Topics

Modular uBitx - "Ex: Harmonics"

Nick VK4PP
 

Hi Allison/ Kees/ Glenn/ other technical competent hams...

Would you consider working on a uBitx v2 so to speak, advice, criticisms and such?
Tweaking the current design as much as possible to perform better, address the major issues (spurs + harmonics)? 
Better components (2n2222a) ect,
Extra driver stage?
LPF layout..
proper BPF using QRP Labs Modules..

I would like to make it very modular, so its easy to fix/upgrade a section.
I will make some boards, happy to send to you for testing and evaluation at no cost.
Also smaller boars fit in a DL envelope (110x220mm) for DX shipping at $3.50. so that kind of defines the foot print.
Would be cool, 4 boards each about 105x105mm Stacking on one another.
Nano socketed on one board, SI5153 integrated, either SMT or Adafruit module ($$$ vs convenience)

I am not aiming to build a cheap copy, just an upgraded uBitx that you can assemble your self if you don't mind spending a bit more.

I want to enjoy the process and the radio, learn stuff along the way, contribute to the community.
As soon as this is no longer happening, there is no point in carrying on for me.

What are your thoughts people?

Cheers & 73.
Nick VK4PP 

Jack Purdum
 

All:

I think this makes a lot of sense, but I'd want Farhan to be involved so we don't kill of HF Signals important business in India. I do know it would keep costs down a bunch is the boards are a maximum of 100mm x 100mm, as that's the price bump point for a lot of PCB houses. I can't say much about the hardware, but I would suggest additional horsepower for the software. The Nano has relatively few I/O pins, is fairly slow, and has very limited memory resources. The Protoneer is 3x as fast and has 4x the SRAM, which is a primary bottleneck. The Blue Pill is another alternative. I would, however, strongly urge that the controller be capable of using the Arduino IDE for code development. More pins would enable more experimenting, too, probably to everyone's benefit.

I would also argue for an I2C or SPI display interface, simply because we're seeing the Nextion, Jim Sheldon's display, the JackAl board by AC8GY and myself, and probably others extending the basic display. Those interfaces also reduce the pins necessary for the interface compared to some LCD displays.

I would be happy to help with the software end of things, and I will be releasing JackAl to Open Source when it's ready. This could really be interesting!!

Jack, W8TEE


On Tuesday, August 14, 2018, 8:37:48 PM EDT, Nick VK4PP <nickpullen@...> wrote:


Hi Allison/ Kees/ Glenn/ other technical competent hams...

Would you consider working on a uBitx v2 so to speak, advice, criticisms and such?
Tweaking the current design as much as possible to perform better, address the major issues (spurs + harmonics)? 
Better components (2n2222a) ect,
Extra driver stage?
LPF layout..
proper BPF using QRP Labs Modules..

I would like to make it very modular, so its easy to fix/upgrade a section.
I will make some boards, happy to send to you for testing and evaluation at no cost.
Also smaller boars fit in a DL envelope (110x220mm) for DX shipping at $3.50. so that kind of defines the foot print.
Would be cool, 4 boards each about 105x105mm Stacking on one another.
Nano socketed on one board, SI5153 integrated, either SMT or Adafruit module ($$$ vs convenience)

I am not aiming to build a cheap copy, just an upgraded uBitx that you can assemble your self if you don't mind spending a bit more.

I want to enjoy the process and the radio, learn stuff along the way, contribute to the community.
As soon as this is no longer happening, there is no point in carrying on for me.

What are your thoughts people?

Cheers & 73.
Nick VK4PP 

Nick VK4PP
 

Hi Jack, 
Thanks for the ideas.
99.99x99.99 for board size.
I was thinking maybe the Arduino Nano 2560 Mini Pro, About $13... lots of IO...
But then, with the nano, when using I2C, there are 6 extra IO ports. Its just program memory...
I did want to limit FW changes, I was hoping to only have to change the code relating to LPF and BPF...
I'm thinking 5 LPFs and BPF that are switched in. Builder selects the 5 bands they want to operate on and builds the radio/software for that...

