[minima] Re: Linear Output Filter Switching

  • From: Wayne McFee <nb6m@xxxxxxx>
  • To: "minima@xxxxxxxxxxxxx" <minima@xxxxxxxxxxxxx>
  • Date: Thu, 6 Feb 2014 09:28:12 -0800

Yes,

parallel the two poles of a DPDT relay at each end of each filter.

So you need eight relays for five filters, and make the RF connections in and 
out to the highest frequency relay, so as to mimimize stray capacitance and 
inductance.

And use 200V or higher capacitors and T50 cores.

Wayne NB6M


> On Feb 6, 2014, at 9:13 AM, Mark G0MGX <mark.g0mgx@xxxxxxxxx> wrote:
> 
> Hi Wayne
> 
> You mean use two polls in parallel at each end of the filter i.e.two 
> switches? The components of the filter itself will need to be capable of 
> handling that kind of power also.
> 
> I see smoke from my little ceramic disks!
> 
> M
> 
> 
>> On 06/02/2014 17:11, Wayne McFee wrote:
>> That way you will have enough current and switching capability to go up to a 
>> little higher power, 50W at least, should you care to, and it provides a 
>> little extra capability for lower power, which won't hurt a thing.
>> 
>> 73,
>> 
>> Wayne NB6M
>> 
>> 
>> On Feb 6, 2014, at 9:01 AM, Wayne McFee <nb6m@xxxxxxx> wrote:
>> 
>>> Hi Mark,
>>> 
>>> I would suggest using the Omron 2Amp DPDT relays to switch the filters and 
>>> parallel the two poles.
>>> 
>>> Wayne NB6M
>>> 
>>> 
>>> On Feb 6, 2014, at 3:52 AM, Mark G0MGX <mark.g0mgx@xxxxxxxxx> wrote:
>>> 
>>>> Hi Team
>>>> 
>>>> I've done a bit more work on the output filter switching using a 4028 
>>>> (which arrived today!).
>>>> 
>>>> The wiki is updated:
>>>> 
>>>> http://www.hfsignals.org/index.php/Final_Output_Filters
>>>> 
>>>> Including a link to a simple sketch to try and illustrate how it works and 
>>>> enable others to prototype the ideas as I have.
>>>> 
>>>> There will be more on this topic from me....
>>>> 
>>>> Mark
>>>> G0MGX
>>>> 
>>>> 
>>>>> On 04/02/2014 19:05, Dan Reynolds wrote:
>>>>> Thanks Mark. I'm learning a lot but you know how it is when you're 
>>>>> dreaming - you never learn fast enough. I'm pouring over tutorials on the 
>>>>> web to help me understand better. 
>>>>> 
>>>>> I think I know what the schematic will look like but I just want to see 
>>>>> it from a more credible source than my brain! 
>>>>> 
>>>>> I hope to have the Boarduino and the front panel all mocked up by the 
>>>>> weekend. I have an Si570 on the way. I'm going to use the WB6DHW Si570 
>>>>> board for the level shifter circuit. 
>>>>> http://wb6dhw.com/For_Sale.html#Si570
>>>>> That should also keep me out of trouble with modifying that one library...
>>>>> 
>>>>> Then I can start mocking up / playing with the LPF selection logic 
>>>>> perhaps...
>>>>> 
>>>>> Thanks everybody. This is a neat project and I'm going to learn a whole 
>>>>> lot!
>>>>> 
>>>>> 
>>>>> 73
>>>>> Dan -- KB9JLO
>>>>> https://sites.google.com/site/on30ng/
>>>>> 
>>>>> 
>>>>>> On Tue, Feb 4, 2014 at 12:53 AM, Mark G0MGX <mark.g0mgx@xxxxxxxxx> wrote:
>>>>>> Hi Dan & Team
>>>>>> 
>>>>>> When I get the CMOS chips I have ordered I will publish to the Wiki the 
>>>>>> schematic for filter switching, details for interfacing to the bare 
>>>>>> bones Arduino and also publish my suggested code modifications/changes 
>>>>>> to control the switching based on radio frequency. I will also put 
>>>>>> extensive comments into the code to explain what's going on.
>>>>>> 
>>>>>> The ULN2803a does look like a great option - I have just ordered some of 
>>>>>> those from eBay - so I will experiment with this option also in due 
>>>>>> course.
>>>>>> 
>>>>>> Mark
>>>>>> G0MGX
>>>>>> 
>>>>>> 
>>>>>> 
>>>>>>> On 03/02/2014 22:18, Dan Reynolds wrote:
>>>>>>> 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
>>>>>>>>>>> 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>
>>>>>>>>>>> >> Sent: 01/02/2014 05:00
>>>>>>>>>>> >> To: minima@xxxxxxxxxxxxx <mailto: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>> 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>> 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>> 
>>>>>>>>>>> >> 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
>>>>>>>>>>> >>
>>>>>>>>>>> >>
>>>>>>>>>>> >>
>>>>>>>>>>> >
> 

Other related posts: