VK3RTV
DIGITAL ATV

REPEATER STATUS : Fully operational DIGITAL TV Output

Latest VK3RTV information


19 August 2013

Hello all

After discussions with Richard Carden VK4XRL and Danny Granger VK4KI, a trial 446.500 MHz output using QPSK for VK3RTV may be a good thing. (We are currently using QAM16) I am advised that the signal is likely to travel further and to more difficult locations, be received at an enhanced signal level generally  and that output power can be increased. Both Richard and Danny have indicated that there is no degradation of signal quality. We are already using QPSK on the digital uplinks.

Danny advises that some Set Top Boxes and TV's will just accept the new modulation process while others may need to be re-scanned. As a result, I would not suggest undertaking this move until after the coming ATV QSO Party. Richard has provided me with the required settings which will only take a minute or so up at the site.

Comments re the proposal welcome from Melbourne ATV operators and any others in the group that can add information.

Regards Peter VK3BFG


1 August 2013

Hello all ..

Well it looks like the ATV QSO party this year will be Friday August 30 and Saturday 31 August (AUS dates)

Friday will be VK (and maybe G’s ??) and Saturday VK and hopefully the guys in the US. I will again take in remote stations via Skype. Friday will start about 8 PM and Saturday about 10 AM Melbourne local time (GMT +10Hrs). Any remote or local stations who wish to participate via Skype should send a request to Skype name atvqsoparty. I will use the VK3RML (146.700 MHz) repeater for local liaison to ensure good coverage. Hopefully this year we will have our friends from VK4RKC (which is the Brisbane DATV repeater) participating.

More news as the event develops. 

Regards Peter VK3BFG

  

19 December 2012

Hello all ..

I have finished temperature testing the new PA and have it running 100 watts out and quite cool. (Can easily touch the heatsink, only mildly warm). I am waiting on a temperature sensor to arrive and have designed a power supply sequencer that will run the fans for 10 minutes after key off and inhibit any DC power to the amplifier should the temperature of the heat sink rise above a pre set value ( about 50 degrees). When I have all that in place I can bring the DVB-T exciter down to set up drive levels and monitor IMD products at the output. It will be interesting to see what the difference is between QAM 16 and QPSK. Danny, VK4KI and Richard VK4XRL have kindly provided appropriate settings for QPSK. At the same time I am working on antennas to improve Melbourne stations into VK3RTV2 and also a new antenna with better coverage for VK3RTV1.

Regards Peter VK3BFG


13 December 2012  

Hello all ..

I am just in the first testing stages of the 500 Watt PA funded by donations from Melbourne ATV Operators. It was a bit painstaking to assemble and you are always nervous before the first switch on. I also have to be a bit careful as most of my dummy loads will be sorely taxed by this device. I don’t really have any power measurement instruments for this level of power. I am currently just using a Revex Through Line for this purpose. The gain is quite high as predicted and I can easily get 100 watts out with about 300 milliwatts in. I will need to bring the DVB-T exciter down from the hill soon to interface accurately from a power drive point of view. I will thoroughly test the amplifier before this so VK3RTV should be back on the air the next day. The 50V power supply donated by the EMDRC looks as though it will do the job nicely although it was a bit of an adventure working out how to get it to switch itself on.

At this stage the amp looks very stable ………….. will let you know more soon.

Regards Peter VK3BFG


28 November 2012

Hello VK3RTV Users

I am gauging the response to building a new P.A. for the repeater that will be more linear and have a higher output making it easier for users to receive. To do this funds are required as detailed below.

There is a 70 cm amplifier kit ex US that uses dual FETS specifically designed for digital operations. The amplifier has a huge 25 dB of gain and is capable of powers in excess of 500 watts. (In fact there is a kilowatt version)

The amplifier runs on 50V and I am looking at running it at about 100 watts output. This would mean the elimination of the current PA which is a brick amplifier biased up towards Class A.

I have had donated a very large rack mounted heatsink which in itself would be very expensive if purchased.

I have found a switch mode power supply ex HK for about $150.00 and the complete kit for the amplifier landed here is $500.0 ( The FETS alone are $188.00)

The amplifier would be driven directly from the current German low level amplifier in the existing DVB-T exciter. (500 milliwatts in ---- 100 watts out.)