The more I think this over the bigger it becomes.

Farhan has achieved so much already! I would only do stuff if he was OK with it,

Cheers,

Nick VK4PP
 

One of these?
Image result for mini mega 2560

Glenn
 

Nice idea Nick, Jack,

I'm currently doing a HF rig based on works from the book by EI9GQ. [ Not a qrp rig. No real attampt to lower Rx current)]

I first built all the sections as DIY boards then consolidated them into the magic 100x100mm for Chinese supplier.
Receiver is working, low level Tx side all tested up to 1W level.    Uses 9MHz crystal filters available on ebay at least for now, from a "Telrad" board. Might possibly build own filter also as the Telrads are bit wide. No CW.
Band pass filters plug into a 100x100 motherboard and are used in Rx and Tx modes.

I'm not suggesting we go down this road but that the idea of using 100x100mm boards has a lot of merit.

I'm yet to decide on the control Micro but for initial testing uses a NANO and Si5351. Your suggestion Jack to use a more capable Micro is a good one.



BPF, one fitted to mother board.

Nick VK4PP
 

HI All.
Blue Pill looks to be a winner too me, I have 2 laying about actually. VERY cheap, 2x the nano memory. and 32bit.
Should fit the bill perfectly, extra IO too. (26)
Just got to get the Code running on it, Jack?

Cheers
Nick VK4PP

Adrian Waiblinger
 

Keep a option for 630m band too. 
If to hard an output from the Nano to drive the external 630m pa relay / 

Regards 
Adrian 


On 15 Aug 2018, at 10:44 am, Nick VK4PP <nickpullen@...> wrote:

One of these?
Image result for mini mega 2560

Jack Purdum
 

This is what we used for the antenna analyzer (QST, Nov., 2017). The only reason I switched away from it was its clock speed. At 16MHz, it just wasn't up to the DSP power we needed.

Jack, W8TEE


On Tuesday, August 14, 2018, 9:57:21 PM EDT, Adrian Waiblinger <vk5zbr@...> wrote:


Keep a option for 630m band too. 
If to hard an output from the Nano to drive the external 630m pa relay / 

Regards 
Adrian 


On 15 Aug 2018, at 10:44 am, Nick VK4PP <nickpullen@...> wrote:

One of these?
Image result for mini mega 2560

Tom, wb6b
 

I agree, we don't want to see anything happen that would kill off Farhan's business and the incomes for the people it helps support. 

It may be that the uBITX has become somewhat of a victim of its own success. Bringing in many folks more expecting the first generation of the uBITX to be perfected, rather than a experimenters/hackers radio to transform, improve and modify.  

When I look over the message board I see 14 years of history for the BITX transceivers. I've gathered from some messages the BITX40/20 of today is much improved over the original design. Did this happen because Farhan went back to his corporate research lab and demanded they improve the design of the transceiver and develop advance proprietary manufacturing technology to produce millions of these at low unit costs? 

These improvements came not from a highly funded corporate lab, but from the Ham Radio operators that embraced the transceivers and worked enthusiastically to make it better. With a radio that's design is accessible, open source and made from parts that are available off the shelf.

The cost of the uBITX is low enough that when Farhan and the many folks that are on the front line, doing the improvements of the uBITX, efforts come together in a new improved board from Farhen, buy another one. Use your current uBITX as a second receiver or do a few mods to use to a a second transceiver on one or two bands; for example. The cost of the uBITX is less than components people upgrade and replace without feeling it is a big issue in many other situations.

The money you will spend to upgrade to a newer uBITX board will be less than many are spending to buy the items they are buying to upgrade their current uBITX transceivers. Not much different from when people would regularly buy a new motherboard for their computer because technology improved.

So, at least for the next generation of the uBITX, it should be able to bolt into the cases people have already build for their radios. 

