Protection board(s) for transmitters.

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radio-berlin
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Re: Protection board(s) for transmitters.

Post by radio-berlin » Fri May 12, 2017 4:31 pm

Albert H wrote:
Fri May 12, 2017 10:09 am
My PA boards have 10A FF fuses in their supply rails. There is a big thyristor across the supply rail that goes into conduction on high VSWR or high temperature and blows the fuse. The VSWR detection is done with the usual line going to the output socket, and the temperature sensor is an ordinary plastic-encapsulated NPN silicon transistor (I use a 2N3904). The detectors feed into an LM393 dual comparator. With a bad enough fault condition, the fuse blows and a red panel LED lights. We supply one spare fuse inside the case. We found that the user of the rig will take proper notice of a blown fuse!

We also run transistors at about 60 - 65% of their full rated output. A favourite 28V device is the Thomson-CSF SD1019, which is capable of as much as 160 Watts (at "pirate rating"), but we use them as 75 Watt drivers (or outputs on smaller rigs). They're virtually indestructible at 75 Watts, and we drive them with SD1013, which is also under-run. We have hundreds of these devices, and so designed a standard PCB which fits directly on to a Redpoint heatsink and includes the protection circuits. It makes for a rugged, broadband PA which doesn't need critical adjustments of match or bias. It's old-tech, but it's pretty bomb-proof!
Any photos ?

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Re: Protection board(s) for transmitters.

Post by sinus trouble » Sat May 13, 2017 12:21 am

Nice Mr Sietedj! It seems the relay is single pole single throw! But that is not a problem since the relay state is software defined! Quite impressive!
Also Mr Albert has a point teaching pirates that would not normally be familiar with load characteristics!
I don't expect anyone to "re-invent the wheel" Options are already available, Its just what suits your needs?
I have never built Mr Yellowbeards example? It seems to compare a reference voltage (fwd) to an input (refl) and would give a great visual effect to your front panel if that's what you desire?
The same result can be achieved with a comparator!
I am as stupid as I look! :|

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Re: Protection board(s) for transmitters.

Post by sinus trouble » Sat May 13, 2017 12:32 am

Just to add! Once you experiment with directional couplers (SWR Bridge) and see the differences? It should make your goal much clearer!
I am as stupid as I look! :|

Albert H
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Re: Protection board(s) for transmitters.

Post by Albert H » Sun May 14, 2017 2:49 am

radio-berlin wrote:
Fri May 12, 2017 4:31 pm
Any photos ?
I'll post a couple when I build some more boards next week.
Is it meant to smoke like that? :shock:

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Re: Protection board(s) for transmitters.

Post by radium98 » Sat Jun 03, 2017 4:37 pm

do tha se
protect-sch.jpg
rve ? is it working ?
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Re: Protection board(s) for transmitters.

Post by radionortheast » Sun Jun 04, 2017 10:21 am

my new pcs is always causing me problems, the protection always shutting down, it gose on and off when it dose it, tune the output section on it going beyond a certain wattage, even if the display shows a cool temprepature, no reflected watts it still might decide to turn off, draws excessive current, i think is whats causing it to shut down. I don't have a location here for broadcasting so I just test stuff, i can't put an aerial outside so i've been heating the roof tiles with a loft aerial, i've been using a gp aerial, 1 radial i point at the nearest town, remade it with the calculations from the pcs website, but anyway this is taking over a thread thought this is about protection, :D

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Re: Protection board(s) for transmitters.

Post by Albert H » Sun Jun 04, 2017 11:40 pm

radionortheast wrote:
Sun Jun 04, 2017 10:21 am
My new PCS is always causing me problems, .......... I can't put an aerial outside so I've been heating the roof tiles with a loft aerial,
The PCS rig isn't the problem. You just can't use an indoor aerial. At the very least you'll waste 90% of the expensive RF energy and there is no way you'll get a consistent and accurate impedance match.

There is always a way to get an outdoor aerial. Take a look at the simple Slim Jim - it's just made out of a piece of 300Ω twin feeder, and can be put into a plastic pipe. The pipe can easily emerge from a chimney or even through a vent brick.... There's always a way!

One trick I used on a rented house was to replace the TV aerial pole with one that had a nylon section joining two ¼-wave lengths of mast. The coax ran up the inside of the lower half, and there was a Pawsey Stub stuffed inside there too. The two TV aerials were fitted to the top of the whole effort and the lower section was isolated from the supporting mast with another nylon "joiner". Because the elements were so fat, the bandwidth was quite wide, and I could get 1.2 : 1 or better over about 5 MHz at the top of the band! I ran 25 Watts into that aerial almost every night for a year or so, and even had the GPO lads trying to track it. It was never sussed, and I think that I only threw it away about two years ago when having a clear-out. The house was at the top of a fairly high hill, and the coverage was excellent despite the fairly low power.

