Date   

Re: DISASTER !!

LKNDAVE
 

the diode on the bottom of the nano. near the usb conn. i put in a 1n400xs, fixes most of them. stinky


Re: boosting the power on 28 MHz #ubitx

K9HZ <bill@...>
 

“However, the new PCB has pads for the RD16HHF1”

 

Thank you !!!!!!

 

 

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

 

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

 

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com

Like us on Facebook! facebook icon

 

Moderator – North American QRO Group at Groups.IO.

 

email:  bill@...

 

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of Ashhar Farhan
Sent: Sunday, May 6, 2018 6:14 AM
To: BITX20@groups.io
Subject: Re: [BITX20] boosting the power on 28 MHz #ubitx

 

Yes, the plan was to use an RD device for the new version. We ran into availability issues. The lead time from Mitsuibishi was 10 weeks. So, I took a call to continue with the IRF510s. However, the new PCB has pads for the RD16HHF1 as well as the IRF510s.

- f

 

On Sun, 6 May 2018, 16:05 G1KQH via Groups.Io, <g1kqh=yahoo.co.uk@groups.io> wrote:

Ashar,

Is this mod going to be implemented on new production?

Thanks!

73 Steve

G1KQH


Virus-free. www.avg.com


Re: ND6T AGC implementation for uBIT-X

K9HZ <bill@...>
 

Yes, you’ve got it.  The Nyquist sampling theory sets the limit of resolving the Power (and hence SWR), and the A/D rate needs to be faster than that or it won’t work properly. For a 3 KHz signal that’s about 10 KHz…and as you point out that’s above the default sampling rate.  58.6 KHz would be ok, but to get that rate probably assumes that the processor is dedicated to the task, not off doing other uBITx work, although there is probably some clever way to get the measurement pairs close to each other by ignoring some other operations momentarily.  Averaging is the only way to overcome this and, statistically, the quality of the answer depends on the symmetry of the wave form (e.g. will probably work perfectly for CW and be mixed for SSB).

 

 

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

 

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

 

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com

Like us on Facebook! facebook icon

 

Moderator – North American QRO Group at Groups.IO.

 

email:  bill@...

 

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of Jerry Gaffke via Groups.Io
Sent: Saturday, May 5, 2018 10:17 PM
To: BITX20@groups.io
Subject: Re: [BITX20] ND6T AGC implementation for uBIT-X

 

That's a good point, skew between ADC reads could trash the SWR readings.

I'd prefer to stick with a Nano analogRead() of the two TandemMatch detector signals somehow.
If it jumps around too much during SSB use, can just send CW for a second or two.
Or whistle into the mike.

This webpage says the Nano's analogRead() by default can sample at 8.9 khz.
However, by adjusting the ADC's prescaler, it can be cranked up to sample rate of 58.6khz.
By moving away from the analogRead() function and running the ADC in freerun mode,
he got the sample rate up to 76.8khz.  I don't know if freerun mode allows us to read 2 pins.
    http://yaab-arduino.blogspot.com/2015/02/fast-sampling-from-analog-input.html

I would guess this speedup will impact the accuracy of the ADC somewhat. 
Perhaps once each second during transmit we pump up the ADC prescaler for the
reads of forward and reverse power, then set it back to the default. 

If we can use the ADC at 50khz or more and the audio is changing at 3khz or less,
I doubt the SWR readings will jitter all that much. 
Perhaps we average all SWR readings taken over a period of a second,
then update the display with that average once each second. 

The power meter notes Bill pointed to in 
    https://groups.io/g/BITX20/files/K9HZ%20Projects/Notes%20on%20TF3LJ%20Power-SWR%20Meter%20by%20K5EMI.pdf
do suggest the cheap eBay AD8307's  have an anomaly not found in parts purchased from Mouser.
Though if the error is ever of concern, perhaps it could be calibrated out with a lookup table?
I wonder if those cheap parts could all use the same lookup table?
He was comparing only one cheap part against one Mouser part, so I'd guess it's real,
but it's not yet conclusive.

