ATNA

On January 9^th, 2005, the ATCO ATV Repeater, WR8ATV, was up-graded by W8RUT & WA8RMC with a Digital-ATV (D-ATV) output running QPSK (DVB-S) on 1260 Mhz. Among the first to see the new D-ATV output as soon as it came on for the first time was KB8YMQ (16 Miles) W8SJV (22+Miles), KB8SSH (6miles). Leaving the repeater site after installation, W8RUT/mobile watched the D-ATV output all the way home (route of 6 miles). All receiving stations were using Free to Air (FTA) satellite receivers.

We believe that we are the first ATV repeater in the US, and maybe in all of the America’s, to start-up D-ATV on an amateur repeater.

The addition of the D-ATV output comes after two and half years of planning and waiting for components. The new output, running only one (1) watt of power as of this writing is built from D-ATV modules supplied by Spectra BV in Holland.

All of the report received on that first day were P5+! Given the nature of D-ATV, we have since informally up-dated the signal reporting standard to “Yes and No!” meaning Yes, I see it!... or....No, I do not see it!. For those stations that are already capable of receiving the 1250 MHz FMATV repeater output, they only need to add a “Free-To-Air” (FTA) DVB-S compliant Satellite receiver to their existing 23-cm antenna to receive D-ATV from the repeater. In fact some stations loop the antenna to both their analog satellite Rx and their DVB-S Rx to watch both outputs at the same time with one antenna. In mid-January, have near 20 stations in Central Ohio who are equipped to see the D-ATV output from WR8ATV.

The current D-ATV exciter/PA was received for a European supplier in early December 2004. A number of points to point tests and configurations were explored by W8RUT while WA8RMC package the modules to be integrated with our existing repeater. Most of this work and learning (a lot new learn with D-ATV!) took place over the holidays.

The basic exciter is a 3-board set including the MPEG 2 encoder, the DVB-S I/Q board and the 23-cm synthesized exciter. The exciter is capably of operating anywhere in the 23-cm band. The exciter set of PCBAs is configured via an RS 232 link to a PC with a very capable supplied configuration software application.

Given the complex waveform of QPSK, Power Amplifiiers need to be very linear as not to distort the QPSK signal as decoded by the digital receivers. The only PA available in my shack was a 10mW in/3-watt out Power Amplifier using a M67715 hybrid brick from Down East Microwave. Looking at the specs, this PA it appeared likely not linear enough for DVB-S service, but we tried and it works! Stations over 22 miles away from the repeater site report strong signals as shown on the spectrum analyzer picture from W8SJV (see figure 2). With 1.8mW from the exciter, the PA output just over 1 Watt. We may have, by dumb luck, found the sweet spot of this PA to run in DVD-S service! More tests are required to confirm this conclusion however.

Our target level of power out is 60 watts of D-ATV on 23 cm. With a 10-dB gain antenna, located 650 feet above street level, the signal should cover most of central Ohio. Since all of our WR8ATV repeater transmitters 70 through 10 GHz cover central Ohio, we confidence to expect our D-ATV signal to do as well.

Receiving D-ATV

One of the main reason for selecting Quadrature Phase Shift Keying (QPSK, a.k.a. DVB-S) as our ATCO D-ATV standard was the relative inexpensive receiver availability. Selecting 8-VSB/ DVB-T (Terrestrial) or QAM (DVB-C) would have been more difficult and expensive for station to acquire receiving equipment ready to use in amateur service. We do have a transmitter capable of 8-VSB running on 70 cm, but that will be another project!

Receivers for DVB-S are from the “Free to Air” service normally used in C and/or Ku band down links from satellites. THIS IS NOT TO BE CONFUSED WITH “DirecTV OR DISH NETWORKS- they use another standard, not compatible with DVB-S. Receivers for DirecTV or Dish will not work with our D-ATV repeater out put. The most popular receiver in service by our ATCO members are used receivers purchased from a broker on eBay for $59 delivered. I understand this broker has well over 1,000 available for sale! N8IJ has been able to make a group purchase to get the price in the $50 range, delivered. The receiver comes with a power cord and a remote. The user manual can be down loaded from his website or his eBay listing.

