[minima] Re: Parts list spreadsheet, still work in process

  • From: Thomas Sarlandie <thomas@xxxxxxxxxxxxx>
  • To: "minima@xxxxxxxxxxxxx" <minima@xxxxxxxxxxxxx>
  • Date: Sat, 15 Mar 2014 21:41:55 -0700

Jeremy,

Great initiative! Some replies in text based on my experience building it.

Hello,
>
> I've systematically gone through the schematic and made a comprehensive
> parts list from it. I'm hopeful this will be useful to both myself and
> others!
>
>
> https://docs.google.com/spreadsheet/ccc?key=0AkbVpmVim4O7dGM2SGZaYkJvTU1DNnloak1RZnpDZ2c&usp=drive_web#gid=0
>
> I still have many questions that I want clarification on though. If anyone
> can give more detail about the following please reply:
>
>    1. Is there a recommended inductor type for all of the filter
>    components? (A toroid type, etc.)
>
>
I have used what Mark recommended and just had to slightly adjust the
number of turns. Maybe because my magnet wire was smaller.

I thought this information was on my website but nope :( I just added it.

ValueQtyCoreN-Turns (Mark) N-Turns (Thomas).33 uH2T37-610 9.39
uH2T37-61110.66 uH
2T50-21210.78 uH 3T50-213113 uH3 T332524



>
>    1. Can the 3u inductor near T3 be the same type as the inductors in
>    the filter?
>
> I guess you are referring to the inductor labelled "RFC" on Farhan's
schematic. Farhan said: "The RFC is 10 turns on FT37-43" According to
toroids.info, that is 35 uH.

So no you cannot use the same inductors. And where did you get the value
3uH?


>    1. What is the 'BAND SELECT' part connected to PD6 and PD7 of the
>    Arduino?
>
> This is a connector that would go to your power amplifier to switch
different band-pass or low-pass filters depending on the band that you are
on. The original idea was to use those 3 bits to select one band (3 bits =
8 possibilities). We have since then explored other options and Farhan has
chosen the CD4017 option.

Read "Bandswitching the low-pass filters" on the RF386 page for more info
on the new design that will only take one line:
http://www.hfsignals.org/index.php/RF386

>
>    1. Can all 4 relays be of the same type? I know nothing about relays;
>    what should I be looking for?
>
> The two relays in the LPF and the relay in the BFO are SPDT. The one that
switches the audio and tx/rx (bottom of the schematic) is a DPDT. You could
replace it by two separate relays if you wanted to stick to just one model.

The most important characteristic is the voltage of those relays. Get 12v
dc relays. They should be adapted to small signals. Some are labelled for
"RF signals" and are a bit more expensive but I am not sure it makes a huge
difference for us.

I have used BESTAR BS-102B for the LPF and the BFO. Bought them in a
surplus where they were the cheapest 12v small size relays. They seem cheap
online too:
http://www.alibaba.com/showroom/bs--102b--12vdc-bestar-standard.html

For the DPDT I have used OMRON G6H-2.

You can see pictures of them on my minima webpage.

>
>    1. There are capacitors labeled "0.01" near Q20, but they don't have a
>    unit. What size are these capacitors?
>
> Micro Farads.

>
>    1. There are unmarked electrolytic capacitors. One is near Q11; what
>    size are these unmarked electrolytic caps?
>
> I have asked about those a few times and did not get a clear answer. I
have read articles that claim that only the "+" symbols call for
electrolytics and that it is perfectly fine to use the curved+flat symbol
for ceramics. This matches what you see on the schema: the electrolytics do
have a "+" sign.

I have used the same capacitors than everywhere else for those (0.1 uF). I
would love to hear from Farhan why some have a different symbol!

>
>    1. There are electrolytic capacitors labeled +50, are these actually
>    50u?
>
> Yes. But I have used 47uF. Much easier to find.

>
>    1. There are four 22p variable electrolytic capacitors; Are these trim
>    caps? Can I see an example? What am I looking for?
>
> Look on my pictures or mark's pictures:
http://www.sarfata.org/ham/images/minima-lpf-top.jpg

>
>    1. I see 2 10k trim pots, a 1 turn 10k variable pot and a 1 turn 100k
>    pot. Is this accurate?
>
> Yes. You might want to get a logarithmic pot for the 10k because it
controls the audio but the 100k must be linear.

>
>    1. There is a crystal labeled 16M connected to X2 of the Arduino. Is
>    this a 16Mhz crystal?
>
> Yes.

Enjoy!

73,
thomas


> Thank you very much!
> 73 de K2CHA
>
> --
> Jeremy Chase
> http://twitter.com/jeremychase
>

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