[minima] Re: Linear Output Filter Switching

  • From: Dan Reynolds <on30ng@xxxxxxxxx>
  • To: minima@xxxxxxxxxxxxx
  • Date: Mon, 3 Feb 2014 16:18:16 -0600

I wish someone could draw up a schematic and show a modified codes segment
so someone dense like me can get his head around it.

I looked at that CD4028 example and Mark, your second chart is starting to
make sense...
I think the ULN2803a is a good idea too.
Do you ground the unused inputs on that chip?
And then I assume the common on the output side would go to +12V for relay
energizing power.

This project could be an excellent learning project for me all the way
around! :-)

73
Dan -- KB9JLO
https://sites.google.com/site/on30ng/


On Sun, Feb 2, 2014 at 12:51 PM, Wayne McFee <nb6m@xxxxxxx> wrote:

> Mark,
>
> I'm using a ULN2803a Darlington Driver chip to drive the relays for LPF
> selection in a homebrew amp.  These have the back current diodes in them,
> so no external diodes needed across the relays.
>
> Just a thought, as it saves building individual drivers with transistors
> (like I did in another project).
>
> Wayne NB6M
>
> On Feb 2, 2014, at 6:54 AM, Mark G0MGX <mark.g0mgx@xxxxxxxxx> wrote:
>
> Hi Gang
>
> I've completed a proof of concept of the output filters today; it uses a
> 74141 as a BCD to individual selection connected to a 74LS00 used as NOT
> gates or inverters for the output lines.
>
> I can control this OK from the Arduino code, so I have ordered some of
> these CMOS 4028s as this has a HIGH output state when an output is selected
> whereas the 74141 is a LOW state when an output is selected (I have used
> 74141 previously to ground cathodes of Nixie tubes!). This is the logic of
> the chip:
>
> <74141 logic.png>
>
>
> So I now wait for the postman before I can complete the filter output
> stage.
>
> I am thinking that we might like options in the code/filters as it seems
> to me we need to keep the current RX filter selection pin usage, but also
> use this for filter selection. We can go with very simple as suggested by
> Farhan and have 4 filters, or we can have 5 to include either top band or
> 60M (5MHz).
>
> I will post more when I have the final design and code mods once built and
> tested. I am definitely going with a 3 line BCD output from the Arduino
> processor to select filters based on radio tuned frequency. This will be
> accomplished in the existing function "setBandswitch". Maybe (only maybe)
> something like this:
>
> <Filter Ideas3.png>
>
>
> In the code we will declare three digital outputs (including the existing
> BAND_HI) and set all three each time we change frequency, the state (HIGH
> or LOW) of each output will be dependent on frequency and in accordance
> with the truth table and output usage above.
>
> Mark
> G0MGX
>
> On 01/02/2014 18:47, Mark G0MGX wrote:
>
> very good. That CMOS chip used in the link looks the same as the TTL 74141
> - but I am no expert.
>
> This does seem to be the way to go
> Mark
> G0MGX
>
> On 01/02/2014 18:24, mpcharlton@xxxxxxxxxxx wrote:
>
>    Mark
>
> Have a look at this halfway down the page...
>
> http://www.vk5tm.com////homebrew/filter/filter.php
>
> Mark
> G6ZQS G-QRP 2247
>
>
>
>
> *-------Original Message-------*
>
>  *From:* Mark G0MGX <mark.g0mgx@xxxxxxxxx>
> *Date:* 01/02/2014 17:29:09
> *To:* minima@xxxxxxxxxxxxx
> *Subject:* [minima] Re: Linear Output Filter Switching
>
> Isn't this:
>
> http://www.g3ynh.info/digrdout/74141.html
>
> exactly what we need to go from Binary outputs on our 3 digital lines to
> individual relays controlling filters?
>
> Mark
> G0MGX
>
>
> On 01/02/2014 15:26, farhanbox@xxxxxxxxx wrote:
> > Mark,
> > There's something not right about the curve. The stopband is quite
> nominal. You must get atleast 60 db stop-band.
> >
> > Sent from BlackBerry® on Airtel