Tom, wb6b

Ashhar Farhan
 

Peeps, Jack, 
I hope that it is clear to everyone that ubitx is an open design. There is no restriction on anyone kitting it and selling products based on it. I would encourage people to try their hand and running it even as a business.
There is no challenge to hf sigs, really. There are more radios to be built and shipped than what hfsigs can ever do. Do go ahead and branch off. Cooperation beats competition each time!
Happy independence day to all my friends who believe in the idea of India! 
73, f. 

On Wed, 15 Aug 2018, 08:23 Jack Purdum via Groups.Io, <jjpurdum=yahoo.com@groups.io> wrote:
This is what we used for the antenna analyzer (QST, Nov., 2017). The only reason I switched away from it was its clock speed. At 16MHz, it just wasn't up to the DSP power we needed.

Jack, W8TEE


On Tuesday, August 14, 2018, 9:57:21 PM EDT, Adrian Waiblinger <vk5zbr@...> wrote:


Keep a option for 630m band too. 
If to hard an output from the Nano to drive the external 630m pa relay / 

Regards 
Adrian 


On 15 Aug 2018, at 10:44 am, Nick VK4PP <nickpullen@...> wrote:

One of these?
Image result for mini mega 2560

Jack Purdum
 

We ended up using the Teensy 3.6. 1Mb of flash, 256K of SRAM, 4K EEPROM, 62 I/O pins, I2C, RTC, 25 analog pins with 13-bit resolution and 2 analog output pins with 12-bit resolution (Mega has 10-bit). True, the blue pill cost less, but the libraries for the Teensy include most of the Arduino plus many others (FFT and audio). While this screen doesn't show everything:

Inline image

we're using less than 20% of its memory resources. The companion audio board allows us to do some pretty cool stuff, like an 8-band equalizer (plot is on the left):

Inline image

It's not cheap ($30), but is sure brings a lot to the table.

Jack, W8TEE

On Tuesday, August 14, 2018, 9:34:21 PM EDT, Nick VK4PP <nickpullen@...> wrote:


HI All.
Blue Pill looks to be a winner too me, I have 2 laying about actually. VERY cheap, 2x the nano memory. and 32bit.
Should fit the bill perfectly, extra IO too. (26)
Just got to get the Code running on it, Jack?

Cheers
Nick VK4PP

Jack Purdum
 

Our goal with the JackAl board is to give enough memory resources and horsepower to let the hacker run wild. We also bring out on the board 12 unused I/O pins to play with. (There are some unused pins "under the board", too.)  The display uses the SPI interface and all of the video processing is on the display card, so it's not sucking cycles away for screen updates.

The critical bottleneck is not the flash memory, it's the SRAM. That were the stack and heap space come from...where you data live. Some Nano users think that, when SRAM is at 75%, there's still a lot of memory available. Not so...that's a compile-time statistic and it's static. Because every function call pushes the stack deeper and deeper at runtime, what looks like a lot of available memory at compile-time results in disaster when the stack crashes into the heap space. With a Nano, all of your data plus the stack must fit in 2K of SRAM. Compare that with 256K of SRAM on the Teensy.

What Allard and Dr. Lee have done with the Nano is truly amazing. Me? I'm not that clever, so I need more elbow room and the Teensy 3.6 makes that a pretty nice environment to work in.

Jack, W8TEE


On Tuesday, August 14, 2018, 9:09:12 PM EDT, Nick VK4PP <nickpullen@...> wrote:


Hi Jack, 
Thanks for the ideas.
99.99x99.99 for board size.
I was thinking maybe the Arduino Nano 2560 Mini Pro, About $13... lots of IO...
But then, with the nano, when using I2C, there are 6 extra IO ports. Its just program memory...
I did want to limit FW changes, I was hoping to only have to change the code relating to LPF and BPF...
I'm thinking 5 LPFs and BPF that are switched in. Builder selects the 5 bands they want to operate on and builds the radio/software for that...

