) After duplexer 22W SWR 1.4 (With antenna)
Tested sensitivity direct on repeater (3.5uV) Investigated repeater. In process of investigation sensitivity went down to 0.55uV, but lots of rain) Could not measure 12db sinad, but suspect it to be around 5uV (the by ear test). Sensitivity was at 0.55uV at end.
Finshed around 14:30 and drove down.
Summary More thinking will need to be done about Heliax state. VHF Repeater TX side: improved output by swapping out band pass filters (2.1 dB improvement, output now 15W) RX side: removed 2 cavity bandpass filters (improved RX by 3.63 dB) UHF Repeater TX side: improved by 0.83 dB RX side: improved by 4.7 dB UHF repeater is not healthy.
TODO: Investigate Antenna options VHF Investigate why 1.4 SWR on UHF Decide on Feeder Think about linking Service UHF Repeater
VHF and UHF stacks below dish on right pointing toward left of Robben Island
Measured Power and SWRs
Batteries 13.3V and 13.2V Power Supply Unit right 26.64V Power Supply left (DC to DC) 13.7V Power Supply RHS against rack (DC to DC) 13.8V (Negative grounded on rack)
Between Duplexer and Heliax 10W SWR 1.4 Between T4002 and circulator 30W SWR 2 Between Circulator and Band Reject Filter 16W SWR 1.7 Between Band Reject Filer and Duplexer 13W SWR 1.4
Tested Heliax and Antenna
Used hand radio as source Bottom 6W SWR 1.4 Removed antenna and replaced with dummyload Bottom 6W SWR 1.4 Top 5W SWR 1 Reconnected antenna Top 5W SWR 1
The 2 stage circulator was retuned to correct SWR problem (145.750 before -1.2dB SWR 2 after tuning -0.38 dB SWR 1) The first cap in circulator is suspect. Bandreject (Notch) filter on 146.2375 was measured and the one nut was tightend The duplexer was measured and retuned to get a beter insertion loss on 145.150 (before -1.95db after -0.74db) (One cable in harness was found to be wrong length and was replaced) Wideband bandpass filter was measured. This was connected between cavity bandpass filter and preamp. Moved to be between circulator and bandreject filter. Cavity bandpass filter was retuned for beter pass band. (before -5.71dB after -4.6dB) Tested gasfet preamp (145.150 +16 dB)
Tuning VHF Duplexer
All equipment was labeled with measurements.
Repeater sensitivity measured -0.4uV
Everything reinstalled and some final measurements
Between T4002 and circulator 30W SWR 1 Between ciculator and Wideband bandpass 27W SWR 1 Between wideband bandpass and band Reject filter 12W SWR 1 Between band reject filter and duplexer 11W SWR 1 After duplexer, just under 10W Sensitivity after duplexer 0.3uV
VHF Repeater and UHF Repeater
Tested UHF dipole antenna on side of building (good strong signal to 438.800)
Cleaned up and drove down +_ 15:30.
Summary More thinking will need to be done about Heliax state. TX side: losses was improved and corrected, but with the introducing of the wideband bandpass in the correct place, no power was gained. RX side: removed wideband bandpass (2.2 dB improvement), returned cavity bandpass (1.1 dB improvement), retuned duplexer (1.2 dB improvement) Total 4.5 dB improvement
TODO: Investigate Antenna options Decide on Feeder Think about linking Retuned Wideband bandpass Filter to have less loss on 145.750 (currently -2.7db) Move preamp before cavity BP filter. (This would just make more sense to amplify, before filter) Remove one can from Cavity BP filter, retuned for 145.750 and replace wideband BP filter. (Will make about 1.2db more sensitive on RX and about 2dB less loss on TX) Service UHF
On 23/24 July the Motorola repeater was damaged in a storm. It is suspected that the repeater was damaged by static from lightning.
Roof damaged by storms
On 26 July Jan ZS1VDV and Paul ZS1V investigated and found the repeater damaged. The repeater and duplexer was removed. The antenna SWR (1:1.03) was checked.
In the following weeks a new install was planned:
a backup repeater serviced by Verstay (ZS1VDV, ZS1V)
correct length coax acquired (ZS1VDV, ZS1YT)
duplexer tuned (ZS1VDV, ZS1V)
circulator tuned (ZS1VDV)
power supply connector replaced (ZS1V)
The morning of 31 August started at 06:00 with the last few tests of the configuration. Backed all equipment and tools. Left for site around 07:30
Repacked all into 4×4 vehicle at ZS1DDK.
View of Hout bay
On site around 10:00
Duplexer and circulator
Installed duplexer (Decibel Products 6 can). It was tuned to -2.04 dB insertion loss on RX, -2.5 dB insertion loss on TX, and -115 dB isolation between RX and TX). Next was the installation of the rack mount power supply (13.82 V) and Vertex VXR 9000 (sensitivity set to 0.25 uV) repeater.
Power Supply and Repeater
SWR was rechecked between repeater and circulator, circulator and duplexer as well as after duplexer, all was found to be perfect flat (1:1.05). The power output after the duplexer is 14W.
Folded Dipole just above first landing
A few test contacts was made to confirm all working.
Packed all equipment and boxes and returned home at around 11:30
A quick lunch sponsored by ZS1DDK was enjoyed at Peddlers on the Bend.
Problem: About 2 months after the big rebuild in September 2018, the UHF repeater was starting to drop out after a few seconds of transmission.
This lead to a long fault finding process with help from the high site managers’ personnel to save on trips to site, on a very bad road.
After 4 months of problem finding, it was concluded that was not the repeater and not the antenna, but most probably the duplexer.
The WCRWG do not have a spare 1.6MHz split UHF duplexer. One was constructed out of spare notch cans. This happened over a process of 2 months, to make up a custom duplexer coax harness and trying to get the pass-through SWR as low as possible. With everything ready, it took some planning to get the vehicle, weather and correct people aligned to go do the swop out repair on site.
It started at around 06:30 today. Packed the repeater, swop-out duplexer and all required tools. Next was the pickup of keys.
Vehicle packed and ready, All in good spirit after the coffee ZS1V provided
The team (Sybrand ZS1SJ, Paul ZS1V and Jan ZS1VDV) got together at around 08:00 to repack all equipment into the 4×4 to go up.
Hanskop in the clouds
Around 08:15 the trip up started. Sybrand got a few chances to use the 4×4 capabilities of his vehicle.
On site the repeater was reinstalled. Next the debugging of the high SWR around the duplexer was completed. SWR straight on antenna 1.2. SWR through duplexer to antenna 1.8. SWR through duplexer to dummyload 1.0. It was concluded that the current duplexer on site was also not the problem. With a bit of head scratching a short patch lead was added to the antenna feedline. That took the SWR through the duplexer down from 1.8 to 1.3.
The last part was to correct the power sensing of the controller. Suddenly the UHF repeater started to restart on transmission. With some debugging it was found that the 10 A PSU used on the UHF repeater was suspect. This PSU was removed and the UHF repeater moved over to the main 30 A. The total current draw is just below 20A on full transmit. The calibration of the power sensing was updated and the voice responses also updated.
DTMF:
8323 – Controller Voltage (This is the main power supply when on mains, and battery when on backup power)
8324 – Main PSU voltage
8325 – Battery voltage
Team photo in the clouds with tower in the back
Everything was packed up and returned home. Home around 13:00 and unpacked by 13:30.
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.
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 toneRepeater without filters at low RF level; 0.683uV 88.5Hz CTCSS @400Hz and 1.5kHz deviation @1kHz toneRF 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 51dBmRepeater 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)
