Topics

VK4PP uBitx LPF BANK add-on Board

Gordon Gibby <ggibby@...>
 

....was  supposed to read  "a low pass filter above 20 METERS"  (not MHz)

cheers,  gotta go cut some grass before it pours again....


gordon




From: BITX20@groups.io <BITX20@groups.io> on behalf of Gordon Gibby <ggibby@...>
Sent: Friday, August 31, 2018 2:41 PM
To: BITX20@groups.io
Subject: Re: [BITX20] VK4PP uBitx LPF BANK add-on Board
 

Warren, you are right on, but you might not have seen all the posts where I did exactly what you are saying.   Both BEFORE the daughterboard and AFTER the daughterboard so i had proof of its effectiveness.   I also did some calibrations of the S-meter using BNC attenuators (which is all I have).   I then did the suggested measurements of today, measuring bleed-through (unmeasureable, whereas I was clearly able to measure the harmonics and able to measure their reduction by moving the input side of the relay chain OFF the board.)


Here, I'll see if I can find the posts (I'm not too used to that):


(1)Very first "before" measurements:   https://groups.io/g/BITX20/message/57840

(2)Complete baseline data:   https://groups.io/g/BITX20/message/57974

(3) Calibration of the S-meter and proof that the measurement setup itself didn't have bleed thru:  https://groups.io/g/BITX20/message/58070

  [This distinctly showed that 1 S unit in the range of 7-9 is 12 db onthat receiver on that frequency)

(4)Photos of the measurement setup:  https://groups.io/g/BITX20/message/58070

(5) DAta AFTER daughterboard:   https://groups.io/g/BITX20/message/58070



What I CANNOT prove is that the receiver maintains identifical response at all frequencies (hence, is "flat")  however it is reasonable that the differnces aren't mroe than a few dB based on specifications for rigs of this price range etc.   


Poor man's spectrum analyzer.   What is problematic is the 24MHz harmonic range --- here I achieved only 6 dB reduction so there is something else going on there...maybe a series resonance in a filter or somethign I haven't thought of.   Every other range was dramatically reduced by the daughterboard system.   So for my purposes --- a low pass filter above 20 MHz and I have every digital band I need for what I need out of the radio and I don't need to use the bands where the "spurs" are a thorn.   



Hope that makes more sense.   

Cheers,


gordon




From: BITX20@groups.io <BITX20@groups.io> on behalf of Warren Allgyer <allgyer@...>
Sent: Friday, August 31, 2018 2:24 PM
To: BITX20@groups.io
Subject: Re: [BITX20] VK4PP uBitx LPF BANK add-on Board
 
Gordon

Your reasoning makes perfect sense. But I think you can measure at the actual harmonic frequencies which is where the issue would be . Your IC-718 can tune the third, fifth and 7th harmonics of 80 meters. So you can know exactly (within the limits of the S meter calibration and linearity) what the residual level is at the harmonic frequencies themselves. You have checked your S-meter and you know what represents 45-50 dB below S9+30 (normally one S unit = 6 dB but in real life S meters rarely replicate that). So just tune the harmonics directly and measure them. Or am I missing something?

WA8TOD

Jerry Gaffke
 

Seems whatever I had in post 58293 is contagious.
Everyone should take precautions!

Wear a mask fitted with an appropriate low pass filter.   ;-)

Jerry, KE7ER



On Fri, Aug 31, 2018 at 12:12 PM, Gordon Gibby wrote:

....was  supposed to read  "a low pass filter above 20 METERS"  (not MHz)

cheers,  gotta go cut some grass before it pours again....

 

gordon

 

Glenn
 

Gordon, the Common terminals being 5 & 12 in the uBITX Sch numbering scheme, -32dB

Approx -40dB from Common one set (5)  to the NO contact on the other contact set (16)

Picture is between common terminals as above. Typical curve of standard relays.




On Sat, Sep 1, 2018 at 02:17 AM, Jerry Gaffke wrote:
I interpret this measurement from Glenn:
    "-32dB from one set of contacts to the other. (common terminal)"
as being from KT1 pin 14 to pin 16 as seen in the uBitx schematic.