The more I think this over the bigger it becomes.

Farhan has achieved so much already! I would only do stuff if he was OK with it,

Cheers,

Henning Weddig
 

Nick,

I already started to do "my" improvement on the µBITX, but then stopped, after reading and trying to understand all the issues involved and going back to ideas about a spec and blocks to be designed.

As I am an retired electrical engineer specialized in RF and communication techology (I started my profesional career in 1980 at the company Hagenuk in Kiel Germany designing part of the ship´s main communication receiver RX 1001 and later RX1001M, then working on the RF part of the ST900 cordless telephone) 

As I posess a "good equipped home lab" witrh used commercial equipment (spectrum analysers, networt analyser, signal generators and so on), I can test my disgins properl.

Before going to design something  we first should think about a specifiaction and wirte it down. Yes I know seldom engineers like it,  but this will give some insight into what has to be designed. Very important are also level diagrammes of the bolocks involved to see if the to be designed unit will fulfill the desired spec.

From this point of view Glenn´s way of doing a new design in  first to test sub modules is a brilliant idea as it was also used in the industry (and my last occupation within a physics high energy research lab). We often only developed a single unit wioth the use of connectorized "Mini Circuit modules" and built into a case.

As SMD compoents are used the size of the "cheap" chinese pcb´s should be < 100 * 100 mm.

I believe that this forum including Farhan can and shuld be a good potential for an optimized new µBITX!

My previous ideas:

modular design on pcb´s (<100 * 100 mm)

frequency range 10 kHz to 30 MHz

first IF > 45 MHz (to avoid the 2*IF - LO problem) using four pole xtal filters  e.g. 70 MHz (if easily avaliable)? Another "popular IF could be 58 MHz or 58.1125 MHz (used in Hagenuks cordless phones) My be enough NOS filters are laying around.

1) receiver/exciter pcb

2) xtal filter board for the second IF (e.g. 5 MHz) with filters for SSB; AM; FM(?), CW

2) input lowpass filter (corner freq. 1.6 MHz) plus  overlapping bandpass filters (e.g. 1.6 - 4MHz; 4 - 8 MHz, 8 - 16 MHz; 16 - 30 MHz)

3) driver board

5) PA board

6) lpf´s

7) VSWR bridge

8) VFO (several SI5351 ? to avoid crosstalk between outputs of a single SI5351 driven from a single reference (TCXO; or VCXO which could be synchronized to a GPS reference?)

RF signals to be routed via SMA connectors

Of course AGC should be inclueded!

For the mic amp I remember that for maritime ship transmitters there is a requirement to limiting the max RF output via a Mic compressor. Chips like the SSM2167 could easily fulfill such a (similar) spec!

Comments are welcome
Henning Weddig
DK5LV

Am 15.08.2018 um 02:37 schrieb Nick VK4PP:

Hi Allison/ Kees/ Glenn/ other technical competent hams...

Would you consider working on a uBitx v2 so to speak, advice, criticisms and such?
Tweaking the current design as much as possible to perform better, address the major issues (spurs + harmonics)? 
Better components (2n2222a) ect,
Extra driver stage?
LPF layout..
proper BPF using QRP Labs Modules..

I would like to make it very modular, so its easy to fix/upgrade a section.
I will make some boards, happy to send to you for testing and evaluation at no cost.
Also smaller boars fit in a DL envelope (110x220mm) for DX shipping at $3.50. so that kind of defines the foot print.
Would be cool, 4 boards each about 105x105mm Stacking on one another.
Nano socketed on one board, SI5153 integrated, either SMT or Adafruit module ($$$ vs convenience)

I am not aiming to build a cheap copy, just an upgraded uBitx that you can assemble your self if you don't mind spending a bit more.

I want to enjoy the process and the radio, learn stuff along the way, contribute to the community.
As soon as this is no longer happening, there is no point in carrying on for me.

