Built with

Latest posting was on 2019-06-11 in Clubnews Member login


2017-09-27 The 70cm Repeater at Midrand has been repaired. We had to replace a capacitor and currently been tested. Will be back on the air by Saterday afternoon. My apologies for the inconvenience. Die 70cm Herhaler te Midrand is herstel en word tans getoets tot Vrydag 30 September. Ons moes n kapasitor vervang en sal die Herhaler weer teen Saterdag middag in werking wees. Jammer vir die ongerief
Back to top

Midrand Link repeater back on the air!

On Tuesday afternoon Craig ZS6RH and Pierre ZS6PJH cleaned out the repeater and replaced the damaged cable and the siezed fan. All was tested on the bench and functioned well again. The power thru the duplexer was a bit low with 3dB loss, so that was tweaked back to 1dB loss, with around 10w out now. 

On Wednesday 21-04-2016 Pierre re-installed the repeater on the Midrand High site and it's working well again.  There is still work to do on Radcliff to optimise the antenna, this is in progress with a contractor appointed by the committee to handle maintenance on the towers.

73 de ZS6RH 

Back to top

Wonderboom 439.025, Midrand 438.825 Rpts off-line due to maintenance. 

 Please watch this space for further information as the Midrand repeater gets a service and new link radio, and Wonderboom undergoes a complete refurbishment.


Back to top
Back to top

PARC main antenna destroyed by first storm of 2016!

145.725 on backup 2m antenna, 438.725 off the air.  Repeater coverage negatively affected. 

While we were all very relieved to have the first real rain of the season, the rain in the first weekend of the New Year came in the worst lightning storm of the season.

In previous years the installation, a co-linear near the top of the Radcliffe tower, was protected by the large aluminum monitoring antenna that adorned the top of the tower for the past two and a half decades. 

This installation was removed in winter 2015. After it's removal there was no spike placed on the top of the tower to discharge the static.

 PARC has permission to place the spike on to and replace our antenna system. We have "inherited" a second antenna, currently a 2-stack with a good 1/2" feedline, which will be upgraded to a co-linear for use on digital modes, both D-star and DMR eventually. 

The Repeaters survived, thanks to the superb earthing of the feedline and entry point, with the 145.725 coming alive when switched to the spare 2-stack visible in the pictures below the damaged dual band co-linear. Since the antenna is 2m dipoles only, the UHF is off the air.

UPDATE : Reports are that the temporary antenna is not performing well, with the Midrand link struggling to override the noise on the repeater input frequency in the mornings, some noise identified from a newly launched Chinese amateur satellite. 

I plan on getting a new antenna up before the weekend's bulletin.  

 73 de


Repeater custodian,


Back to top

Repeater network status update, mid December 2015:

The 145.725 repeater located on the Radcliffe tower on Johan Rissik Drive near fort Klapperkop is functioning fairly well. Occasional bursts of interference are heard, especially in "drive time" as all systems get busy on the site. Noise overrides the weaker stations as the ctcss keeps the receiver quiet when the rpt is in standby. 

In the North the 439.025 UHF linked repeater was swapped out for the third time in as many months. The original repeater was drifting after about 20mins use. The transmitter radio was swapped out, but suffered audio failure after 30 mins or so use. It is suspected that the duplexer is off frequency creating a high swr and consequent tx failure due to overheating. The original system has been operating without much trouble for approx 5 years. The second replacement repeater was fine on audio, didn't drop out, but has no CTCSS (88.5 out only) and suffers periodic lockup from a noise source on or near the site. A third repeater/link has been slotted in in the last week, but this seems to have an intermittent audio problem on the UHF TX. The latest system has excellent cooling and the duplexer is good, but the Vertex VX2100 transmitter seems to have a dry joint in the audio path. 

Midrand's 438.825 link has a noise burst on the VHF link, it doesn't interfere with the 2m, but interference bursts are noticed on the UHF.

The central UHF repeater (co-located with the 2m on Radcliff) on 438.725 is still the temporary backup low power repeater. Johan ZS6JPL assures me he has made progress on the Motorola and has isolated the audio failure and awaits info on replacement parts. The Motorola boasts 50w continuous power, and has superb audio. we look forward to having it back on the air soon. Please feel free to use the frequency, it works well enough and is great when the 2m is busy. 

