EMRFD Message Archive 13853

Message Date From Subject
13853 2017-05-11 04:09:54 k1rf_digital_stev... Low cost test equipment
Hi folks.  I gave a presentation last night at our local amateur group (gnarc.org.)  I put together a presentation on low cost test equipment that I thought might be interesting to many of you.  This equipment was either personally used by me or known to have been used by other hams with good results.

Steve K1RF

http://gnarc.org/wp-content/uploads/Low-Cost-Test-Equipment-that-you-can-buy-on-EBAY-RevB.pdf


13854 2017-05-11 05:46:56 Nick Kennedy Re: Low cost test equipment

​Good summary.  Thanks.

​Nick, WA5BDU​

Hi folks.  I gave a presentation last night at our local amateur group (gnarc.org.)  I put together a presentation on low cost test equipment that I thought might be interesting to many of you.  This equipment was either personally used by me or known to have been used by other hams with good results.

Steve K1RF

http://gnarc.org/wp-content/ uploads/Low-Cost-Test- Equipment-that-you-can-buy-on- EBAY-RevB.pdf



13855 2017-05-11 07:37:12 bobtbobbo Re: Low cost test equipment
Very nice summary, Steve. Thanks for posting it.

Bob, K1AO
13859 2017-05-12 03:34:08 John Re: Low cost test equipment
Great article.

Warning on the Cen-Tech multimeter though. Many of the cheap meters put
out as much as 5 volts on the leads when measuring ohms. Desirable is
one that puts out less than 0.6V so it doesn't turn on semiconductor
junctions causing inaccurate readings for in circuit tests or even
damaging semiconductors. A good meter will have low voltage for ohms
function and have a diode function which measures voltage drop through a
diode junction with a constant current applied. Anyone have an example
other than Flukes, which are expensive even on ebay?

John

13860 2017-05-12 04:03:21 Lee Hiers Re: Low cost test equipment
I have a BK Precision 2709B, which measures R using .45 volts, except on the lowest scale (660 ohm) where it uses 1.2 volts.....too high?

73 de Lee, AA4GA


13861 2017-05-12 08:59:45 Ken Chase Re: Low cost test equipment
Hi Steve

I want to order one of the AD8307 power meters in your presentation. Is the seller(alicehappy858) depicted in the ebay screen grab reliable?

73

ken VA3ABN

13862 2017-05-12 09:03:12 jgaffke Re: Low cost test equipment

I have the K5BCQ Vector Impedance Analyzer:  http://www.qsl.net/k5bcq/Kits/Kits.html 
An antenna analyzer, L and C meter, signal generator, freq domain reflectometer ...   I'm happy.  Haven't done it yet but can be hacked into a two port device, so a VNA for under $100, good to 150mhz.  Sends two square waves separated by 2khz from an Si5351 out into the world, the detector distinguishes the fundamental from the harmonics by looking for that 2khz separation using DSP on an Arm.  Their mechanical construction seemed less than ideal, I wound up bolting the ends of two boards together and mounting it to the lid of a Hammond 1455K1601BK extruded aluminum box.

Some very good pointers in that pdf file.  But not sure I'd call that spectrum analyzer a spectrum analyzer, it assumes a linear test subject.  Would not be any good for looking for harmonics from a linear amp, for example. 

I'm thinking hard about building a simple spectrum analyzer for low HF using 2 PX1002 SAW filters after the first mixer, around 50khz wide at 86.85 mhz.  A diode ring mixer driven from an Si5351, a discrete LPF up front, some MMIC's for gain, and an AD8310 into an Arduino Nano.  About $30 total in parts, quick and straightforward.

If that works, add a second mixer to bring that 30khz slice down to around 150 khz and replace the AD8310 and Arduino with a TI ADS127L01 512 ksps 24 bit ADC into a RasberryPi Zero's SPI port, use DSP algorithms on the Pi and display out the HDMI port.  Move to something better than an Si5351, perhaps an Si5338 or Si5341.  And add a an extra mixer and 900 mhz SAW filter up front.  Still down around $50 in parts.  But now we're talking months or years of spare time to get this fully developed.  
 
