Re: Analysing Input Impedance Matching Circuit for the NE602
With my newly wound transformers, 1 to 8 ratio, I now get the following results (see images) when they are placed back to back.
As shown in the S21 plot I am getting a loss of 3 to 6dB
The matching on the smith chart is also pretty far off, at 7.15MHz it is about 27 ohms
I have done the experiment as shown in where I wound 2:5 turns and terminated it in 330 ohms (the page says 470 ohms but when I calculate the secondary impedance with this ratio and 50 ohms on the primary it comes out at just over 300 ohms) - I will put up these results in a separate reply.
|
Herb,
I've been waiting for the V2 since I read the outlined specification in fall. My main interests are in 20m, 2m, 70cm bands and I'd like to be able to probe 1.575GHz as well, hence my wait for a 3GHz version. I was willing to risk it for the price and test it myself, but since the situation with the shipping is what it is, I'll most likely get to see the first reviews before I order after all.
Tomas
|
I followed the discussion about making BALUNs and the reference to "Beverage Antenna" which was new to me.
With the Google I found the Wikipedia page on it and then the US patent application which will be 100 years old in a few weeks.
Glad I was lurking in and hope others are entertained by seeing the patent.
(F) Lee Erickson
|
Re: Analysing Input Impedance Matching Circuit for the NE602
I noted the 73 material good LF material but not so good at over 10 mhz.
When going for odd ratios adding turns sometimes works better.
Or if minor loss is tolerable use a lower ratio and load down to it with
resistor. It can be more predictable as the input admittance of the
ne/sa602 does change with increasing frequency. Use the spec numbers of
1.5K (single ended/3K balanced input, and 3pF plus layour capcitance
across it). Internal capacitance inter- and intra- winding of the transformer
is a factor as well. FYI balanced input doen't not have a bypass cap to ground
from pines 1 or 2 and uses a centertap. So the typical with a 100nf to ground
on pin-2 is single ended 1.5K. Its often confused or at worst never stated.
The 4x50 inductance is rather low and would hopefully be at a frequency below
your extreme bottom frequency. My rule of thumb is 5x or higher and then
do analysis on how the source may interact with that.
Allison
-----------------
No direct email, it goes to bit bucket due address harvesting in groups.IO
|
Re: Analysing Input Impedance Matching Circuit for the NE602
First 1 turn is always though both hole there is no .5 turn.
Also if the inductance of the winding is not high enough you get a low
frequency cutoff. Changing the ferrite to higher mu (43 to 73) will help
but more turns would have as well. The reason I removed a bit of a turn (and then called it half a turn) was this seemed to make a better match. Though in reply #11793 I accidentally called it 'one turn' when I meant 'half a turn', this may have caused the confusion. This message should have said 'half a turn' was 7.38uH and 'one turn' was 12.5uH. When I calculated the required inductance needed using Xl = 4 x 50 ohm and then putting the 200 in to L = Xl / (2 x pi x f) I got 4.5uH. With one turn this measures 12uH on my inductance meter but with 'half a turn' it measures 7.38uH which is closer to the calculated value and why I tried removing a half turn to see what would happen. I am currently using a BN-73-202 73 material binocular core for my tests, originally I was using an FT37-43 toroid.
|
On Wed, Mar 18, 2020 at 10:32 AM, Roger Need wrote:
It is my understanding that after you do a Clearconfig 1234 you must turn off the power and after turning the power on do a touch calibration and then a calibration with a save to Channel 0.
=============================================================
If "clearconfig" didn't fix your situation then you might try to confirm the calibration is not going wrong when you use the on-screen display. Try performing a calibration using a software package such as Rune's NanoVNA-saver. A cautionary note is that NanoVNA-saver may not be able to properly interface with your unit if it is not properly calibrated.
Other questions you might consider are:
1. Did the device perform properly when you first received it?
2. If so, what firmware revision are you using and have you upgraded since then?
3. If you've upgraded, have you tried a more recent firmware from either edy555 or hugen?
- Herb
|
Re: Analysing Input Impedance Matching Circuit for the NE602
I assume you are using insulated wire or you will get shorted
turns due to Mix 73 low resistivity. Does your S21 read close to 0 dB when CH0 is connected to CH1 with the SMA
cables? I was using magnet wire to wind the transformers but have rewound them this afternoon using insulated wire. They now look like the transformer shown in the W8JI link you sent. They are wound 1 to 8 (with one full turn, not a half turn). I have attached two images to this reply, one shows the S21 gain and the other the S11 return loss when CH0 is directly connected to CH1.
|
On Wed, Mar 18, 2020 at 10:33 AM, TT7 wrote:
Sadly, they are not shipping to the Czech Republic yet.