 

Jerry, KE7ER

On Sat, May 5, 2018 at 06:26 pm, K9HZ wrote:

Arv…

 

I’m quite familiar with the 8307 characteristics… there is a an effective 12.5K on chip resistor that forms part of a low-pass filter in shunt form basis that external capacitor.  It’s designed to reduce the ripple of the output and as I recall has a corner frequency of about 5MHz with the suggested capacitor (10 or 100nF from memory).  As you change the corner is also loads the output and changes the slope factor.  Not a big deal but you need to recalibrate.  It being faster than an analog meter is not really relevant and actually part of the problem.  What is relevant though, and what you see in the lab is that the P-forward resolved by the Nano A/D pin “x” finishes at “t” and P-reverse is resolved by Nano A/D pin “y” at “t+n” where “n” is what makes the difference.  Because of that filter above, it’s frequency dependent.  Most folks just calculate away for SWR and get a number and figure its right.  Might be.  Might not.  Someone actually wrote an article for QST on this.

 

Anyway… I tried.


Virus-free. www.avg.com


Re: Using MPSA18 darlington in the driver? #parts #ubitx

Ghericoan
 

Also have some MPSA13 coming in, those are the darlington, not the MPSA18, sorry about the confusion. Part number is pretty well the same except one number. 

The 13 is what I meant to ask about using in the drive circuit and realized that after checking the data sheets again this morning.

https://www.jameco.com/Jameco/Products/ProdDS/26489.pdf

That part has a really high hfe, which is what made me curious. On the range of 5000.
--
----------
N5WLF, Greggory (or my nickname, Ghericoan)
General Class, Digital Radio Hobbyist


Re: Using MPSA18 darlington in the driver? #parts #ubitx

Ghericoan
 

The hfe on these is typically 1150. Max is 1500, min is 500. I was curious as to if the higher gain might help with the drive on 30 meters and up.

https://www.jameco.com/Jameco/Products/ProdDS/210681.pdf
--
----------
N5WLF, Greggory (or my nickname, Ghericoan)
General Class, Digital Radio Hobbyist


Re: Using MPSA18 darlington in the driver? #parts #ubitx

LKNDAVE
 

my favorite to92 npn gain guy. bes
ide the xx390x twins the best transistor you can buy. tayda sells .12 each hfe ~400-500


Re: Need help understanding a line of code in ubitx_si5351.cpp (msxp2 = ...) #radiuno

David Feldman
 

Thank you, Jerry - that helps guide me through the code and chip documentation (I was getting puzzled at doing all of these computations in unsigned 32-bit integer space with overflows and stuff to worry about.)

Dave


Re: boosting the power on 28 MHz #ubitx

Ashhar Farhan
 

Yes, the plan was to use an RD device for the new version. We ran into availability issues. The lead time from Mitsuibishi was 10 weeks. So, I took a call to continue with the IRF510s. However, the new PCB has pads for the RD16HHF1 as well as the IRF510s.
- f

On Sun, 6 May 2018, 16:05 G1KQH via Groups.Io, <g1kqh=yahoo.co.uk@groups.io> wrote:
Ashar,

Is this mod going to be implemented on new production?

Thanks!

73 Steve

G1KQH


Re: boosting the power on 28 MHz #ubitx

G1KQH
 

Ashar,

Is this mod going to be implemented on new production?

Thanks!

73 Steve

G1KQH


Re: No PTT

Geoff Theasby <geofftheasby@...>
 

HI John & Jerry,

Now see other thread...

Geoff


On 2 May 2018 at 15:55, Geoff Theasby <geofftheasby@...> wrote:
Hi John,

I'm back! Loaded Arduino IDE on Ubuntu, but can't make it run. Been trying all afternoon. Hlelp!

Regards
Geoff

On 27 April 2018 at 15:31, Geoff Theasby <geofftheasby@...> wrote:
Hi both,

4.7k pullup resistors fitted to Raduino board as instructed. There is now 5 volts at the encoder pins A & B, which varies 0-5-0-5-0 as the tuning knob is turned. This makes no difference, the display does not change.