> >
> > -----Original Message-----
> > From: Mark G0MGX <mark.g0mgx@xxxxxxxxx>
> > Sender: minima-bounce@xxxxxxxxxxxxx
> > Date: Sat, 01 Feb 2014 13:47:38
> > To: minima@xxxxxxxxxxxxx<minima@xxxxxxxxxxxxx>
> > Reply-To: minima@xxxxxxxxxxxxx
> > Subject: [minima] Re: Linear Output Filter Switching
> >
> > Hi Team
> >
> > I've started the output filter Wiki page here:
> >
> > http://www.hfsignals.org/index.php/Final_Output_Filters
> >
> > and have so far put info on 4, 11 and 19MHz cut off Low Pass Filters. I
> > am very unhappy with the 19M filter sweep, so will let you guys take a
> > look before doing any more. The next filter needs to be 30M cut off - we
> > already have one of those!
> >
> > As an aside I have dug out my CD from EMRFD and mine is a 2002 version
> > of the software which I can't find a filter designer? I can enter values
> > myself but cant get the software to come up with the filter for me -
> > hence I have stuck with what I know and used QUCS for my designs.
> >
> > I do think that we could still use the existing D5 line for output _*as
> > well as*_ the existing input filter switching just so long as the line
> > stays HIGH for > 15MHz and LOW for <= 15MHz. This would give us room for
> > a 1.8M filter and another if we find we need i. I  have only focused on
> > those highlighted yellow below, but clearly with the three digital lines
> > we could have up to 8 filters if we needed them.
> >
> >
> >
> > I personally like the idea of simple logic chip or BCD type logic to
> > control relays as I feel that we want to avoid more programming and
> > complexity where it's not needed. The 74LS139 idea is a great one and
> > probably the way I plan to go, but lets see what we decide.
> >
> > I've tried to explain some of this in the Wiki - please take a look and
> > lets decide between us how we are going to do this part of the project.
> >
> > We could of course go with the idea of a separate amplifier completely,
> > maybe with the tubes others are suggesting! I've never built anything
> > with tubes....
> >
> > Mark
> > G0MGX
> >
> > On 01/02/2014 06:48, Mark wrote:
> >> Thanks to everyone for the suggestions and ideas.
> >>
> >> If we go with 4 filters have we scrapped top band?
> >>
> >> I'll try and run some designs for the four suggested filters and build
> >> some prototypes and stick the results on the wiki.
> >>
> >> We can then decide and discuss what we think we should do.
> >>
> >> M
> >> ------------------------------------------------------------------------
> >> From: Ashhar Farhan <mailto:farhanbox@xxxxxxxxx <farhanbox@xxxxxxxxx>>
> >> Sent: 01/02/2014 05:00
> >> To: minima@xxxxxxxxxxxxx <mailto:minima@xxxxxxxxxxxxx<minima@xxxxxxxxxxxxx>
> >
> >> Subject: [minima] Re: Linear Output Filter Switching
> >>
> >> Mark,
> >>
> >> I have been mulling over this ... and I am trying to balance quite a
> >> few things here.
> >>
> >> 1. Can we make do with just four filters? I have attached a screenshot
> >> of a simulation I ran (both these programs are available on the EMRFD
> >> CD). As you  can see, a filter can be cut for 7 and 10 mhz. The 7
> >> mhz's second harmonic at 14 is down by 25db. Which means, if we don't
> >> distort the linear too much, we can get more 43 db suppression of the
> >> harmonics. If  you guys agree to this , then, I propose as follows :
> >>   1st filter for 3.5 MHz
> >>   2nd filter for 7-10 mhz
> >>   3rd filter for 14-18 mhz
> >>   4th for 21-28 mhz
> >> These will have to be three section filters, which is alright. A
> >> 1-of-4 decoder like 74LS139 could do the switching with just 2 lines.
> >>
> >> 2. The switching of the main filters is at variance with this scheme.
> >> so, we will have to use a dedicated line (as we are doing now) to
> >> switch these filters.
> >>