This would be a huge 10dB boost to the existing output power, with a potentially cleaner output signal using FETS specifically designed for DVB-T.

I am trying to find out if we can raise enough money by subscription / donation. Please do not send any money at this time, only respond indicating what you could offer. There is no pressure for you to respond at all if you do not wish.

Responses received will give me an idea if the project is viable. Responses can be emailed directly to Peter VK3BFG or to VK3RTV@hotmail.com and I will pass them on to Peter.

Peter VK3BFG


23 October 2012

Hello all .. 

For Melbourne ATV stations, Winston VK7EM will be on 1283 Mhz analogue this summer leaving the transmitter on for extended periods when the band looks a possibility across Bass Strait.

 You will need an analogue Sat Receiver and probably a pre-amplifier to receive the signal. A very good pre-amplifier is available from Minikits and an analogue receiver from HamTVstore ($56.00

Peter VK3BFG


27 August 2011

Hi all ..

I think overall the DATV QSO Party was a success. Importing stations via Skype direct worked quite well with reasonable audio and video.

The feed from W6ATN needs some work as does the switching processes my end.  We had line audio and video operating with reasonable quality our end but Don, KE6BXT was not able to achieve quite as good  this time, using microphone into speaker on occasions which resulted in poor control/quality of audio.

The BATC audio feed was not very good on the Friday night, but I do not have any control over that. I have noticed the quality varies from time to time, I guess dependent on traffic conditions.

We had 13 Australian ATV stations participate and I lost count of the number from the USA. We also had a number of stations monitoring the BATC. Don and I will do a reconciliation and list all participants when we look at the recordings and jotted notes.

It seems that with the number of users in the USA, they do not enjoy the same amount of time on the repeaters as we do here. This was evidenced by the short timing  of their overs and the number of stations.

One of limitations my end was the VGA to video converter only  handled up to 1280 / 1024. There is lots of room for improvement there.

A BIG thank you to all the ATV stations who joined in, we will probably do some more experiments, hopefully with improved performance in the future.

Peter VK3BFG


25 August 2011

Hello all ...

Briefly here is what I plan to occur for the DATV QSO party on Friday 26 August 2011 and Saturday 27 August 2011 ...

1.  For Melbourne stations, liason will be via VK3RML (146.1/146.7). This will ensure all stations will be able to hear what is going on.

2.  For interstate and international stations liason will be with myself, Peter Cossins VK3BFG via Skype.

3.  The concept is to come up with a short show and tell of self/activities, probably up to 5 – 10  minutes in the first instance.

4.  After that we will go around the loop again, just like a normal net QSO.

5.  I will be transmitting continually on VK3RTV2, bringing in interstate and overseas stations via Skype.

6.  Melbourne stations will transmit on VK3RTV1.

7.  Stations can watch  VK3RTV1, VK3RTV2 and the BATC stream dependent on their locations/facilties.

 

Friday night 26 August 2011  7.45 – 8 PM Melbourne time.

1.  Establish Melbourne stations able to participate via VK3RML

2.  Establish contact with VK7TW ... patch through to VK3RTV2 for show and tell.

3.  Call in first Melbourne ATV station for show and tell.

4.  Establish contact with VK4XRL .... patch through to VK3RTV2 for show and tell.

5.  Call in 2nd Melbourne ATV station for show and tell.

6.  Establish contact with VK7EM .... patch through to VK3RTV2 for show and tell.

7.  Call in 3rd Melbourne station  for show and tell.

8.  Establish contact with VK3BCU (Thailand) .... patch through to VK3RTV2 for show and tell.

9.  Call in remaining Melbourne stations for show and tell

10. Go around the loop again for those that wish to participate.

 

Saturday 27 August 2011  12.30 PM  Melbourne time.

1.  Establish contact with KE6BXT.

2.  Establish Melbourne stations able to participate via VK3RML

3.  Call in stations alternatively from each end to participate similarly as Friday night.

 

Hope to see you all to celebrate 100 years of Amateur Radio Victoria.

Regards Peter VK3BFG


15 August 2011

Lining up for TV hook-up

The world’s first DATV QSO Party later this month is to have stations taking part directly from Melbourne VK3RTV, regional VK3, VK4 and VK7, Thailand, the USA and beyond via the internet.

