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RAYLINK-90 Article on Yorkshire TDF involvement

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g6rib View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote g6rib Quote  Post ReplyReply Direct Link To This Post Posted: 06/February/2015 at 09:36
We did look at 4m and low band PBR.  The first problem is the amount of equipment we would need to buy.  Probably 40 – 50 operator radios for a start.  If we had that sort of money and members were willing to move to using PBR radios, we would probably have looked at going entirely PBR on VHF. 

 The linked repeater network that formed the backbone on the TdF was extended with ten or more cross band Talk-Throughs to allow local HH use, linking into buildings and fill-in for areas of poor reception.   We use TT so much in Yorkshire that we have plenty of FT-8900s between the members and groups.  This can be done on 4m but we don’t have the equipment.  We looked at the 6/4/2/70 Wouxun but its 4m coverage is very limited (70MHz to 76.9MHz according to ML&S).  Cross linked SRM-9000s would work well, but that would be another 10-20 radios to buy and second hand low band SRM9000s are rare – if anyone knows of one for sale, please let me know!

We have also considered digital.  Networking digital repeaters needs high speed data connections.  Even D-star is designed for repeaters to link through the internet.  We’re working without any fixed sites and many of the locations we use barely have 2G coverage.  If we had the money and could be sure that digital would work for us, we would probably look at Motorola because of the second voice channel.

On balance, I think we found the right technology for the present: just about all the existing 2m equipment belonging to members and the groups can be used without modification.  146MHz would have made life easier, although we would have needed to spend approaching £1800 on three 2MHz split duplexers.  In the longer term, a pure PBR capability may be required.

 The requirement to use transportable VHF repeaters is appropriate to the terrain, size of area and the type of events that we deal with, particularly in North and West Yorkshire.  A few other areas have expressed an interest.  The initiative has been led from Yorkshire although it is supported by CoM.  At this time we will be funding the mid band PBR licences to cover our operating area.  Extending this nationally would require additional channel capacity as well as national coverage and I’m not sure that most members would accept a 75% rise in membership fees to pay for it!

 

Andy Evans
Zone 2 - Yorkshire and Humberside
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Post Options Post Options   Thanks (0) Thanks(0)   Quote g7gmn Quote  Post ReplyReply Direct Link To This Post Posted: 07/February/2015 at 02:04
Hello Andy,

Have I got the details right here....    You will be paying for a 157 MHz PMR Area-Assigned frequency.  Will this be simplex or a dual-frequency pair ?  If it were a dual-frequency pair it could be used as a linking medium for the many other talk-through setups you mention.  Is that the intention...

Best wishes all, I will watch this space.

Ian. D.
Ian, G7GMN.
Controller, NE Hampshire RAYNET.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote g6rib Quote  Post ReplyReply Direct Link To This Post Posted: 08/February/2015 at 12:21
On the TdF, the outstations transmitted on 144MHz and listened on 157MHz.  That way only the repeaters, which are compliant with the PBR Interface Requirements, transmitted on the PBR frequencies.

The repeaters were linked to each other using a common simplex 70cm frequency so that they formed a single net.  

Where we needed to extend the network with a local TT, we used FT-8900s programmed to use the duplex pair (RX-157 & TX-144) on the VHF side and a simplex 70cm frequency for UHF.

The repeaters that we have are Kenwood TK-750s and the 70cm link is done with SRM9000s which Jim interfaced to the Kenwood repeaters for us.  They work well for us.

The plan is to replicate this on a more permanent basis.  We will need two simplex PBR frequencies to operate two repeaters.  A third would be nice, but for the cost, as we have three repeaters. Currently we are modelling the coverage from most of the likely repeater sites to see how big an area we need to "buy" to comply with signal strength limits at the boundary.

Andy Evans
Zone 2 - Yorkshire and Humberside
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