A gb3ey injection..?

Discussion in 'Discussion' started by Wolfie, 13 November 2018.

  1. Wolfie

    Wolfie New Member

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    Lets see if we can't inject a bit of life into the Forum, it seems awfully quiet on here..

    As many probably know, there are plans afoot to move GB3EY to a new location on the ridge west of Beverley, I recently spoke to Clive at a Rally and the guys behind these plans and equipment are busying themselves with the task(s) in hand.

    The new location is going to illuminate a huge swathe of Yorkshire (N, S, E and W) and a fair old chunk of North Lincolnshire too, bringing ATV within reach of many of us. My aerial is already up and pointed east!

    There must be things we can talk about before it all kicks off..

    But meantime, the sooner it's on air the better. So if I can be of any assistance with the change over please ask guys. I'm pretty handy with spanners n stuff and can still climb like a monkey.. ;) (Hurry up before that changes).
     
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  2. Clive G3GJA

    Clive G3GJA Active Member
    Staff Member Website Admin Chairman

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    Hi Graham

    Progress is being made. All of the equipment that was at Aldbrough has been removed and has been checked. One of the Alford Slot antennas broke as it was being removed and the other has suffered from the best part of two decades of being only 100m from the North Sea! However, it's not too badly corroded as the aluminium tube is OK but the copper jacket of the 141 has a fair bit of verdigris on it.

    On the analyser it's showing a poor SWR at 1308MHz. The diameter, slot width and tube gauge combination don't match the G3JVL recommended sizes which suggests it's wrongly made and could account for the match being best around 1367MHz.

    I'll probably have to make a replacement if some copper pipe can be found as I don't think this one can be made usable. I want to try copper so that a soldered connection to the feed can be made. Using aluminium means that you get dissimilar metals in contact at the feed point which is a recipe for a disaster with single antenna working.

    The recommended tube sizes are:
    35.8mm OD, 1.1mm wall with a 8mm slot (but the ex GB3EY one is 1.8mm wall thickness)
    38.1mm OD, 1.6mm (16swg) wall with a 11mm slot
    If you know of a source of one of the 'right' diameter/wall thickness combinations in copper let me know!

    The logic has been overhauled by G3RMX and will need a lock input from the Comag receiver as it is all analogue but that will suit the DTX-1 that we'll use to get the box on air. We'll probably run it in beacon mode initially.

    The PA and driver has been ordered from Bert PE1RKI and paid for. Delivery should be before the end of the month. We're going for the 75w MOSFET PA that will run at about 15w out. The driver is the Mitsubishi MOSFET brick and built in pre-driver that will be run at about 3w out.

    We were thinking about running the PA at masthead but as we have enough LDF5-50A and connectors that will only incur 1.1dB loss it makes sense to put the PA, pre-amp and duplexer in the shack where it can be protected from the elements and be more easily accessed. There's a lot of work to do at the repeater site replacing feeders and antennas so if you are able to help you'd be very welcome.

    The duplexer as tested probably has enough isolation to allow single antenna working but we need to run it all together to see if that is the case. We have available the original four section G3JVL filter that would give even more isolation if needed. Its size would definitely preclude putting it masthead which is another reason for keeping most of the gear at ground level.

    73
    Clive G3GJA
     
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  3. Wolfie

    Wolfie New Member

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    IMG-20160617-WA0005.jpg

    Hi Clive

    Sounds like you have a fair bit of work going on at various levels.

    Ken VDP built one a few years back using regular copper pipe which sounds like what you're wanting to do, it was tested at the Finningley DARC Rally and shown to be pretty good (better than my commercial one (Grrr)).. I'll ask him what the dimensions are.

    I'm visiting a Wind Turbine installation this coming Sunday and one Sat or Sun (pre Christmas) I need to visit Family, but after the New Year every weekend is pretty clear (unless my missus decides differently).
    I don't mind cold if there's coffee around, but I don't do cold AND wet.. bit of a bugger when I go diving like.. :D.
     
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  4. Wolfie

    Wolfie New Member

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    Did Ken get in touch Clive? We reckon that both himself and the other S Yorks guys will be within the new coverage, Ken received my pics the day you came up to visit me in the gateway.

    I thought you had given me a "business" card or summink but couldn't find it so gave him the BATC email you have.

    Meantime, I realised that we have a milling machine at work so all I need is the tube stock, I have some Alu tube in the garage, but its 34 and 40mm.. I bet the stuff on the chimney is the 38mm size needed.. Grrr.

    I'll be looking out for some more and have a go at making an AE myself.
     
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