 Please enjoy the use of the repeater network over the holidays. I will attempt to get to some of the maintenance over the holidays, weather, schedule and funds permitting. 

Please remember:

1) The linking adds a delay of 1.5 seconds between the UHF and VHF systems, don't be too hasty on the trigger ;)

2) Mobile stations have priority. 

3) There is a 3 minute time out timer on the Midrand UHF link to 2m, keep overs tight.

4) Follow the amateur code when using the repeater. Courtesy toward fellow radio amateurs will go a long way. 

73 de Craig ZS6RH 

Back to top

Happy new year and good DX to all

I must apologise to all for the long space between my last posting, life and passwords have a way of distracting one and disrupting communication! I have resolved to post here on a monthly basis to keep users informed of any changes to the repeater network. 

Main antenna replaced after 6 years of good service. 

In the past year we replaced the antenna on the 145.725 repeater. The co-linear antenna had been in service for more than 6 years. Corrosion had crept in over the years. Results from the new antenna were again as in "the old days".

 2m 145.725 has 88.5 tone squelch again

As a result of the increased receive sensitivity we have again opted for the 88.5 tone squelch. This is now the standard on almost all GP repeaters. Remember to ensure that your radio is set to FM narrow or the deviation is set to 3kHz max deviation. Where possible turn the deviation down and the mic gain up (especially on commercial radios that have a "thin" strictly 2.2kHz deviation) to keep a punchy audio while not splattering. Assistance with this is available from myself, Hans ZS6KR or other amateurs and some commercial guys with the necessary lab equipment. MRK has a tone board for 88.5Hz tone generation and various amateurs can assist with the installation. 

438.725 UHF 

2014 also saw the commissioning of the 438.725 repeater on the Radcliffe primary transmitter site on the highest spot in Pretoria, near Fort Klapperkop. This repeater was purchased in 2012 and eventually moved from it's former site on the CSIR tower.  Technical issues (no tx audio) saw the replacement of the high power Motorola Quantar with a simple "back to back" repeater comprising a Motorola CM-140 receiver and Motorola GM 350 transmitter. Sadly the dated GM350 randomly shifts approx 1kHz and later restores itself, so I'll run up another transmitter and drop that in while the Quantar is in for repairs. Although the power is low on the 438.725 repeater is "low" at 15w, the coverage is remarkable. There is no tail on this repeater. 


Look out for news on the D-Star repeater on the D-Star page. We aim to have the repeater up and running soon, and then the data link to www will follow if the RF side of the RPT is okay. The site on which we are placing the rpt should be cleaner than a hi-site, being located on om Fritz ZS6SF's qth in Grootfontein, East of PTA.



Back to top

CTCSS off for the moment.

Mid April the Kenwood TKR 720 was placed back in service. this has no ctcss/tone squelch, but does still transmit 88.5.

We are still experiencing pulse type noises "kerchunking" the repeater from the highsite. This seems to be a problem on all amateur repeaters that don't use CTCSS in GP.  

Communications have been disrupted by both interference coming up the powerline to the Nav lights next to the antenna on the top of the tower, and noisy tx on the site from time to time. The lights were attended to by ZS6RH and are quiet for the moment. 

UHF link repeaters continue to perform well. They operate on 439.025 (88.5: 10w) from Wonderboom  in the north and 438.825 (88.5: 5w) from Midrand in the south. Both have a 3 minute Time out timer, watch out for the crocodile! Midrand has a "busy channel lockout", so wait for the '725 tail to drop out.



Back to top

PARC forced to use CTCSS on 145.725 repeater.

Due to the increased levels of interference on the high site housing the 145.725 repeater the PARC committee has no choice but to re-introduce the ctcss/tone squelch of 88.5Hz. We apologise for the inconvenience to those without the ability to generate tones, but the interference is unbearable and reduces the repeater to virtually a useless noise. The Site owners have been contacted, the offending station owners notified and nothing appears to have been resolved. ICASA has been asked to look into the matter.