===================================================
Tomas,
Probably just as well. There have not been any full reviews from customers who have received a V2, so its not easy to judge if the V2 will meet your needs better than the NanoVNA-F or NanoVNA-H4. Erik received a pre-production unit but has only provided minor details. The price is attractive but you have to also factor in the cost of OSL standards, RF cables, a battery and protective case.
Might be better to wait awhile until the first wave of buyers start posting their reviews on the unit, software and bugs in either.
I already have suitable OSL standards, RF cables, and a battery so it was worth a gamble for me to order the V2 unit. Between the world health crisis and normal transit time from China, I don't expect to receive it until April.
- Herb
|
Sadly, they are not shipping to the Czech Republic yet. In an email response, the seller said they were looking into adding other shipping methods, but no time frame was given.
Tomas
|
It is my understanding that after you do a Clearconfig 1234 you must turn off the power and after turning the power on do a touch calibration and then a calibration with a save to Channel 0.
Maybe Heb can confirm this sequence...
Roger
|
Re: Analysing Input Impedance Matching Circuit for the NE602
First 1 turn is always though both hole there is no .5 turn.
Also if the inductance of the winding is not high enough you get a low
frequency cutoff. Changing the ferrite to higher mu (43 to 73) will help
but more turns would have as well. The cost of higher mu ferries is
higher loss at higher frequencies.
The coefficient of coupling is never 1, it may be very close.
Typical for a binocular core is around .997 or less depending
on how the winding is structured as well as lead lengths.
The latter contribute leakage inductance that degrades
transformer action.
Allison
-----------------
No direct email, it goes to bit bucket due address harvesting in groups.IO
|
|
|
Hello,
If one uses *nanovnasaver*, what do you think it will be the best firmware?
I am fortunate to have a small PC at my desk to use with the VNA.
*73 de Lu¨ªs, CT2FZI*
<>
toggle quoted message
Show quoted text
On Mon, 16 Mar 2020 at 21:59, hwalker <herbwalker2476@...> wrote: Hot on the heels of his beta 0.8 firmware release for the NanoVNA,
DiSlord has followed it up with an additional beta firmware release which
adds user selectable averaging via a "DISPLAY->BANDWIDTH" menu. Bandwidth
can be set to 1 kHz, 300 Hz, 100 Hz, 30 Hz or 10 Hz. As any who has used a
commercial VNA can tell you, using averaging can smooth out your data but
at the expense of sl-o-o-owing down sweep rates. Truly no such thing as a
free lunch.
Latest beta is located at
.
This is a preview of where the next edy555 firmware release is headed.
I thought there were no more tricks in the firmware developers bags to
add more features to the limited flash space of the NanoVNA-H. That was t
the main reason I begin gravitating towards the NanoVNA-H4 and NanoVNA-F.
DiSLord's re-write and optimization of the NanoVNA's firmware, shows the
NanoVNA-H is not quite ready to relinquish its crown. Looks like the -H4
and -F will be behind the curve until the upcoming edy555 firmware releases
are ported to them.
Per DiSLord:
"When you drop below 1kHz, the scanning speed is significantly
reduced, and the responsiveness of the menu drops, but is generally
workable."
Also as previously noted, this beta firmware release is not for the
NanoVNA-H4 or NanoVNA-F.
- Herb
|
clearconfig 1234 did not seem to help
To calibrate I:
Connect open to CH0, OPEN
Connect short to CH0, SHORT
Connect 50 ohms load to CH0, LOAD
Remove 50 ohms load from CH0 and connect to CH1, ISOLN
Connect CH0 to CH1, THRU
I tried both connecting the loads directly to the VNA, and through male-male cables with female-female adaptors in the ends (then remove one of the adaptors to perform THRU).
|
Re: Wich one the get ? nanoVNA F or H4
In fact this issue is not a big deal to fix it by adding washer. However, it would be frustrated when happens. I did encounter the issue with my 2.8 inch H version so that I simply go back without the enclosure.
VR2XHQ
toggle quoted message
Show quoted text
On Mon, Mar 16, 2020 at 08:53 AM, Larry Rothman wrote:
Yup, the issue with the plastic housing is a 'potenial' problem but almost all
H4 units are just fine.?