I will order a Nano or two, just in case.

I shall be out of touch for a couple of days, be back then.

Geoff

On 27 April 2018 at 12:07, John <vk2eta@...> wrote:
Hello Geoff,

Here is the beta version of the Diagnostic Software. It should at least get you started. Some instructions are in the README.MD file in the top directory.

Only main menu items 1 and 2 are implemented at this stage (core I2C tests and Analog I/Os).

I need to write a manual for this but I have been too busy coding it so that you could assess your Arduino..hihi

The main menu number 2 (Analogue inputs), brings a second level menu for testing the encoder inputs, the push button, the PTT, the Keyer and the spare analogue input.

Results are displayed in a horizontal bar graph with a scale from 0 to 5V representing the value read by the inputs. That way you can see how it matches the values your voltmeter indicates on the respective pin.

Results are shown only on changes to the values read, for example when rotating the encoder, pushing the PTT or the encoder push-button etc...

If no results are shown then your Arduino cannot read analogue inputs and it would mean plan-B unfortunately.

Let me know how you go with it.

All the best,

73, John (VK2ETA)





Re: Removing nano from radiuno #nano #radiuno #ubitx

Geoff Theasby <geofftheasby@...>
 


Hi John, Jerry etc,

After stumbling about in the dark, I realised I had not entered Newline or 57600 baud as required. I ran it again and Lo! 
1 gives "Equal inputs read by Arduino"
2 gives nothing
3 gives same as 1
4 gives scrolling display, saying "I see a dot, 1-2-3-4-5-"
5 gives scrolling display saying " 1-2-3-4-5-"

This is with the Raduino/display only, connected to USB on a Windows 7 laptop. 

Is this of any help?

Regards
Geoff G8BM



On 4 May 2018 at 12:01, Geoff Theasby <geofftheasby@...> wrote:
Hi John, 

I abandoned the Ubuntu installation and followed your excellent Windows instructions above. 
The display now reads "uBITX Diagnostic Version V0.1"

What now? I tried running the program and got "OEOFO OO OEOOX  COO OO IOA O OO OO"

Regards
Geoff



Re: 45Mhz crystal filter specification

freefuel@...
 

Hi Tim,

I'm interested to know how your connecting your SA to the circuit, from my recollection the majority of SA equipment has a 50 ohm input impedance, an input impedance that low is not conducive to hanging a probe off the circuit at any convient location. 

-Justin N2TOH  


ubitx_20.ino does not compile, anybody else encounter this? #ubitx-help #ubitx #arduino #firmware

freefuel@...
 

Has anyone else encountered a failure to compile the Arduino Sketch for the ubitx? I am getting an error code for some type of return in the menu portion of the code. 

-Justin N2TOH 


Re: ND6T AGC implementation for uBIT-X

K9HZ <bill@...>
 

Arv…

 

Hmmm… we should probably take this off-line at this point.  This has to do with A/D resolution time vs. filter time.

 

I’m rethinking…that diodes would be a better choice just because they are less complicated.  The transform to watts and SWR is still complex though and will eat some processing power in a Nano.

 

My tuner is prototyped and the hardware is done.  The firmware is in the writing stage… I’m waiting for Jack to finish his Jackal project and a another second follow-up project before I officially ask for his help in coding.  It can tune 100 watts from any source (meaning it can be stand-alone… or I2C linked to the uBITx), uses latching relays to conserve power for QRP, has a 1:4 transformer for very low loads like the illusive short length impedances at very low frequency (12 ohms), CL-LC swap for high-low impedance matches of us to almost 12,000 ohms,  an AD8302 to generate phase and magnitude information of the load impedance like a point on a smith chart and then calculates the LC transform directly and instantly… no clicking-clacking relays searching for lowest SWR.  SWR and power is calculated and can be retrieved over the I2C or analog via the onboard dedicated Arduino (for those interested, the LP-100A watt meter generates power and SWR readings this way).  There is also a low power tune mode Dig Out to save the relays and protect the transmitter by commanding lower power (works down to about 250 mW).  So far it fits on a 5”x3” board but I may be able to shrink it.  Stay tuned.

