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NATURN
                              Repeater System
 

 


Repeater antenna maintenance: DKW Kloof Tower 28-02-2013

 

The day was spent isolating the faulty connector at the base of the tower in order to repair the second X-200 as the current X-200 was blown to pieces by the lighhtning .

 

This was the sweep before repaired faulty connector at base of tower.

 

 

 

This one below shows normal expected sweep for the x200 .

 

This sweep showed problem at 20,8m which was at the base of the tower and this is the place I repaired the corroded water damaged 7/8 connectors.

 

Photo’s to follow

 

6m loop :Feb 2013

 

This antenna I made using a circular aluminium loop with a ganged capacitor from a piece of old equipment .

 

It tuned up straight away and have done some short distance testing on it and it has good side-null characteristics as expected .

 

 

Bicycle_Rim_multiband loop antenna: Feb 2013

 

I have had this idea for a few years but have never found the time to try it out .

 

I then found that there were other hams around the world that have tried the use of an aluminum bicycle wheel so I put mine together in one afternoon (mountain bike rim used.).

 

The results are quite remarkable for such a small antenna.

 

I have been using this antenna on 50 W having good comms with Capetown ,USA and Canada on the 20m band.

 

With the current 200 nF capacitor I have the 20m /17 /15/12 bands that tune up well .

 

The reading material one reads on the net and books tell you that the antenna is extremely narrow.This is true but one does not have to retune every few Khz for RX .

 

My experiemce when comparing this antenna to my fixed wire antennas is that the receive is superior in that it is much quieter and thus the preamp can be used in the way it should be used..I have also made a few comparisons with other stations in my area that can hear a station but not make out the inteligence – with that same station being Q5 readability on my loop .I have also made a number of comparisons with my own wire antennas off the AH-4 and the loop is definitely my choice on reception .

 

I have been operating this antenna for two weeks from inside my radio shack changing the direction and tuning by hand .I look forward to taking this antenna on camping and other trips and experiment with this antenna in the outdoors.

For those that are stuck in town houses or Flats , this is the ideal antenna to get active on the bands.

I am in the preocess of making a base-plate with a bearing mechanism to steer the direction of use.

I have noted that the antenna has great directivity being narrow in the direction of the physical plain of the antenna.The radiating loop is ’ coaxial cable with inner shorted to outer on botyh sides.

 

I did not follow any other design except for the standard suggested transmitting loop diameter being about 1/5th .

 

Good luck with your building and let me know how it goes.

 

 

 

HF AH-4 project:

 

Been looking at a way to get some antennas up for HF in my radio workshop .

 

Having an AH4
Icom automatic tuner I needed a way to extend my options.

 

This lead me to the Relay switching control box.

 

Consists of a Control unit that selects the various unbalanced antennas such as ;

Vertical 108” whip / two long wires and more to follow.

 

This should allow a wider variety of options and the beauty of this design is that one can select any combination of verticals or horizontal long wires – all remaining antennas if not selected are added onto the ground.

 

This I believe is the best option for multi unbalanced antenna elements.

 

Here are some pictures leading through the project – does not include the surge arresing nor lightning pspark- gap as yet .

 

 

26 Aug 2012:

 

Mounted selector .

 

 

 

I would be interested in hearing from other hams regarding similar projects.

 

Once I have it all wired uo in a week or two I will upload my findings.

 

 

 

 

Ch6-UHF Kensington : 439-275 (-7.6 Mhz) 31\12\2009

 

 

Finally got to place the CH6 repeater back at Kensington site .

This repeater will cover in and around the new Mosis Mabida Soccer stadium in Durban central.

Please update the CTCSS tone to 88,5 hz encode/decode.

 

The pic controller is the great VK5DJ Pic controller which I have modified for my own workings, included are COS indicators and a dual alarm indication .

 

Thanks must go to John Drew , VK5DJ who has done a great service to all those using his code.

 

Here is the early stages of the micro Controller made on vero board and lacing twine .

 

 

Saber Battery repack /modification: Dec-2009

 

I decided to try something different when I repacked a few of my saber battery packs .

 

I added a small charging housing from an old ICOM type battery pack and this is the result .

 

This allows the use of the charger as well as a wall charger or cigarette charger as used for Icom radios .

 

 

 

Now the radio can trickle and get topped up wherever I go and one does not need to lug the big charger around .

 

05 October 07: Repeater update:

The Alverstone HUB repeater has been problematic and it has been decided to redo the old Storno 662 with more recently produced hardware.Special attention to the flat audio to negate the associated problems with multi-staged hardware issues.The new test repeater will consist of m120 motorolas modified , and an audio graphic equalizer to maintain the flat audio repose required for the HUB.

New power supplies and antennas have been ordered for the UHF hub and the 145-600 repeater sites.This has been forth-coming due to the renewed interest in getting these back up to spec .

 

Current Repeater Project: 1)The channel 7 Umhlanga repeater project has been discontinued at this point .. 2)Channel 5 soak test September 2006 3)Channel 4 antennas replaced 4)Kloof cable s to be pulled through pipes to container

 

16 June 2007:

The 145-625 (CQF900) repeater has been mounted on the wall brackets.