Organised by Peter Cossins VK3BFG as control station, it will include the Amateur Television Network (ATN) of California and be streamed live by the British Amateur Television Club (BATC).

Peter VK3BFG said that 8pm (AEST) Friday the 26th is quite good timing to kick off the two-day event as part of the Amateur Radio Victoria celebration of its centenary.

Under current arrangements the regional stations will use skype to have their video reach the controller. Their video will then be put on DVB-S to VK3RTV2.

Melbourne and Geelong stations will respond via VK3RTV1. VK3BCU is in Thailand on holidays and expects also to be skype-linked.

On Saturday the 27th of August at 1pm (AEST) there be a link up with Don Hill KE6BXT in California and also connected with the W6ATN ATV Repeater.

As on Friday, VK3BFG will take the Skype feed through to VK3RTV2.

A lot of buzz about the ground-breaking event already exists with stations in many parts of the globe getting ready to be part of it, including the completion and testing of equipment.

Anyone anywhere in the world can watch the proceedings via the BATC streaming website (AEST is plus 10 hours UTC).


Jim Linton VK3PC


11 August 2011

DATV QSO Party

A DATV QSO Party to celebrate the 100th anniversary of Amateur Radio Victoria is planned for the last weekend in August, 2011.

A hook up with the W6ATN stream is coming from the Amateur Television Network ATV repeater on Santiago Peak in Southern California at 8 PM (California time) on Friday August 26th in Southern California (USA). This will be 1 PM (Melbourne time) on Saturday August 27th in Melbourne, Victoria (Australia).

All participants will be able to watch via streaming video on this website.



8 August 2011

DATV QSO Party - World first for digital television

The final touches are being put on World’s First DATV QSO Party to be held by the Melbourne repeater VK3RTV and around the world via the streaming media portal of the British Amateur Television Club (BATC).

Organiser Peter Cossins VK3BFG said it was most fitting that the event is part of the Amateur Radio Victoria Centenary which runs from August 1 through to November 30.

He has been with the amateur television scene through its black and white days, to colour imagery and more recently has, with the help of others, the digitisation of VK3RTV.

Peter VK3BFG said, “Major funding of VK3RTV from Amateur Radio Victoria and $1000 from the WIA Club Grants program enabled it to be digitised well ahead of time, and renewed interest in it throughout the expanded coverage area.

“What is planned is a DATV QSO Party to celebrate the 100th the anniversary of Amateur Radio Victoria. While the actual times are not fixed, it’s planned to be over the last weekend of August starting on the Friday evening.”

Already there’s interest around Australia and testing has been held while negotiations are being finalised with the BATC and the Amateur Television Network of California via Don Hill KE6BXT.



Jim Linton VK3PC


16 December 2009

Hello all ..

Signal reports are now available on both the analogue and digital inputs.

The code for analogue is TT*.TT1.TT3.TT# (as before) and for digital TT*.TT1.TT1.TT#

The analogue system reads the AGC line and the controller A-D converts it into a code to select a track on the DVD player. S5 to S2 will be reported. The digital report brings up the ‘On Screen Display’ and selects the signal report option. You get a signal strength and signal quality reading. If the OSD gets stuck as it has been observed, TT*.TT2.TT2.TT# is the exit command, use it as often as may be required. TT* is the controller read command, TT# is the load command. As I do not have dual IR Controllers and we use 2 identical Humax Digital Receivers, a signal report request will occur on both VK3RTV1 and VK3RTV2. If this becomes a problem somewhere in the future, a new PCB in the IR Controller would provide independent control. As this feature is only used infrequently it should not be too much of a problem. I am preparing a new information page for the DVD.

Regards Peter VK3BFG


11 December 2009

Hello all ...

I have built a small bowtie antenna that will fit on the boom between the existing 3 element yagi's. This antenna will face west and is an experiment to see how it performs. It is very small and compact and should have a wide beamwidth. If it does work then an array of three or even four would still fit on the existing antenna boom without disturbing the yagis. The antenna will be installed as soon as a convenient time is arranged. The antenna is for a new input frequency that will be 1255 Mhz.