It is noted that the interference has increased after a series of violent lightning storms. ZS6RH has re-tuned the cavities, swapped the repeater, and replaced the feed line with no reduction of the noise. Spectrum readings reveal several errant transmitters nearby.

It was noted that by this afternoon the noise seems to have increased, indicating that something else has significantly changed on the site.

73 de


Back to top

PARC 145.725 repeater feed line upgraded 04 March 2012

 At about 07h30 a group of radio amateurs gathered at the foot of the tower hosting the 145.725 repeater at the site known as Radcliff, on Johan Rissik drive in Pretoria. Eddie Ras, ZS6RAS and Robert Degossely, ZS6PRO arrived first, followed by Craig ZS6RH with Andre ZS6GCA and later by Hendrie ZS6HFE. 

Craig had summoned this crew after a request by Eddie to get some tower experience and, knowing that the season is perfect for such strenuous activities, chose this day based on availability of personnel.

The aim was to install the "new" LMR 1200 feed line that had been donated some two years before. Since the feed line was donated shortly after the LMR 600 was installed by Craig ZS6RH and his staff, the cable remained in storage until recently, awaiting THE day. 

Back to top

Wonderboom repeater linked to 145.725

Handheld coverage: 

439.025, 7.6 mHz Split, 88.5 tone. 3 min time out timer from UHF to VHF, unlimited from VHF to UHF for bulletins. By default connected to IRLP and Echolink through 145.725. Please note the 200ms delay between the repeaters (press ptt before you speak).  

Back to top

Midrand High UHF Linked Repeater, to 145.725

Mobile coverage, 10w with 1/2wave antenna 

438.825, -7.6MHz split, 88.5 tone. Also 3 min Time-out timer,  slight delay between the VHF and UHF. Tail 1 second. Still under development.

73 De ZS6RH 

Back to top

Suspended (jammer hieroor Hendri).

Bronkhorstspruit (Ekandustria) UHF Repeater Linked to 145.725

Mobile coverage: 

 439.075, -7.6 MHz split, 88.5 tone. 3 min Time-out timer from UHF to VHF, unlimited from VHF to UHF for bulletins. Slight delay between repeaters, automatically linked to IRLP and Echolink. 

NOTE: This repeater has a BCLO (busy channel lockout) between UHF and VHF to prevent interference to 145.725, wait for the tail to drop on the VHF before transmitting.

Back to top

VHF 145.725 Radcliff Repeater given a "haircut". 

On Saturday  18 February 2012 Craig ZS6RH, Andre ZS6GCA, Caleb and Callan (Sons of ZS6RH) attended to the 145.725 repeater at Radcliff, on Johan Rissik Drive, Groenkloof Nature Reserve. Reports had been received that the coverage had waned. There has been no work done on the repeater for a whole year, save the testing of the D-Star on the same site and in the same rack. Since moving the equipment into the new rack, and performing some modifications to the power and RF connections (N-Types replaced SO239), the "old faithful" Kenwood TKR 720 is stable and reliable. A proper functioning aircon helps too :)

The first thing to be tested was the SWR and power output. The SWR needle moved slightly, all good, so the power was measured and attended to.The repeaters output was erratic, varying between 35 to 40w. A couple of wipes of the pot cleaned the output and stabilised it. The loss through the cans was almost 2.5 dB, so it was tweaked till it came back to it's expected 1.7dB. The squelch was also tweaked, and a couple of wipes of the pot cleaned that up. The squelch threshold was adjusted to allow weaker but intelligible signals through. The PSU voltage had crept up to 14.7v, this was lowered to 14v

Field test proves that the repeater to be functioning well again.

Interference has been traced with a "Spec Anny" to a spurious paging and alarm repeater and reported to the site managers. A commercial voice repeater that has bugged us before was attended to the day after reporting (Wednesday last). I'll keep an eye on the progress of the clean-ups and pass details of continual offenders to ICASA.

73 de ZS6RH

Back to top

145.725 Interference tracked and executed.

Tuesday evening on the way home from work I managed to trace the interference to a commercial repeater that needed a haircut. The repeater opened the squelch on 145.725 almost every time it keyed up. This interference has been bugging us intermittently for months, but would disappear whenever I thought of tracking it down.

