Date   
AGC and FT8

Daimon Tilley <daimontilley@...>
 

I have the ND6T / K5BCQ AGC kit to build and install and use my rig mainly for portable FT8 with a built in Raspberry Pi, with only occasional SSB use.

I don’t need the AGC for FT8, but if I install it, has anyone experienced negative impact on decodes?

I am thinking that if I set the jumpers to “short” (fast?) the. I might be OK, or should I have a switch to switch it in and out when using different modes?

thanks.

Daimon.
G4USI.

Re: Unexpected measurements

jim
 

Have not seen this -exactly- but ..all my testing was in ssb mode

DK7IH has a simple two-tone  test oscillator (copied below)  I add  2 switches to turn off each oscillator (to test for maximum warp) ...Tho he calls it a wien bridge, its really a phase-shift oscillator ...inject into mike input

Jim


On Thursday, January 17, 2019, 6:04:52 PM PST, Evan Hand <elhandjr@...> wrote:


I did some testing on my v4 board and found interesting correlation (though not able to verify mathematical accuracy):



At this point I will be going back and coming up with a better way to inject a 1 or 2 tone audio signal into the uBitx to then measure the harmonics.  

Has anyone else seen this type of behavior?

73
Evan
AC9TU

Re: Wild and crazy uBITX, Arduino FPGA idea. #arduino #ubitx #sdr #fpga

Tom, wb6b
 

Hi Josh,

Very good points. I've been worrying a bit about the 120Mhz DAC, termination and signal length matching, especially as the DAC would most likely be connected through the mini PCI connector on the Arduino Vidor board. It may be possible to do without oversampling. Oversampling should provide an easier to clean up with the existing low pass filter signal. But, no oversampling may be OK. The tradeoff for oversampling vs more depth, on receive, could indeed be better with more depth. As nearby strong signals (such as a field day situation) could be in the bandpass of the roofing filter. 

Tom, wb6b

Re: Wild and crazy uBITX, Arduino FPGA idea. #arduino #ubitx #sdr #fpga

Joshua Blanton
 

Hello Tom,

I think that's a very interesting idea - a couple of thoughts that might be useful (or not) - you may already be well aware of these:

1) 120MHz signaling can be hard to wire, especially in wide parallel buses - this may be difficult to wire without signal integrity errors, unless you're laying out a board for the task.  12-bit sampling just increases the number of lines you're trying to keep synchronized.  Modern FPGAs shouldn't have an issue running I/O at 120MHz, but you will probably need terminated signal paths and matched cable lengths to ensure data transport

2) Your dynamic range will be limited by the 10- or 12-bit sample depth; oversampling can help, but it might be more effective to get a 14- or 16-bit ADC at a slower clock rate than to oversample at a lower depth.  It's been a while since I've looked at the math; I'm sure several people on the list are smarter than me about this!  If you incorporate AGC, this should help considerably (but close-in signals will still affect your dynamic range, obviously).  I might even consider sub-sampling, although I don't know if you can get ADCs (significantly better than 16-bit, for reasonable cost) that would support 12MHz sub-sampling...

Very, very interesting - I've been thinking about building just such a configuration (at least single-conversion, and then sampling at an HF IF with a fast ADC) for a while, but I'm not really a hardware guy - and I would feel compelled to lay out the ADC and FPGA portion, at minimum, and sounds tedious.  I've seen high-speed FPGA designs, and I know that I'm not competent to lay them out :-)

Anyway, good luck - I'd love to hear about the project, if you proceed!

Josh, KB8NYP

On Thu, Jan 17, 2019 at 10:11 PM Tom, wb6b <wb6b@...> wrote:

Hi,

 

I just received a Arduino MKR Vidor board. It is a higher powered Arduino with a medium sized FPGA included on the board. 

 

My thought was to add a fairly fast (around 120Mhz to allow oversampling) 10 or 12 bit DAC to supply the transmit signal directly to the low pass filter at Test Point 1. And use a 50Mhz 12 bit ADC (again to allow oversampling) for receive picking up the signal at test point 17. 