The existing bandplan for 23 cms has two FM allocations based on 1250 and 1283 Mhz. On either side of these frequencies are two AM allocations.  Our DVB-S at 5K Symbol rate takes up about 6.5 Mhz so they fit into the AM allocations quite OK. The possible frequencies for DVB-S are ... (rounded off) 1245, 1255, 1278 and 1288. 1255 and 1278 are ATV repeater inputs, so 1245 and 1288 are available for simplex using DVB-S.

Also ... some small tweaking of the software will improve the drop outs on analogue and also the signal reporting system for digital will appear soon, request by DTMF.

Summarising

1.  Existing Inputs

        1250 Mhz Analogue        VK3RTV1

        10.41 Ghz Analogue       VK3RTV2

        1278 Mhz Digital            VK3RTV2 

2.  New (Soon)

        1255 Mhz Digital             VK3RTV1

Regards Peter VK3BFG


29 September 2009

Hello all ......................

After 30 + years VK3RTV Analogue has closed. VK3RTV1 and VK3RTV2 is now on the air.

First results are excellent.

A few minor adjustments to make, but very pleased with the result. Took me from 7.30 AM to about 5.30PM (10 minutes for lunch) to make the change over. The old Controller will be going to the Bendigo ATV Repeater. S/N input on Analogue is much better with Digital Processing. At 1 Watt I am about an S3 pic on the old system, now it is S4 +

1250 and 10.41 Analogue are now active 1250 and 1283 DVB-S to follow soon.

Regards Peter VK3BFG


27 September 2009

Hello all..

Expect VK3RTV to off air for a few days this week. Get your Set Top Boxes out and monitor VK3RTV1 or 2 (or both) . Manual tuning is required to tune in a Set Top Box...any auto scan will not work. Frequency is 446.5 Mhz, but VK3RTV needs to be there. DVB-S uplinks will follow a bit later, have to modify some receivers before this can happen.

Regards Peter VK3BFG


25 September 2009

Hello all ..

I am sitting here with VK3RTV DVB-T running under the new Controller. Weak signals can be re-transmitted quite OK. If you get a blue screen it means that the decoder has not got enough info to work ... ie signal too weak. .. needs about an S2 pic to be a goer.

I have modified BIG power supplies which had the nice facility of remote switching ... very handy. They give us a max of about 46 A capability. They are mounted in a rack with four fans. Thanks to Robert Broomhead for those.

I have also had a $100.00 donation from NERGS ... very nice as I was getting to the point where I was out of pocket.

All things being equal, I will start to de-commission VK3RTV next week. All I have to do now is make up some leads.

VK3RTV DVB-T soon.

Regards Peter VK3BFG


13 June 2009

Digital VK3RTV will be back on air again Saturday 20th June with an expected even bigger audience due to a lot of talk on air about people buying set-top boxes. The test will start at 1.30pm and include varying the transmit power level from 8-watts down to possibly just 1-watt and to establish relative performance against the existing analogue TV transmission. The new DATV video ID, to be a permanent part of the repeater, will have its first airing. Other activities will be measurement of the voltage on the AGC line from the 1250 MHz receiver as having a relatively accurate signal report capability in the new controller.

Signal reports can be given on the 2-metre 147.400MHz ATV liaison frequency or to vk3rtv@amateurradio.com.auu

During the inaugural test on Sunday 7 June high quality signal reports were received up to 40kms away.

In common use by those receiving the test were domestic set-top box (STB) tuned to 446.500 MHz. One viewer saw it using a miniature USB DVB-T receiver connected to his computer.

Below is the latest list of suitable set-top boxes:: 1. Teac SDB451 2. Compro Videomate PCI TV Tuner Card DVB-T300 3. RCA TRC 501AU 4. Humax DV-1000T 5. Tevion TV-1202 Product No 8436 Tel 1300 766 659 6. Strong SRT 5006 7. Twinhan DTV Alpha ---- used by Joe Martinez VK3TMS 8. SKU HVBT 2000B 9. DVX55U Cheap PVR (Set Freq manually as a Channel No 446500 fairly deaf, - Eastern Suburbs only) 10. Yess DVBT288U USB (Unconfirmed but specs look OK) 11. Wintal STB-X5 12. Olin HVBT2000, HVBT2000B, and HVBT2200B


1 June 2009

Melbourne ATV repeater digital progress report.