 

 

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

 

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

 

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com

Like us on Facebook! facebook icon

 

Moderator – North American QRO Group at Groups.IO.

 

email:  bill@...

 

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of Arv Evans
Sent: Sunday, May 6, 2018 12:05 AM
To: BITX20@groups.io
Subject: Re: [BITX20] ND6T AGC implementation for uBIT-X

 

Bill K9HZ

Not sure I follow your analysis.  The added capacitance lowers upper frequency limit by a significant amount.

You can even go as high as 0.1 MFD so that the detector output is filtered to virtually DC, leaving no HF

knee in the passband.  This does cause a charge period error unless there are multiple samples to charge
this capacitor.  Same thing applies to simple diode detection with it's post-detection filter capacitor. 

The Arduino ADC provides 1023 distinct voltage steps.  It's internal voltage reference is used for calibration.

With a maximum of 5V and 1023 steps this gives a minimum sensitivity of around 0.005V and 5V full scale.

That range and resolution seems adequate for most transmitter RF measurements.

 

It may be interesting to try using conventional diode detection with a small forward bias to overcome the

diode offset.  This is not usually done in conventional SWR bridges because they are mostly non-powered

units.  But if the SWR bridge is to be inside a powered transceiver then the bias is readily available.

Now that AD8307 prices are more reasonable this device may be a viable alternative detector but it's

log slope ADC requires a bit more complex software if you want to derive the full compliment of FWD and

REV power, FWD and REV SWR, RF Voltage, RF Current, and possibly RF Impedance. 

With either diode or AD8307 detectors it should be relatively easy to make the software support automatic

calibration.  Possibly this could be based on measurement of the known output of one of the Si5351a ports.

Using and displaying this output could also be a test point to verify that the synthesizer chip is actually

operating at normal levels.

 

Some time ago you mentioned work on a QRP ATU of your own design for use with BITX transceivers.  How
is that coming along?  Are you planning on including SWR and power measurement capability at both input

and antenna ends of this unit?  Might be interesting to include calculation and display of impedance, particularly

at the transmitter end of the ATU to help get a good 50 ohm match to the IRF510 finals and associated LPF.

As you know, impedance is important when using an LPF designed for a specific cut-off frequency in order to
make the LPF operate within its design parameters.

 

Arv  K7HKL
_._

 

On Sat, May 5, 2018 at 7:26 PM, K9HZ <bill@...> wrote:

Arv…

 

I’m quite familiar with the 8307 characteristics… there is a an effective 12.5K on chip resistor that forms part of a low-pass filter in shunt form basis that external capacitor.  It’s designed to reduce the ripple of the output and as I recall has a corner frequency of about 5MHz with the suggested capacitor (10 or 100nF from memory).  As you change the corner is also loads the output and changes the slope factor.  Not a big deal but you need to recalibrate.  It being faster than an analog meter is not really relevant and actually part of the problem.  What is relevant though, and what you see in the lab is that the P-forward resolved by the Nano A/D pin “x” finishes at “t” and P-reverse is resolved by Nano A/D pin “y” at “t+n” where “n” is what makes the difference.  Because of that filter above, it’s frequency dependent.  Most folks just calculate away for SWR and get a number and figure its right.  Might be.  Might not.  Someone actually wrote an article for QST on this.

 

Anyway… I tried.

 

 

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

 

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

 

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com

Like us on Facebook! facebook icon

 

Moderator – North American QRO Group at Groups.IO.

 

email:  bill@...

