Power

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kevycorsa
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Power

Post by kevycorsa » Wed Feb 06, 2019 7:49 am

What is best options for powering a rig up a mountain.
Generator or power inverter.
I've got a 600w pure sine wave inverter but that does not power the 200w rig ive got.
So i need something new ?

Albert H
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Re: Power

Post by Albert H » Thu Feb 07, 2019 12:17 am

The way I've just done this was to have 2200m of power cable provided by the local power company. It was an expensive installation (the power provision cost more than the transmitter, mast, aerial, coax and STL receiver!)
"Why is my rig humming?"
"Because it doesn't know the words!"
;)

kevycorsa
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Re: Power

Post by kevycorsa » Thu Feb 07, 2019 7:51 am

That's one way to-do it...
Can i plug an extension in ? To my location ? :lol:
No seriously now something available for the average Joe blogs to go sit in a van up high somewhere.
Would a inverter of a van battery power a 200w rig.
My 600w inverter cuts out after about 5seconds only when powering the tx I've tested it on power tools ect.
Would a bigger inverter work ?
Would a generator be better ?

nrgkits.nz
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Re: Power

Post by nrgkits.nz » Thu Feb 07, 2019 10:00 am

The 200w Rig is probably too inefficient or its got a bad load/antenna connected to it, eg for 200W output power its probably pulling atleast twice that from the inverter - probably more once you include the exciter and any pre drivers/amplifiers and other circuitry. Also a bad match with no built in VSWR protection will only cause the current draw to go even higher again. For remote stations where there's no power source handy and you have to operate from solar/batteries/inverters etc... ideally you'll want to use modern LDMOS PA's which are generally 75% to 80% efficient and have some serious gain, these can be driven with as little as 500mW for 150W out.

kevycorsa
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Re: Power

Post by kevycorsa » Thu Feb 07, 2019 11:06 am

Could be inefficient.
Can't be a load missmatch as I've tried with dummy load and antenna what both work ok with mains power.
I've tried turning bias down and voltage for amp and pll so its running about 100w.
This is the amp pictured below powered by a nrg pro3.
Tx works fine powered from mains.
Inverter cuts out around 5 seconds after switching tx on.
I've even tried with tx and inverter 20 odd meters apart.
Could it just be the inverter just can't handel it.
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nrgkits.nz
Neckmin
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Re: Power

Post by nrgkits.nz » Thu Feb 07, 2019 11:59 am

You really need to measure the current draw from the PA to find out what that is in amps. Watts = Amps * PA supply voltage. Also adjusting the bias down will reduce the power but at the same time will create a mismatch in the output matching network of the PA because the output impedance of the transistor is going to increase as the power goes down. You’re best to reduce the DC supply voltage to the PA, this will help keep the output impedance and matching the same. The other thing you could do is rework the output matching and tune it up for a better match on one freq so it’s not broadband, this will also improve its efficiency.

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yellowbeard
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Re: Power

Post by yellowbeard » Thu Feb 07, 2019 4:37 pm

Could be RF interfering with the inverter circuitry also, try checking it with a bunch of light bulbs to draw the same current and see what happens. If this is the case then a filter on both the DC and mains side may sort it out. RF can be a right bastard to equipment that is not primarily designed for it. There are small "silent" petrol generators on fleabay for £150 - these are for caravans. Another way out may be to use the transmitter at 100 Watts and put up a stack of antennas to compensate.

s2000

Re: Power

Post by s2000 » Thu Feb 07, 2019 6:04 pm

What inverter is it?

Wouldn't it be better to just put 4 leisure batteries in series (to make 48v) and power the rig straight off that, with no inverter. When you use an inverter, the unit has to convert the dc to ac... and then the rig has to convert the ac back to dc! There will be losses doing this double conversion... I would of thought the most efficient solution would be a DC source.

Obviously you will need a change of batteries when they are dead but it's not much different to the other solutions you have.

Also if you are up a mountain, you will have a great advantage of covering a good amount of area, so less power could be used and make the batteries last longer.

Albert H
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Re: Power

Post by Albert H » Fri Feb 08, 2019 12:54 am

I've run rigs from Leisure Batteries, and the results are excellent. However, you have the hassle of recharging, and it's not really practical for really lengthy broadcasts.

One set-up I put together in the Hollywood hills a few years ago was powered by a couple of Leisure batteries, alternately charged and discharged, with a relay changeover, with a big photovoltaic cell array (came from International Rectifier as a "sample"!) and a couple of small wind turbines. The rig transmitted at 40 Watts, and used stacked Yagis pointing at the target audience (giving hefty antenna gain). The consumption from the battery was just under 70 Watts (the PA transistors were a MRF237 driving an MRF238), and the circuit was carefully optimised for our frequency of choice - I needed all the efficiency I could get!

The link receiver was on UHF, using a 24-element TV Yagi at each end, and we only needed about 400mW at the studio to get a completely noise-quietening signal at the site.

The first set of gear was found and removed by some Park Rangers, but was returned when we went to their depot and explained that it was "amateur radio" equipment! That gear lasted for over a year before the FCC collected it. The second set of gear was similar technology, but used a "translator" (UHF in, mixed down to Band II and amplified).
rxefront.jpg
The picture shows the translator board - UHF in to about 1 Watt out on Band II. Both the receiver LO and the transmit mixer LO were synthesised from a common crystal oven module, using a dual-PLL chip designed for mobile phones. This was the fifth version of the translator (versions 1 - 4 didn't work well for a range of reasons), and was used overnight every night for nearly five years. You'll notice that there are copious Molex connectors providing test points for alignment.

The 40 Watt PA was housed in a separate diecast box, to keep its heat away from the PLLs. The crystal oven module ran at 125°C - hotter than it ever gets in California - to make the frequencies insensitive to changes in ambient temperature. Each part was housed in waterproof diecast boxes - one each for the translator, PA, and battery charging / monitoring and switching circuitry.
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"Why is my rig humming?"
"Because it doesn't know the words!"
;)

kevycorsa
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Re: Power

Post by kevycorsa » Sat Feb 09, 2019 5:47 pm

Right I've got a few good ideas to try from reading all this
Ill let you no how i get on

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radionortheast
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Re: Power

Post by radionortheast » Wed Feb 13, 2019 9:55 am

remember when I got my 15w tx, it kept shutting down it took ages to find out it was because I was using the power supply that was meant for the 3w transmitter it couldn’t supply the amps even thought the aerial could cope, it would shut down after a while and draw excessive amps. I imagine you could have problems running a transmitter off batteries, they always used generators in ireland, theres a video posted here not so long ago, they are very noisy..

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