 

For receive this should be better than trying to push the ADC close to the antenna, as the digital receiver will then have a fairly cleaned up signal to work with and the signal frequency (12Mhz) is fairly moderate. In fact, if the frequency could be mixed down even lower, it might be possible to use fairly low speed ADCs.

 

Another advantage of the band pass filtering ahead of the ADC for receive is there should be no need for quadrature (I/Q) mixers, and dual ADCs, as the digital processing will not need to determine which signal frequencies are above and below the center frequency. (Internally, for SSB demodulation, depending on method, there could be I/Q processing. But that can all be handled in the FPGA). 

 

So the uBITX could be a really good starting point for the RF parts of a FPGA SDR transceiver. It's possible the specs for the ADC and DAC chips could be toned down a bit and reduce the costs further. 

 

Here are a couple of possible designs that could be used as a starting point.

 

http://k6jca.blogspot.com/2017/02/an-fpga-sdr-hf-transceiver-part-1.html

https://www.tapr.org/pdf/DCC2010-FPGA-BasedTransceiver-KD6OZH.pdf

Tom, wb6b


Re: Cooling fan Shroud

Tom, wb6b
 

Very good. By the way, I do like your shroud and I appreciate your putting it up on Thingiverse.

Tom, wb6b

Wild and crazy uBITX, Arduino FPGA idea. #arduino #ubitx #sdr #fpga

Tom, wb6b
 

Hi,

 

I just received a Arduino MKR Vidor board. It is a higher powered Arduino with a medium sized FPGA included on the board. 

 

My thought was to add a fairly fast (around 120Mhz to allow oversampling) 10 or 12 bit DAC to supply the transmit signal directly to the low pass filter at Test Point 1. And use a 50Mhz 12 bit ADC (again to allow oversampling) for receive picking up the signal at test point 17. 

 

For receive this should be better than trying to push the ADC close to the antenna, as the digital receiver will then have a fairly cleaned up signal to work with and the signal frequency (12Mhz) is fairly moderate. In fact, if the frequency could be mixed down even lower, it might be possible to use fairly low speed ADCs.

 

Another advantage of the band pass filtering ahead of the ADC for receive is there should be no need for quadrature (I/Q) mixers, and dual ADCs, as the digital processing will not need to determine which signal frequencies are above and below the center frequency. (Internally, for SSB demodulation, depending on method, there could be I/Q processing. But that can all be handled in the FPGA). 

 

So the uBITX could be a really good starting point for the RF parts of a FPGA SDR transceiver. It's possible the specs for the ADC and DAC chips could be toned down a bit and reduce the costs further. 

 

Here are a couple of possible designs that could be used as a starting point.

 

http://k6jca.blogspot.com/2017/02/an-fpga-sdr-hf-transceiver-part-1.html

https://www.tapr.org/pdf/DCC2010-FPGA-BasedTransceiver-KD6OZH.pdf

Tom, wb6b

 

Re: Cooling fan Shroud

_Dave_ K0MBT
 

I choose to run the fan full time. The reason I run the fan while receiving is that it pulls heat out of the small heat sinks.

On my original ubitx, I run the finals at 20 volts and use it for digital. The heatsinks that I use on that radio weigh about 4x as much with a lot more finning. The fan is a regular 3" computer fan with a snug fitting shroud. I can run the transmitter at 20 watts into a dummy load in cw mode for an indefinite amount of time without making the transistors hot.

This set up is not as effective but it pull heat out of the heatsinks. I may well use larger heatsinks and design a different fan shroud.

Not planning on running a temp controlled fan nor just run it whilst the tx is on.

Re: Cooling fan Shroud

Bob Lunsford <nocrud222@...>
 

The power to the transmit wire is always connected so
there would have to be a relay to only apply power to
the relay when the PTT line is enabled. More complexity.