What are your thoughts people?

Cheers & 73.
Nick VK4PP 

Gordon Gibby
 

Those are great ideas, but what about a limitation on cost? Should be under $140.


On Aug 15, 2018, at 04:42, Henning Weddig via Groups.Io <hweddig@...> wrote:

Nick,

I already started to do "my" improvement on the µBITX, but then stopped, after reading and trying to understand all the issues involved and going back to ideas about a spec and blocks to be designed.

As I am an retired electrical engineer specialized in RF and communication techology (I started my profesional career in 1980 at the company Hagenuk in Kiel Germany designing part of the ship´s main communication receiver RX 1001 and later RX1001M, then working on the RF part of the ST900 cordless telephone) 

As I posess a "good equipped home lab" witrh used commercial equipment (spectrum analysers, networt analyser, signal generators and so on), I can test my disgins properl.

Before going to design something  we first should think about a specifiaction and wirte it down. Yes I know seldom engineers like it,  but this will give some insight into what has to be designed. Very important are also level diagrammes of the bolocks involved to see if the to be designed unit will fulfill the desired spec.

From this point of view Glenn´s way of doing a new design in  first to test sub modules is a brilliant idea as it was also used in the industry (and my last occupation within a physics high energy research lab). We often only developed a single unit wioth the use of connectorized "Mini Circuit modules" and built into a case.

As SMD compoents are used the size of the "cheap" chinese pcb´s should be < 100 * 100 mm.

I believe that this forum including Farhan can and shuld be a good potential for an optimized new µBITX!

My previous ideas:

modular design on pcb´s (<100 * 100 mm)

frequency range 10 kHz to 30 MHz

first IF > 45 MHz (to avoid the 2*IF - LO problem) using four pole xtal filters  e.g. 70 MHz (if easily avaliable)? Another "popular IF could be 58 MHz or 58.1125 MHz (used in Hagenuks cordless phones) My be enough NOS filters are laying around.

1) receiver/exciter pcb

2) xtal filter board for the second IF (e.g. 5 MHz) with filters for SSB; AM; FM(?), CW

2) input lowpass filter (corner freq. 1.6 MHz) plus  overlapping bandpass filters (e.g. 1.6 - 4MHz; 4 - 8 MHz, 8 - 16 MHz; 16 - 30 MHz)

3) driver board

5) PA board

6) lpf´s

7) VSWR bridge

8) VFO (several SI5351 ? to avoid crosstalk between outputs of a single SI5351 driven from a single reference (TCXO; or VCXO which could be synchronized to a GPS reference?)

RF signals to be routed via SMA connectors

Of course AGC should be inclueded!

For the mic amp I remember that for maritime ship transmitters there is a requirement to limiting the max RF output via a Mic compressor. Chips like the SSM2167 could easily fulfill such a (similar) spec!

Comments are welcome
Henning Weddig
DK5LV

Am 15.08.2018 um 02:37 schrieb Nick VK4PP:
Hi Allison/ Kees/ Glenn/ other technical competent hams...

Would you consider working on a uBitx v2 so to speak, advice, criticisms and such?
Tweaking the current design as much as possible to perform better, address the major issues (spurs + harmonics)? 
Better components (2n2222a) ect,
Extra driver stage?
LPF layout..
proper BPF using QRP Labs Modules..

I would like to make it very modular, so its easy to fix/upgrade a section.
I will make some boards, happy to send to you for testing and evaluation at no cost.
Also smaller boars fit in a DL envelope (110x220mm) for DX shipping at $3.50. so that kind of defines the foot print.
Would be cool, 4 boards each about 105x105mm Stacking on one another.
Nano socketed on one board, SI5153 integrated, either SMT or Adafruit module ($$$ vs convenience)

I am not aiming to build a cheap copy, just an upgraded uBitx that you can assemble your self if you don't mind spending a bit more.

