PA2TG (Trevor Gale)'s Radio Web Page.


UPDATED AGAIN FINALLY! - 23rd June 2014 (not so late this time... !).

ATV !!! My ATV station is fully on-air, with work going on for new bands as well. With this update, old and ambiguous film content has been cleaned up and old video removed.

Well, I had already (a couple months ago) decided that instead of building "yet another box" for the next ATV band (6 cms) that it would be better to get a bit cleaner in orgasining the whole ATV setup instead of having things in so many places - so I've commenced the design and building of a full dedicated-computer-controlled 6-band ATV main rig. One more board is complete as of this day, and the next work is probably centred around the case / housing for the rig and the 5.6GHz antenna.

The design of it all is 99% complete, and I am well on the way in the building process; it is a rig for 70cms, 23cms, 13cms, 6cms, 3cms and 1.2cms (for 6cms, 3cms and 1.2cms the final multipliers and power amplifiers plus the preamps and downconverters are located in mast-head units). The mast-head units for 6cms transmit are done and tested but have to be integrated in their sealed enclosure; the 3cms ones exist already in operation but have to be re-configured for the slightly different operation modes; the 1.2cms / 24GHz ones have to be built and this will be the last stage of the project, probably after the other bands are in full opearation.

There are a few photos of the progress in the workshop for this rig below, and it is to be noted that since the overall concept allows it there have been quite a few 'extras' and features that I have brought into it which means that the overall project is more than twice (!) as much work as I had originally thought it to be - but hopefully it will be well worth all the extra efforts and perspiration that's involved.
Basically the rig comprises a central dedicated computer system (around a 680x0-series CPU) which handles most operability and the user interface and control, a co-processor CPU unit which is dedicated to intensive video generation and control, a switched dual-PLL which works for all the bands, a video and audio control / interface unit with an on-board sound-subcarrier PLL section, exciters for each of the bands which take the PLL output for frequency control and take the control / interface outputs for modulation, a video sources selection board, and a power control unit with an incorporated sequencer for TX/RX switching and timing. Obviously there is a comprehensive control panel and display interface together with such features as masthead telemetry (as I first implemented in the existing 3cms rig), multiple band and setup memories (including items such as modulation width, subcarrier frequency and the like), R.F. power monitoring & display, power-amplifier and temperature protection.

The overall unit housing has yet to be built but the dimensioning and layout is basically already drawn up and the display and metering I've decided upon and am planning into the panel. The whole thing can be operated from the front panel but is also comprehensively operable through the use of a video window or an external serial link to (e.g.) some desktop or laptop P.C. or even a tablet computer over a network. Just a few photos of some boards or units are shown below for an idea of what is going into this unit:-

Earlier developments:

The latest work here at PA2TG includes the upgrade revision of the 23cms ATV final amplifier, which now delivers the 150W and has proved to work well into several of the repeaters receivable here. Using just the "monitor" 10GHz / 3cms facility it's been possible to receive and capture some of the received signals from, notably, PI6ZTM in Zoetermeer (10.150GHz), PI6HLM in Haarlem (10.250GHz), a well as PI6ATV in Ijsseltein (10.475GHz): at the time of this update it seems that the repeater PI6KPN in Den Haag (10.490GHz) is temporarily out of service. Some captures of my retransmissions to these repeaters are shown below:-

PI6ATV with 70cm:-

PI6ATV with 23cm:-

PI6ATV with 13cm:-

PI6ATV with 3cms:-

PI6HLM with 23cm:-

PI6ZTM with 13cm:-

The signals when using my "main" 10GHz long gain-horn and LNB are appreciably better but for this test I dedicated the main horn set-up to the occaional 10GHz transmit tests. I receive a stronger 10GHz signal from PI6ATV then others using the monitor horn.

For the 'next' band, the 6cms antenna will be a waveguide-fed Yagi, I really have very limited space in my mast installation as it is now made, with the many antennas involved. I also have to take care of wind considerations.

Other news from my workshop: the finalized version (version 4) of my video processor has now been completed. It is far more stable and at the same time flexible (if you know what you're doing and choose to use one or more of the 'manual' controls rather than the in-built automatic ones). Here's an idea of the basic board layout:-

All that remains to do now is the audio side of things, including auto-A/V reduction when the microphone is used, audio vox, and tone equalization plus adaptive noise reduction. All of this latter enables the best to be got from the audio as well as the video when, for example, re-sending received ATV from another band, or replaying received ATV from another station that was recorded previously.
I've decided to build a reduced version of this processor, for use on the receive side, to make the most of live ATV received from other stations as well.

NOTE!!! A NEW A.T.V. INTRODUCTION / TEST VIDEO is now available, and since there are so many different video decoding and playing software options available for one's computer nowadays, I have elected to make it available via the YouTube resource facility which is far more universal and more widely acceptable.
You can view it (it is approximately 4 minutes long) by clicking this link here.