An ambitious project to digitise the VK3RTV amateur television repeater that was established in 1977 to service Melbourne and Geelong, will soon see it on air using DVB-T standard. This is the 'terrestrial' version of the digital broadcasting standard and can be received on commonly used household Set Top Boxes and digital television sets. Peter Cossins VK3BFG reports that experiments are being undertaken with the basic system on the bench, but linear amplifiers have been built to provide a reasonable level of output power for the coming live testing. Funded by Amateur Radio Victoria which has spent $3,300 on the project so far, it received a welcome and timely funding boost from the WIA Club's Grants Scheme. WIA President, Michael Owen VK3KI presented a $1,000 cheque to Peter VK3BFG during the Amateur Radio Victoria Annual General Meeting held on 19 May. Michael told the meeting that the WIA's independent grants committee had recommended the grant in recognition of the project's innovation and promising benefits to the amateur radio community. At the heart of the project are German made boards with the system to be configured to have three inputs and two channel output, making it the first of its kind in Australia. More news about the live VK3RTV tests to be carried out from Mt Dandenong are expected soon. Later a full blown technical article will be submitted to the WIA journal Amateur Radio magazine.


January 2009

The upgrade to a digital picture being transmitted from the repeater is still on track. The boards are coming from a SR Systems in Germany who are out of stock until Feb 2009. A lot of the work required to interface the new system has been completed, including a new repeater controller. As long as things go to plan the conversion should take place in Feb / Mar 2009 and the repeater should be transmitting a digital picture sometime in March / April 2009. The inputs will remain exactly the same as they currently are so there will be no changes required by users transmitting a picture into the device.

The parts we will be purchasing are, a Minimod, an MPEG encoder for each channel and a multiplexer for the 2 channels.

This is the link to the products that we will be using :

SR Systems Web Page


December 2008

The repeater sound problem has been fixed by replacing the feed line from the audio transmitter to the antenna. The old feed line that had been in use for many years had developed a leak and was constantly filling with water. After replacement it was noticed that the cable had many nicks and holes in the outer covering and had been crushed in some spots. A day of work by Geoff VK3GE, Phil VK3GMZ, and Peter VK3BFG had the sound transmitter feed line replaced with a new run kindly donated by the site owners (Vertel). Measurements show the sound transmitter is working better than ever.


October 2008

The WIA has funded VK3RTV to the value of $1000.00 for the digital upgrade. It is likely that AR Victoria will provide the balance of the funds required, The upgrade will include a MUX for two independent channels and of course two channel sound. It would be possible to stream 1283 and 1250 inputs at the same time. In anticipation I am redesigning the control system which will include some nice new IC’s from Maxim. One is a video AGC unit that will keep the output at 1 v p-p standard for a 6dB range of input levels. Will keep you all in the loop as the project develops Peter VK3BFG would like feedback on how we could set up the system.


July 2008

There are still problems with the repeater sound transmission. The heliax cable from the sound transmitter to the sound antenna needs to be replaced as it is damaged and no longer usable. As climbing the tower is a labour of love by some of the ATV users they are waiting for warmer weather to change out the cable for a new one. Swapping the cable is a day long job and tower during winter is usually in the cold, wet, and wind so hopefully the job will be complete in a couple of months.


August 2007

To make the repeater beacon and signal reports a bit more exciting Peter VK3BFG has installed a DVD player at the repeater. The signal reports are now a short video clip giving you your signal report. The beacon mode also has more content thanks to Peter. There has been no change to the touch tones used to access any function at the repeater.


July 2007

The sound carrier from VK3RTV has recently been very noisy and low in power. A check found water egress into a cable splice on the sound transmitter cable. The cable had been cut by one of the many others that have access to the repeater site and repaired but not sealed properly against the weather. The join has been sorted out but there is still a small problem in the cable / antenna somewhere. The sound output from VK3RTV is now adequate but a proper overhaul will have to wait for warmer weather.


2007

The 10GHz input to the repeater is working well from the greater Melbourne direction. This input requires equipment that is easy to build and small. Here is your chance to play on the microwave bands without too much effort.


2005

G'day from Geoff VK3JDG, Long between updates on the web page.

We now have a 1283MHz input on the repeater with an antenna pointing towards the Yarra valley.