Once the receiver has been acquired, connect the Sat-Rx to a monitor. If the picture is rolling or only in B&W, make sure the output of the Sat-RX is NTSC- the “next” button on the remote of the $59 Sat-Rx. Go to the set up menu via the remote: Put in the following numbers:

LNB L.O.                               10750000        Khz
Down link Frequency               12010000        Khz
Symbol rate                             3125                K/bits
LNB Power                            Note*              * no Preamp set to zero/or 14V if preamp

Our output frequency on the repeater is 1260 MHz. To set the reciever to receive 1260, you need to tell the receiver a transponder frequency of 12.010 Ghz , minus the L.O. of 10.750Ghz and you get 1260 Mhz! These numbers are entered as KHz however, that is why all of the extra zeros!

The symbol rate of the transmitter was set at 3.125 M/Bits, which is about a 4 MHz total bandwidth. I used a highly analytical approach to select this symbol rate that I will not repeat here. The other parameters such as FEC (Forward Error Correction) the Rx will automatically adjust for them.

After configuration, connect your 23-cm antenna via the “F” connector and look for the signal! Pressing the “info” on the remote will put an on-screen Signal Level and Signal quality display as an overly to the repeater output. Any values over 30% is OK for signal level. If you don’t get a picture at first, select info anyway and it may give you a hint of the problem.

So what’s next?

Items 2 & 3 are easy to do (we already have the Rx for the repeater), item 1 however, will take a lot more time!

The Digital-ATV link was 26,5 km long, transmitter site was "Hotel Schoenblick" in Eichenberg, Austria, 748 m ASL (beyond Lake Constanz). The operators Horst DB2DF, and Rudolf DJ3DY, enjoyed themselves very much after removing some faults, and when the sun appeared a brilliant video quality was produced out of mountain sights, the lake with Lindau harbour in the distance, some cows on a meadow near by and the operators in front of the camera.

The receiver site at the special stand of DARC and AGAF - thanks to DARC committee member H.-J. Unglaub DL4EBK - in hall 6 of the Friedrichshafen fair was crowded with interested visitors from Germany and abroad. Supervising staff were Klaus DL4KCK, Willi DC5QC, Hans DJ8VR, Uwe DJ8DW, Karl-Heinz Pruski and Heinz DC6MR. The receiving antenna system with preamplifier on the roof of hall 6 was mounted by Joachim DJ9JA, Klaus DL4KCK and Willi DC5QC.

At the start the transmitted power was 12 Watt with 6 MHz rf bandwidth on 1255 MHz (QPSK). After reducing to 200 mW the video quality out of the receiving digital satellite TV settop-box did not change, and only with 50 mW some glitches appeared. This test confirmed the outstanding performance of digital TV transmission.

TX was the latest version of DATV sets from the DATV team at "Bergische University Wuppertal" with MPEG-2 coder and digital exciter (DVB-S standard). In this concept all components have standard in- and output interfaces. Each board has 12 Volt supply input and a seperate processor, available modulations are GMSK, QPSK (DVB-S), QAM (DVB-C), 8-VSB (US-HDTV standard), OFDM (DVB-T). The first generation 2 years ago had now somehow antiquated analog I/Q signals and an analog I/Q modulator. Exciter output is on 434 MHz with 10 mW, being amplified and transmitted on 70 cm if the resulting rf bandwidth does not exceed 2 MHz (GMSK), otherwise transverted to higher GHz bands.

More than 100 hams showed interest in aquiring the DATV set, the professional production and sale will be organized by AGAF, DARC and the DATV group at "Bergische University Wuppertal". For amateur applications only licensed Radio Amateurs will get the boards with the price calculated on a no profit no loss base. Date of delivering will depend on availability of special parts.

The DATV working group in Wuppertal received this year`s "Rudolf-Horkheimer award" from DARC committee member Dr. Walter Schlink, DL3OAP, during the opening event of HAM RADIO 2002 fair end of June in Friedrichshafen. The donated money will be used for developments on DATV, especially the 70 cm GMSK receiver.

In his lecture on DATV Uwe, DJ8DW, explained internal functions of the new TX boards as well as usage possibilities for direct contacts or repeater traffic. He reported on the successful long time test on 23 cm (QPSK) at the Cologne ATV repeater DB0KO and on 70 cm (GMSK) around Wuppertal. A student from the "Bergische University" performed the field strength measurements and discovered his enthusiasm for amateur radio - he recently sat the AR test and got his callsign DO2CW.