On Thursday morning I got hold of the company responsible for the repeater, and they responded immediately and installed their backup unit. The interference has not been heard since, even though the offending box has been returned to service repaired. Thanks to SP, ZR6SPD for attending to the matter so promptly.




Back to top

Repeaters Update

Beginning December 2011 

The constant background interference bugging us on 145.725 seems to be resting for the last few weeks.

Wonderboom is again active on 439.025 and is linked to 145.725. Use a standard 7.6 MHz split and 88.5 tone.

Midrand is again active on 438.825 (with a little more power and deviation), also permanently linked to 145.725.




Back to top

North Gauteng Repeater Working Group

The idea was recently discussed by Sander ZS6SSW and myself (while working on the donated Icom D-star system) to provide a wide area coverage fm voice radio network in Northern Gauteng, using existing infrastructure. With the speed and distances often traveled by hams in Gauteng, coverage that is wider than that provided by current VHF and UHF repeaters is often desirable. Furthermore, repeaters are often not used because of poor coverage and interference, but are not maintained due to lack of use!

I believe that by making it easier for new hams to communicate over greater distances using the minimum of equipment, we will create further interest in our hobby and have a better uptake of newly licensed hams, as well as making it easier for those in restrictive environments to participate in the hobby.

To this end I would like to form a repeater working group in North Gauteng in order to link all (unused) UHF repeaters and thereby creating a coverage area that stretches our entire geographic zone, From Midrand to Nylstroom, from Hartebeespoort Dam to Bronkhorstspruit, and further.

I'm looking at the models of the Cape linked system and the NZART national system. . I envisage that the group can take responsibility for the local APRS systems as well.

The linking of these repeaters will enable mobile users to enjoy communications further than they currently enjoy, it will enable coverage for handheld users (due to the nature of UHF comms) and provide extended coverage for both National and Club bulletins and activities like rallies, cycle races, youth events, Hamnet exercises, etc.

We would like to get together with parties interested in being part of this working group on a technical level. We envisage using all available technologies and skills. I foresee that the D-Star system, donated for use in Pretoria by Icom Japan via Multisource and The Icom Hamshack Pretoria, will become part of this system.

The first phase will be to bring the repeaters up to a standard, which we will determine. We will need to co-ordinate between the clubs who will select representatives to be part of the working group. 

Contact me if you are interested, we would like to get together this week and get started. (Please forward this to anyone who I may have missed.)


Craig Symington
craigsym at hotmail,com
Back to top

The week (month/year) in review, week ending 17 July 2011

(ZS6RH’salternative to “lengthy” reports in meetings and on bulletins!)

Thanks Hans ZS6KR for re-enabling my permissions on this site!


See the report by Sander and myself in Club News. The project is still in tweak and test phase.


Indications are that the recently installed UHF gap filler links work well. Please remember the 3 min TOT, and that the gap-fillers are not repeaters (yet). I’m investigating the viability of making the gap-fillers into permanently linked stand-alone repeaters. Your thoughts and participation would be appreciated.

Echolink and IRLP

The connection was repaired by Johan ZS6JPL earlier in the month. The open circuit on the audio line was causing the incoming calls not to be heard. We are enjoying good connections especially with frequent (late night) echolink calls from the ‘States. Harry ZS6HRD seems to get more frequent connections to Tony in Australia.

Power Failure:

Last week-end the power failed at Radcliff due to a municipal pole/cable fault. The generator kicked in and everything carried on operating. The site is fitted with a generator capable of supplying power to all the equipment including the air conditioner. As a result of theft last year the backup batteries were not installed. I also found that the backup battery circuit on the TKR 720 repeater was the most common cause of failure on the repeater. Generally at Radcliff the power is restored before the generator runs out of fuel, and the downtime is less than 5 minutes.

On Monday at around lunchtime the repeater went dead. The UHF repeater was dead as well, so power failure was suspected. After 10 minutes I called Greg ZR6JDD from Webb Industries, the owners of the site. He informed me that the power had been off for a day and that they were re-fuelling the generator. 20 minutes later the repeater was back on the air.

