SV1GAP

Sunday, 26 March 2017

Comparison of 2 RS-232 programming circuits

Update 2017_3_28

Sources:

http://www.sm5nvc.se/erak/mod/index.php?sort=date&path=rig/YAESU/kabel/

http://www.sm5nvc.se/erak/mod/rig/YAESU/kabel/icq7-int.gif

http://www.cqham.ru/un7gm_icom.htm

http://www.cqham.ru/opc478.gif

http://image.prntscr.com/image/dc424cad890843f79765360a4fd1cde7.gif

2017_3_28 Start of update

The comparison concerns 2 circuits for connecting a transceiver to a RS-232 port. Recently someone reported a problem when his transceiver (Yaesu VX-7) was sending data to the RS-232 using the circuit below:

I searched for similar circuits and I noticed that in all the other circuits that I found, a different topology with a PNP transistor (instead of a NPN one) was used to connect the transceiver to the RxD (pin 2) port. Looking at the above circuit I suspected that it provides insufficient voltage and insufficient output resistance when connected to a load (RxD port).

http://www.ti.com/lit/an/snla037b/snla037b.pdf: "Receiver Input 3 kΩ to 7 kΩ"

http://www.arcelect.com/rs232.htm: "Receiver Input Resistance (Ohms) 3k to 7k, 4k min."

So I added R_Load to the outputs. As it is obvious from the following images, the effect of the R_Load on the circuit on the left (Label Net: Out_NPN) is very high. I tried collector resistors of lower value than the original 4.7kΩ and I chose a 1.5kΩ resistor. With the 1.5kΩ resistor, even in the worst-case scenario of the 3kΩ receiver input resistance, a voltage above 3V occurs in RxD port during logic level 1.

Addition of R_Load

Out_NPN, collector resistor=4.7kΩ, parameterisation of R_Load

The PNP version doesn't show any sensitivity to the R_Load.

Out_PNP, parameterisation of R_Load

Collector resistor=1.5kΩ

Out_NPN, collector resistor=1.5kΩ, parameterisation of R_Load

2017_3_28 End of update

73 de SV1GAP

Thursday, 5 January 2017

Laptop 2017, SSD, DDR4

I am in search of a new laptop. I share with you some findings.

1. CPU
I am interested in low heat emission and at least medium speed. The CPUs that I came across in late November 2016 were: i3-5005U, i3-6100U, i5-5200U, i5-6200U, i7-6500U. For the 2017 I think we should forget the 5th Generation Intel® Core™.

Source: http://ark.intel.com/search/...

Source: Ibid.

2. RAM

In late 2016, the prices of DDR3L and DDR4 were exactly the same. As far as the cost of the memory itself is concerned, there is no reason for the DDR3L to be preferred to the DDR4 counterpart. The only reason to buy a laptop equipped with DDR3L is if it is sold at a decreased price. Be aware that in, let's say, 2 years from now the DDR3L will be more expensive than the DDR4. So in case you will upgrade (increase) the RAM, do it soon.

1. SO DIMM DDR3L, 4GB http://www.e-shop.gr/...

2. SO DIMM DDR3L, 8GB http://www.e-shop.gr/...

3. SO DIMM DDR4, 4GB http://www.e-shop.gr/...

4. SO DIMM DDR4, 8GB http://www.e-shop.gr/...


Source: http://www.e-shop.gr/...

3. Hard Disk

Forget hard disk! The only reason to buy a laptop with a H/D is if its SSD is small.

4. SSD

128GB is insufficient storage space, 256GB is acceptable, 512GB is fine. In the accompanying Google spreadsheet I mark with red (=bad) color if it is <200GB and with green (=good) color if it is >300GB. In case you have only 128GB SSD, you can have your files in an external drive.

Form factor: Serial ATA or SATA, mini-SATA or mSATA, M.2

Bus: SATA 3.0, PCI Express 2.0 x4, PCI Express x4 NVMe M.2, PCI Express 3.0

1. https://rog.asus.com/articles/hands-on/easy-guide-to-ssds-sata-msata-m-2-and-u-2/

2. http://rog.asus.com/articles/product-news/ssd-guide-pci-express-m-2-msata-and-sata-express-the-differences-explained/

3. http://www.tomshardware.co.uk/answers/id-2947712/sata-ssd.html

4. http://www.computershopper.com/feature/2016-guide-the-best-m.2-solid-state-drives-tested

5. http://www.mydigitaldiscount.com/everything-you-need-to-know-about-slc-mlc-and-tlc-nand-flash.html

5. Display

IPS is the way to go, but they are rare and expensive. I mark with red (=bad) color the TN displays. I am not sure about resolution. On a 15.6" screen the 1366*768 resolution has its advantages over the 1920*1080 one. So I don't use a color coding system for the resolution.

http://www.laptopmag.com/articles/laptop-screen-resolution-ripoff

Some searches according to the previous criteria:

1. >=15", CPU: i5, i7, Windows 10, <=800€ http://www.e-shop.gr/...

2. >=15", CPU: i5, i7, 8GB, <=800€ http://www.e-shop.gr/...

3. >=15", CPU: i5, i7, 8GB, Windows 10, <=800€ http://www.e-shop.gr/...

4. CPU: i5, 8GB, Windows 10 http://www.skroutz.gr/...

5. CPU: i5, 8GB, Windows 10, SSD https://www.skroutz.gr/...

https://docs.google.com/spreadsheets/...

Perhaps my choice: http://www.mgmanager.gr/..., unboxing: https://www.youtube.com/...

73 de SV1GAP

Saturday, 8 October 2016

Supplement to a comment

Recently I read some articles of a terrific guy (N6QW). Among many other circuits that I have found on his blog is a mic amplifier using PNP (and not NPN) transistor. Firstly I simulated it by using a NPN transistor and after that by using the exact transistor of the original schematic. The related posts are http://n6qw.blogspot.gr/2016/09/40m-junk-box-ssb-transceiver-microphone.html and http://n6qw.blogspot.gr/2016/09/taking-break.html. I posted a comment in the article of the 2nd link and here I post some screenshots related to my comment.

I made a rearrangement of R1, R6+C5 and C4. Although there is no difference in the operation of the circuit, for perception and uniformity purposes perhaps it would be better if in the drawing the R1, R6+C5 and C4 were directly in parallel. As far as audio frequencies is concerned there is no difference (voltage source V1 acts as a short circuit at audio frequencies).