Also, interpret his -39 and -41 dB numbers to be from one relay section to the other,
which I averaged as -40dB.    For example, KT1 pin 12 to pin 5.

I now suspect those assumptions are incorrect, but the analysis could easily be adjusted to for any change to those two numbers.

Jerry


On Fri, Aug 31, 2018 at 03:40 AM, Glenn wrote:
All good points Warren.   I did some checks of isolation using a typical DIP relay, type HK19F. DPDT

I made a small jig to hold the relays and measure isolation across contacts etc.
Typically it was -34dB across open contacts,
-32dB from one set of contacts to the other. (common terminal)
-41dB from open terminals on each side
-39dB from common of one pole to open on the other pole.
-48db from common to coil.
 At 30MHz.  Better as freq drops of course.
That's without effects of a PCB and various other traces.

glenn

Jerry Gaffke
 

Losses in dB are additive.
So loss from pin 12 to pin 16 is 40-32 = 8 dB when pin 16 is open?
That would be killer, doesn't seem right.



On Fri, Aug 31, 2018 at 03:11 PM, Glenn wrote:
Gordon, the Common terminals being 5 & 12 in the uBITX Sch numbering scheme, -32dB

Approx -40dB from Common one set (5)  to the NO contact on the other contact set (16)

Glenn
 

perhaps my terminology wasn't clr.  Relay in resting state:

Loss from 12 to 16 (NO contact, uBITX pinout) is ~ -34dB at 30MHz

Loss from 12 to 1 (to NO contact of the opposite side) is ~-39dB

Loss from 12 to 5 is ~-33dB

Loss from 12 to coil ~-52dB

Timothy Fidler
 

The flaming obvious and yet trivial  has  just occurred. How are people going to mount the PCB as shown ?  Three hole posns at a minimum will be required for say 3.4mm holes.  Edge distances have to be allowed.  As long as it can be mounted on a bit of AL with a return on one side it can be bolted anywhere. As it stands it will have to be (hot melt glued ??) to something ..a bit like skyhooks required on some engineering projects in a way.   Even if people have to drill out prescribed rondels for the screw down on Rx of the board to keep the price down,  they still need to be nominated. 

MadRadioModder
 

My thinking is that this whole discussion of  butchering the uBITx board and cobbling in another board that, in itself, will have some sensitivities to things like cable runs and connections etc. will scare the unseasoned builder away from the uBITx completely. 

 

I used what I thought was a better solution for some of the hams near me… by simply jumpering/cutting out the whole LPF network… so there is raw straight from the PA RF at the output.  I then used one of Hans’ BPF modules outside the box with a minimal BNC to pins – BPF – pins to BNC that is about $5 worth of parts including the filter.  Now granted you must buy all of the filters for bands you want to operate… but it’s the same with any LPF replacement.  A complete board in an outboard box is even less scary to most.  Yes the rest of us will be at the uBITx endlessly with our hack saws, hot glue, and soldering irons… but that will only work for us hackish engineering students.


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Jerry Gaffke
 

Yes, it would be a lot easier to simply disable the LPF's and use external filters.
As per the final sentence here from long ago, keeps things very simple:  
    https://groups.io/g/BITX20/message/30530

Given the uBitx board layout, trying to get more power on the upper bands
will likely add to the spurs due to coupling from power amp to the IF stages.
Board layout around the IRF510's is not that good for 30mhz, and the upper
bands have more trouble with spurs.  I'd be happy with 80m,40m,20m,
which the current uBitx can do a reasonable job of using external filters.

But replacing the power amp would solve most of those issues. 
No need for the hacksaw, just disable the uBitx power amp.
Use coax for signals, I doubt the cabling will be much of an issue.
Can experiment with band specific filters in that coax from exciter
to power amp if necessary.