There are many schemes to make work what you suggest
which is essentially a good idea. Big rigs do this. Would
need a relay and a relay driver that is connected to the
PTT line. As the old saying goes, "It's doable."

On the other hand, drawing air out of a rig's box is the
best way since it is removing the hot air. But if the fan
is placed so air is forced into the box at the bottom, the
placement of the fan reduces the sound of the fan if the
box is elevated on feet, for example. In other words,
placement of the fan is an essential element in the noise
produced. Also, if the fan is mounted on rubber bushings,
the sound is not transmitted mechanically back into the
box. If the box is a hunk of iron, no problem but most of
them are small and light which invites some coupling
of the vibrations back into the box and makes the box
a soundboard for the noise. However, most sound is
acoustic and with mine, all I heard was wind noise and
this is why merely slowing down the fan is a way to
eliminate a lot of the sound. The exhausted air does
not need to be very high so slowing it down does what
is needed: Removing the hot air from the box. The
proper value of resistor is therefore a way to do this
and it's now something new or unique. Also, the fan
I used is essentially like the one suggested previously
only slightly larger. It was a 2-in fan measuring from
side to side.

Bob — KK5R

--------------------------------------------

On Thu, 1/17/19, Tom, wb6b <wb6b@...> wrote:

Subject: Re: [BITX20] Cooling fan Shroud
To: BITX20@groups.io
Date: Thursday, January 17, 2019, 9:02 PM

Another easy solution is
to simply run the fan from the 12V transmit power, assuming
that is not what you are already doing. No reason to run the
fan while receiving.

Tom,
wb6b

Re: Unexpected measurements

Evan Hand
 

I did some testing on my v4 board and found interesting correlation (though not able to verify mathematical accuracy):

The lower the signal at TP1 in CW transmit, the lower the output power.  This would have nothing to do with the LPFs either in the front end prior to the transmit amps, nor on the output.

This went on until above 14mhz, where the power starting dropping with out a decrease in level at TP1.

To me this suggests that there is something in the way that the design unbalances the first mixer to allow for the "bleed through" of the changed frequency of Clock#2.

I then used a constant tone through my mic for the ubitx using a signal generator connected to a powered speaker.  I kept the postion of the mic constant and changed the bands.  With this test, the 7.2mhz signal had more power than the 14.3mhz signal.  This suggests that the transmit power that others and I have been measuring is not indicative of the SSB power.

Again, this points to the CW process of unbalancing the first mixer has having side effects that impact power on some of the bands.

I should also note that the signal I measured with my scope was not at all sine wave clean in CW mode. It was almost square.  Would also explain the large amount of harmonics that I have measured with my inexpensive RF Explorer SA.

At this point I will be going back and coming up with a better way to inject a 1 or 2 tone audio signal into the uBitx to then measure the harmonics.  

Has anyone else seen this type of behavior?

73
Evan
AC9TU

Re: Cooling fan Shroud

Tom, wb6b
 

Another easy solution is to simply run the fan from the 12V transmit power, assuming that is not what you are already doing. No reason to run the fan while receiving.

Tom, wb6b

Re: Unexpected measurements

Jerry Gaffke
 

You might check that the toroids for the 40m LPF have the correct number of turns
as described under "Coil Details" near the bottom of:  http://www.hfsignals.com/index.php/ubitx-circuit-description/

At least one board went out with the wrong number of turns:
    https://groups.io/g/BITX20/message/63947


Jerry, KE7ER



On Thu, Jan 17, 2019 at 01:14 PM, Evan Hand wrote:
Of the 3 boards (all v4) that I have had contact with, and the reporting of power to frequency on multiple BITX20 threads, the dip in power on 40 meters is fairly consistent.  No one has jet explained why, and as Jerry stated, it is further away from the LPF than the 30 meter band using the same LPF.

On the one board that I have tested for harmonics, 40 meters is the worst.  I believe that some of that is because the 3rd is below the 30mhz LPF that is in on all bands.  However why then is 80 meters not as bad?