DJ8DW also showed future possibilities like High Definition Amateur TV, the DATV TX set is already capable of HDTV because of its high processing power. At the DARC/AGAF stand in Friedrichshafen a TX programmed to the 8-VSB ATSC standard (19,3 Mbit/s with 6 MHz rf bandwidth) sent HDTV video from a PC harddisc into an RCA receiver and a 20" PC monitor. His lecture papers are available online at http://www.datv-agaf.de

In 1985 it was planned as ATV beacon, but did not get the "ok" from DARC. 1987 the repeaterversion received a license and was tested at the shack of DL7AKE. From October 1989 it worked in Berlin-Tempelhof near the airport on 1252 MHz RX and 1285 MHz TX (5 Watt). Because of radar interference we tested an alternative input on 13 cm. From 1993 the new site was on a high building in Berlin-Lichtenberg, later on TX power was raised, 23 cm input closed, 70 cm SATV input (narrow band FSTV) test abandoned because of interference, a new 10 GHz input and output built.

Three 10 GHz RX aerials (waveguide slot antenna with omni-directional radiation pattern, a LNB in a dish in eastern and a LNB with horn antenna to southern direction) have a seperate receiver for registration. So the video quality from several hams was improved, switching is automaticly. Teletext and a wheather station were added, and since 1999 DL7TF is sysop. DL7VD performs editing of the Teletext and some video information pages sent each first sunday every month as a bulletin transmission. The weather station has lost some input components because of severe weather on the high building, only two temperature sensors inside and outside have remained.

A very interesting development are our links to the second Berlin ATV repeater DB0BC and to DB0ZS, in Zossen south of Berlin. DB0BC had to move and is on the air again, but not linked to us at present. DB0ZS is receiving the DB0KK 10 GHz output ufb, the return video link is on 6 cm. Control of several functions is made via DTMF on the transferred ATV sound channel only in order to prohibit external interruptions. If a ham forgets to reset the special connection when closing his transmission DB0KK can reset all functions automaticly. A beacon mode for 10 minutes duration is enabled with 1750 Hz on 144,750 MHz, resulting in a Morse code reply by DB0KK on the same qrg with "R" meaning successful activation or "?" meaning "already open". So the disturbing "whistling" for hours on the 2 m calling frequency has been reduced a lot.

Another plan is to install a highly directional remote controlled input antenna on 13 cm with a graphical interface (for direction and field strength) on the repeater output test pattern. The transmitting station must not modulate a video signal, otherwise the repeater registration would switch over to the input... After proper optimization the modulation can resume, function control will be made via DTMF (for details see www.db0kk.de). DH7AEQ has sponsored and filled the web pages with descriptions and technical data.

On September 7, 2002 at 1235UTC, WW2R/5 and W5LUA made a record breaking contact on 24192 MHz. Dave was operating portable in EM41HC near Natchez, Miss and W5LUA was operating from his home in EM13QC, Allen, Texas. CW signals of 549 were exchanged. DX based on 6 digit to 6 digit grid square is 337.3 miles or 542.8 km

The equipment at WW2R/5 consisted of a 2 ft dish fed through 2' of flexible waveguide by a retuned Hughes 12-18GHz TWT running 11W output. The 1.8dB HEMT preamplifier was mounted directly on the waveguide switch. The homemade transverter fed an IC402 at 435MHz. Frequency calibration was achieved by a frequency counter locked to GPS by an HP Z3801A time/frequency standard. Signals on 10GHz were consistently around 10dB above the noise. After the QSY to 24GHz, and overcoming the surprise of hearing anything, initial signals were estimated at around 6dB above the noise but by the end of the QSO were barely audible above the noise.

The equipment at W5LUA consisted of a 2 ft MACOM dish with azimuth and elevation control at 65ft. LNA noise figure at the dish measured 3 dB. I was using an Alelco TWT producing 50 watts in the shack. The actual power getting to the dish was considerably less. I had two 1.5 dB loss WR-42 flexible pieces of waveguide in the shack feeding about 60 ft of EW-180 waveguide with about 4 dB loss and another 1.5 dB loss WR-42 flexible jumper at the antenna. The transmit losses add up to 8.5 dB giving me about 7 watts at the feed. My azimuth rotator is an Orion 2800 which allows me to get to within tenths of a degree. I use a small actuator to give me about -1 to +16 degrees elevation control. This worked OK for horizon shots for AO-40. We first tried 10 GHz where signals were 5 to 10 dB over the noise. We made an easy contact and then QSYed to 24 GHz where I was much surprised to hear Dave about 10 to 15 dB over the noise on a nice peak. The initial peak may have been due to airplane scatter but afterwards the signals became more constant, they settled in about 10 dB over the noise for several minutes and an easy QSO resulted.

