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Re: ND6T AGC implementation for uBIT-X

 

Jerry,

What is the goal here? Is a wattmeter function really needed inside the
ubitx? Or would it be better as an external attachment that can be used
with other equipment?

For me, measurement of the reverse power is the primary measurement
needed inside the ubitx. It is useful for adjusting an external tuner
and for deciding if the ubitx is at risk from a bad load. I am using
the simple circuit at the nd6t site to get the reverse power
measurement. Right now I am using an external analog meter but I have
an adafruit ADS1015 that I am going to use when I get my ubitx working
again. I am using a little 4x4 breadboard to make an I2C bus expander
and the ADS1015 will feed into this along with the I2C lcd.

Coding for this is extremely simple. You don't even have to convert to
volts. Just display the reading from the ads1015. As it goes down you
know the reverse power is going down. If you want to do it with an
analog pin on the nano you can do that too.

Just my 2cents. FWIW.

On Sat, 05 May 2018 15:52:36 -0700
"Jerry Gaffke via Groups.Io" <jgaffke@...> wrote:

Kees,

Consensus on the EMRFD yahoo group was that the ebay AD8307's worked
fine:

Some posts there are guessing that when boards get autostuffed from
reels there are often a few parts remaining at the end of the reel,
and the ebay sellers make the remnants available cheaply. Though if
that were truly the case, I'd expect more parts to get sold at 95%
off list price like that.

Diz already has a Stockton/TandemMatch kit at what I think is a
reasonable $12 plus shipping:
Shipping probably has to be
more than $0.70 because of the toroids. Uses 1n5711 schottky diode
detectors.

I mentioned here that I was planning to substitute a couple AD8307's
but Arv convinced me to first try biasing the 1n5711's to make them
more sensitive. /g/BITX20/message/47628
You probably already saw that, it's in this same thread.

I wrote Nano code for the Tandem Match? to display forward and
reverse power in Watts, also SWR. but it's also a major rewrite of
all the uBitx code and I got lost in the weeds fiddling with other
stuff for a few weeks.? I'll try to get my code going in the next few
days. The AD8307's would give more dynamic range, but I think the
1n5711's with bias will be plenty polite. Displaying Watts and SWR
from the AD8307's linear-in-dB output would be slightly more
difficult on our computationally challenged Nano.? I'm planning to
use A6 and A7 for the bridge, move the paddle to digital pins D0 and
D1 (which are currently unused except when downloading firmware).

Anybody worried about smoking their expensive RD16HHF1 FET's could
use the reflected power reading to shut down the transmitter when
their EFHW antenna falls to the ground in the wind.? ? ;-)

Jerry, KE7ER

On Sat, May 5, 2018 at 01:30 pm, Kees T wrote:


I just uploaded the current AGC and Click kit requests. This list
is to help me asses demand so I can have the correct sets of parts
ready. There does not appear to be much demand for boards only,
just complete kits.?

I'll post prices later, when I receive the boards and some testing
is done.?

I was looking into Don's ND6T Polite Antenna Tuner, but there does
not appear to be much interest and using it effectively may be a
problem, so it's out. I did receive a request for a "Power Level
Upgrade" kit but decided against that because there is a whole lot
of testing to be done when you get into RF Amplification.

What may make sense, unless it's already out there as an add-on
upgrade kit, is a Power/SWR capability using? a simple Stockton
Bridge and a couple of AD8307's. I'm quite familiar with the bridge
and the AD8307 parts are getting really cheap <$0.50 each. Wonder
if those Chinese parts are usable at QRP specs ? Would need two
analog inputs on whatever microcontroller .......and, of course,
the ever present requirement for *someone* to provide support
firmware.?