 

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of Arv Evans
Sent: Saturday, May 5, 2018 7:48 PM
To: BITX20@groups.io
Subject: Re: [BITX20] ND6T AGC implementation for uBIT-X

 

Bill K9Hz

Adding a small external capacitor (o.001 mfd) at the input of each ADC provides extra stabilization

versus time for the voltage samples.  This added capacitance can be thought of as part of the
detector filter.   The sample rate of an AVR Mega-328 is quite fast but this adds a bit more pre-hold
or averaging to the traditional sample-and-hold function. 

I would not worry about time shifting of ADC measurements because it is still faster than a ballistic
meter movement that we have all relied on for many years.  If you really want traditional mechanical
meter results you can slow down the sample rate or average several samples to arrive at an 

averaged voltage reading.

In addition to measuring forward power, reverse power, and RF voltage, you can measure RF current

by using a current-transformer (like those in the Stockton or Bruene bridge) to get a voltage reading

that translates from RF current.  This may be very interesting for those who are using a uBITX or QCX

Arv  K7HKL
_._

 

Arv  K7HKL
_._

 

 

On Sat, May 5, 2018 at 6:23 PM, K9HZ <bill@...> wrote:

The I2C isn’t all that important.  What is important is the sample and hold.  Otherwise your forward and reflected power signals can be time shifted and won’t make sense.  But maybe again, if accuracy isn’t important to you, this isn’t either.  Ten turns of any small transformer wire on the T50-43 or smaller core works perfect.

 

 

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

 

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

 

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com

Like us on Facebook! facebook icon

 

Moderator – North American QRO Group at Groups.IO.

 

email:  bill@...

 

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of Kees T
Sent: Saturday, May 5, 2018 6:59 PM
To: BITX20@groups.io
Subject: Re: [BITX20] ND6T AGC implementation for uBIT-X

 

The eBay sellers (many) are providing boards with AD8307s on them and also strips of AD8307 parts. On my mWattmeter II kit I provided a "matched set" of HP diodes which were forward biased with a few uA (AAA cell) to allow readings <1mW.....and it worked very well as measured in a local professional lab. I don't think that accuracy is required here. I can provide an I2C interface as Bill, K9CZ, suggested but don't know if that's really required here either.

I later gave the mWattmeter II design to Ron, W4MMP, for production because I got tired of making mWattmeter II kits. 

I realize Diz makes a coupler but this one would be smaller  ...maybe 1" x 1-1/2" and use the dual double #61 FT-37 size toroids with Faraday shield and 23 turns, which I found to work best. A LOT of coffee cup coasters were made during that time. I have an old schematic but it's in .bmp format and won't load into the Files section.  

73 Kees K5BCQ  

 

Virus-free. www.avg.com

 

 


Re: boosting the power on 28 MHz #ubitx

K9HZ <bill@...>
 

Thanks.  This confirms what we tried two months ago.

 

 

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

 

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

 

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com

Like us on Facebook! facebook icon

 

Moderator – North American QRO Group at Groups.IO.

 

email:  bill@...

 

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of Ashhar Farhan
Sent: Saturday, May 5, 2018 11:29 PM
To: BITX20@groups.io
Subject: Re: [BITX20] boosting the power on 28 MHz #ubitx

 

So, here are the final mods, 

Replace C81 from 0.1uf to 470pf

Replace R83 from 10 ohms to 2.2 ohm

(you can short R83 as well) 

Replace 97, R98 from 47 ohms to 220 ohms

Remove C261, C262. 

 

So, what happens is that removing the C261 and C262 increases the gain of the finals. They are run open. Hence greater gain at 28 mhz. 

However, the gain is very high at lower frequencies. So, in order to reduce the gain at the lower frequencies, the 0.1 uf cap is replaced by the 470 pf. As the frequency of the signal drops, less and less RF flows through the 470 pf, decreasing the gain of the predriver. 470 pf is not a magical value, 220 pf works almost as well. 

Here are the pictures at 14 mhz. The two tone test reveals 20 db IMDR, which is alright. If you want to see better, buy yourself two RD16HHF1s. 

