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Yes, it was also something for the final DC block from the 6146 plate
voltage to work against.

Dave - W?LEV

On Tue, Aug 17, 2021 at 11:40 PM Brian D <
g3vgz-groups.io@...> wrote:

"David Eckhardt" <davearea51a@...> wrote:

I
remember my Novice transmitter, the Heathkit DX-40. It had a

large-valued

RF choke from the back of the PL-259 to chassis. The sole purpose of

that

RF choke was to keep voltages from building up on the feedline - same as
the resistor in question.

Manly to prevent dangerous voltages on the feedline due to breakdown in the
plate capacitor leaking HT onto the feedline, essential on high power valve
PAs.




--
Brian D
G3VGZ G8AOE G3T
IO94im

--
*Dave - W?LEV*
*Just Let Darwin Work*

"David Eckhardt" <davearea51a@...> wrote:

I
remember my Novice transmitter, the Heathkit DX-40. It had a large-valued
RF choke from the back of the PL-259 to chassis. The sole purpose of that
RF choke was to keep voltages from building up on the feedline - same as
the resistor in question.

Manly to prevent dangerous voltages on the feedline due to breakdown in the
plate capacitor leaking HT onto the feedline, essential on high power valve
PAs.




--
Brian D
G3VGZ G8AOE G3T
IO94im

Hi Vladimir, Larry, and Group:

Thanks so much for your advice. The references that you sent basically go in the direction of using the Cypress driver. I tried this, but to no avail - also get similar symptoms as with the STM driver. Given that I get the yellow warning triangle when I install the driver, i.e. before the VNA is connected, my guess is that the problem is at the Windows level, rather than at the nanoVNA level.

Has anyone else experienced (and overcome) this problem?

Regards,
Ray
4X1RB

From the home of
Prof. Emeritus Raymond (Reuven) Boxman
School of Electrical Engineering
Tel Aviv University
Cell: ???? +972 544 634 217

CEO Clear Wave Ltd.? ?????????????
Scientific Writing Courses: ???????

Search the group for "traps". Several posts on this topic.

Roger

I wondered if anyone has measured Mosley traps with the NanoVNA? I have one on order.
Currently I used a MFJ259c to try to get some results.

I took the trap apart and put a 50 pica farad in series to measure a frequency but cannot measure the trap inside the tube. It has two parallel traps in a typical Mosley trap. The cap was used to at least measure the inductors.
Goal is to measure the Mosley trap frequency of each trap.

Dear Vladimir,
Thank you for your suggestion. I will look into it today.
73
Ray
4X1RB

From the home of
Prof. Emeritus Raymond (Reuven) Boxman
School of Electrical Engineering
Tel Aviv University
Cell: ???? +972 544 634 217

CEO Clear Wave Ltd.? ?????????????
Scientific Writing Courses: ???????

On Wed, Dec 11, 2019 at 03:19 AM, <nanovnauser@...> wrote:

think its more about the guys ego

I have a lot of respect for the gentleman in question. He must be independently wealthy as he seemingly tests every multimeter in existence and then posts the results of his testing for FREE. I have never asked any questions of him, but he seems very courteous and knowledgeable and giving in his replies he posts.

Hopefully, disparagement will get you nowhere! It is his to do with what he wants. Perchance remarks like yours dissuades him - why deal with people who .........

Larry

Hi DiSlord, numbering instead of random "RTC" naming is a great idea, but I understand it may not be easy to implement, need to add reading files and "logic".

An updated fw v1.0.69 from 31.7 with "ulocked uSD Card" is available somewhere. ? Thank you for your work.

Thanks for the suggestion! I will investigate it later today....

Ray

From the home of
Prof. Emeritus Raymond (Reuven) Boxman
School of Electrical Engineering
Tel Aviv University
Cell: ???? +972 544 634 217

CEO Clear Wave Ltd.? ?????????????
Scientific Writing Courses: ???????

Just wondering if you hit the parts you're testing with a heat gun and/or freezing spray to see how how well the consumer level parts react.

DiSlord,
For the V2 Plus units with no RTC, can the SDcard filenames be read and the next file saved has its last character incremented by one?

This assumes a fully numeric filename so there are no illegal ascii chars used.