There is a trial 10410MHz input to the repeater that appears to work well with lots of local building of equipment to utilize this input.

Cheers Geoff VK3JDG


20 Mar 2000

Well the new sound TX is all but complete. Required RF output is achieved and most of the associated wiring is complete. Having increased the output power all the way around, I require another small fan (about 70 MM would do the job), preferably 12V DC, but any port in the storm !!!.

The sound level is quite comparable to commercial and I have been able to net fairly accurately to 449.75 MHz. The quality sounds good here locally.

I have installed a AAZ proof VU meter (electronic type), but have had to install it back to front for mechanical reasons. The bar runs from right to left instead of left to right and has 3 dB logarithmic steps.

Contributors to the project were Peter, VK3BK (Mitsubishi Module), Joe, VK3TMS crystal and ring mixer, Mark, VK3JMA heat sink, Swinburne University, PCB's and misc. components, and myself VK3BFG, misc. components.

Rob, VK3KOS has sent over a replacement PC for the old crock up the mount. It includes a CD ROM drive that will help out with loading software. It is in mint condition except that one of the regulators has a vastly underrated heat sink. I would hesitate putting the system up the mount in this condition. The easy fix would be (guess what) ... yes another small fan !!!!. Any offers ????

I have investigated two antennas available from the Severnside TV Group in the UK. They are quite reasonably priced and the airfreight quote is quite low. Give me a call on 147.4 for details.

Regards Peter

VK3BFG

A possible project for others in the group would be to develop some new graphics. If you are interested contact me and I will advise the parameters.


21 Feb 2000

G'day from Geoff VK3JDG, Well Sunday the 20th Feb 2000 was an exciting day for at least 2 local ATVers. Joe VK3TMS and Geoff VK3JDG played with a bit of 10 GHz ATV. Joe was transmitting from near the top of Mt Macedon and was being received by Geoff in Sydenham ( a path of approx 43 Km ). A strong P5 picture was received, the received picture was then uplinked to the repeater on 1250 MHz for everybody ( anybody ) to see. Equipment used was all home brew by Joe, who using 10mw and a 60cm dish for TX and a modified satellite LNB and 60cm dish for RX. Video quality suffered slightly as the tx fell in the rear of the car on a bumpy road up the mountain and field adjustments at 10 GHz is not advised. Received signal was roughly 25 - 30db above a full quietening signal. Joe ( and Tony VK3AAZ a few weeks earlier ) also transmitted and received 1250 MHz signals to and from some of the Melbourne locals who were around. Again it was discovered that minimal power ( < 1W ) can achieve noise free pictures across distances of 50 - 60 Km. Joe was able to get a very noisy picture into the VK3RTV repeater on 1250 MHz, firing through a large plantation of pine trees ( no direct view, and a path of approx 85 Km ).

Cheers Geoff VK3JDG


18 Feb 2000

Sunday 20 Feb 2000 is 10 GHz experimenting day ( well for a couple of us ). The plan is to transmit a 10 GHz ATV picture from Mt Macedon to Sydenham and then uplink that picture to the repeater on 1250 MHz from Sydenham to Mt Dandenong ( if all goes well ). Participants are Jose VK3TMS ( at Mt Macedon ) & Geoff VK3JDG ( Sydenham ). Try watching the repeater to see what's happening, we should be trying from mid morning until mid afternoon.

Regards Geoff VK3JDG


16 Feb 2000

The system seems to have settled down and is performing well with a number of fans operating 24 Hours/day cooling the PA, PA Power Supply and the Receiver !!! ( RX only has a very modest heatsinking facility )

Rain is still a problem, with the reason for the loss of input signal sensitivity a topic of debate within the group.

I have a friend who has agreed to make a stainless steel box to house the 23 cm input BPF and the masthead pre-amp. Unfortunately he has been a bit busy and has not been able to complete the job to date. Hopefully this will be soon.

I had a call from Peter Mill who is the Vic Division Repeater Coordinator, re the letter I sent to the Vic Division requesting some funds for a new 23 cm antenna system. Apparently the President, Jim Linton is very supportive and hopefully this will go through at the Vic. Council meeting this week.