UHF Repeater

I had the club’s backup battery (105AH deep cycle) that I had removed from Wonderboom last week in my garage, so I loaded it into the bakkie and took it to Radcliff en route to Rooihuiskraal. I have connected the backup battery to the UHF repeater as its switched mode power supply will not drain the battery as the analogue supply on the 2m rpt does. At least we will not be without a repeater on this site in a power failure. The clubs UHF repeater on 438.825 (-7.6 split, 88.5 tone) has been running for over a month now without the CTCSS, and with a long 3 second tail. I left the tail long for a while as this assists in getting an indication of the usable range of the repeater when there is no activity. I have “Cut off” the tail to enable linking. There is a little commercial breakthrough occasionally, though not enough to warrant the re-activation of CTCSS at this time. With the short tail you hardly notice the breakthrough. I noticed that I had used a BNC T-Piece when I re-installed the transmitter a few months ago (the Motorola GM300 mobile radio that serves as our transmitter is fitted with a mini-UHF connector, having no adaptor, a mini-UHF to BNC fly lead is used). I noted that I needed to replace this with a barrel connector, which I did on Saturday afternoon.

Isolator, battery low warning and cut-off required.

In order to connect the VHF RPT to the backup battery, a diode block or similar is needed to isolate the VHF PSU from the battery. I might have connected the two repeaters to the same supply (the combined current is well within the rating of the supply), but the SM PSU seems to modulate the rpt and make it spurious (?) as experienced a few months ago! I’m also hesitant to “put all our eggs into the same” power supply “basket”. A comment was made by someone on the repeater that we should have a tone that warns us if the power is on battery, and Roy ZS6MI popped up and said that there was one some years ago. I have no memory or record of this, so if you know what happened to this circuit, or wish to design a new one, please let me know. What is needed is an audio indication on the repeaters tail in the event of battery operation. A further enhancement would be the activation of a TOT of say 3 min should the repeater be on battery supply. Lastly a warning of imminent battery failure should precede the low voltage cut-out. A further enhancement could be the lowering of the output power. I have some ideas; if you’re interested let me know.

DTMF remote control

As the network grows, so more control is required. We discovered this with the rollout of the voting system, needing to disconnect troublesome sites from time to time. To this end Pieter ZS6SPY donated a DTMF remote control box, aparrently designed in KZN some time back. We require the circuit diagram and the programming chart to integrate this into the repeater system.

Donation of earthing kits and connector sealing heat-shrink.

Another thanks to Pieter, ZS6SPY who donated the earthing kits for our 7/8th LMR 1200 coax. Pieter has earlier supplied us with the cable mounting kits for the cable, which was donated, with connectors, by Webb industries a while back. The plan is to replace the now damaged LMR 600 feed line that has been up the tower since 2007, before the rainy season.

Help needed installing feedline.

This LMR 1200 cable is thick and heavy, and we were instructed to install it on the back of the cable tray to avoid damage by careless installers of Wi-Fi who walk on cable trays and drag tens of meters of cat5 cable over one spot of coax. All the components are on hand, and the cable is on site, so let’s get it installed ASAP. I’ll repair the damage with SV tape and use the old feed line for the alternative antenna we need on the western side of the tower.

Future plans: The Microwaves

I am looking into linking all the sites with Wi-FI for management purposes. I’m getting onto the PTA WUG, and for that I wish to thank Roy ZS6MI. The PTA Wuggers are keeping the vandals at bay on our Keewykop highsite. This site will be re-integrated into the network once we have ironed out the voting bugs, and have some form of remote control on the system.

Finally, the light bulb in the NAV beacon!

At the beginning of the year I ascertained, beyond the shadow of doubt, that the use of energy saving “CFL” lights in the navigation beacons on Radcliff cause an unholy level of interference on the 145.725 repeater. This was determined to be the case regardless of the make of repeater in use and occurred even after the re-positioning of the antenna on the tower and was re-checked after the moving of the equipment rack within the reservoir in December. The temporary solution has been to regularly replace the incandescent bulbs (PARC agreed to do this on behalf of the site owner who uses noisy CFLs). Enquiries regarding LED solutions offered exorbitant quotes (15k). Nobody, it seemed, could offer us an ES 60w LED equivalent. Then I found one, at a hardware store for R60 each. The wattage on this one is a bit low, 40w equivalent, but I had to get one to check it out, and I did so yesterday. It works, no QRN!!