Keep it simple so that on a unit with no RTC, all screen dumps and S files stored would be start with a filename of "00001" and be incremented from there.
That would solve the issue on the V2 devices and should only be active on those devices.
...Larry

This is the code I use to find the PLL min/max limits, but any desired code will do ..

uint32_t si5351a_pllLocked(const uint8_t pll, const uint32_t timeout_us)
{
uint8_t pll_bit;
uint32_t locked_cycles = 0;

if (rev_id == 0 || pll >= 2)
return 0; // error

switch (pll)
{
default: return 0;
case 0: pll_bit = 1u << 5; break; // PLL-A
case 1: pll_bit = 1u << 6; break; // PLL-B
}

if (timeout_us > 0)
{ // wait for the PLL to lock (with timeout)
uint32_t lock_cycle = 0;

//ITM->LAR = 0xC5ACCE55; // unlock the debug registers
//CoreDebug->DEMCR |= CoreDebug_DEMCR_TRCENA_Msk; //
DWT->CTRL |= DWT_CTRL_CYCCNTENA_Msk; // turn on the cycle counter
const uint32_t start_cycle = DWT->CYCCNT; //

const uint32_t timeout_cycles = ((uint64_t)SystemCoreClock * timeout_us) / 1000000;
const uint32_t lock_cycles = ((uint64_t)SystemCoreClock * 10) / 1000000; // PLL needs to stay locked for at least 10us

while (1)
{
const uint32_t cycle = DWT->CYCCNT;
const uint32_t cycles = cycle - start_cycle;

if (cycles >= timeout_cycles)
break; // timed out

if (si5351a_read(SI5351_DEV_STATUS) & pll_bit)
{ // unlocked
lock_cycle = 0;
locked_cycles = 0;
continue;
}

if (lock_cycle == 0)
lock_cycle = cycle; // start of lock

// length of time it's been locked
locked_cycles = cycles - lock_cycle;

if (locked_cycles >= lock_cycles)
break; // been locked for long enough
}
}

return (si5351a_read(SI5351_DEV_STATUS) & pll_bit) ? 0 : ((uint64_t)locked_cycles * 1000000) / SystemCoreClock; // 0 = unlocked, otherwise return the time it took to lock
}

void si5351a_findVCOLimits(void)
{ // scan the PLL's VCO's across a frequency range to find their min and max tuning limits

const uint32_t start_Hz = xtal_Hz * 15;
const uint32_t stop_Hz = xtal_Hz * 90;
const uint32_t step_Hz = 20000000; // step the PLL's in 20MHz steps .. seems as good as any?
/*
uint32_t min_lock_time_us = 0;
uint32_t max_lock_time_us = 0;
*/
uint8_t pll;

min_pll_Hz = 0;
max_pll_Hz = 0;

// scan both PLL's across a wide frequency range
for (pll = 0; pll < 2; pll++)
{
uint32_t min_Hz = 0;
uint32_t max_Hz = 0;

uint32_t fvco_Hz = start_Hz;

// disable PLL INTEGER mode
si5351a_write(SI5351_CLK_CONTROL + 6 + pll, si5351a_read(SI5351_CLK_CONTROL + 6 + pll) & ~(1u << 6));

// scan from low to high frequency
while (fvco_Hz <= stop_Hz)
{
uint32_t pll_a;
uint32_t pll_b;
uint32_t pll_c;

// calculate the PLL register values
const uint32_t vco_Hz = calcPLL((uint64_t)fvco_Hz * SI5351_FREQ_MULT, &pll_a, &pll_b, &pll_c) / SI5351_FREQ_MULT;

if (vco_Hz == fvco_Hz)
{
// set the PLL registers
si5351a_setPLL(pll, pll_a, pll_b, pll_c, 1);

// see if the PLL locks OK
const uint32_t lock_time_us = si5351a_pllLocked(pll, 1500); // wait for up to 1.5ms for the PLL to lock .. avg around 618us, max around 1200us

if (lock_time_us > 0)
{ // PLL acquired lock at this particular frequency
if (min_Hz == 0)
min_Hz = vco_Hz; // remeber the min frequency
max_Hz = vco_Hz; // remeber the max frequenct
}
}

fvco_Hz += step_Hz;
}

if (min_pll_Hz == 0 || min_pll_Hz < min_Hz)
min_pll_Hz = min_Hz;

if (max_pll_Hz == 0 || max_pll_Hz > max_Hz)
max_pll_Hz = max_Hz;
}
}

On Wed, Jun 30, 2021 at 11:31 AM, DiSlord wrote:

Disable calibration, set frequency range 280-300MHz
See frequency point there start this
Change THRESHOLD frequency to this (avaible in expert menu settings).

I've been using the Si5351 in another project and decided to test the chip at boot-up to find each individual chips (Si5351) possible PLL frequency range rather than having the 300MHz parameter be user settable.

All I do is to do a quick boot-up sweep of each PLL (A and B) in the chip to find their min and max frequencies by monitoring the PLL lock bit in the chip. Each PLL typical takes around 600us to lock to a desired frequency, so if it takes longer than say 1ms to lock then I take that as being the PLL's min and max limits. I'm finding the PLL's usable frequency range (specified as 600MHz to 900MHz) in each can vary by quite a bit, so auto finding the real limits is very useful and handy. Rather than storing the min/max PLL limits for each of the two PLL's I use the same min/max limits for both PLL's - a range that reliably works for BOTH PLL's (ie, I use the worse case min/max scanned frequency range from the two PLL's).

