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General Discussion / Re: Introduce yourself topic!
« Last post by eleczo on January 18, 2018, 08:02:12 AM »
Hello all, am a newbie to this forum. Great pleasure to be participating here.
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General Discussion / Re: What happened to Martin..?!
« Last post by MJLorton on January 13, 2018, 09:27:20 AM »
Well done Martin, a construction shed which will double as your studio later, and with what looks like a great view as well to come.

Thanks Sean. It's a very nice location with great views in winter and nice privacy in Summer. It's about 1.5 acres with a fairly long and steep (12-20%) driveway to the pad where the shed is. I'll show more in the video. The odd bear and deer wander around the woods here. Beautiful grey eagles as well.
The picture is of a bear cub my timelapse camera captured.
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General Discussion / Re: What happened to Martin..?!
« Last post by MJLorton on January 13, 2018, 09:15:04 AM »
Hi Martin. I wondered where you'd gone.

Glad to know you like the new place. Doesn't seem like that long since you left South Africa.

I'll look forward to the T4D video.

Thanks, it is a very nice area to live in. South Africa almost seems a life time away as we have been very busy since leaving.
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Product Reviews / Re: True RMS meters and RF signals
« Last post by SeanB on January 12, 2018, 10:18:48 AM »
The voltage measurement side will probably only run to around twice the spec amount, but only for largish signals for the range. Yes the input impedance will take a nasty dive as frequency rises, but the thing to remember is the DMM does not normally provide the 50R load, it just shows the voltage relative to an external 50R load with the meter in parallel.

The Brymen frequency counter will go pretty high in measurement mode, JoeQSmith on YT did review it, and the input was quite good at showing frequency up in the MHz region.

https://www.youtube.com/watch?v=K-4L2JarVxA

However for best RF measurement it probably would be best to use a RF probe with a diode detector in it, and use the meter as a display only, least loading on the circuit and the least disturbance due to stray capacitance.
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Product Reviews / Re: True RMS meters and RF signals
« Last post by m0rjc on January 12, 2018, 08:05:02 AM »
Answering myself based on various searches:

Stack Exchange has a comment that any DMM is likely poor at RF, not only due to its measuring technique but also because the impedance of its input at RF is likely to be lower and complex. To date I've used a PC based oscilloscope which is designed for use up to 20MHz. I'd need specialised kit to go higher.

Brymen give accuracy over frequency ranges in their spec sheet http://brymen.eu/wp-content/uploads/biall/102092/102092.KARTA_EN..2015-07-09.1.pdf
Accuracy is spec'd up to 100kHz in the low voltage and current ranges that may be used on an audio pre-amplifier or processing circuit. It drops to about 5% at the higher frequencies, which to be fair is not too bad when thought of in dB.  (20*log(1.05) ≅ 0.5dB)

It could be interesting to compare against other meters including an non-true-RMS. Fluke in their "Extended Specs" for the 170 series (similar price range) only specify an accuracy up to 1kHz. The 280 series specifies 100kHz and impressive accuracy, but costs well over twice as much in the UK.
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Product Reviews / True RMS meters and RF signals
« Last post by m0rjc on January 12, 2018, 05:07:02 AM »
I was looking at the Brymen 869 meter after reviews here, and thought that its ability to show dBm relative to 50ohm load looked useful. I guess it won't work for RF signals though, as these will be well above the bandwidth of the meter? Could I even use it to find RF signals through the circuit or will these always show up as 0V? Would a non-true-RMS meter perform better if it's using a simple rectify approach to measuring?

Thanks
  - Richard
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General Discussion / Re: What happened to Martin..?!
« Last post by steve30 on January 11, 2018, 02:39:35 PM »
Hi Martin. I wondered where you'd gone.

Glad to know you like the new place. Doesn't seem like that long since you left South Africa.

I'll look forward to the T4D video.
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General Discussion / Re: What happened to Martin..?!
« Last post by SeanB on January 11, 2018, 07:39:04 AM »
Well done Martin, a construction shed which will double as your studio later, and with what looks like a great view as well to come.
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General Discussion / What happened to Martin..?!
« Last post by MJLorton on January 10, 2018, 10:55:05 AM »
Hello Everyone,

I thought I would pop in a quick post as to what's been going on in my life.

It's been a busy and sometimes stressful eight months since packing up and moving to Black Mountain in North Carolina.  We love it, both my wife Louise and daughter Chloe have settled in quickly.

Unfortunately I ended up with no space to work or setup a lab / studio. We are in a rental while we plan the building of our new home. The rental has two bedrooms and an open plan loft space upstairs that Louise uses as an office as she works from home. This leave no space for me to film or tinker.

I have scouted around for ages looking at renting office space, buying a small cabin / trailer to work from. Unfortunately several options did not work out as issues came up during due diligence. We did buy a small piece of land on the side of a mountain that went "cheap" as it's not the easiest place to build...but it will make a great spot for a little studio / lab. I hope to have that built later this year but at the moment I'm busy building my own shed which will act as a temporary studio until the cabin is built. More about these "adventures"  in a T4D which I hope to film in Feb. 

Cheers,
Martin.
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Solar Power / Re: Separate battery banks feeding one output
« Last post by SeanB on January 10, 2018, 08:58:56 AM »
Connecting the inputs will lead to the 2 MPPT controllers ( if that is what they are) trying to fight each other, leading to some oscillation in the chargers. Connecting the outputs leaving the input on the one open should do nothing, as the controller is generally expecting voltage on the output.

However the internal mechanisms of the controllers determines what they will do with commoned terminals, it really depends on the particular charger.

Simple non MPPT chargers you can connect in parallel, as the one with the highest float voltage on the bank determines the end of charge by dumping solar panel power, while the lowest battery hogs all the current till they all reach the same charge state with the same float voltage.
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