The new sound exciter is well on the way thanks to donations from Mark VK3JMA ( Heatsink ) and Joe, VK3TMS ( Crystal and SBL1 Schottky Ring Mixer ). I am still looking for the following transistors ....

BFX89 BFW92 and BFW16A. Two of each would be good, one for spares should trouble eventuate. If you have one, pop it in the mail, QTH OK in the Callbook. All donatees are acknowledged on the Website.( Please note Geoffrey !!)

The exciter has an FM Modulator at 33.4 MHz which is extremely wideband and quite 'linear'. It has a discrete PLL which locks the freq. very well. A low level mixer/amplifier board will drive a Mitsubishi Module to about 5 Watts. (only require 3 Watts for -10dB relative to Vision Carrier)

I notice that VK3AOB is building a 18W amp that he is going to mount at the antenna. He may well burn out the GASFET in the Rx front end !!!

Regards Peter VK3BFG


28 Jan 2000

We try again !!!!

VK3BFG, VK3AOB and VK3JDG will conduct an ATV flight out of Moorabbin airport on Sunday 30 Jan 2000, weather permitting. (Should be OK)

The expected departure time will be between about 5:00 PM and 5:30 PM. VK3BFG will be the pilot, VK3AOB the camera man and VK3JDG will be the supervising engineer. (He points the antenna out the window in the appropriate direction and makes sure the transmitter does not fall off the seat)

The flight will take us over the City of Melbourne (providing a clearance is available) and then on to Mt Dandenong. We will transmit on 1250 Mhz for as much time as possible, depending on battery drain. If you will not be home, set your tape recorders up for 5:00 or so with a three hour tape.

Regards Geoff VK3JDG


23 Jan 2000

As most will now know, the signal report is now working. This function measures the voltage on the AGC line which is then fed to four adjustable comparators which produce a BCD code for the micro-controller.

The report is a bit arbitrary as after trying a few different ways of setting up, I settled on the good old have a look and see guestimation. No sig or a very weak sig will register S1.

An interesting fact was that Geoff, VK3JDG and Tony, VK3AAZ both had about the same AGC voltage. The S/N of the picture was far better for Geoff than Tony. The difference is the noise inherent in the baseband (video) signal before or during RF modulation and amplification.

A second fact was that there was only a relatively small window (compared to AM) between an S1 and an S5.For example, a 3 - 4 dB increase from Geoff or Tony would probably lift them to S5. This could be achieved by stacking beams or may be by the forthcoming mastheading exercise. >From my measurements today I would estimate about 12 - 15 dB is all there is between the extremes. (S1 - S5)

I am still looking at a new, higher quality wideband sound exciter with audio AGC to replace the old system which has not transferred to the new lower frequency too well.

The cost of this would be for two crystals (one is a common garden CB freq.) a local osc chain and a ring mixer and a low level amp to about 50 mw. The system would be based around a 33.4 Mhz F3 oscillator with PLL control. It is relatively easy to get good linear deviation at this freq. and the existing video modulation is at 38.9 Mhz, so you can see the reason for the selection.

I have a 70 cm Power Amp with a Mitsubishi Module in it donated by Peter, VK3BK . A bigger heatsink would be required to make it practicable.

I would think about $80.00 would do the trick. The PCB's and some components can be 'provided' by Swinburne TAFE.

Regards Peter VK3BFG


17 Jan 2000

First minor problem ......... the transmit chain local oscillator has decided to drop out. Not a major drama really, but obviously causes no vision RF output.

The system has two similar LO's and multiplier chains (only one currently in use) so there should not be too much of a problem. Will try to get to it in the next day or so.

Regards Peter VK3BFG


14 Jan 2000

The Winersat Satellite Receiver is now in operation. My observations at the repeater end are that the waveform is far superior to the Pansat and that the inbound chroma is about 50% more. The line and frame syncs are also square. (Rather than sloping with poor LF response etc.)

The video also has a lot more headroom. The A5 modulator is reaching peak white + now rather than the FM RX. There is no more streaking on the sigs as far as I can see.

In Electronics there is nothing you get for free ...... the gain-bandwidth product theory says more bandwidth, less gain and more noise. From what I can see here, the western suburbs stations are not quite as strong as with the Pansat, although we have not had enhancing propogation since installation.