 

- f

 

On Sat, 5 May 2018, 22:02 Kees T, <windy10605@...> wrote:

Are you able to measure compression for linear operation (SSB) ? Harmonic content and levels ?

73 Kees K5BCQ


Virus-free. www.avg.com


Re: boosting the power on 28 MHz #ubitx

Ashhar Farhan
 

Jerry,
The outputs are as follows (from the log book):
3.5 MHz - 12W
7 MHz - 14W
10 MHz - 11W
14 MHz - 10W
21 MHz - 7.8W
28 MHz - 4.4W
(The preset was kept at maximum)

- f


On Sun, May 6, 2018 at 10:14 AM, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:
Very cool, thanks for digging into this.
I tried various schemes in LT-Spice, but improving the final is more
difficult than it seems going in. 
I could seldom correctly predict the results I got.
Need to re-read a few chapters of EMRFD. 
And of course, real hardware is likely quite different than the simulation.

So is this still the previously reported  4W at 30m, 13W on 80m?

Would raising the PA-PWR voltage to 24v improve that IMDR?
Perhaps if keeping power down to something reasonable with RV1,
we could get by without up-sizing the heatsinks.

Jerry


On Sat, May 5, 2018 at 09:28 pm, Ashhar Farhan wrote:
So, here are the final mods, 
Replace C81 from 0.1uf to 470pf
Replace R83 from 10 ohms to 2.2 ohm
(you can short R83 as well) 
Replace 97, R98 from 47 ohms to 220 ohms
Remove C261, C262. 
 
So, what happens is that removing the C261 and C262 increases the gain of the finals. They are run open. Hence greater gain at 28 mhz. 
However, the gain is very high at lower frequencies. So, in order to reduce the gain at the lower frequencies, the 0.1 uf cap is replaced by the 470 pf. As the frequency of the signal drops, less and less RF flows through the 470 pf, decreasing the gain of the predriver. 470 pf is not a magical value, 220 pf works almost as well. 
Here are the pictures at 14 mhz. The two tone test reveals 20 db IMDR, which is alright. If you want to see better, buy yourself two RD16HHF1s. 
 
- f



Re: ND6T AGC implementation for uBIT-X

Arv Evans
 

Bill K9HZ

Not sure I follow your analysis.  The added capacitance lowers upper frequency limit by a significant amount.
You can even go as high as 0.1 MFD so that the detector output is filtered to virtually DC, leaving no HF
knee in the passband.  This does cause a charge period error unless there are multiple samples to charge
this capacitor.  Same thing applies to simple diode detection with it's post-detection filter capacitor. 

The Arduino ADC provides 1023 distinct voltage steps.  It's internal voltage reference is used for calibration.
With a maximum of 5V and 1023 steps this gives a minimum sensitivity of around 0.005V and 5V full scale.
That range and resolution seems adequate for most transmitter RF measurements.

It may be interesting to try using conventional diode detection with a small forward bias to overcome the
diode offset.  This is not usually done in conventional SWR bridges because they are mostly non-powered
units.  But if the SWR bridge is to be inside a powered transceiver then the bias is readily available.

Now that AD8307 prices are more reasonable this device may be a viable alternative detector but it's
log slope ADC requires a bit more complex software if you want to derive the full compliment of FWD and
REV power, FWD and REV SWR, RF Voltage, RF Current, and possibly RF Impedance. 

With either diode or AD8307 detectors it should be relatively easy to make the software support automatic
calibration.  Possibly this could be based on measurement of the known output of one of the Si5351a ports.
Using and displaying this output could also be a test point to verify that the synthesizer chip is actually
operating at normal levels.

Some time ago you mentioned work on a QRP ATU of your own design for use with BITX transceivers.  How
is that coming along?  Are you planning on including SWR and power measurement capability at both input
and antenna ends of this unit?  Might be interesting to include calculation and display of impedance, particularly
at the transmitter end of the ATU to help get a good 50 ohm match to the IRF510 finals and associated LPF.
As you know, impedance is important when using an LPF designed for a specific cut-off frequency in order to
make the LPF operate within its design parameters.