Another big hole in that ebay list:  A good cheap high speed scope.  Yes, you can buy perfectly good 40 year old scopes on ebay, or a $400 Rigol.  But I'm intrigued by the thought of a really cheap sampling scope head feeding the 12 bit ADC's on something like the PJRC Teensy 3.2 Arm processor.  Sampling head could be along these lines:  http://www.redrok.com/sampscope.htm   Houtman claims he saw a 1GHz bandwidth.  Total cost including the Teensy of around $50.  And months or years of spare time.

Jerry, KE7ER


13863 2017-05-12 09:15:26 Steve Dick Re: Low cost test equipment
The PHSNA yahoo group has a file in their files section called Yana_K1TRB. In his parts writeup, he says this:
 
“On eBay search for “RF Power Detector Meter”. You want one with an
AD8307 and a voltage regulator. Do not buy the shielded version: it is
more expensive and limited in bandwidth.”
 
He used:
 
-Steve K1RF
 
13864 2017-05-12 10:11:39 Roy Appleton Re: Low cost test equipment
Hopefully, I ordered a couple from them! :-))

Roy
WA0YMH

13865 2017-05-12 10:12:19 Ken Chase Re: Low cost test equipment
Thanks Steve. The link just happens to be the seller alicehappy858 as shown in your presentation.

73

Ken VA3ABN

13866 2017-05-12 10:13:51 roy_appleton Re: Low cost test equipment
Concerning a good cheap Oscilloscope, I bought this for $300 and couldn't be happier. Some things just are better bought then built. :-))

https://www.circuitspecialists.com/hantek-200mhz-digital-storage-oscilloscope-dso5202p.html

Roy
WA0YMH
13867 2017-05-12 10:35:34 DuWayne Schmidlko... Re: Low cost test equipment

I have had good luck with a Chinese SNA that connects to a Pc.  It is listed on eaby as NWT70-frequency-sweep-meter  and is usually under $100 with shipping

http://www.ebay.com/itm/NWT70-frequency-sweep-meter-0-05-85-MHZ-with-0-to-50-db-attenuation-/121372362938?hash=item1c425b48ba:g:MboAAOSw-nZTq5V5

Usable up to 85 Mhz, software allows you to use as a signal generator, power meter, and SNA.  If used with a Return Loss Bridge it will also measure SWR. A couple other functions in the software are only available with slightly different versions of the equipment.

You can download the software  for both windows and linux  and user manual at http://www.dl4jal.eu/hfm9.htm.

The manual is very complete, the original was in German so some of the wording in the English version reflects the translation.

DuWayne KV4QB




13868 2017-05-12 11:21:52 jgaffke Re: Low cost test equipment
On re-reading, this might be a bit confusing:
>  If that works, add a second mixer to bring that 30khz slice down to around 150 khz 
>  and replace the AD8310 and Arduino with a TI ADS127L01 512 ksps 24 bit ADC
>  into a RasberryPi Zero's SPI port

Should read "50khz slice", not 30khz.  The PX1002 SAW filters have a 50khz wide 3dB passband centered on 86.85mhz.  The second mixer would have a local oscillator of 87.0 mhz, moving the 50khz wide output of the SAW filter down in frequency to be centered on 150khz.  With two SAW filters stacked, the datasheet graphs suggest the skirt is plenty steep to avoid the image from 87.15mhz.  But may need to move things up some from 150khz as their graphs don't agree with the fc+/-60khz rejection figures they give in the table.

The AD8310 is pin compatible with the AD8307, improved and cheaper.  Looks like Analog Devices is trying to kill the AD8307, but hams are a stubborn lot.  I don't see anybody out there using the AD8310.

Advice welcome.

Jerry, KE7ER

13871 2017-05-12 13:27:23 Bill Carver Re: Low cost test equipment
The AD8310 has an internal op amp and a buffered voltage output. The AD8307 has just a current output and needs an external op amp if you want a voltage output. Basically the same front end guts but different outputs.

