A new High Definition Digital Television repeater is being installed on Ophir this summer. If you can put a good signal with a handheld into the 147.39 repeater, you should be able to receive and transmit to this repeater using the proper equipment—sorry, your handheld will not work on this machine.
The Repeater uses the DVB-T modulation system with 6MHz bandwidth. This allows for a very weak signal of about -95 dBm to provide a clean, 1080P picture. It is also resistant to multipath signals. It is a crossband repeater with the input on 23 cm and the output on 70 cm. This was done to avoid having to acquire very expensive low loss narrow bandpass filters.
The DVB-T signal needs a 'set top' box to change the signal to HDMI output for your monitor or TV. Televisions in Europe use this system as opposed to the ATSC modulation used here in the US. Commercial set top boxes can be had for $30 to $130 BUT they must be able to use channels in our ham band between 420 and 450 MHz, a lot of them do not have that capability… The one we are using is the HiDes HV-110 which is actually designed for ham radio and is quite easy to set up. Information on setting up the HiDes gear can be found here: https://kh6htv.com/wp-content/uploads/2021/11/an-18e-hidessetup-1.pdf and the basic programming information is at the bottom of this article. It is best to have the repeater transmitting or another proper signal on the 70cm band when you are setting up your receiver. Contact Jim W6US at nvjims@gmail.com or on telegram to arrange a signal for programming your unit.
There are also some SDR 'dongles' that will work with the proper software that also provide an inexpensive way to be able to monitor the system. Information on one of these dongles is in this newsletter-- https://kh6htv.com/wp-content/uploads/2024/12/atv-journal-177.pdf
For best reception, a gain antenna like a yagi pointed at Ophir and an inexpensive LNA will do the best for your ability to have a good picture. The antenna is vertically polarized. Low loss coax like LMR400 or RG-6 will be usable. Some of the set top boxes will have 75 ohm connections, but since you will not be transmitting, either coax is acceptable. The repeater has an output of about 10 watts into a 6dB gain antenna.
Transmitting to the repeater will be done on the 1240-1300 MHz band. The Hi-Des HV-320E will do the modulation job on the 1.2 GHz band as well as being able to do simplex with other users on the 70cm band. However, it only has about +6dBm output (0.004 watts) which means you will need a good linear power amplifier and a gain antenna for each of the bands. They do make a version of the HV-320 that will put out a tenth of a watt which makes it easier to find a proper amplifier to get a couple of watts to your antenna but it only has that power on one band.
Full audio is transmitted with the video. The callsign is also imbedded in each frame of the video. The person sending the video should have a printed copy of their callsign in the background as the signal transmitted by the repeater will have the repeater's callsign. Programming info is listed below.
Initially, since there will only be a couple of hams capable of transmitting, we will be sending out transmissions at pre-arranged times with talk back on a 2m repeater for those who can only receive. Once we get more hams on the air, we can do nets and make more contacts, and there may be more simplex contacts being made on 70 cm. We will be showing ham radio content at scheduled times.
Being able to receive will cost about the price of a cheap handheld using the dongle and software. Transmitting will cost more due to the prices of modulators and amps. A whole system costs about the same as a decent HF radio.
Did I mention that you can go mobile??? The equipment is small, lightweight, and the signal is also resistant to Dopler Shift… This would be great for public service events like races, parades, and even some emergency services use. Anywhere there is a direct line of sight to Ophir will work.
There is potential in the future to link into the Amateur Television Network for some linkage to other areas. This will take some additional equipment, but there are locations like Las Vegas, Phoenix, Boulder, and Los Angeles that have DATV networks, and more are coming on.
Here are a bunch of links to equipment, other networks, and other things necessary to get started in the fun...
Equipment:
Further information:
Transmitter settings: DVB-T, 6MHz bandwidth, 1.243GHz center frequency, Video encoding-H264, Video resolution-1920x1080, Audio encoding-MPEG2, Audio encoding bit rate-96, and Service Name set to your callsign...
Receivers will scan in the proper details when set to DVB-T, 423.000MHz, 6MHz. A valid signal will be needed on the air to be able to scan these details. Contact Jim W6US at nvjims@gmail.com to schedule test transmissions or if you have any questions about the system.
DATV receive system showing W6US taking a picture of the setup at the SeaPac Convention