Arv  K7HKL
_._


On Sat, May 5, 2018 at 7:26 PM, K9HZ <bill@...> wrote:

Arv…

 

I’m quite familiar with the 8307 characteristics… there is a an effective 12.5K on chip resistor that forms part of a low-pass filter in shunt form basis that external capacitor.  It’s designed to reduce the ripple of the output and as I recall has a corner frequency of about 5MHz with the suggested capacitor (10 or 100nF from memory).  As you change the corner is also loads the output and changes the slope factor.  Not a big deal but you need to recalibrate.  It being faster than an analog meter is not really relevant and actually part of the problem.  What is relevant though, and what you see in the lab is that the P-forward resolved by the Nano A/D pin “x” finishes at “t” and P-reverse is resolved by Nano A/D pin “y” at “t+n” where “n” is what makes the difference.  Because of that filter above, it’s frequency dependent.  Most folks just calculate away for SWR and get a number and figure its right.  Might be.  Might not.  Someone actually wrote an article for QST on this.

 

Anyway… I tried.

 

 

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

 

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

 

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Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com

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Moderator – North American QRO Group at Groups.IO.

 

email:  bill@...

 

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of Arv Evans
Sent: Saturday, May 5, 2018 7:48 PM
To: BITX20@groups.io
Subject: Re: [BITX20] ND6T AGC implementation for uBIT-X

 

Bill K9Hz

Adding a small external capacitor (o.001 mfd) at the input of each ADC provides extra stabilization

versus time for the voltage samples.  This added capacitance can be thought of as part of the
detector filter.   The sample rate of an AVR Mega-328 is quite fast but this adds a bit more pre-hold
or averaging to the traditional sample-and-hold function. 

I would not worry about time shifting of ADC measurements because it is still faster than a ballistic
meter movement that we have all relied on for many years.  If you really want traditional mechanical
meter results you can slow down the sample rate or average several samples to arrive at an 

averaged voltage reading.

In addition to measuring forward power, reverse power, and RF voltage, you can measure RF current

by using a current-transformer (like those in the Stockton or Bruene bridge) to get a voltage reading

that translates from RF current.  This may be very interesting for those who are using a uBITX or QCX

Arv  K7HKL
_._

 

Arv  K7HKL
_._

 

 

On Sat, May 5, 2018 at 6:23 PM, K9HZ <bill@...> wrote:

The I2C isn’t all that important.  What is important is the sample and hold.  Otherwise your forward and reflected power signals can be time shifted and won’t make sense.  But maybe again, if accuracy isn’t important to you, this isn’t either.  Ten turns of any small transformer wire on the T50-43 or smaller core works perfect.

 

 

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

 

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

 

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com

Like us on Facebook! facebook icon

 

Moderator – North American QRO Group at Groups.IO.

 

email:  bill@...

 

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of Kees T
Sent: Saturday, May 5, 2018 6:59 PM
To: BITX20@groups.io
Subject: Re: [BITX20] ND6T AGC implementation for uBIT-X

 

The eBay sellers (many) are providing boards with AD8307s on them and also strips of AD8307 parts. On my mWattmeter II kit I provided a "matched set" of HP diodes which were forward biased with a few uA (AAA cell) to allow readings <1mW.....and it worked very well as measured in a local professional lab. I don't think that accuracy is required here. I can provide an I2C interface as Bill, K9CZ, suggested but don't know if that's really required here either.

I later gave the mWattmeter II design to Ron, W4MMP, for production because I got tired of making mWattmeter II kits. 

I realize Diz makes a coupler but this one would be smaller  ...maybe 1" x 1-1/2" and use the dual double #61 FT-37 size toroids with Faraday shield and 23 turns, which I found to work best. A LOT of coffee cup coasters were made during that time. I have an old schematic but it's in .bmp format and won't load into the Files section.  