(don't look at the "440" and "500" MHz and think the front ends are different: just specified differently. The AD8310 is specified to 440 with 0.4 dB linearity, the AD8307 is 500 but 1.0 dB linearity).

W7AAZ

P.S.   I use the AD8310 because I'm driving a return loss analog meter movement


13872 2017-05-12 13:41:49 Steve Dick Re: Low cost test equipment
The AD8307 data sheet page 15 (adobe page 16) states in part under output interface:
“An on-chip 12.5 kΩ resistor, R1, converts this current to a voltage of 25 mV/dB”
 
So it still can be used directly as long as you are feeding a high impedance scope. It’s built-in resistor converts the internal current output to a voltage.
 
-Steve K1RF
 
13873 2017-05-12 15:13:12 Will Kimber Re: Low cost test equipment

Hi Jerry,


I have an old Philips dual beam scope with a problem in the high voltage diode multiplier.  Been keeping it with the idea of using ADC and replacing crt with a led display.


Worth the effort?


Cheers,

Will


13874 2017-05-12 16:44:35 Bill Carver Re: Low cost test equipment
True when a 12.5K ohm source impedance is low enough for what you're trying to do.
W7AAZ

13875 2017-05-12 17:09:32 jgaffke Re: Low cost test equipment
Certainly the easiest and fastest is to fix the hv supply.  To move away from the CRT would be to completely redesign the scope.  Which might be fun, but a major project.  Probably makes more sense to start from scratch, then it can be easily reproduced.


---In emrfd@yahoogroups.com, wrote :

Hi Jerry,


I have an old Philips dual beam scope with a problem in the high voltage diode multiplier.  Been keeping it with the idea of using ADC and replacing crt with a led display.


Worth the effort?


Cheers,

Will

 
13901 2017-05-21 10:46:23 jgaffke Re: Low cost test equipment
Correction, the AD8310 is in a 0.65mm pin pitch MSOP8 package, not SOIC8.
Pins got stirred up considerably.

---In emrfd@yahoogroups.com, wrote : 
The AD8310 is pin compatible with the AD8307, improved and cheaper.   
 
13913 2017-05-25 20:54:49 Ashhar Farhan Re: Low cost test equipment
have you also considered stuff that can be built using the ebay stuff? for instance, the frequency counter could be used in a signal generator, etc.

- f

13915 2017-05-26 04:32:20 Steve Dick Re: Low cost test equipment
Jim, file sent.
-Steve K1RF
 
13940 2017-05-30 13:21:19 Jack Boswell Re: Low cost test equipment

Hi Steve,

Might I also have your permission to make use of your Presentation for a program for the Builders Group in Jefferson City Mo. We are part of the Mid-Mo ARC. And if so could I also have a copy of your slides. Thank you for your help.

73's Jack Boswell N0KSF www.n0ksf.com

13941 2017-05-30 14:12:16 Ashhar Farhan Re: Low cost test equipment
I would add this capacitance tester for $15 dollars to the list 


it is a life saver if you are dealing with smd components or regular caps that are unmarked.

- f

13942 2017-05-30 15:51:01 jgaffke Re: Low cost test equipment
I have not tried it yet, but this looks like an excellent way to measure capacitance.
Especially if the project already involves an arduino (or similar uC).


Jerry, KE7ER




---In emrfd@yahoogroups.com, wrote :

I would add this capacitance tester for $15 dollars to the list 


it is a life saver if you are dealing with smd components or regular caps that are unmarked.

- f
 
13951 2017-06-02 03:53:18 leon_heller Re: Low cost test equipment
Hello Steve,

Thank you for making the PDF of your presentation available. I've taken the liberty of publishing the link in the next edition of the Hastings Electronic and Radio Club newsletter, Vital Spark.

73, Leon
G1HSM
13952 2017-06-02 05:24:20 Steve Dick Re: Low cost test equipment
Thanks. Hope the info is useful – Steve K1RF