Based on 6 digit grid square to 6 digit grid square EM13QC to EM41HC DX = 337.3 miles or 542.8km. Based on actual latitude/longtitude locations, the DX calculates to be 338.2 miles or 544.3 km establishing a new world record on 24192 MHz.

W5LUA 33 deg 6 min 53 sec north by 96 deg 36 min 54 sec west WW2R/5 (from map) 31 deg 7 min 22 sec north by 91 deg 20 min 33 sec west Weather at EM41HC was 75 degrees F and 88% relative humidity with relatively clear skies with some high clouds. Weather at EM13QC was 72 degrees F and 70% relative humidity with skies partly cloudy.

Attempts to repeat the contact over the same path 12 hours after the initial QSO resulted in no signals being identifiable either way on 10GHz, suggesting the morning QSO was under enhanced tropo conditions. No signals were heard on 2 meters or 70 cm at the time of the contact. The sked was setup earlier in the week via email with no liaison on any band including cellular! Numerous attempts over a slightly shorter TX-MS path on 10GHz in July also resulted in no signals being identified.

Submitted by W5LUA and WW2R on September 9, 2002

QTH: Stockyards Inn, 1065 Springfield St, Dayton, Ohio 45403, Phone 937 254-3576

President W3SST
John H. Shaffer

Senior V.P. K3ZKO
Ronald B. Cohen

Treasurer N3KYR
Harry F. DeVerter Jr.

Secretary KC3AM
Dave Stepnowski

V.P. Activities W3HMS
John A. Jaminet

V.P. Technical K7VE
John D. Hays

Sgt at Arms
W8STB
John O. Hey

V.P. Membership
WA8RMC
Arthur C. Towslee

As I type this note for our Newsletter, much concern is being expressed on the various list servers concerning the use of our 440 MHz amateur band by the Beverly Hills Police Department. This is but one of the dangers confronting the amateur bands. We as amateurs need to work together to face these challenges. This is one of the challenges that ATNA was formed to attempt to solve. One of the possible solutions is technical; we must attempt to work towards a more efficient use of the spectrum. I feel that the most promising technical option is digital TV.

We, as amateurs, have shown very little progress in the past two years. Let us strive to work towards choosing a direction and testing some possibilities that exist with present hardware in the near future.
I would like to ask anyone with any ideas to communicate to use our ATNA List server to conduct a search for people and ideas that can be explored via e-mail in an attempt to push our efforts forward. The technical expertise among the Ham community is there; all we need is to activate it. Our Vice President of Technology, John Hays, K7VE, is available to help direct the effort but cannot conduct all the necessary testing and investigation alone. He can be reached at jhays@hays.org.

At our combined ATNA/CAATN Amateur Television Seminar on 17 September 2000 at the York, PA Hamfest, Ravi Goonasekeram, KA3NNJ of Videolynx Corporation, Gaithersburg, Maryland spoke to us about his concept and experiments with digital ATV. He manufactures a very small Video Transmitter marketed by PC Electronics. His web site is www.transmitvideo.com……very appropriate! He can be reached at videolynx@transmitvideo.com

One project I would like to see developed this year is a set of guide lines compiled to be sent to all Frequency Coordinating groups stating the needs and operating parameters for ATV repeaters to co-exist with 440 MHz FM repeaters. Many of our groups do not understand that the video carrier frequency is not the only part of the spectrum that is used by the ATV signal. We need to make sure that the people doing the coordination understand the limitations and our needs. This was very apparent when I received a call from our local FM repeater group with very basic questions.
Additional information that every ATV group with a periodic Net could provide is “ What are your Net activities? . I'm sure there are a lot of good ideas that could be discussed on our ATNA List server, and for that matter, in our Newsletter.
We are also looking for a few people that could report and promote activity in various parts of the country. Just look at our list of officers and volunteer if you are in an area without representation. In addition each state needs one state representative….surprise your Area Rep and volunteer.

It is with a sadden heart that I pass along the news of John O. Hey W8STB passing. John pass away 6/21/01 from a massive heart attack. His family was with him. John will be missed here in the Dayton, Ohio area.He did alot to get new hams into ATV. John also was net control of the Wed night ATV net.
Ron Piatt ( KB8GUE)