Repeater background music supplied by Artlist

Latest News Updates:

Click to stream GB3JV Live!

• 16/05/2022. Want a fantastic deal on a UK SIM-only card? Don’t forget you can help GB3JV and earn yourself a month free with SMARTY! 30 day contract by using the referral link below, great pricing and superb performance (as used by GB3JV for the network and streaming connectivity) and 5G is included (where available) and there’s 10% off every SIM in a group plan. Smarty is a Which? Best Buy provider to boot. GB3JV uses the “unlimited” plan, which is truly unlimited with no throttling or fair use policy. http://referme.to/rfRHCux
• 02/05/2022. From time-to-time I’m running some experiments to see how PiP might work, the idea is to allow (encourage) full-duplex QSOs via the repeater. Moving forward there are some sophisticated automation options, and/or manual user control of input switching from the GB3JV web site. (Yes, Justin is currently reading all about SMEE and Jenkins!). The idea is that if the repeater is already in use, a second user can join on another input. In its first implementation when you access the repeater a PiP box will appear in the top left corner showing the unused input; if a station then accesses that input they will take over the main screen and the original user will be relegated to the PiP window. When either user ceases transmission the repeater will revert to the media player, to restore video it will be necessary for the remaining station to momentarily drop transmission, or for a new user to access the (now available) input. We’ll have to see how it works out in practice, but at least it’ll be fun finding out! 🙂
• 29/04/2022. Testing of the new 70cm input had been very successful, one station accessed the repeater using just 16mW of power from over 3 miles away
• 28/04/2022. Following reports of an issue, a software update implemented this morning has resolved an issue where, under certain circumstances the “Lower Third” graphics are continually displayed
• 28/04/2022. The repeater is programmed to send “colour bars” from midnight each day. Colour bars will be transmitted until the next user accesses the repeater
• 25/04/2022. Justin, G8YTZ is delighted to announce that the NoV (OFCOM License) was today renewed for a further 3 years. Many thanks to everyone at the ETCC and at OFCOM for their help
• 25/04/2022. Justin G8YTZ will be giving a talk about GB3JV and how to get on the air with Amateur Television at the Bromley & District Amateur Radio Society on Tuesday 17th May 2022. Details at: https://bdars.wordpress.com/programme/
• 18/04/2022. 
  • 23cm Input: The repeater’s 23cm input (1249MHz) supports 333kS/s and 2MS/s. from a west facing “WIMO” flat plate antenna
  • 70cm Input: The repeater’s 70cm input (437MHz) supports 333kS/s and 2MS/s. from an omnidirectional WIMO “Big Wheel” antenna with a gain of 5dBi 
  • 2m “talkback” Input: Accessed via the ATV calling channel 144.750MHz FM/Vertical, CTCSS 103.5Hz
  • New repeater controller: This is now operational, when you transmit into the repeater there will be a smooth transition from the sustaining media server to the active input. If a second station transmits into the other input the newest signal gets preference. Every 10 minutes a “lower third” ident graphic is displayed.  
  • Repeater Streamer: 1080p/25; URL for VLC and other H.264 media players is: rtmp://rtmp.batc.org.uk/live/gb3jv
• If you have received the repeater, a reception report would be very welcome in the blog/comments section to the right. To increase the range still further I’ve switched the FEC to 1/2 so a received C/N of just 1dB should ensure a stable picture.

Tuning a domestic satellite receiver to receive GB3JV:

Firstly, you’ll need a “Titanium C1W-PLL “LNB, designed for the “C Band” and to check that you are in the service area. A standard “Sky” LNB will not work. You can obtain the correct type of LNB at the Titanium Satellite Store

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 Products “Heat 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