Recent Posts

21

Test Equipment / Re: New Zoyi multimeter+oscilloscopes - ZT-70xS, up to 50MHz/250MSps (nov 2022)

« Last post by ksxx on Today at 02:39:35 pm »

The measurement values in Scope mode seem to have more problems than I thought before when in DC input mode(FW1.32). I measured the switching on signal of my PSU at 12V setpoint. I set the scope to 100ms/div and 5V/div. The signal on the screen clearly shows the 12V amplitude of the voltage ramp. The vpp,max,min values are completely off and do depend on where I set the vertical offset.
Zoyi please fix this. I cannot imagine that this is hard to do.

looks like this issue is fixed in fw 1.35. The min/max measurements still give funny results in roll mode and stopped. Btw, the trigger level value shown at the top is nonsense. Note , the trigger vert position on the Zoyi is always related to the screen coordinates. When you switch the vert sensitivity , the trigger arrow stays at the same position. A bit unusual for me, but for this small unit maybe not a bad choice. 

22

Projects, Designs, and Technical Stuff / Re: ESR meter with extended scale.

« Last post by iet on Today at 02:34:34 pm »

How does the scaling work?

The values on the ohms scale of the multimeter are indicated in red.
The ESR values in mohms are indicated in blue.

23

RF, Microwave, Ham Radio / Re: MFJ Shutting Down Production and Going Out of Business

« Last post by Sal Ammoniac on Today at 02:32:48 pm »

It's generally acknowledged that MFJ products are best considered to be 90% assembled kits.

Some of the MFJ products I've had over the years have had loose screws rattling around in the case and poor solder joints that needed to be redone.

24

Test Equipment / Re: Hacking the Rigol DHO800/900 Scope

« Last post by ebourg on Today at 02:31:37 pm »

Is it possible to remove the RIGOL logo in the top left corner to save some space ?

25

Buy/Sell/Wanted / FOR SALE: Fancy, General, RF and Microwave SMD components

« Last post by cincin on Today at 02:30:34 pm »

I have a pile of random SMDs and bits that came from the workbench of a late RF engineer, that are of no use to me.
Some of it is old, some of it is Russian, some of it I have no clue what it is.
Google tells me some of it is pretty expensive to buy retail, so here it is for half of retail.

Please feel free to shame me publicly if my prices are off (and suggest accurate prices), and please let me know if something is utterly obsolete and no use to anyone.

They are in Canadian Dollars ($1CAD = $0.75USD as of today), and do not include shipping.

100 x Analog Device LT1124CS8 Precision SMD Amps Dual Low Noise, HS - $850
21 x Macom Varactor Diodes MSV34 (various) - $600
2 x Macom AT-263 PIN Digital 5 Bit Attenuator 31dB - $400
4 x Texas Instruments LM119J Comparator DTL, Open-Collector, RTL, TTL - $250
25 x Motorola MV2108 Varactor Diodes - $190
1 x Texas Instruments ADS1602EVM ADS1602 ADC Evaluation Board - $100
2 x Avantek ATF-46101 2-10 GHz Low Noise Medium Power Gallium FET - $100
1 x EPCOS B4053 465Mhz UHF filter board - $60
5 x Mini Circuits PSCQ-2-160 Power Splitter/Combiner 2 Way 50Ω 100-160 - $50   
4 x Mini Circuits LRPS-2-1 Signal Cond. 2 Way Power Splitter 5-500 - $40
2 x Mini Circuits PSW-1211 SPDT Coax switch - $30
2 x Analog Device AD8310ARM Log Amp IC Receiver Signal Strength Indic. - $20   
12 x Knowles Johanson Thin Trim Variable Capacitor trimmers SMD - $55   
2 x Telegartner 112-2319 BNC to 4mm Banana Test Lead, 50 Ohm, 1m - $40
5 x Hewlett-Packard ATF-46100-GP1 RF Small Signal GaAs FETs - $40
22 x EMC TVA0300N07 Microwave attenuators - $60
220 x G894A TriQuint RF Medium Power Amplifier dies - $80
189 x SMDs (74AC191, 72ACT32, 74AC32) counters & OR gates - $25



Lot of various General, RF, and Microwave electronic SMD components - $60:

12 X ASI ASB8000 100V SILICON PIN DIODES
18 X ASI ASB8001 100V SILICON PIN DIODES
10 X BGC405 SELF BIASED RF TRANSISTORS
20 X BG405 SELF BIASED RF TRANSISTORS
10 X BFP405 SELF BIASED RF TRANSISTORS

6 X COILCRAFT WB1040 WIDEBAND RF TRANSFORMER
7 X TEXAS INSTRUMENTS LF353 OPAMP JFET 2 CIRCUIT 8SOIC
2 X INTERSIL ES5375IU TRIPLE DIFFERENTIAL LINE DRIVEN 350MHZ SINGLE OUTPUT AMPLIFIER

