bias tees

They are getting "better", e.g. there are now safety rails at Gullfoss waterfall.

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When I last went they took the attitude that if you couldn't work out that spray+rocks+chasm means you might fall and die, then that would merely improve the species.

Isn't H2S wonderful.

Reply to
Tom Gardner
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John Larkin wrote

Insane high pricing, here is the inside of my home made one for 1.5 GHz:

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The little square thing on the left is a E4000 RTL-SDR tuner, the mouse like thing is a GPS mouse.

Basically a SMD capacitator and indiductor on a peeseebee.

Reply to
<698839253X6D445TD

here is the inside of my home made one for 1.5 GHz:

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The little square thing on the left is a E4000 RTL-SDR tuner, the mouse like thing is a GPS mouse.

Basically a SMD capacitator and indiductor on a peeseebee.

AND mine has a LM317 build in voltage stabilizer!!!!! All from the junk box at zero dullers :-0

Reply to
Jan Panteltje

Except that farts are supposed to stink of skatole

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otherwise 4-Methyl-2,3-benzopyrrole,

A bit of googling suggests that the actual stink in Iceland is mainly sulph ur dioxide, which is unpleasant enough, but rather different from either H2 S (rotten egg gas) or skatole. SO2 dissolves in water to give sulphurous ac id, which oxidises in contact with air to sulphuric acid which fits the ref erence to "hot sulfuric slime".

H2S is remarkably toxic - on par with carbon monoxide - and it saturates th e olefactory system above 150ppm, which means you may stop smelling it befo re it hits the lethal level of 500ppm or higher.

One of the party boats on Sydney screwed up its sewage tank management, and killed a passenger recently. The autopsy isn't in yet, so we can't be sure if it was H2S that did her in, but it is the prime suspect.

--
Bill Sloman, Sydney
Reply to
bill.sloman

Well, think about it. If there's more than 1/4 wave of wire there, then it must fall over at some frequency of interest, and the fields will be very different along the coil, not just a simple gradient. The first resonance is good, it's a parallel resonance, high Z. The second resonance, and every other one thereafter, is bad. The only way to keep impedance high, is to absorb those resonances in a loss element.

If you use a tapped coil, you can add taps at strategic points, to dampen across the antinodes of each resonance of interest.

If you use a solenoid or toroidial coil, a lossy material inside -- and outside, mind, because the fields are external at these frequencies -- can dampen that.

This keeps impedance flat, and a flat impedance must necessarily be lossy. The loss sink is the core material.

Note that you can't simply taper the coil (coreless), or do a progressive wound solenoid or whatever. There _must_ be a loss sink somewhere, otherwise you're just making resonators in different shapes!

If you use a conical coil, you're really making a conical spiral antenna, which has circular polarization and good directivity. Direct that energy into a wad of ferrite, and it's gone forever -- rather than reflecting and causing peaks and dips.

I don't think there's really anything very special that you can do with a conical. The self-similar shape may make it easier to get a flat impedance, but that impedance still isn't going to be very high, on account of how much of the spiral is inducting versus how much is absorbing.

Tim

--
Seven Transistor Labs, LLC 
Electrical Engineering Consultation and Design 
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Reply to
Tim Williams

A conical inductor is the distributed equivalent of the old trick of putting progressively larger damped inductors in series.

Take a look at these impedance curves:

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--
John Larkin         Highland Technology, Inc 

lunatic fringe electronics
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Reply to
John Larkin

Just one inductor? Magic L1 covers 0.01-6Ghz!

piglet

Reply to
piglet

Mmmmh. I wonder how truthful these plots are. Just looking at the S11 plot for the 0.22uH coil, we see S11 starting off at a little below -40dB at 50MHz. Presumably, this is basically the coil in parallel with the NA Port 2. Yet, at 50MHz, the coil is only j11 Ohms at most, with losses making it appear even lower. I'd have expected S11 to be pretty poor. (I'm too lazy at this point to drag out a Smith chart to see how poor.)

Jeroen Belleman

Reply to
Jeroen Belleman

When I was there, the "rotten eggs" smell of H2S was the one I noticed.

I know it was H2S since I made it in the kitchen when I was a kid. My father brought home iron (II) sulphate (?) and conc HCl in his coat pocket :)

Only found out about the toxicity much later!

I always assumed that the stench made people "be somewhere else" long before the toxicity would be a major problem. But if they are dead drunk then all bets would be off.

Reply to
Tom Gardner

You'll ruin it if you open it.

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These things have been around 20 years.

Reply to
bloggs.fredbloggs.fred

And the patents have expired! The Piconics prices were outrageous.

I think there's too much emphasis on SRF, as if a part becomes instantly useless above SRF.