My vote is to leave it in operation and see how the masthead pre-amp reduces S/N. I have a friend currently making a stainless steel box to house the filter and pre-amp so it should not be too long.

Your observations and responses would be appreciated.

The power output of the system seem to be settling at a fairly fixed value to date as measured here under similar weather conditions. There is still a slight fall in output with time. The difference between the old system and the new is that the old design was Class A and continuously rated and the new is Class AB and intermittently rated. Please give the system a break, particularly when it is hot.

I noticed in AR Magazine that there is a one year extension on Ch35 for all current users, subject to any interference problems from digital TV experiments. Our move was apparently a bit premature, but I had no indications at all from Vic. Division WIA. The move for us got rid of the Bendigo problem in the western suburbs, increased output power and better propagation due to lower freq. and still primarily within most TV tuners. Also we are still using 70 cm effectively as before.

A day or so ago someone was re-transmitting either CNN direct or a video tape. This is not a good idea as we are now much more public than we have ever been.

Regards Peter VK3BFG


6 Jan 2000

Flight over Melbourne did not take place due to potential fuel problems currently being experienced with light plane's.

Regards Geoff VK3JDG


5 Jan 2000

VK3BFG, VK3AOB and VK3JDG will conduct an ATV flight out of Moorabbin tomorrow ( 6 Jan 2000 ) afternoon, weather permitting. (Should be OK)

The expected departure time will be between 3.30 and 4.00 PM. VK3BFG will be the pilot, VK3AOB the camera man and VK3JDG will be the supervising engineer. (He points the antenna out the window in the appropriate direction and makes sure the transmitter does not fall off the seat)

The flight will take us over the City of Melbourne (providing a clearance is available) and then on to Mt Dandenong. We will transmit on 1250 Mhz for as much time as possible, depending on battery drain. If you will not be home, set your tape recorders up for 3.30 or so with a three hour tape.

Regards Peter VK3BFG


5 Jan 2000

The new 28dB pre-amp and bandpass filter is currently in test operation fitted at the receiver end. It is being powered as a masthead via the co-ax. The BPF is a high quality unit (ex Tullamarine I think ... ask 3BCU) with a very low insertion loss of less than 1 dB.

I have written a letter to the WIA Vic. Division seeking some financial support for further development. VK3RTV has, however, always been mainly funded by donations of both hardware and $'s from the users.

To continue development, I think we need to again set up the '3RTV Fund' that has existed previously. I have kept all receipts of expenditure over the years with this fund and would continue to do so if a new fund was established. I suggest that an initial donation of $20 - $30 from each user would be a good starting point for this. Donations could also count towards this contribution.

Obviously there would be no charge for viewers unless they volunteered.

Projects for the future could be ........ New 23 cm Antennas Switchable 23 cm Antennas New PLL controlled high quality sound exciter. Improved graphics capability. 2 Metre graphics upload capability for user framestore. etc etc etc Your response to the fund proposal would be appreciated.

Regards Peter VK3BFG


30 Dec 1999

VK3RTV is now both keyed (Sync Detection) and driven with line video from a SCART Connector at the rear of the receiver. The result of this change is there is no longer any 'blue screen' showing 'no signal'. This means that the repeater will not turn on without composite sync. present.

Brett 3AOB is doing a short mod. job on a different receiver to try out. The transformer runs extraordinarily hot, so we need to cool it down. (There does not seem to be any fault other than the transformer design is poor. It may have been designed for 60 Hz which would explain the problem)

The receiver is a PLL locked Winersat and as far as I can see, the video quality is superior to the existing Pansat. (Not that the pics are too bad from it at the moment !!)

I am currently putting together a 28 dB pre-amp which we will masthead in the new year. (Will also try it 'at the bottom' in the interim) This is a minor task compared to recent tower operations and should result in greatly improved signal strength, especially for those who are struggling a bit at the present.

The only remaining project for the near time is new antennas for 23 cm. I have suggested a few options in the past, but perhaps an array of three co-linears may be the best option. I suggest we wait and see how the pre-amp goes.

The existing 23 cm antenna will need to be replaced, however, as the current mechanical design will probably not stand up too much longer.

I would expect the new 70 cm antennas will be good for quite some time yet. ( A reasonable number of years)

Regards Peter VK3BFG