Still need to address mixer levels, IF gain distribution, and a layout issue
that allows the carrier to sneak around the 12mhz crystal filter.
But the uBitx does give us a very simple analog SSB exciter/receiver to work with.
Hacking up a uBitx to perform well with minimal cost and complexity
might help give direction to future versions from hfsignals.

Note that the G0UPL power amp will require nearly 20 dBm of power from the exciter. 
Final mixer of the uBitx exciter should have about -3dBm max going in (10 dB below
the 7dBm local oscillator), and loses 6dB.  So will want up to 30dB of gain between the uBitx
exciter and the G0UPL power amp, perhaps two MMIC's built ugly style
on the back of the uBitx.  Not exactly trivial.

Jerry


On Sat, Sep 1, 2018 at 06:29 AM, MadRadioModder wrote:

My thinking is that this whole discussion of  butchering the uBITx board and cobbling in another board that, in itself, will have some sensitivities to things like cable runs and connections etc. will scare the unseasoned builder away from the uBITx completely. 

 

I used what I thought was a better solution for some of the hams near me… by simply jumpering/cutting out the whole LPF network… so there is raw straight from the PA RF at the output.  I then used one of Hans’ BPF modules outside the box with a minimal BNC to pins – BPF – pins to BNC that is about $5 worth of parts including the filter.  Now granted you must buy all of the filters for bands you want to operate… but it’s the same with any LPF replacement.  A complete board in an outboard box is even less scary to most.  Yes the rest of us will be at the uBITx endlessly with our hack saws, hot glue, and soldering irons… but that will only work for us hackish engineering students.

 

Timothy Fidler
 

If it is done cleanly it could look quite nice. Specifically small copper lugs can be soldered on the bottoms of the existing control relay pins to attach to braided core Cu wires which are then hot melt glued to the underside of the PCB for strength and brought out to a  green plastic header male plug 
that is why I suggested the click in header carrying all voltage GND and the three signals to the PCB designer.

If there is a known good solution to the existing issues that does not require a masters in EE to source and solder up then A Farhan has a prayer at moving 
the remaining uBitx boards in Inventory.  Some people will chose to operate the thing unmodded and some with legal sensitivities will want a fix.

After that inventory is moved, I suspect a full rework of the PCB will be out of the Eastern Horizon. My guess. Hopefully with AGC  and so on. Maybe with BS170 x 2  in the driver stage . 

But what is set up as a standard as to what the relay control signals mean now will have to be carried through,  or all hope of  forward software compatibility will fly out the window. That is why a one of ten decoder to use those three lines makes a whole lot of sense even if it adds dollars to the price of the finished board. If you start pulling 15 and 17 metres off the table,  (combined filter) the multiband nature of the beast is compromised. 
 

Timothy E. Fidler : Engineer BE Mech(1) Auckland , NDT specialist AINDT UT /RT3 , MT2 
Telephone Whangarei   022  691 8405
e: Engstr@...



----- Original Message -----
From:
BITX20@groups.io

To:
<BITX20@groups.io>
Cc:

Sent:
Sat, 1 Sep 2018 08:29:31 -0500
Subject:
Re: [BITX20] VK4PP uBitx LPF BANK add-on Board


My thinking is that this whole discussion of  butchering the uBITx board and cobbling in another board that, in itself, will have some sensitivities to things like cable runs and connections etc. will scare the unseasoned builder away from the uBITx completely. 

 

I used what I thought was a better solution for some of the hams near me… by simply jumpering/cutting out the whole LPF network… so there is raw straight from the PA RF at the output.  I then used one of Hans’ BPF modules outside the box with a minimal BNC to pins – BPF – pins to BNC that is about $5 worth of parts including the filter.  Now granted you must buy all of the filters for bands you want to operate… but it’s the same with any LPF replacement  A complete board in an outboard box is even less scary to most.  Yes the rest of us will be at the uBITx endlessly with our hack saws, hot glue, and soldering irons… but that will only work for us hackish engineering students.


Virus-free. www.avg.com

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ajparent1/kb1gmx
 

Timothy,

Have you ever looked at the board?  
Fixing the driver moved the problem sage back to the predriver and first amp.