A 47uF 1206 cap might have 1 nH of ESL, hence an SRF around 700 KHz. But above 700 KHz, it's still only a nanohenry. It doesn't become useless above 700K.

Same with inductors. A fraction of a pF is still a high impedance.

--
John Larkin         Highland Technology, Inc 

lunatic fringe electronics
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Reply to
John Larkin

Thanks Tim, John, very enlightening. I'd seen that pattern on the PSPL bias T photos but didn't understand the significance. The series RC loading on successive inductors depends on the SRF of each inductor.

Clifford Heath.

Reply to
Clifford Heath

We've done that, a series string of inductors. The fast end is usually a small ferrite bead, then a bigger bead, then a real inductor or two with shunt resistors to kill the Qs.

Lately, we buy iron-powder filled inductors, solenoid or conical.

It's a challenge to make a truly wideband, stable current source.

--
John Larkin         Highland Technology, Inc 

lunatic fringe electronics
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Reply to
John Larkin

Huh, can I ask a stupid question? (too late :^) I made a bias tee, I didn't think too much about the inductor*. (I picked one that fit in my form factor.) Upstream is a bigger inductor and resistor, all fed by a current source.

Why should I care about the inductor so much?

(Oh, it sucks the RF from my laser diode?)

George H.

Reply to
George Herold

There are a bunch of photos of the guts found with Google Images.

These all claim 10 to 6000MHz and appear NOT to use conical inductors: etc...

My guess(tm) is that when you open up the package, you'll find an ordinary solenoid wound chip inductor. I tried to find a Bias-Tee that uses a conical inductor and failed. I did find some conical inductors hiding inside an SMD package: However, it's possible that I didn't recognize it on the photos because those have an upper frequency limit of 15 to 65GHz and a 6GHz conical inductor would be larger and probably be more obvious.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
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Reply to
Jeff Liebermann

Ugh. Using the 1mm dia SMA center pin as a measurement reference, the device seems to have about 3mm of exposed and ungrounded center wire on the RF port and about 2mm on the RF+DC port. Those appear as inductors and can radiate of appear as a mismatch loss. The self inductance is 0.215 nH/mm. At 6GHz, that would be XL = 2Pi F L = 2 * 3.14 * 6*10^9 * 0.215*10^-9 = 8.1 ohms/mm So, the RF port would have 16 ohms of added reactance to the 50 ohm input impedance, and the RF+DC port would add 24 ohms. That's NOT a great impedance match. The PCB should butt right up to the SMA connectors leaving as little exposed center conductor as possible. At least they used the correct SMA connector type and milled the package to the correct wall thickness. However, the PCB was cut too small.

Did it really look good on a TDR?

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
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Reply to
Jeff Liebermann

I wonder what's special about 6 GHz. Most tees spec 6 GHz.

Mine seems to use a small inductor or, likely, a ferrite bead.

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It has about a 60 ps rise time, which corresponds to about 6 GHz.

This one is 12 GHz:

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$9.95.

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John Larkin         Highland Technology, Inc 

lunatic fringe electronics
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Reply to
John Larkin

Am 06.02.19 um 05:58 schrieb John Larkin:

That is meant to suggest that they have a HP8753 opt 006 network analyzer. Without opt 006 it only goes to 3 GHz; the option is a frequency doubler.

The 8753 was user friendly in comparison to the really fast ones, and good price/performance. Very popular. The S-parameters of a lot of RF transistors end at 6 GHz for this.

I have just opened a Mini circuits ZFBT-4R2G-FT. <

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>

The first impression was OMG! everything was wrapped in some teflon tape / goo and I was thinking: Whatever is inside, I can do that better. So I cut it open, which was more work than expected.

There are 2 toroids close to the stripline and 3 larger two-hole cores.

2 of them have a lot of windings, trifilar or worse and all in series. There are also some resistors and a lot of red glue to fix everything. So, there seems more to it than meets the eye, but only one 1210 cap.

Tonight, I'll take some photos.

That SMD housing is a good thing. The Piconics I have must be soldered with their ultrathin wires, and glued to the board or they'll rip loose.

for no reason. Unity gain stable. Pah!

regards, Gerhard

Reply to
Gerhard Hoffmann

Please!

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John Larkin         Highland Technology, Inc 

lunatic fringe electronics
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Reply to
John Larkin

Well, it is China Export. [1]

I use cheap edge-launch SMAs that have a big center pin that we solder onto a microstrip. It's a pretty good connection for 30 ps edges. One can neck down the trace at the pin end and make it even better. We used ATLC to tweak that.

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I'll post later.

[1] Japan had a similar quality reputation once, but they got that under control.

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John Larkin         Highland Technology, Inc 

lunatic fringe electronics
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John Larkin

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