Get an aerial outside and stop blaming your rig!!!
Is it meant to smoke like that? :shock:

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Re: Protection board(s) for transmitters.

Post by radionortheast » Sat Jun 10, 2017 6:14 pm

i will try to get the aerial outside, i struggle to make end fed aerials, did push an aerial up next to the chimmney throught the loft, i don’t remember what the results where, it would have to be a long pole to clear the top, there is also a round tube which gose up throught the roof tiles to the outside, theres only 1 foot clearace at the bottom, guess i could saw into it.. The other option is maybe drill a hole in the top of roof, there is already small hole, maybe get the radiator section outdoors, have to make it out of thin material, if i make it from a telescopic aerial it might work, have copper wire but its too flexible on its own, i don't want something wide poking out of the top.

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Re: Protection board(s) for transmitters.

Post by radionortheast » Tue Jun 13, 2017 9:50 am

so i've decided against drilling into the ridge tiles don’t know what their made of, i’ve gone with the tube instead, I was thinking the tube is problaly not held onto anything, could just silde up and down and sucess to my suprize it dose just slide up and down. I measured it to be about a meter long, it can also move from 1 side to side, silding something up there shouldn’t be any problem, it is just open at the top with chris cross round mesh simliar to naughs and crosses board.

I may still have to saw into or drill, don’t know yet, could see what the reception like with the top element inside the tube, don’t know weather to use part of tube as the aerial, have it inside of it, heard some plastic can be conductive, or I could take the tube out fasten an aerial to top. This may turn out to bit like escape from alcatraz or something where put a fake grill in place. (don’t want birds flying in).

Another option would be to have my gp aerial with 1 radial, fold out at the top, both the radiator and the radial would be vertical and could be pushed up, anyway this is all very exciting, the best thing is I won’t of done any damage to the roof. At the moment I don’t think my cable will reach that far, i’m waiting on new cable.

I've been making myself cringe thinking of the aerial falling over silding down the roof, even thought a 6 inch hole isn't big enough for me to fall out of, its still scaryerly high, will have to worry about rain aswell

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Re: Protection board(s) for transmitters.

Post by nrgkits.nz » Wed Jun 14, 2017 8:03 am

I hope that large tower block fire today wasn't a result of someones faulty rig. I wonder if there were any stations up on that one.

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Re: Protection board(s) for transmitters.

Post by Analyser » Wed Jun 14, 2017 8:54 am

nrgkits.nz wrote:
Wed Jun 14, 2017 8:03 am
I hope that large tower block fire today wasn't a result of someones faulty rig. I wonder if there were any stations up on that one.
Historically that area has been quite popular with stations in the past, the location is quite central and all the blocks round there are pretty tall so the signals cover most of London.
The last time I drove past I didn't see any aerials on the roof and I have a feeling that the council made roof access quite difficult a few years ago so personally I doubt anyone is up there.

Having woken up to images of the fire on the news it looks absolutely horrendous, I can't imagine how terrifying it must be being in that situation. Just awful.

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Re: Protection board(s) for transmitters.

Post by radionortheast » Wed Jun 14, 2017 6:14 pm

asbestos is fire retarden they take it out, can’t see how they would go without fire protection nowadays, I can’t understand what happened, sad day for those poor people, weather they where good or bad all human life is precious.

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Re: Protection board(s) for transmitters.

Post by yellowbeard » Wed Jun 14, 2017 6:51 pm

The fire brigade are saying it started on the 4th floor, so its probably not a rig fire. I was watching it last night when it kicked off, bloody scary to even think about.

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Re: Protection board(s) for transmitters.

Post by Albert H » Thu Jun 15, 2017 1:29 am

The rumour mill is working overtime. The recent "refurbishment" of the block was purely cosmetic. They didn't even bother to check the dry riser mains. It looks like the cladding was sub-standard - done on the cheap (though the Council would have paid the damned thieving contractor top Dollar!).

There should be a comprehensive Public Enquiry into this disaster, and the contractors, project managers, safety inspectors, Council managers and anyone else involved with the refurbishment project - and particularly those who signed off on the job - need to be tried for manslaughter (at least) and put away for 10 years.
Is it meant to smoke like that? :shock:

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Re: Protection board(s) for transmitters.

Post by Analyser » Fri Jun 16, 2017 11:18 am

Albert H wrote:
Thu Jun 15, 2017 1:29 am
The rumour mill is working overtime. The recent "refurbishment" of the block was purely cosmetic. They didn't even bother to check the dry riser mains. It looks like the cladding was sub-standard - done on the cheap (though the Council would have paid the damned thieving contractor top Dollar!).