73 Kees K5BCQ
Re: ND6T AGC implementation for uBIT-X

 

Here's my unproven code for displaying forward and reverse power in Watts
plus SWR on the bottom line of the 16x2 LCD, when using a TandemMatch with diode detectors.
It's actually quite simple and not computationally expensive..? Hereby released under GPL v3.0

Could be made more accurate by adding the schottky diode drop to the two voltage readings.
Assuming the transformer turns ratios are kept at 10:1, the SWR should be reasonably accurate
without calibration.? Especially if a few uA of bias is added to the diodes.
Power readings should be reasonably accurate if the SWR is close to 1:1
since they assume a 50 ohm load.

Maximum analogRead() return value is 1023, and represents a peak RF voltage of 5 volts.
Given the 10:1 turns ratio and assuming there is zero reflected power, that's an RF peak
voltage at the antenna jack of 50 volts, and an rms RF voltage of? 50/sqrt(2).? Assuming an
antenna load of 50 ohms, that's a power of? ?(50/sqrt(2)) * (50/sqrt(2)) / 50 ohms = 25.0 watts.
From this, we determine the value of PSCALE in the code below.

Using the linear-in-db ad8307 could be done with the same code, but first using
a table lookup to convert to RF volts.
I don't really want to be computing anti-logs on a Nano.
A table lookup will burn some flash.

################################################################
// Print val as d digits with r digits after the decimal point
// Will print any leading zeros, if r==0 then no decimal point
void pnum(uint32_t val, uint8_t d, uint8_t r) {
? uint32_t? div=1;
? uint8_t? ?n;?
? for (n=1; n<d; n++)? div*=10;
? while (div>0) {
? ? if (d--==r)? ?lcd.print('.');
? ? ? ? lcd.print((val/div) + 0x30);
? ? val = val%div;
? ? div = div/10;
? }
}
?
// Read TandemMatch's 2 detectors, display forward and reverse power, swr
#define PSCALE? (1023L*1023/(25*10)) // ADC max of 1023 is 25 Watts, display Watts*10
void? show_swr() {? // SWR = (1+1.0*vr/vf)/(1-1.0*vr/vf);
? uint32_t vr, vf, swr; // Voltage squared proportional to power
? vf = analogRead(RF_FWD); // Peak RF volts from forward detector
? vr = analogRead(RF_REV); // Peak RF volts from reverse detector
? if (vr>=vf) swr=0; // If vr,vf illegal, force SWR to zero
? else {
? ? swr = (vr*1024)/vf; // Voltage ratio, 10 fractional bits
? ? swr = (1000*(1024+swr))/(1024-swr); // 1000*swr, nearly 10 fractional bits
? ? swr = (swr+50)/100; // 10*swr, rounded to nearest tenth
? ? if (swr>99) swr=99;? // Display a max SWR of 9.9
? }
? lcd.setCursor(0, 1); // Fill bottom LCD line, example:
? lcd.print('f'); pnum(vf*vf/PSCALE,3,1); // "f12.4 r03.1 s1.7"
? lcd.print('r'); pnum(vr*vf/PSCALE,3,1); // with fwd,rev power in watts
? lcd.print('s'); pnum(swr,2,1); // and swr to max of 9.9
}
#################################################################

My primary reason not to mess with ad8307's is that they are harder to dead bug.
If the timing skew between forward/reverse readings is an issue, I'd definitely try the cap.
Likely still accurate enough.?

Bill wrote:

>?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,


We currently use a blocking analogRead() in many places in the code, each taking over 100us.
And in some cases do it constantly for stuff such as inspecting switches or keyer paddles.
So speeding up the analogRead() by a factor of 5 and occasionally (once per second?)?
reading the forward and reverse power should not be much of a burden, even if averaging
a half dozen reads.?

Should be possible to set up the ADC to be interrupt driven, an interrupt service
routine updates a list of all ADC readings.? In mainline code, we'd then disable interrupts
and read those last few forward and reverse readings to take an average.? Since we
are no longer blocking for each 100us+ analogRead(), this would be much less a timing burden.

Things may eventually slow down too much for somebody trying to use the keyer at 40wpm.
Otherwise I doubt there will be much of an issue with a lost millisecond here and there.
And I'm inclined to avoid interrupts till they are absolutely needed, as they are prone to?
errors that would be inscrutable to the several thousand new programmers we want to
be playing with this code.