> >> 3. There is a third line A0 (pin 23) that is unused. this can be used
> >> to switch in a higher bandwidth filter (more than 10 Khz). with this
> >> filter, the broadband audio can be fed to an 'SDR' back-end like
> >> linrad. The serial port can provide the tuning control.
> >>
> >> - f
> >>
> >>
> >> On Sat, Feb 1, 2014 at 7:01 AM, Dan Reynolds <on30ng@xxxxxxxxx
> >> <mailto:on30ng@xxxxxxxxx <on30ng@xxxxxxxxx>>> wrote:
> >>
> >>      I'm not any kind of an expert but could you use a Microchip
> >>      MCP23017 I/O expander on the 5 V side of the I2C bus. I was
> >>      thinking something like I saw on the Tronixstuff page here:
> >>
> http://tronixstuff.com/2011/08/26/tutorial-maximising-your-arduinos-io-ports/
> >>      Instead of a LED an I/O line could drive a transistor to drive a
> >>      relay(?).
> >>      Then the code could "watch" the frequency and as it changes the
> >>      output line for that particular LPF could be switched.
> >>
> >>      Or could you use a 74HC595 to accomplish the same thing.
> >>
> http://tronixstuff.com/2010/04/30/getting-started-with-arduino-chapter-four/
> >>
> >>      I was going to approximate the Minima front panel with a bare
> >>      bones Arduino and some parts and see what I could dream up.
> >>      I don't really know what I'm doing. I'm just muddling through
> >>      trying to patch bits and pieces together...
> >>
> >>
> >>      73
> >>      Dan -- KB9JLO
> >>      https://sites.google.com/site/on30ng/
> >>
> >>
> >>      On Fri, Jan 31, 2014 at 6:10 PM, Wayne McFee <nb6m@xxxxxxx
> >>      <mailto:nb6m@xxxxxxx <nb6m@xxxxxxx>>> wrote:
> >>
> >>          Hi Mark,
> >>
> >>          If the three outputs were set up as you suggest, a Picaxe chip
> >>          could be programmed to control either individual relay driver
> >>          transistors or a relay driver chip like the 2903(?).
> >>
> >>          I've been using that arrangement for filter selection  in a
> >>          homebrew rig.
> >>
> >>          Or, if one of those output lines could be programmed to output
> >>          a stepped voltage such as that provided by the FT817 for
> >>          bandswitching info, that makes the programming even easier.
> >>
> >>          Wayne NB6M
> >>
> >>
> >>          > On Jan 31, 2014, at 1:24 PM, Mark G0MGX
> >>          <mark.g0mgx@xxxxxxxxx 
> >> <mailto:mark.g0mgx@xxxxxxxxx<mark.g0mgx@xxxxxxxxx>>>
> wrote:
> >>          >
> >>          > Farhan & Team,
> >>          >
> >>          > I can see that we have provision in the schematic for 3
> >>          digital outputs for band selection, but can only see one of
> >>          these (BAND_HI - pin 11 - Arduino D5) being used within the
> >>          function "setBandswitch". It is this function that currently
> >>          selects the LPF used based on frequency.
> >>          >
> >>          > We could set the state of the three outputs based on
> >>          frequency something like this:
> >>          >
> >>          > <Filter Ideas.png>
> >>          >
> >>          > But someone far cleverer than I would need to explain how to
> >>          create relay on/off switching based on the logic states of
> >>           the three lines - I have no idea how to do that!
> >>          >
> >>          > If we were to implement something like this was the
> >>          intention to use these additionally switched filters in RX as
> >>          well as TX?
> >>          >
> >>          > I would be interested in your thoughts and ideas on how you
> >>          saw this working before I head down the wrong road with my
> >>          construction!
> >>          >
> >>          > Many thanks,
> >>          >
> >>          > Mark
> >>          > G0MGX
> >>
> >>
> >>
> >
>
>
>
>
>
>
>

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