On Sun, 15 Mar 2020 at 8:14 PM, Ben Yuen<benyuenkc@...> wrote: I
have 2.8 and 4.3 inch version. They can do TDR with updated firmware.?
Personally I would prefer the F version with metal case which is free from the
potential problem of "plastic case" issue at this moment.
VR2XHQ
|
Re: Analysing Input Impedance Matching Circuit for the NE602
Kerr,
I don't how you are winding or measuring these transformers but something is definitely not right. The coefficient of coupling K is very close to 1 with binocular cores and the core losses are not very high. You should only have a dB or so of insertion loss as I showed you in the W8JI link and from my own measurements. I assume you are using insulated wire or you will get shorted turns due to Mix 73 low resistivity.
Possible errors:
- Winding wrong way. 1 turn is going through one hole and back through the other
- Not using insulated wire
- S21 not set up correctly on your nanoVNA
Does your S21 read close to 0 dB when CH0 is connected to CH1 with the SMA cables?
Take a picture of your setup and maybe we can help.
Roger
|
Re: Analysing Input Impedance Matching Circuit for the NE602
On Tue, Mar 17, 2020 at 12:21 PM, David Eckhardt wrote: Physically, yes. Circuit-wise and considering magnetics, its is a full
turn. I have never heard of anyone counting a pass through one hole of a binocular core as a full turn. Fair-rite states: "The 61 and 67 material multi-hole beads are tested for AL value. The test frequency is 10 kHz at < 10 gauss. The test winding is five turns wound through both holes." Note: both holes. TDK says: "Magnetic characteristics and AL value are based on winding of center leg." A winding around the center leg is a winding through both holes. If you look at the graphic posted in post number 11791,you will see that it says: "2 passes = one turn" and "6 passes = 3 turns" and the graphic illustrates that. You can count turns any way you like, but if you want to use the manufacturer's data, or anybody's instructions for winding a certain inductance value, then one turn is a pass through both holes. A pass through one hole of a binocular core is a half turn.
|
Re: Analysing Input Impedance Matching Circuit for the NE602
So, the good match is likely mostly due to loss. Of course, since you have
two transformers in the measurement, the loss through one is half the S21
values. Still, most of the good match is due to losses. A 2:1 SWR is 10
dB return loss. Most of your earlier plots and SWR indicated at or less
than 1.5:1. This is certainly in line with the loss measurement. 1.5:1
SWR is return loss of 13.98.
Dave - W?LEV
Dave - W?LEV
toggle quoted message
Show quoted text
On Tue, Mar 17, 2020 at 10:47 PM Kerr Smith <kerrsmithusa@...> wrote: So, the match is good over HF. Thinking after I hit send: Why not connect
the secondaries together as you did for the S11 measurement and do an S21
measurement to assess loss? That way, both ports are in a 50-ohm system. I have just removed the 50 ohm resistor off the second transformer and
attached CH1 of the NanoVNA instead. The attached image is the S21 plot of
the sweep from 1 to 30MHz. At 7.15MHz the gain shows as -22dB.
--
*Dave - W?LEV*
*Just Let Darwin Work*
*Just Think*
|
Re: Analysing Input Impedance Matching Circuit for the NE602
Here are some tests I did with 1 full turn on primary with 5 full turns on
secondary. Primary wire comes out one side and secondary out the other.
Ratio of 5 turns gives impedance transformation of 5 square = 25 so 50:1250
First graph is impedance with transformer terminated in 1200 ohms. Second is
VSWR with 1200 ohm termination. Tests were done on another type of analyzer. Below are S11 plots of R + jX and |Z|, these look quite similar to yours I think - the Y-axis scales on mine are zoomed in a bit (I did try to set them from 75 to -75 on the Y-axis to match your scale but this caused NanoVNA Saver to crash). Both these plots have CH1 of the NanoVNA attached to the second transformer's output (with a 50 ohm load the results are identical).
|
Re: Analysing Input Impedance Matching Circuit for the NE602
So, the match is good over HF. Thinking after I hit send: Why not connect
the secondaries together as you did for the S11 measurement and do an S21
measurement to assess loss? That way, both ports are in a 50-ohm system. I have just removed the 50 ohm resistor off the second transformer and attached CH1 of the NanoVNA instead. The attached image is the S21 plot of the sweep from 1 to 30MHz. At 7.15MHz the gain shows as -22dB.
|
Roger Need
Andy UA3RAW
CT2FZI
Jim Allyn - N7JA
