Electronics – JackenHack

DIY Coaxial Collinear Antenna for ADS-B SDR Receiver – Measuring The Cable

October 26, 2017 by Jack Zimmermann 6 Comments

My first attempt of a Collinear Antenna. Professional mounting!

Part 1 – Checking the Velocity Factor of the Coax Cable

I have a homebuilt Collinear Antenna on one of my two ADS-B receivers. It’s an eight element antenna, built without any real effort of making sure that all the elements where the right length. So it’s about time to try to do it properly. The easy way is to get Flightaware’s great ADS-B antenna and filter, but it’s fun to build your own as well.

To build a good antenna, you would preferably use a Vector Network Analyzer so you can do proper measurements of your antenna design. With it you can quickly check stuff like SWR and optimize the impedance of the antenna at the frequency it’s intended to be used. In my case 1090MHz for ADS-B. But if you don’t have the money to spend, you have to improvise. I’m going to build a 12 element Collinear Antenna out of cheap RG-58 coax cable. But to calculate the right length of each element, we need to know the Velocity Factor, or the signal speed through the cable compared to light traveling in a vacuum. So let’s do the measurements.

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Aneng AN8008/AN8009 Modify For Better Accuracy Faster Readings

October 12, 2017 by Jack Zimmermann 56 Comments

If you are on the lookout for a sub $30 Multimeter (or $15 on eBay) for working with low voltages, the best one right now in my opinion is the cute and tiny Aneng AN8008 TrueRMS Multimeter or the newer model, the Aneng AN8009 with NCV and temperature measurement. They have a lot of functions and can measure µA current, and both are a 9999-count meter. The continuity tester is reasonably fast, but there is one little problem that bothered me. It takes 5 to 10 seconds for it to settle on a correct voltage reading. When it finally ends, it’s spot on, but the waiting is annoying. But fortunately, there is a simple fix for this problem.

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Calibrating Brymen BM-Series Multimeters

September 27, 2017 by Jack Zimmermann 2 Comments

Easy Way To Calibrate a Bryman BM869s Multimeter

After replacing my lost Fluke 87V multimeter with a new Brymen BM869s (rebranded Greenlee in the US) about a year ago, I’ve been delighted with the multimeter. It has every possible function I could ask for and then some. It’s been my go-to meter when working on electronics projects. I do have a Siglent SDM3055 DMM that is very good, but due to its startup time, I usually reach for my Brymen BM869s when I need to measure something, and it has higher resolution. But after getting a broken HP/Agilent 34401A DMM from eBay, fixing it up and replacing all the capacitors, I now have a better reference. I’ve compared it to my friend’s calibrated 6 ½-digit multimeter, and it’s still within spec, so naturally, I want my Brymen to be as close to my HP 34401A as possible. Turns out that calibrating and adjusting the Brymen is quite easy. Here’s how to do it.

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NTP Server Extreme accuracy for under $200 Using SI5351C

April 13, 2017 by Jack Zimmermann 2 Comments

When you make your own NTP server, you probably spend a lot of time trying to get it as accurate and stable as possible. To get good results, you need to connect your server to a good time reference, like an atomic clock, GPS or a GPSDO to get the PPS (Pulse Per Second) to sync your server with the reference clock.

In both Linux and BSD, there is kernel support to slave the very inaccurate CPU clock crystal to the PPS signal, continually adjusting the frequency, because the crystals of computers continuously drift due to temperature and barometric pressure differences. So most of the work is to get a crappy crystal to behave. What if you just jumped over that step, so the CPU clock gets synchronized with the same lab reference that the PPS signal uses, using a SI5351C Clock Generator?

Read on to see a simple way of doing it and get an extremely accurate NTP server for under $200.

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Atten 8502D Pinout Replacement Iron Heating element

March 23, 2017 by Jack Zimmermann Leave a Comment

So you need to replace the soldering iron on your Atten 8502D Soldering Station. You could just buy the heating element, but you can find a complete soldering iron with cable for less than $12 on eBay. So It’s easier just to replace the whole thing.

It Doesn’t Work!

I have ordered replacement irons before (I’m very rough with my soldering station) just to find out that they don’t work. You get the dreaded S-E or H-E message on display and, obviously, something is wrong. What do you do now? Read on to find out.

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