The LED lightbulb even looks good, and has no warm up time, and at 3.5w consumption, could be a worth while investment for the home. The suppliers offer a two year warranty, locally, nogal. Next task is to get some more beefy ones, and I’ll not be climbing tower to change light bulbs for a whileJ.

Donate suitable LED lights and we'll advertise your product on this site, while we prove them on the highsite!! (NO DIRECT SALES FROM CHINA PLEASE)

73 de

Craig Symington


Back to top

JULY 2011

Gap Filler Repeater testing in Midrand and Wonderboom

We are testing gap filler repeaters on 433.725 simplex 88.5Hz tone. (I'm trying the cellular principle for frequency re-use). 

MIDRAND and JHB Northern Suburbs

The first cross-band linked gap filler was tested by ZS6RH in Midrand for a few weeks at a temporary site in June 2011, and has subsequently been installed on a High Site next to the Midrand High School. The UHF link has a two-stack antenna located about 15m above the ground, and it's transmitter is set to 10w. The UHF gap filler transmits whatever it hears on the 145.725 repeater without TOT, but limits the input from uhf to 3 minutes (to prevent lockup of the VHF rpt from the UHF). Set your TOT to 3 mins when using the link to prevent the crocodile chopping you!!.

The site is positioned to cover the deep RF valleys between the New Road bridge and the JHB northern suburbs. Use low power on UHF or high power VHF where possible to avoid clashes with other users and other gap fillers. Feel free to "play" and report your findings to me.

I apologise if the link sounds better than your VHF transmission, but the Motos used in the links have such nice DSP ;-).

Wonderboom, North of the Magalies

A second gap filler was installed on Wonderboom and operates identically. This site is a bit more prominent and the antenna is a simple dipole (donated by Jean, ZS6ARA), (I'll screen it to the south on my next visit). To avoid clashes on the UHF frequency with other gap fillers and users in the VHF shadows I recommend theat it only be used on the north of the Magalies where VHF coverage is poor. As these gap filler links are not full duplex repeaters, be aware that other users of your link would only be heard if they are in simplex range. I am seriously looking at putting a proper UHF repeater (low power) on Wonderboom (permanently linked to 145.725), so let me know what you think.  

Lookout for another filler in the west, details will appear here. 

73 de ZS6RH

Back to top

May 2011


The 145.725 repeater is still operating in stand-alone mode. I have exchanged the box with another and we are now able to lose the 88.5 ctcss, as the front end is not as wide as the other repeater. Some mods to this repeater (Kenwood TKR720) have resulted in greater efficiency and we now run this at 50w rf power. Thanks to Charles ZS5CH who assisted on the repeater site when I had to do the late shift tracing a PSU fault. 


The 438.825 repeater has had some attention as well. The transmitter was removed and the low audio was traced and rectified. The tx power is 10w. I have replaced the flylead to the RX as well and the ctcss is off. The repeater is now working well and sounding good according to tests and reports. 

Both repeaters are located at Radcliff (Klapperkop) and share a common feedline and antenna, combined by an improved (I replaced SO239 with N-Type) Diamond diplexer. 

73 de ZS6RH

View     Back to top

Hi All


The voting system has been removed for repairs (Mid Feb2011). I have resolved some issues, and await advice re the LDG RVS-8.

The Repeater now runs with the CTCSS 88.5 tone due to pulsing interference on the site.


73 de


Back to top

The newly relocated repeater setup in Radcliff Tower now with the Wonderboom and Donkerhoek remote receivers running. Installed end 2010 by ZS6RH with assisstance from ZS6MVA.

Back to top
2010-10-09 Voting system off. Per committe decision the 145.725 is running as a stand-alone repeater located at Radcliff. The voting system is on ice pending resolution of challenges and re-commissioning. Contact Craig Symington ZS6RH for more information. In the meanwhile polsh up your own station for maximum ERP.
Back to top