Pulling bands at the time of its design was not considered as it was desired to
have a 3-30mhz radio unbounded by "bands".   I agree a bounded transmitter
is a must  but at that time it wasn't heard.

Allison

mark bodlovich
 

How did you go about adding the qrp labs filters I built mine up but haven't put them in yet. Experience is valuable in these cases. Did you remove kt1 relay and drop it in it's place?

ajparent1/kb1gmx
 

For any of the low pass fitlers the easy mod is to wire around the whole built in LPG and 
save the losses.  Then put the 3rd party filters between the antenna jack and the board.

All KT1-3 do is contribute loss and consume power.  You can use the three outputs
TX-A, TXB, And TXC with software changes to control the new board or whatever then.

Allison

mark bodlovich
 

Mad Radio Modder;
I'm interested in how you put the qrp labs filter board into the ubitx. I built one and have not put it in yet. Looking for good ideas. 
Thanks, Mark N7HWR

MadRadioModder
 

I just soldered female BCN connectors to the 4-pin DuPont connectors and plugged the DuPont connectors onto the filter(s).  I then use a double barrel male to connect the filter to the back of the radio.  It’s very simple.  I’m not currently at home or I could post a picture but I think you get the idea.  I suppose you could put this onto a small proto-board easily…or even use Kees board if you wanted to do something more official.  This approach takes this whole spur removal well within the capabilities of even the person that barely knows which end of the soldering iron to hold.

 

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of mark bodlovich
Sent: Saturday, September 1, 2018 11:04 PM
To: BITX20@groups.io
Subject: Re: [BITX20] VK4PP uBitx LPF BANK add-on Board

 

Mad Radio Modder;
I'm interested in how you put the qrp labs filter board into the ubitx. I built one and have not put it in yet. Looking for good ideas. 
Thanks, Mark N7HWR


Virus-free. www.avg.com

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MadRadioModder
 

I suppose that does depend on a person’s skill at executing the myriad of expert opinions opined on this group.  I myself do this for a living so I’ve redesigned the entire radio.  That’s one end of the spectrum.  However there is the other end of the spectrum… the guy who may have just received his license and bought a uBITx thinking it was a nice cheap way to enter the world of HF that now has to deal with this (like some friends of mine).  They can either rely on the experts (self-proclaimed or otherwise) to bail them out of this mess or be given a very simple solution that is possible for them to execute.  “Hellish crude” in your own words for you… the only option for someone else.

 

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of Timothy Fidler
Sent: Sunday, September 2, 2018 1:17 AM
To: BITX20@groups.io
Subject: Re: [BITX20] VK4PP uBitx LPF BANK add-on Board

 

All understood but it hellish crude for a radio which allegedly has push button RF operation selection.

 

Well it had it ....

 

Just too many design compromises made. If they had gone for 80 40/30 20 and Ten  mtrs   with four filters and a diode OR ..(given the limits ofthe Arduino ) all standard stuff ...the whole thing would never have happened. 

 

so it goes.

Timothy E. Fidler : Engineer BE Mech(1) Auckland , NDT specialist AINDT UT /RT3 , MT2 
Telephone Whangarei   022  691 8405
e: Engstr@...

 


----- Original Message -----

 

To:

<BITX20@groups.io>

Cc:

 

Sent:

Sun, 2 Sep 2018 01:06:02 -0500

Subject:

Re: [BITX20] VK4PP uBitx LPF BANK add-on Board

I just soldered female BCN connectors to the 4-pin DuPont connectors and plugged the DuPont connectors onto the filter(s).  I then use a double barrel male to connect the filter to the back of the radio.  It’s very simple.  I’m not currently at home or I could post a picture but I think you get the idea.  I suppose you could put this onto a small proto-board easily…or even use Kees board if you wanted to do something more official.  This approach takes this whole spur removal well within the capabilities of even the person that barely knows which end of the soldering iron to hold.