4 X ST 4HCS74 SCHMITT-TRIGGER INPUT DUAL D-TYPE POSITIVE-EDGE-TRIGGERED FLIP-FLOPS
4 X MOTOROLLA ACT160 BCD DECADE COUNTER
20 X K591KH3 16CH CMOS MULTIPLEXERS DIP
9 X 74F191D UP/DOWN BINARY COUNTER WITH PRESET AND RIPPLE CLOCK
4 X ONSEMI 74ACT32 QUAD 2-INPUT OR GATE
5 X HEWLETT PACKARD 5082-0885 STEP RECOVERY DIODES
3 X ANALOG DEVICES LTC1040CSW MONOLITHIC CMOS DUAL COMPARATOR

18 X MITSUBISHI MGF1405 61-16 GAAS MICROWAVE FETS
1 X MITSUBISHI 1303 GAAS FET
1 X NEC NE71083-08 GAAS FET
4 X NEC NE72084 GAAS FET
7 X 55SC40 GAAS FET

9 X HARRIS MICROWAVE SEMICONDUCTORS HMP-100008-1
1 X SAMSUNG GPSSC SP8910 9721A
4 X ALPHA INDUSTRIES 93890012 ?
2 X J5A G208 2478 ?
3 X TRW 1175N7C30 ?

26

Test Equipment / Re: Choosing between entry-level 12-bit DSOs

« Last post by Mechatrommer on Today at 02:30:09 pm »

This image shows where it comes from - the amplitude changes depending on the phase difference between the samples and the signal:

by theory, Sinc should be able to reconstruct grey wave (original wave) from blue dots (sampled points) but since we saw AM modulated reconstruction by Sinc interpolation earlier meaning its not perfect according to theory. or possibly nyquist limit was already violated due to presence of harmonics (imperfect BW limited scope). ymmv.

27

Programming / Re: Linux Dependency Black Hole

« Last post by mag_therm on Today at 02:29:18 pm »

Hi tatel,

I wanted to get MCUX on Fedora because I thought (perhaps in ignorance, and should have asked)
that it would be the proper and maybe only way to access and update the firmware on the LPC4320 MCU in the HackRF1.
The firmware is updated like this:
 hackrf_spiflash -w hackrf_one_usb.bin

MCUXpresso  has been a nuisance with dependencies, and it is going to be another nuisance working outside of Fedora,
as everything here including all computers and the ham radio station runs on Fedora.

I would like to ask " How would a pro developer do this, do they just accept setting up a dedicated o/s to work on a particular MCU? "

I have started to examine the HackRF firmware math in C that sets up the frequencies for the Si5351 clock.
Not sure, but I can see two likely areas where approximations are made. one is integer divisions by prime numbers, and one is a frequency homing function that iterates until a result is in a tolerance.
 It is likely that approximations were made because the HackRF1 covers a very wide frequency range of 1 MHz  ~ 6000MHz.

So I have intention of building a firmware version for myself with a limited frequency range ,  say  1 ~ 200 MHz and better accuracy to 1 Hz if possible.
The reason for accuracy for hams on HF: I have been collecting data for ionospheric research ( HamSci) requiring ~ 10 milliHertz resolution and also the digital modes are being used with frequency lock to GPSDO , ( and new mode FSTW4)

I have corresponded with github GreatScott, with confirmation of the frequency selection accuracy limits and that there is no feedback of the actual frequency calculated..

28

Projects, Designs, and Technical Stuff / Re: (Yet Another) DIY Multislope ADC

« Last post by iMo on Today at 02:27:07 pm »

I've updated above table, there are RDN and RDP "fixed" clocks (5 as an example), and the zero values returned by RDN and RDP (an example) to see the runup values and diffs, where the RDP always returns at least "1" (we make the decrement before the comparator check).

Also my understanding is the rundown process above returns max 31+1 "net" counts, where one count == 2 SM clocks.

29

RF, Microwave, Ham Radio / Re: MFJ Shutting Down Production and Going Out of Business

« Last post by pienari on Today at 02:26:45 pm »

I have owned a few products but each time has been a disappointment.
MFJ is been late all the time in product development.

30

Beginners / Re: Connector name

« Last post by tooki on Today at 02:24:09 pm »

What zanfar said: we cannot possibly begin to identify it based on the uselessly blurry photos (and lack of other info) provided. There are literally thousands of connector series out there, and many of them look extremely similar, especially without any scale. (Some essentially are scaled up/down versions of others, so without scale, they are the same!) You need to provide sharp, well lit photos from every side, and either a carefully placed ruler in the photos, or provide accurate measurements. Also, give us context of what the connector is used in: someone might already know what it is.

Just to be clear, though, pin pitch is NOT the distance between pins, it’s the distance between pin centers.