I want to enjoy the process and the radio, learn stuff along the way, contribute to the community.
As soon as this is no longer happening, there is no point in carrying on for me.

What are your thoughts people?

Cheers & 73.
Nick VK4PP 


Yaya
 

Hi Nick,

We think alike you and I, this is exactly what I have been doing for some time now. Progress is slow due to work and family commitments unfortunately. Will be happy to share thoughts and work.

73 Elia, M0ZHN

Russ Hines
 

Here's to a free and independent India.  Happy birthday. 

And thank you, Ashhar Farhan, for making this versatile platform available.

Salute!
Russ Hines
JMS & Associates, Inc.
SBE CSRE
WB8ZCC
--
Reply to: russ@...
On 8/14/2018 11:10 PM, Ashhar Farhan wrote:

Peeps, Jack, 
I hope that it is clear to everyone that ubitx is an open design. There is no restriction on anyone kitting it and selling products based on it. I would encourage people to try their hand and running it even as a business.
There is no challenge to hf sigs, really. There are more radios to be built and shipped than what hfsigs can ever do. Do go ahead and branch off. Cooperation beats competition each time!
Happy independence day to all my friends who believe in the idea of India! 
73, f. 

On Wed, 15 Aug 2018, 08:23 Jack Purdum via Groups.Io, <jjpurdum=yahoo.com@groups.io> wrote:
This is what we used for the antenna analyzer (QST, Nov., 2017). The only reason I switched away from it was its clock speed. At 16MHz, it just wasn't up to the DSP power we needed.

Jack, W8TEE


On Tuesday, August 14, 2018, 9:57:21 PM EDT, Adrian Waiblinger <vk5zbr@...> wrote:


Keep a option for 630m band too. 
If to hard an output from the Nano to drive the external 630m pa relay / 

Regards 
Adrian 


On 15 Aug 2018, at 10:44 am, Nick VK4PP <nickpullen@...> wrote:

One of these?
Image result for mini mega 2560

ajparent1/KB1GMX
 

All,

Thoughts mostly as applied to making ubitx or bitx modular.  From start good idea.
Breaking it into modules allows one to solve issues as they arise like power amp
isn't good enough build and replace a new one.  IT takes all the ugly fixes out as 
now a module deemed less than desired can have a new or modified one substituted.

Now lots of questions:
Many of the uBitx problems are related to:
 Board layout (many cases of good circuit compromised)
 Filtering circuits (and their layout)
 Gain distribution, some places not enough other way too much.
 Power amp performance (power fall off and instability).

These are for  TX path only:
How much gain is planed for the path starting at the balanced modulator
(not the audio before that is also low gain) though all the filters and possible
mixer to the last mixer?

How many devices are needed to supply that?

How much audio gain, gain control, or compression?

once you have a signal(s) at the last mixer what is the filtering scheme to
insure a reasonable spectral purity ant the input to the power amp?

How much gain and its distribution in the power amplifier?

Just an opening set of questions.

Building a radio is like building a house or bridge, you need an idea of what
size and how its going to look.  The foundation must be sound and support
the planed design.  For a Transceiver that is the basic RF core.  Everything
else builds from there.

Also for the moment unless the MCU is doing DSP its not part of this save
for its integration must be clean referring to the paths from 5351(s) to the 
various points that signals are needed.  The MCU is the user interface only
and as stated unless its doing DSP it cannot enhance the signal.

On a different path.
Items I see as useful as in should have:

*SWR/power out measurement built in its trivial and everyone needs that.
*Ways and tools built in to help diagnose.  Others have done this and please
 read the Elecraft  K1 and K2 manual if this is not clear.  Its handy for those
 without lots of gear and a kindness for those of us that will use it.
* Consider BITE, Built In Test and Error report.  It can as simple as
 measuring the 12V in to assure you have enough DC power during
 transmit!  Another could be excess SWR, Excessive PA current (from
high SWR or Fault).  Simple and easy measurements.