Jerry, KE7ER?


On Sat, May 5, 2018 at 10:45 pm, K9HZ wrote:

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.
Re: 45Mhz crystal filter specification

 

I'm using a direct probe. The 815 has a 50ohm input which should be a
match to most points in the ubitx. At least a close enough match to not
directly affect the circuits operation. I suppose I could use a 10x
scope probe but I'm not sure that would make much difference.

tim ab0wr

On Sun, 06 May 2018 01:03:42 -0700
freefuel@... wrote:

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
FW: [BITX20] RD16HHF1 power curve flattening...some

 

¿ªÔÆÌåÓý

Ashhar¡­ see this result too.? The PA output transformer is sub-optimal so some of us have found.? Needs to be 2T:3T and frequency compensated by a cap across the primary.? My simulations show something in the 330-450pf range as optimal for this configuration, but that is through simulations.

?

?

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

?

Owner - Operator

Big Signal Ranch ¨C K9ZC

Staunton, Illinois

?

Owner ¨C Operator

Villa Grand Piton ¨C J68HZ

Soufriere, St. Lucia W.I.

Rent it:

Like us on Facebook!

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Moderator ¨C North American QRO Group at Groups.IO.

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email:? bill@...

?

?

From: [email protected] [mailto:[email protected]] On Behalf Of John
Sent: Wednesday, March 21, 2018 6:42 AM
To: [email protected]
Subject: Re: [BITX20] RD16HHF1 power curve flattening...some

?

Hello Nik,

How did you go with the feedback issue?

My power amp mods in summary:? finals as RD16HHF1s, feedback resistors R261/R262 as 820 Ohms, Transformer 2T primary / 3T secondary on BN43-202, 180pF across the output transformer primary and 330pf across R87/R88. That's all...in a way.

Heavily inspired by Erhard's (DF3FY) information as displayed on uBitx.net.

Results per band at 14V supply, RV1 at %60, RD16's biased at 250mA each:
Band? ? ? output power? ?Total current
80M? ? ? ? 22W? ? ? ? ? ? ? ? ? ? ? ? ?2.9A
40M? ? ? ? 20W? ? ? ? ? ? ? ? ? ? ? ? ?3.2A
30M? ? ? ? 16W? ? ? ? ? ? ? ? ? ? ? ? ?2.3A
20M? ? ? ? ?16W? ? ? ? ? ? ? ? ? ? ? ? 2.7A
17M? ? ? ? ?15W? ? ? ? ? ? ? ? ? ? ? ? 2.4A
15M? ? ? ? ?12W? ? ? ? ? ? ? ? ? ? ? ? 1.6A
12M? ? ? ? ?12W? ? ? ? ? ? ? ? ? ? not measured
10M? ? ? ? ?12W? ? ? ? ? ? ? ? ? ? ? ? 1.7A

At 22W the output transformer does get warm but not the LPFs.

Wound back RV1 to get 9-10W on the high frequency bands and 16-18W on the lower ones.

All the best,

73, John (VK2ETA)


Virus-free.

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

 

It is admittedly obtuse code.??
Pretty much by nature, as the registers on the si5351 are rather obtuse.
But I convinced myself it was correct (with no overflows) before releasing it.
I doubt most users of other si5351 libraries ever manage to figure them out either.

I invented the scheme for downshifting b and c of (a+b/c) till c fits in its 20 bit register
as a way of doing these computations in 32 bit integer math.? But later found a
similar trick in apnotes for sister part si5338, so the technique has been blessed by SiLabs.
The si5338 notes were created before my re-invention.

A new set of eyes may find bugs I didn't see.
Let me know if you find anything.
Or have any further questions.