There is something going on with the 40 meter CW transmit side that does not add up with the data that I have seen so far.

Anyone any ideas?

73
Evan
AC9TU

Re: Using 2nd Nano for S meter

wcars05
 

Hi Brian,

A few follow up questions after thinking about the setup process a bit more.

1) Which version of CEC did you flash to the radiuno?

2) Which display are you using?

3) Does the FFT/DSP1 display anything and is it set to use it in the config menu?

4) My signal level is usually very low, from playing with it I have enough capacitance to touch its input and get noise to show on the meter. I have mine setup inline with a TJC screen as per the instructions. The only hardware mods I have installed are the smeter and Nextion(TJC) display.

5) Have you looked at the settings in the uBitx Manager?

I have my CEC built with:

ubitx.h line 239

    "#define I2CMETER_ADDR     0x58"

And the smeter project as per Sacha's suggestion

i2cmeter1.h line 58

"#define I2CMETER_ADDR     0x58  //changed from 0x6A"

The comment at the end of line might be the key since I left the note about changing the address.

Good luck!

Kyle

KE8KNK


On 1/17/19 3:02 PM, Brian Arnott via Groups.Io wrote:
I wired up a second arduino nano to provide an s-meter using the "fun" design from KD8CEC (two 20k resistors and a capacitor). How do I assign an address to the second nano?
Right now it looks as though they are both on the same address, I've tried various combinations of the NX.hex and NX_S.hex without any success. 
Any help would be much appreciated.

de Brian G3YYT

Re: Using 2nd Nano for S meter

Sascha Bohnet | DL5SMB
 

I guess the DSP-S-Meter does not work, if you have installed an AGC, right?

I think it is evaluating the change in volume to calculate the Signal Level. So if the AGC keeps the audio level straight,
this does not work any more. Am I correct?

In the source code you set the adress in  i2cmeter.h (line 58)

Sascha

Re: Unexpected measurements

Evan Hand
 

Of the 3 boards (all v4) that I have had contact with, and the reporting of power to frequency on multiple BITX20 threads, the dip in power on 40 meters is fairly consistent.  No one has jet explained why, and as Jerry stated, it is further away from the LPF than the 30 meter band using the same LPF.

On the one board that I have tested for harmonics, 40 meters is the worst.  I believe that some of that is because the 3rd is below the 30mhz LPF that is in on all bands.  However why then is 80 meters not as bad?

There is something going on with the 40 meter CW transmit side that does not add up with the data that I have seen so far.

Anyone any ideas?

73
Evan
AC9TU

Re: Using 2nd Nano for S meter

wcars05
 

I used the version from the project repo. Built and flash it in the arduino ide.

Repo used:

https://github.com/phdlee/dspmeterv1

73

KE8KNK

On 1/17/19 3:02 PM, Brian Arnott via Groups.Io wrote:
I wired up a second arduino nano to provide an s-meter using the "fun" design from KD8CEC (two 20k resistors and a capacitor). How do I assign an address to the second nano?
Right now it looks as though they are both on the same address, I've tried various combinations of the NX.hex and NX_S.hex without any success. 
Any help would be much appreciated.

de Brian G3YYT

Re: Unexpected measurements

Jerry Gaffke
 

Could be a transmit low pass filter thing, all that stuff around relays KT1,KT2,KT3.
5mhz shares a LPF with 3.5mhz, so if the knee on that filter is a bit low it will attenuate 5mhz.
Likewise 18mhz shares a filter with 14mhz.
Maybe those inductors have too many turns, or wrong caps installed?

However, 10mhz shares a filter with 7mhz, and since it's the low freq that's attenuated 
this suggests something different s going on, but could still be in the LPF somehow.

I'd probably hack the firmware so the 30mhz LPF is always selected, it should then have little effect
on the lower frequencies.  Expect a nasty square wave at your dummy load (lots of harmonics)
but the anomalous readings on 5mhz, 7mhz and 18mhz will disappear if it's LPF trouble.

