GB3JV Digital Amateur TV Repeater

 

Latest News:

  • To receive the repeater, all you’ll need a C-Band LNB and a standard HD satellite receiver that accepts manual frequency input, or a BATC MiniTiouner. The recommended LNB is the Titanium C1W-PLL (Note: It must be the “W” version, the non-W version will not work!). The recommended LNB can be purchased direct from: Titanium Satellite
  • The repeater is liable to interruptions between 22:30 – 08:00 daily. See the GB3JV on-air repeater status with the: GB3JV Transmission Monitor
  • You can view all the live UK repeater streams here

Tuning a Domestic Satellite Receiver

Many domestic TV receivers have an in-built satellite tuner. I’ve successfully tuned a Samsung 6000 series TV, my [pre-Android] Sony set, and a domestic set top box to receive GB3JV. I don’t however recommend any of the “FreeSat” boxes as the setup software seems to conspire against you entering direct frequencies into these products. The method used on the Samsung was to just leave it in the default “ASTRA” mode add the GB3JV frequency manually. To calculate the equivalent C-Band frequency you calculate like this:  9750 + 5150 – 3404MHz = 11496MHz. Enter this frequency into the receiver and then perform a “Channel Scan” so the receiver can detect the programme identifiers. You can also perform a “Blind Scan” if you are confident that you have a good signal being received by the LNB; perhaps you have already aligned the LNB with a Sat Meter like the “GT Media V8 Gold Satellite Finder Meter” that I purchased on Amazon. I’ll post a video in the next week showing how to set up a typical Samsung TV to receive Amateur repeaters on C-Band. Remember to turn off the 22kHz pilot tone (used for LO switching) and to set the Symbol rate to 2000kS/s on the receiver, everything else should be automatic.

It’s worth mentioning that if you have a fairly good line-of-sight from Petts Wood, you’ll most likely only need the LNB with the supplied scaler and without a dish to receive the repeater. Remember that LNB’s are designed to receive tiny signals from satellites 50,000km away, they are very sensitive and really don’t struggle receiving a terrestrial signal just a few miles away. Today I stopped the car near Biggin Hill with my LNB and Satellite meter and received a solid signal with an 85% quality rating just standing in a car park, that’s about 5 miles away.

For a rough calculation, assuming that a typical satellite is 50,000km from us we can calculate the free space path loss to be about 207dB at 11.5GHz. Given the gain of a typical 60cm dish is about 37dB, then  207-37 = 180dB effective path loss to give a good signal and that’s at Symbol rate of 27,500kS/s! If we do the same calculation and assume no gain at the receive antenna (i.e. just the LNB) then the equivalent distance is 2,000km! Obviously this is only a comparison and for terrestrial situation we have obstructions, hills, houses and the curvature of the earth, but you can see that if you have a clear line-of-sight to the transmitter, gain of the receiving antenna is hardly going to be of much concern. For fringe areas I would recommend a Sky Mini-Dish (45cm) as a great compromise between gain and ease of alignment, but start with just the LNB mounted in a good unobstructed location and see how you get on. One thing I have noticed is that the Titanium LNB does not appear very weatherproof, so I would mount it in a plastic box or cover it in a black heat-shrink tubing. I purchased some for the Tx Antenna from Hilltop ProductsHeat Shrink Tubing HSP1″ which is UV resistant and does not inhibit RF transmission. 

Formula used to calculate free-space path loss (above)

Would you like to help?

Justin G8YTZ has 100% funded the repeater hardware and installation. If you’re enjoying this web site or plan to use the repeater and would like to see the repeater develop, please consider making a donation (more details coming shortly) Your money will help fund the ongoing development & maintenance costs. Alternatively, another way you can help is by using our referral link for a SIM only 30-day unlimited voice-text-data mobile phone contract with “SMARTY” (H3G). Every referral is like an £18.50 donation and this covers our internet costs for a whole month: SMARTY-GB3JV

Press Release – GB3JV is on the air!

Petts Wood, 6th October 2019

Justin, G8YTZ is delighted to announce that the from 14:50 on 6th October 2019 the GB3JV Amateur TV repeater took to the air in beacon mode. The new repeater is located in Petts Wood, Kent. It transmits on 3404MHz, The Tx antenna is a slotted waveguide design and gives the station and ERP of 150 Watts. Receiver Inputs are available on 2440MHz and 1249MHz and the repeater output is streamed on the BATC Web Site.

To receive the repeater all that’s required is a tuneable DVB-S2 Satellite Receiver, or a BATC Minitiouner, a small dish and a C-Band LNB. Coverage predictions show reception possibilities across the heavily populated area of South-East & East London as well as parts of Essex.

Justin would especially like to thank Noel Matthews G8GTZ for his help in obtaining the NoV, Bob Dunne for his help in acquiring the site and members of the Bromley & District Amateur Radio Society, Gareth G4XAT, Andy G4WGZ and Mortimer Group for the site facilities.

Technical Details:

  • Tx Frequency: 3404MHz @ 2000 kS/s
  • Power: 15 Watts (150 Watts ERP)
  • Modulation Schema: DVB-S2, QPSK, FEC 3/4
  • Multiplex, 1 x HD and later, 1 x SD channels
  • Tx Antenna: Slot/Horizontal polarisation 14dBi gain
  • Rx/Input 2440 MHz 2000 kS/s QPSK FEC 3/4
  • Coming soon: Rx on 1249MHz (23cm) and 437MHz (70cm)
  • Rx Antennas: 2 x Flat panel 9dBi gain (Diversity) pointing W & NE
  • Output (coming soon) on the BATC Web Stream: GB3JV Streamer
The GB3JV Transmitter