Allison

Jack Purdum
 

The MCU is the user interface only and as stated unless its doing DSP it cannot enhance the signal.

Exactly, which is why I think we need a relatively powerful µC with good library support. With some programming effort, Al was able to define these CW filters:
Inline image
plus we added a user-defined CW filter, too. We have similar filters for SSB. Software filters via DSP make such things so easy when compared to designing a fixed filter in hardware.

Jack, W8TEE



On Wednesday, August 15, 2018, 11:54:17 AM EDT, ajparent1/KB1GMX <kb1gmx@...> wrote:


All,

Thoughts mostly as applied to making ubitx or bitx modular.  From start good idea.
Breaking it into modules allows one to solve issues as they arise like power amp
isn't good enough build and replace a new one.  IT takes all the ugly fixes out as 
now a module deemed less than desired can have a new or modified one substituted.

Now lots of questions:
Many of the uBitx problems are related to:
 Board layout (many cases of good circuit compromised)
 Filtering circuits (and their layout)
 Gain distribution, some places not enough other way too much.
 Power amp performance (power fall off and instability).

These are for  TX path only:
How much gain is planed for the path starting at the balanced modulator
(not the audio before that is also low gain) though all the filters and possible
mixer to the last mixer?

How many devices are needed to supply that?

How much audio gain, gain control, or compression?

once you have a signal(s) at the last mixer what is the filtering scheme to
insure a reasonable spectral purity ant the input to the power amp?

How much gain and its distribution in the power amplifier?

Just an opening set of questions.

Building a radio is like building a house or bridge, you need an idea of what
size and how its going to look.  The foundation must be sound and support
the planed design.  For a Transceiver that is the basic RF core.  Everything
else builds from there.

Also for the moment unless the MCU is doing DSP its not part of this save
for its integration must be clean referring to the paths from 5351(s) to the 
various points that signals are needed.  The MCU is the user interface only
and as stated unless its doing DSP it cannot enhance the signal.

On a different path.
Items I see as useful as in should have:

*SWR/power out measurement built in its trivial and everyone needs that.
*Ways and tools built in to help diagnose.  Others have done this and please
 read the Elecraft  K1 and K2 manual if this is not clear.  Its handy for those
 without lots of gear and a kindness for those of us that will use it.
* Consider BITE, Built In Test and Error report.  It can as simple as
 measuring the 12V in to assure you have enough DC power during
 transmit!  Another could be excess SWR, Excessive PA current (from
high SWR or Fault).  Simple and easy measurements.

Allison

ajparent1/KB1GMX
 

On Wed, Aug 15, 2018 at 01:41 AM, Henning Weddig wrote:

first IF > 45 MHz (to avoid the 2*IF - LO problem) using four pole xtal filters  e.g. 70 MHz (if easily avaliable)? Another "popular IF could be 58 MHz or 58.1125 MHz (used in Hagenuks cordless phones) My be enough NOS filters are laying around.

Henning,

The magic frequency is over 60 mhz. At 58.1125 the half IF is ~29.06mhz 
or the point where the 2IF minus LO will be one loud birdie (RX and TX).  
It moves the current issue up but not out.  Works for cell but not a 3-30mhz radio.

Band pass filters are easier.  As is we are asking a 300mhz transistor to work
marginally at 45mhz.  Going up makes that worse.  Better yet a better transistor.

1) receiver/exciter pcb

Makes the core a module and replaceable with improved or different technology
without having to toss everything else out with it.

2) xtal filter board for the second IF (e.g. 5 MHz) with filters for SSB; AM; FM(?), CW

FM again, why?  For 10M, easier to make a dedicated radio for that with 
a decent limiter for the RX.  Same for AM, 10W radio with full carrier AM
is 2.5W, not a power house.   It forces a decent power amp as well one
that an sustain full power.  Better to limit to SSB/CW.  Switched filters
makes sense.