Everyone incorporating my code feels obliged to make minor changes to style.
The original code is in? ??/g/BITX20/files/KE7ER/si5351bx_0_0.ino

There are errors and inconsistencies and omissions in that AN619 doc.
In particular, the Fvco/Fout ratio of (a+b/c) is restricted to values of 8.0 through 1800.0
inclusive, it's also possible to special case integer values of 4 and 6 but we do not use that.
The PLL msynth ratio is of course restricted to those values of Fvco/Fxtal that give a Fvco
of 600-900 mhz, so for an Fxtal of 25mhz that's values between 24.0 and 36.0 inclusive.??
Register 36 is shown incorrectly in the summary on page 36.
And the document does not give enough information about which registers need to be initialized.
The ClockBuilderPro software from SiLabs can help resolve some of that, but does some stuff
not documented at all in AN619, initializes registers that don't need it, and hunts for elusive
msynth register values using small integers in b and c but avoids the msynth's integer mode.??

Jerry, KE7ER



On Sun, May 6, 2018 at 05:30 am, David Feldman wrote:
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.)
Re: ND6T AGC implementation for uBIT-X

 

On Thu, Apr 26, 2018 at 06:26 pm, Ion Petroianu, VA3NOI wrote:


Thanks...I've downloaded...I'll check it out.

V
n2aie
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

 

¿ªÔÆÌåÓý

¡°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 ¨C K9ZC

Staunton, Illinois

?

Owner ¨C Operator

Villa Grand Piton ¨C J68HZ

Soufriere, St. Lucia W.I.

Rent it:

Like us on Facebook!

?

Moderator ¨C North American QRO Group at Groups.IO.

?

email:? bill@...

?

?

From: [email protected] [mailto:[email protected]] On Behalf Of Ashhar Farhan
Sent: Sunday, May 6, 2018 6:14 AM
To: [email protected]
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=[email protected]> wrote:

Ashar,

Is this mod going to be implemented on new production?

Thanks!

73 Steve

G1KQH


Virus-free.

Re: ND6T AGC implementation for uBIT-X

 

¿ªÔÆÌåÓý

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 ¨C K9ZC

Staunton, Illinois

?

Owner ¨C Operator

Villa Grand Piton ¨C J68HZ

Soufriere, St. Lucia W.I.

Rent it:

Like us on Facebook!

?

Moderator ¨C North American QRO Group at Groups.IO.

?

email:? bill@...

?

?

From: [email protected] [mailto:[email protected]] On Behalf Of Jerry Gaffke via Groups.Io
Sent: Saturday, May 5, 2018 10:17 PM
To: [email protected]
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.
? ??

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?
? ? /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:

´¡°ù±¹¡­

?

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.

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

 

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.



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

 

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

 

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

 

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=[email protected]> wrote:
Ashar,

Is this mod going to be implemented on new production?

Thanks!

73 Steve

G1KQH

Re: boosting the power on 28 MHz #ubitx

 

Ashar,

Is this mod going to be implemented on new production?

Thanks!

73 Steve

G1KQH
Re: No PTT

Geoff Theasby
 

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
 


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

 

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

 

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

 

¿ªÔÆÌåÓý

´¡°ù±¹¡­

?

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 ¨C K9ZC

Staunton, Illinois

?

Owner ¨C Operator

Villa Grand Piton ¨C J68HZ

Soufriere, St. Lucia W.I.

Rent it:

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

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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.

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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.

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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.

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Arv? K7HKL
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On Sat, May 5, 2018 at 7:26 PM, K9HZ <bill@...> wrote:

´¡°ù±¹¡­

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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.

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Anyway¡­ I tried.

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

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Owner - Operator

Big Signal Ranch ¨C K9ZC

Staunton, Illinois

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Owner ¨C Operator

Villa Grand Piton ¨C J68HZ

Soufriere, St. Lucia W.I.

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email:? bill@...

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

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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

transceivers for VLF.??? <>

Arv? K7HKL
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Arv? K7HKL
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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.

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

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Owner - Operator

Big Signal Ranch ¨C K9ZC

Staunton, Illinois

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Owner ¨C Operator

Villa Grand Piton ¨C J68HZ

Soufriere, St. Lucia W.I.

Rent it:

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

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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??

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