73 Kees K5BCQ  

 

Virus-free. www.avg.com

 



Re: boosting the power on 28 MHz #ubitx

Jerry Gaffke
 

Very cool, thanks for digging into this.
I tried various schemes in LT-Spice, but improving the final is more
difficult than it seems going in. 
I could seldom correctly predict the results I got.
Need to re-read a few chapters of EMRFD. 
And of course, real hardware is likely quite different than the simulation.

So is this still the previously reported  4W at 30m, 13W on 80m?

Would raising the PA-PWR voltage to 24v improve that IMDR?
Perhaps if keeping power down to something reasonable with RV1,
we could get by without up-sizing the heatsinks.

Jerry


On Sat, May 5, 2018 at 09:28 pm, Ashhar Farhan wrote:
So, here are the final mods, 
Replace C81 from 0.1uf to 470pf
Replace R83 from 10 ohms to 2.2 ohm
(you can short R83 as well) 
Replace 97, R98 from 47 ohms to 220 ohms
Remove C261, C262. 
 
So, what happens is that removing the C261 and C262 increases the gain of the finals. They are run open. Hence greater gain at 28 mhz. 
However, the gain is very high at lower frequencies. So, in order to reduce the gain at the lower frequencies, the 0.1 uf cap is replaced by the 470 pf. As the frequency of the signal drops, less and less RF flows through the 470 pf, decreasing the gain of the predriver. 470 pf is not a magical value, 220 pf works almost as well. 
Here are the pictures at 14 mhz. The two tone test reveals 20 db IMDR, which is alright. If you want to see better, buy yourself two RD16HHF1s. 
 
- f


Re: boosting the power on 28 MHz #ubitx

Ashhar Farhan
 

I forgot the picture of the experiment.
- f

On Sun, 6 May 2018, 09:58 Ashhar Farhan, <farhanbox@...> wrote:
So, here are the final mods, 
Replace C81 from 0.1uf to 470pf
Replace R83 from 10 ohms to 2.2 ohm
(you can short R83 as well) 
Replace 97, R98 from 47 ohms to 220 ohms
Remove C261, C262. 

So, what happens is that removing the C261 and C262 increases the gain of the finals. They are run open. Hence greater gain at 28 mhz. 
However, the gain is very high at lower frequencies. So, in order to reduce the gain at the lower frequencies, the 0.1 uf cap is replaced by the 470 pf. As the frequency of the signal drops, less and less RF flows through the 470 pf, decreasing the gain of the predriver. 470 pf is not a magical value, 220 pf works almost as well. 
Here are the pictures at 14 mhz. The two tone test reveals 20 db IMDR, which is alright. If you want to see better, buy yourself two RD16HHF1s. 

- f

On Sat, 5 May 2018, 22:02 Kees T, <windy10605@...> wrote:
Are you able to measure compression for linear operation (SSB) ? Harmonic content and levels ?

73 Kees K5BCQ


Re: boosting the power on 28 MHz #ubitx

Ashhar Farhan
 

So, here are the final mods, 
Replace C81 from 0.1uf to 470pf
Replace R83 from 10 ohms to 2.2 ohm
(you can short R83 as well) 
Replace 97, R98 from 47 ohms to 220 ohms
Remove C261, C262. 

So, what happens is that removing the C261 and C262 increases the gain of the finals. They are run open. Hence greater gain at 28 mhz. 
However, the gain is very high at lower frequencies. So, in order to reduce the gain at the lower frequencies, the 0.1 uf cap is replaced by the 470 pf. As the frequency of the signal drops, less and less RF flows through the 470 pf, decreasing the gain of the predriver. 470 pf is not a magical value, 220 pf works almost as well. 
Here are the pictures at 14 mhz. The two tone test reveals 20 db IMDR, which is alright. If you want to see better, buy yourself two RD16HHF1s. 

- f

On Sat, 5 May 2018, 22:02 Kees T, <windy10605@...> wrote:
Are you able to measure compression for linear operation (SSB) ? Harmonic content and levels ?

73 Kees K5BCQ