Doing this in the NanoVNA's when the user turns the device on would remove the guess work, chip variation, temperature PLL lock range dependency and the user command etc from the equation. Each individual unit would auto self select the 300MHz switch point. Could still keep a manual settings if desired I guess.

Yes, old files will overwriting by new

If the file names can be repeated, can older files with the same name be overwritten or is there a "fuse" ? It's a small probability, though...

Tono OM1AEG

On Mon, Aug 16, 2021 at 05:22 PM, Syd wrote:

The link to the pdf file doesn't work for me. And looking again at the TDR
menus, I would think that to measure coax cable length, opens and shorts the
low pass impulse mode should be used.

The Agilent app note is attached.

Roger

The link to the pdf file doesn't work for me. And looking again at the TDR menus, I would think that to measure coax cable length, opens and shorts the low pass impulse mode should be used.
syd

A 2-watt carbon composition resistor has a rated breakdown of only 2 kV.
Inductance really does not matter in this application as we're dealing with
DC and slow bleed of possible accumulating voltages. The complex portion
of the complete impedance expression does not exist for DC. The ±j term
only applies to AC, not DC.

Another application of the "bleed resistor" or inductor: I've lost MMIC
preamps and LNA's due to close-by lightning strikes. These strikes
notoriously induce intense close-by RF fields which can permanently damage
these MMICs. Once I lost enough of them, I started installing a 1 k or 10
k resistor across the input connector with as short of leads as possible,
usually effectively leadless. Since I've made that a practice on my home
brew MMIC LNAs, I've not lost a single one. Even the J-310 series is
susceptible to this failure and can easily be treated with the shunt
resistor. I prefer using the resistor rather than the inductor. Manty
inductors can introduce hits on the noise figure of the MMICs. Resistors
generally when installed properly do not exhibit resonances anywhere near
the frequencies of interest where inductors may.

Dave - W?LEV

On Mon, Aug 16, 2021 at 9:39 PM David Platt <dplatt-groups@...>
wrote:

One useful solution is to use a shunt resistor or a shunt inductor. Many
antenna installations will include a resistor or a choke from the "hot"
side of the coax to ground. The impedance of the shunt element is selected
to be high enough that it's effectively "invisible" to the frequencies of
interest, but low enough that it allows (high-voltage, low-current) static
electricity to drain away safely to ground.

If, for example, you want to measure a typical 50-ohm-nominal antenna
system which has BNC or "UHF" connectors, buy yourself a "T" adapter for
the connector type you use, and buy a spare male plug of that sort as
well. Solder a 10k or 100k-ohm resistor into the spare plug, and (at the
same time) solder a length of wire and a ground clip to the "shell" side of
the connector. When you want to measure an antenna, first clip the ground
wire of the T adapter to a good ground, and then connect the antenna wire
to one arm of the T. This will ground the coax braid, and allow any static
buildup on the inner conductor to drain away through the drain resistor.
Then, connect the other arm of the "T" to your measurement device (e.g.
nanoVNA). 100k in parallel with the actual feed-point impedance won't make
a measurable difference in what you read.

This is one instance in which old-style "carbon composition" resistors are
very well suited - they're non-inductive, and they tend to be tolerant of
high-voltage spikes. The fact that they're often noisy and "drifty"
matters not at all in this application.

--
*Dave - W?LEV*
*Just Let Darwin Work*

One useful solution is to use a shunt resistor or a shunt inductor. Many antenna installations will include a resistor or a choke from the "hot" side of the coax to ground. The impedance of the shunt element is selected to be high enough that it's effectively "invisible" to the frequencies of interest, but low enough that it allows (high-voltage, low-current) static electricity to drain away safely to ground.

If, for example, you want to measure a typical 50-ohm-nominal antenna system which has BNC or "UHF" connectors, buy yourself a "T" adapter for the connector type you use, and buy a spare male plug of that sort as well. Solder a 10k or 100k-ohm resistor into the spare plug, and (at the same time) solder a length of wire and a ground clip to the "shell" side of the connector. When you want to measure an antenna, first clip the ground wire of the T adapter to a good ground, and then connect the antenna wire to one arm of the T. This will ground the coax braid, and allow any static buildup on the inner conductor to drain away through the drain resistor. Then, connect the other arm of the "T" to your measurement device (e.g. nanoVNA). 100k in parallel with the actual feed-point impedance won't make a measurable difference in what you read.

This is one instance in which old-style "carbon composition" resistors are very well suited - they're non-inductive, and they tend to be tolerant of high-voltage spikes. The fact that they're often noisy and "drifty" matters not at all in this application.

I'm glad to hear that the memory card worked, I also really missed this opportunity, so I implemented it for myself (but use different hardware, in it SD card already installed and 32768 xtal present and RTC work).

Unfortunately, the hardware in v2 does not allow the clock to start, and because of this, the file names (RTC used for create filename) may be repeated (the clock starts to run again when starting from 0)