Jerry


On Thu, Jan 17, 2019 at 11:24 AM, Peter Russell wrote:
5Mhz and 21Mhz are a bit of a puzzle, but I'll delve a bit further and see what the drive levels are like.(Could this be a filter thing? I'm not sure what the bandpass filters are tuned to.)

Using 2nd Nano for S meter

Brian Arnott
 

I wired up a second arduino nano to provide an s-meter using the "fun" design from KD8CEC (two 20k resistors and a capacitor). How do I assign an address to the second nano?
Right now it looks as though they are both on the same address, I've tried various combinations of the NX.hex and NX_S.hex without any success. 
Any help would be much appreciated.

de Brian G3YYT

Re: Unexpected measurements

Peter Russell <peter.russell@...>
 

My power supply is home brew 5A with a big capacitor and a LM338.
I've done a bit more work and It seems that the problem was the factory setting of the drive preset.
I've just acquired a rather nice oscilloscope - OWON DS7102 - so I put it to use measuring the voltage at the output bnc connector (into 50 ohms).
Not having used a 'scope for about 20 years, I fell into the obvious trap of measuring the peak - peak voltages and calculating from that! Oh dear, I really should have known better.
Anyway, once I realised my mistake and did it properly, that led me to adjusting the drive level. I've now got it to a point where all bands are happy ( except top band, but who cares about that).
Measured values are now .....

3.5Mhz 6.05W
5 1.88
7 2.4
10 5
14 4
18 1.7
21 5
24 1.03
28 0.85

5Mhz and 21Mhz are a bit of a puzzle, but I'll delve a bit further and see what the drive levels are like.(Could this be a filter thing? I'm not sure what the bandpass filters are tuned to.)

Back to the workbench!

Peter G8FWY


On 17/01/2019 17:14, Curt via Groups.Io wrote:
I agree this seems weird.  You did not mention the type of power supply used nor its current, but perhaps its a good low noise supply used with your other rigs?
Of course to make more power, which is typical at lower frequencies, it must draw more DC current (and dissipate a bit less in heat perhaps).  I have no issues using my uBITX on 160m, into a dummy load or my decently matched vertical with a 3 amp supply made for ham radio use.
I would definitely checking the wiring for both RF and audio interfaces.  Make sure you don't have the ground connection on the board connected to the center pin of the antenna connector.  Please note there are 2 power supply connections - one is segregated to feed only the PAs - of course both need to be connected to your power supply.  I would look to see that audio ground is going to the expected place on the headphone jack.  Use very light audio gain for your testing, maybe 5 or 10% of the volume control should produce headphone audio of the sidetone.
The only other thing I can think of for buzzing is to inspect for any broken or missing capacitors.
As I write doing my own debug - its part of the journey.
Curt WB8YYY
---
This email has been checked for viruses by AVG.
https://www.avg.com

Re: Cooling fan Shroud

Evan Hand
 

I believe the point that Albert is making that it is better to have a quite fan that meets all of the requirements without any extra circuitry that can fail.  I would agree that if a noisy fan is the only choice, then putting in a controller to minimize the noise while still removing the heat is the next best solution.  If properly designed, installed, and tuned, then there would not be a change in the amount of heat that can be removed as the heat sinks get hotter.  I would caution that response time can get in the way of keeping cool quick enough to not cause an issue.  An always on at max fan does not have this issue.

My opinion, use as you see fit.

73
Evan
AC9TU

Re: Cooling fan Shroud

Doug W
 

On Thu, Jan 17, 2019 at 11:18 AM, Albert Peter wrote:
IMHO it is better to start with a capable quiet fan that does not require more circuitry.  It may cost a bit more, but is a simpler solution.
I totally agree with Al.  I have this fan https://www.digikey.com/product-detail/en/sunon-fans/HA60251V4-1000U-A99/259-1793-ND/ running arm's length away from me in a µBITX in an EF-01 enclosure on my desk.  It is so quiet I sometimes have to check that it is still working.
 
--
www.bitxmap.com