2) input lowpass filter (corner freq. 1.6 MHz) plus  overlapping bandpass filters (e.g. 1.6 - 4MHz; 4 - 8 MHz, 8 - 16 MHz; 16 - 30 MHz)

Input highpass at 1.6mhz? Correct?  
Also not octave filter I presume you mean half or 2/3 octave filters so the second harmonic is not able to escape.
The the 2/3 octave lineup results in a large umber of filters unless their corners are suitable to stop harmonics
in the next band up.

3) driver board

5) PA board

This is an approach the driver has to be designed with 50 ohm outputs.  The interconnect can be short wires.

6) lpf´s

Goes without saying easy and its more about layout and switching.

7) VSWR bridge

Should be there and its a very useful and simple thing.

8) VFO (several SI5351 ? to avoid crosstalk between outputs of a single SI5351 driven from a single reference (TCXO; or VCXO which
could be synchronized to a GPS reference?)

Leave out the gps locked oscillator.  we are not designing the next generation Hilberling.  More than one LO device
makes a lot of sense and allows for a better RF layout to put it where its needed.  The 5351 is inexpensive.

RF signals to be routed via SMA connectors

No, as much as I use them and like them they are not cheap and for those that
are mechanically challenged or lack dexterity the word torture comes to mind.
They are not inexpensive  Cables with the connector on them are not cheap.
The base idea that RF should be routed with RF connectors is a vhf and up
thing.  With care at HF pin connectors can work but the board layout has to 
not create RF current loops.

Allison

RCBoatGuy
 

Here's some features I'd like to see in any new design that shouldn't cost much, but would make life/testing/experimentation easier:

- Sockets for CPU boards on any new Raduino design.  (Teensyduino has this already, and I think the JackAl does, too)

- Sockets for relays, as these have been a frequent source of failure

- Move any pull-up resistors required onto the Raduino/Teensyduino/JackAl board and not rely on the user to wire them up.  Many users either failed to wire up the 4.7K external resistor correctly or had the connection fail later, causing the rig to immediately go into transmit on power-up.  This is easily avoided by having the required pull-ups on the Raduino/Teensyduino/JackAl board itself.

- Add 3-pin 0.1" input and output headers/jumpers to each section (Bi-di Amps, Audio Amp, Mic Amp, BPF, PA, LPF, etc) on a given board so that the given section can be isolated and tested independently.  For inputs to a section, 1st pin is output from prior section, 2nd pin is input to current section, 3rd pin is GND.   For outputs from a section, 1st pin is output from section, 2nd pin is input to next section, 3rd pin is GND.  Normal operation uses shorting jumpers across pins 1 and 2 to allow signals to flow thru, but jumpers can be removed and test inputs/outputs connected via molex/etc connectors to pins 2 and 3 (or to all 3 pins if desired).  This also makes it easier to replace a given section with an external circuit for experimentation/modification.

- Room for extra I2C headers on the Raduino (Teensyduino already has this, not sure about the JackAl) that the user can install later if desired

- Would be nice if the modular design had the PA on a separate board so different PAs can be used based on user preference.  Having different boards for a IRF510 PA, a RD16HHF1 PA, etc, would be nice as the user can pick and choose what they want, or build their own much easier.

- Support for adding additional BPF/LPF for those that want 160M, 6M, etc

- As for the LPF relays, I'd recommend using a relay scheme like that on the mcHF transceiver.  Their approach minimized the number of relays (only 4 DPDT relays needed for 4 filters), but still had filter inputs and filter outputs going to different relays.

- Design board so that the Raduino/Teensyduino/JackAl board has no obstructions from parts and/or connectors along the entire edge of the radio board.  The Teensyduino had to design in special cut-outs to use with the current uBitX due to obstructions. It would be nice if cut-outs like this were not needed in the future.

- Si5351 on main board, not on Raduino/Teensyduino/JackAl

That's my 2 cents.  Take it for what it's worth.  :)

73, 

Carl, K0MWC