Below the repeater is the TX cavity .The cables have been pulled through tto the base of the tower and connected to the existing cables to the top of the Tower.

 

Cable reroute and 145-625 relocation to external container .

Thanks to Brad ZS5Z , Lawrie ZS5HV , Paul ZS5PS and of course Brad junior who also worked hard assisting on the day.

 

 

Current Project : Naturn Repeaters: :

 

The rope has been pulled through the draw-pipes and in the next week or so we should have the 1/2 inch cables pulled through these pipes to the base of the tower to join up with the 7/8 inch feeder to the antennas at the top of the 85m tower.At the same time the new crystals should be arriving to run up a repeater to replace the existing UHF on channel 1 .......

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Comrades Marathon Communications :

The Highway Amateur Club is proud to be able to supply the repeaters, below , that will be used on the day . The purpose to relay message handling of emergency communications between central communications centers and field stations situated at various points along the route of the comrades marathon .This exercise plays a vital role in the safety of runners and the public alike.

 

The number of ham radio operators on the day is approximately 40 .The communications control room also houses other parties form the Police services , Ambulance , Fire and rescue as well as various other logistical staff. In the past both VHF and UHF repeaters along the route covering Pietermaritzburg and the greater Durban areas will be used.At this stage HF has not been used but due to the recent unrestricted allocation to the HF band there may be some experimentation done on the day.

 

There will be also be a 144-800Mhz APRS digi-repeater requested for some runners that will be running with handie APRS stations.This digi will repeat the GPS co-ordinates to the I-Gate situated at Pietermartzburg .

 

The IRLP node will be limited on the day due to the nature of the event –restored early eve local time.

 

 

 

 

 

NAT.U.R.N. (Natal Uhf Repeater Network)

       Bi-Level Squelch : As used on the 145-625 there are two means to get access to the repeater .
       First: carrier operation is set very high(3uV ) for good signal access.Strong stations and base use.
       Secondly:Use 88.5hertz CTCSS and you will activate the receiver at 0,21 uV with no modulation.
       This allows for mobile and portable stations to gain the maximum efficiency of this repeater.Use of CTCSS does have a short squelch burst of which has to be accepted.
Repeater Switching: After looking at various methods of how other Ham repeaters arrange their switching I decided to standardize on my own idea which has proven its worth in the field . Due to my experience I prefer using E /M termianology than Rep PTT / Cos /Cor etc.I believe that by keeping the switching simple there will be less downtime. All inputs are open collector driven.Diodes are IN4007 or similar.Controller can depend on the application .I have used straight through as well as the Zetron 38A/ NHRC controller using the 16*84 pic.
Switching of the Naturn system is as follows:
Local repeater has priority –meaning that local repeater receiver activity will override any incoming activity from the hub.This is ideal for emergency break-in .
Most of my repeaters have a conferenced audio network using modified PCM channel cards .3 input-3output(can be cascaded to 6/6 or 9/9.Levels are all Balance 600 Ohm .
Projects
I have had so many projects over the years and am hoping to place some for show on this page.
My on going projects are mainly on repeaters as these systems take up much of my time.I look after 7 repeaters in our local area .I implemented a STAR configured linked system which is rather uniquely linked via uhf while the repeaters being uhf.Good RF practices has helped in these cases.
Having RF Hi-site expertise this has become easier than first anticipated.
The club runs IRLP on the uhf system and has been interesting.Recently VHF has been introduced via a split site 145-600 pl =88.5hz repeater to encourage system use and add benefit to major sporting communications such as the world known Comrades Marathon which takes place between Pietermaritzburg and Durban .
I have special interests in audio encryption (analogue ) and have built a few gadgets .Antennas are my favourite in the sense of non-standard configurations.This includes cross polarization and passive antenna steering. Modifying of commercial radios to the ham bands has been somewhat of a passion but that has reduced due to time constraints.
MPT1327 trunking:
Being involved extensively with one of the largest mpt1327 systems in the world was a unique opportunity at that time. I was responsible for network and end user delivery. Software progression to what is today commonly used ACT NOW VOTE / channel display (tait T-series) messaging that has dramatically improved the systems as used today.
Only in recent times has MPT1327 gained momentum against the larger proprietary systems that have dominated the world market .Reliable and low cost per erlang has made it a valued trunking system in the open market.In South Africa we had three few public systems of which onlt two remain , namely FleetCall and Q-Trunk . A number of smaller systems do exist for in-house communications such as the Petro-chemical industry.
I have written to some manufacturers and see that in future along with amateur radio and commercial the uses of the trialed and tested MPT1327 protocols are valid.
Each time a radio unit PTT’s there is a unique id(short packet sounding chirp-similar to mdc1200) that is sent and again when PTT is let go.Along with timing , channel and id information is held within that burst.This basic standard could become a global open platform for a uniform standard .With the gained momentum of the 1327 standard this would allow unique addressing when interoperating connected systems or even between two different protocols.
 
 
 
 

 

 


 

 

 

 

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