There should be a comprehensive Public Enquiry into this disaster, and the contractors, project managers, safety inspectors, Council managers and anyone else involved with the refurbishment project - and particularly those who signed off on the job - need to be tried for manslaughter (at least) and put away for 10 years.
Agreed 100%.

I was reading that these type of blocks are designed to contain a fire to just one flat, therefore the advice given to residents was to stay indoors in the event of a fire elsewhere. I bet the cause of the fire spreading was that stupid plastic cladding they used to tart the place up.

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Re: Protection board(s) for transmitters.

Post by Shedbuilt » Fri Jun 16, 2017 12:25 pm

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Last edited by Shedbuilt on Fri Jun 16, 2017 12:27 pm, edited 1 time in total.

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Re: Protection board(s) for transmitters.

Post by Shedbuilt » Fri Jun 16, 2017 12:26 pm

Analyser wrote:
Fri Jun 16, 2017 11:18 am
Albert H wrote:
Thu Jun 15, 2017 1:29 am
The rumour mill is working overtime. The recent "refurbishment" of the block was purely cosmetic. They didn't even bother to check the dry riser mains. It looks like the cladding was sub-standard - done on the cheap (though the Council would have paid the damned thieving contractor top Dollar!).

There should be a comprehensive Public Enquiry into this disaster, and the contractors, project managers, safety inspectors, Council managers and anyone else involved with the refurbishment project - and particularly those who signed off on the job - need to be tried for manslaughter (at least) and put away for 10 years.
Agreed 100%.

I was reading that these type of blocks are designed to contain a fire to just one flat, therefore the advice given to residents was to stay indoors in the event of a fire elsewhere. I bet the cause of the fire spreading was that stupid plastic cladding they used to tart the place up.
Agree with both of you here. I'm thinking it could well have spread; from the fire source to the cladding - quite likely via an open window (due to warm weather), up and around the cladding; aided upwards by chimney effect and possibly combustible insulation, and back from the cladding to the flats, quite possibly via more open windows, but once the cladding properly went up, windows probably gave way anyway. I heard (via radio; Sajiv Javid was grilled this morning, by Jon Snow I think), that this particular cladding is banned in the US, for any structure over about 40', and also designed to be used with fire traps on every floor, and around every window. Apparently, to use fire resistant cladding, would have added about £5,000 to the whole project. The photos seem to strongly suggest that the outside of the building was on fire, and that could presumably only be the cladding, and / or the insulation layer.
Neglect, negligence, and design by chequebook, for the redevlopment; with the lack of fire alarms, decent fire doors, sprinklers etc - purely, presumably to save costs, where all of those costs, and far more, were spent on that tarting up of the exterior, so that other locals didn't have to look upon it, or have their property prices affected by the view. Lack of decent fire escapes obviously too; although probably difficult to address properly, without a major rebuild.
Tragic and heartbreaking, and it just shouldn't have happened.
I grew up about a mile north of there.

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Re: Protection board(s) for transmitters.

Post by Albert H » Sat Jun 17, 2017 11:09 am

Grenfell Tower Factsheet

1 - The block of flats was run not by any council but by KCTMO - Kensington and Chelsea Tenants Management Organisation. This body is made up of 8 TENANTS, 4 councillors and 3 independent members.
2 - Labour hold the seat for the area that the block is situated in.
3 - Labour run the Greater London Council who manage the “very under-funded” London Fire Service.
4 – Emma Coad - the sitting Labour MP for that constituency - also sat on the KCTMO.
5 - The advice to stay put - which Sadiq Khan has been so vocal about - was given by the London Fire Service.
6 - The decision to change contractors during the refurbishment was made by KCTMO.
7 - The decision not to spend £138k on fitting sprinklers was the choice of the KCTMO.
8 - The decision to create "ALMO" - Arm's Length Management Organisations - such as the KCTMO, was made under the “Right To Manage” legislation passed in 2002 as part of the “Commonhold and Leasehold Reform Act”.
9 - This Act was put in place to give leasehold tenants a greater say and the ability to self manage, which has clearly proven to be a total disaster.
10 - Which Government was in a charge when this Law was passed? Labour.
11 - Sadiq Khan - as Labour Mayor of London - produced a report to say that the Fire Service did not need any further funding.
12 - Emma Coad the recently re-elected Labour MP was on the board of the Tenant Management group, who are being accused of not listening to tenants.
Is it meant to smoke like that? :shock:

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Re: Protection board(s) for transmitters.

Post by sde-1104 » Mon Jun 19, 2017 11:30 am

Please use the General Chat forum if you want to talk about politics - admin.

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