 

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of mark bodlovich
Sent: Saturday, September 1, 2018 11:04 PM
To: BITX20@groups.io
Subject: Re: [BITX20] VK4PP uBitx LPF BANK add-on Board

 

Mad Radio Modder;
I'm interested in how you put the qrp labs filter board into the ubitx. I built one and have not put it in yet. Looking for good ideas. 
Thanks, Mark N7HWR

 

Virus-free. www.avg.com

 

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Virus-free. www.avg.com

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Mark M
 

On 9/2/18 6:07 AM, MadRadioModder wrote:
... the guy who may have just received his license and bought a uBITx thinking it was a nice cheap way to enter the world of HF that now has to deal with this (like some friends of mine).  They can either rely on the experts (self-proclaimed or otherwise) to bail them out of this mess or be given a very simple solution that is possible for them to execute.  ...
Or they can ignore it all and just use the damned thing. I suspect that's what most users will do. I'd guess that the vast majority of uBitX buyers aren't even aware of the issues and those who are don't care. And, realistically, it probably isn't that big of a deal anyway (which I realize is heresy to many on this forum but is nonetheless the reality of the situation).

My $0.02 worth...as always, YMMV...

Mark AA7TA

Jerry Gaffke
 

It becomes a big deal when they hook up a uBitx to their KW linear.
Especially if they goose up the mike gain to get enough drive.

My primary concern is that any future version of the uBitx meet regs for most jurisdictions. 
Worth keeping these issues visible in the forum till that happens.

Jerry


On Sun, Sep 2, 2018 at 09:34 AM, Mark M wrote:
On 9/2/18 6:07 AM, MadRadioModder wrote:
... the guy who may have just received his license and bought a uBITx thinking it was a nice cheap way to enter the world of HF that now has to deal with this (like some friends of mine).  They can either rely on the experts (self-proclaimed or otherwise) to bail them out of this mess or be given a very simple solution that is possible for them to execute.  ...
Or they can ignore it all and just use the damned thing. I suspect that's what most users will do. I'd guess that the vast majority of uBitX buyers aren't even aware of the issues and those who are don't care. And, realistically, it probably isn't that big of a deal anyway (which I realize is heresy to many on this forum but is nonetheless the reality of the situation).

My $0.02 worth...as always, YMMV...

Mark AA7TA

dfine100@...
 

I would think that Farhan should put a disclaimer on the hfsigs website stating that the ubitx does not meet some countries (i.e. USA) specifications for legal operation and that it will take a considerable amount of modification to make it meet those specs.  I agree that most new hams buy it thinking all they have to do is connect a few cables and the have a legal ready to go transceiver, when in fact they could buy a used 100 watt transceiver for not much more money that would meet specs.  That's my $.02 opinion.
W0DF

James Lynes
 

Received my version of an external LPF board from OSHPark. To second Jerry's comments, OSHPark has a very nice front end process.

This board is 1.5in by 3in sized for T68 cores and 1206 caps to provide flexibility for use in future projects. Footprints are provided for both BNC connectors and header pins for input and output.

Get a copy of "Make Your Own PCBs with Eagle" by Simon Monk and you can make your own boards for the investment of a small learning curve.

James
KEMIQ

MadRadioModder
 

Nice and simple.  Why don’t you give us the OSHPark link and we can just order some of these instead of designing our own…?

 

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of James Lynes
Sent: Sunday, September 2, 2018 3:07 PM
To: BITX20@groups.io
Subject: Re: [BITX20] VK4PP uBitx LPF BANK add-on Board

 

Received my version of an external LPF board from OSHPark. To second Jerry's comments, OSHPark has a very nice front end process.

 

This board is 1.5in by 3in sized for T68 cores and 1206 caps to provide flexibility for use in future projects. Footprints are provided for both BNC connectors and header pins for input and output.

 

Get a copy of "Make Your Own PCBs with Eagle" by Simon Monk and you can make your own boards for the investment of a small learning curve.

 

James

KEMIQ

 


Virus-free. www.avg.com

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