The "starting element" unit for the ATV side of things is an audio/video processor of my design which allows the changing of picture characteristics, establishing of the true black level and true blanking level, the inclusion of a callsign logo, automatic cross-fade of microphone / background-or-selected audio, voice depth control, and audio/video source selection. It also takes care of the sequencing of the transmit/receive switching process, generating drive signals that ensure switching is established before transmit carrier is switched on and so forth. This has just undergone a series of updates, one of which addresses pictre quality aspects and hue control.

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For 70cms (434.250MHz main) we have an audio subcarrier of 5.5MHz as is the standard over here in this part of Europe, and this is F.M. with typically a 35 - 40 KHz deviation, which together with the video is modulated as A.M. such as the standard T.V. broadcasts by the exciter unit. This is followed by a nominal 15-watt driver unit (actually delivering some 18 - 20W), which uses a much-modified 480-MHz linear board and which also contains a R.F. power control based upon the use of PIN diodes.

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A 70cm ATV R.F. filter precedes the driver board, and the losses in this filter are made up by using an MAV-11 MMIC amplifier, which is well-cooled (presettable from the front panel). The last unit in the 70cms transmit chain is the final power unit delivering 100W sync at 70cms, this is based around the use of a 100-W board adapted from the telephony world, using an LD FET as the power device. Temperature sensing is incorporated such that a dual-fan venting is variably switched into use automatically - ONE CANNOT OVER-STRESS the need for adequate heat-sinking and ventilation / cooling especially in the case of truly linear power stages which of necessity operate at an effective efficiency of around 28% at these frequencies.

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An on-board demodulator was added to allow direct off-air transmit monitoring.
On the receive side, many amateurs use a modified television, tuned down to 434MHz, with a FET pre-amplifier. I also have this available but I have chosen to design a separate 70cms dedicated ATV receiver

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which incorporates auto-muting, missing-sync regeneration based around two phase-locked loops, and a small amount of analog signal optimisation electronics: use is made internally of standard I.C.'s but with different-to-standard support circuitry, and the receiver delivers two outputs, i.e. audio and video, for application to an external monitor.

For 23cms (typically 1.252 GHz) the exciter stage is based around the widely available VCO-based and I2C-controlled module which delivers some 4mW after my filtering which

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is amplified to a more acceptable level by the use of two MMIC stages, based on the MAR-8 followed by the MAV-11 which provides the F.M. ATV exciter output (+/- 40mW) at 50-ohms.
This is followed by the driver unit, which contains a PIN-diode power control (similar in principle to that I incorporated into the 70cms design), the output of which is delivered to a Mitsubishi M67715 1.2-watt module designed onto the driver main board; this in turn drives (currently) an RA18H1213G 18-watt device which is essentially a 3-stage FET-based power device also on the main board.

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This is well heat-sinked, with venting presettable from the front panel. This driver actually can provide some 20 - 23 watts of output, and I have used it - bare, directly out to the antenna - with good results. Following this is a 85W (nominal, more may be expected) power amplifier which is driven by an attenuated driver unit signal (using a stripline coupler, the exact coupling co-efficient being non-critical providing it does not result in the over-driving of the P.A. modules). This power amplifier (see below)

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uses 4 of the Mitsubishi modules driven and coupled utilising a combiner set manufactured using semi-rigid quarter-wave matching line lengths to achieve a final power stage delivering some 102 - 110 watts. Here is a pair of the modules, heatsink mounted, under initial testing in the workshop:-

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The complete unit is actually on test in my workshop being built at this time, and makes use of a switched-mode D.C. supply since the current drawn by this final set of modules is of the order of 28 Amps. As much work is involved in the design of the power supply and the cooling / ventilation electronics control (two linearly-controlled vent fans) as is entailed in the actual 1.250 GHz power stages, although the latter does require a little effort on the mechanical side. Again, the proper cooling arrangements for such devices cannot be over-estimated; they are very important and in this power amplifier use is also made of a copper layer as a heat spreader above the aluminium first heatsink pad. The final result will is to be seen:-

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On 23cms for the receive side, use is made of a modified satellite-receiver tuner which has an intrinsically-linear voltage-dependant frequency control (This receiver has actually been superceded by a newer unit just out of the workshop!).

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Whilst this is reasonably sensitive it is still supported by a preceding bipolar R.F. amplifier (a first-stage FET pre-amp is designed and will precede this unit when completed). The composite video output from this tuner is split into 3 paths, i.e. the main video path, the sync/mute path which is used by the auto muting and sync support circuitry, and the F.M. sound subcarrier path, where I use a TA7130P quadrature demodulator tuned by a pair of vari-cap diodes to receive 5.5 - 7.5 MHz sound. To avoid vision-on-sound and to ensure good limiting characteristics I employ a broad H.F. amplifier with a high-pass filter and dual-vari-cap tuning tracked to the 5.5 - 7.5 Mhz demodulator tuning. Due to the wideband nature of the ATV use of this band and the linear nature of the tuner frequency control, I used a simple 270-degree panel meter for main frequency display, but for which I printed a calibrated frequency readout scale. The outputs of this receiver are also two, i.e. an audio and a 75-ohm video output for switching to a monitor.

I am now also on the 13-cm band on ATV, this starts off with an exciter unit which also includes some switching and makes use of a fairly-modified module which can be bought here for ATV use and provides a couple of tens of milliwatts of F.M.-TV and audio (I have chosen 7.2 MHz for main audio carrier). This unit can be seen below:=

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It is followed, not by a driver amplifier, but by the final power amplifier which is adapted and modified from an ex-telecomm unit with a separate power supply:-

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and this unit developes some 50W into the load at 2330MHz, sufficient for the time being.

The 3-cms band is also now constructed for, and the main unit together with it's horn antenna is FINALLY MOUNTED ON THE the mast! At this frequency, the main transmitter electronics as well as the receiver LNB have to be located on the mast since cable losses prohibit feeding this from a unit in the 'den'. This means the design and construction not only of the main 10 GHz parts but also the frequency dividers and power supply regulation and switching and so on to allow the unit[s] in the 'shack' to fully control these transmitter and receiver facilities, an example of which would be the frequency-divided feed down from the mast-mounted transmitter unit to allow a PLL (phase-locked loop) operating from a reference frquency to derive a voltage for returning to the mast unit to achieve full transmit frequency control in addition to video and audio subcarrier modulation signals. A couple of images of the prototype for this transmitter unit, without it's weatherproof enclosure, can be seen below:-

Also here are the main units ready for that long day (over 10 hours!) to be mounted on the mast, the last photo shows the transmit and receive horns fixed:-

SO, all the 'outdoors' units and activities are (hopefully) completed, with a better colour horizon camera from the 10 GHz place as well, and now it is down to finishing the 'indoor' units and putting them into the appropriate cabinets. A lot of prototyping inolved on the workbench, as can be seen from the folowing, first the PLL and modulation gerator and control board, and integrating it:-

This unit (the driver unit) is the most important one indoors for the 10 GHz ATV functionality, for it contains the PLL, the modulation signal inclusion, and the return drive generation for the mast-mounted transmit generator circuitry. As you were able to see, the prototype of this unit is almost complete.

THE FIRST ECHO TESTS HAVE BEEN DONE AT LOW POWER ang the results, without video compensation (which is needed) can be seen below:-

NEW VIDEO!You can see here as promised a (short) 10 GHz test video, the first full 3-cms test video used live, the photos and clips were only made a couple of weeks ago (it's 27th June now), so a more extensive video for this band has been produced and will be linked to here shortly.

The ATV capabilities also include the 10GHz (3cm wavelength) band monitor receiver (not to be confused with the main receiver for this band) - and some interesting experiments did indeed show this to be a very useful feature. There are a number of ATV 'repeaters' here in Holland, as there are in most other countries, and it is most useful to be able to observe ones' own signal as received by a number of others, with no delay, far better indeed than the alternative which is the (delayed) relay of *some* of those repeaters via the Internet on Web sites.

So my own antenna, a smaller gain horn, to place in front of the 10GHz receive LNB and I did some serious mounting work such that this antenna can be rotated on it's own (at the same height as the main mast erection is at) with no relation to the main set of antennas which is on the main rotator. All of that gave me the appropriate aches and pains from the screwing of tight fittings, doing up nuts, etc., as good, firm construction is absolutely necessary. However it was at the time a fine and sunny day for doing all this (until it got dark at the end of the evening!!!) and it was something very satisfying to do.
The more recent ATV test video is produced (there are even more different videos now), the one here is a common one and can be used on any of the bands I use) and the Web version IS AVAILABLE HERE. A new one is under production right now and the Web version will be available once this production is completed shortly.
Included here are some older examples of what I have been able to transmit and monitor:-

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THERE IS NOW A SEMI-LIVE SET OF VIEWS OF THE STATION ACTIVITIES, especially aimed at the ATV side of things, this can be seen HERE!, when the active vies are switched off, the old/last ones are displayed. A totally live stream will shortly be available on another server, I will tell you when this is online.
There will also shortly be a new test video, taking into account the new 10GHz / 3cm facilities and with some of the new gear for that band whis is being modelled.
There is also a new ATV set of receivers, of my own design, for 70cm, 23cm and 13cm which do perform to my satisfaction:

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I have also built a monitor-and-DVD switching unit which allows me to record what I receive from other stations and play that video back to them.
So, all in all I am satisfied with the work done despite other problems that have beset me over the last couple of weeks.

You can see a view of my radio / ATV station when they are 'LIVE' by clicking here . These views will be updated as and when I have the time to devote to the web site, which is not as often as I should but as some people know I am often very busy with other things.

E-Mail... You can E-mail the author of these pages (Trevor Gale) by using this link, or by sending mail to on the Dutch Internet service provider XS4ALL.

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