|
Latest VK3RTV
information
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 VK3K3RTV1 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.
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
|
