开云体育

Thanks for the reply, attached are some photos. Note this was sold in the UK as a 13cm antenna (I think by Sandpiper, but I may be wrong), many years ago.
I've never actually built a helix design myself, so am not that clued up on any theory of them.

Over the years I have tested over 100 Helix antennas on my antenna range,and only about 10% had forward gain and were circularly polarized.
The Kraus formulas are overly optimistic and do not allow for any materialto actually touch the helix.??

Would like to see a photo of it.??? WA5VJB@...
It should have a good SWR/Return Loss from 2.2-2.6 GHz or so, and a resonancedown the VHF band where it looks like a 1/4 wave whip.
At 2.4 GHz is looks more like a Yagi, only in the VHF band does it look likea shortened whip.?

My suspension is more along the lines of a poorly made antenna vs a
VNA issue.? Several techniques to give them a good 50 Ohm match.
A photo would tell a lot.

Have been testing various antennas on my NanoVNA V2 Plus4 and in all but one, the results appear roughly as expected.
The one that doesn't is a 2.4GHz helix, which shows a very poor match there and actual resonance/low SWR is at about 3.4GHz.
I know the helix is an electronically shortened antenna, and may not present an ideal 50ohm impedance, but that still doesn't make sense to me when making these measurements.

Can anyone explain what's going on here?

"...you CANNOT brick the Nanovna..."
Hold my beer!

--
Carey Fisher
careyfisher@...

Brent,
Please browse the forum Wiki and Files sections.
You will find PDFs and links to various User Guides that detail the flashing process and other neat stuff about the nanovna.
plese remember - you CANNOT brick the Nanovna. If the flashing fails, you just try again.
Please ensure you use the correct family of firmware (read the wiki) for your unit (H FW is only for H and earlier units, H4 FW is only for H4 units)
Regards,Larry

Thanks, John. I thought it might be something like that. And I've learned a
second thing from your reply, how to update the firmware. Is there a
specific site or download I need to be connected to?
Brent, K7MEI

On Wed, Nov 4, 2020 at 12:21 AM John Gord via groups.io <johngord=
[email protected]> wrote:

Brent,
My NanoVNA has a couple of circuit pads at that location (VDD and BOOT0).
When shorted together at power-up, they cause the NanoVNA to enter DFU mode
for firmware update. I suspect your unit has a switch provided to provide
that function without an added jumper wire.
--John Gord

On Tue, Nov 3, 2020 at 07:05 PM, Brent W Baum wrote:

I'm a new user to the group. I did a search on the topic but was unable

to

discover what the small momentary push button switch in the center of the
right edge of the nano VNA does. None of the online videos, etc. seem to

know

this control is there. It doesn't seem to do anything when I press it.

Any

ideas?
Thanks.

RESISTANCE IN YOUR COAXIAL CABLE STUB

Your antenna has R = 0 Ω.
The R+jX (Ω) chart allows for positive and negative R values.

1) What is the significance of R = 0 Ω in your “antenna”; Is there an “RR-resonance” (one +R Ω
and one –R Ω meeting and cancelling at = 0 Ω) – in the same way the LC meet in resonance at ±jX = 0 Ω?

This would be like the Negative Resistance Oscillator type amplifier in the old reflex Klystron microwave emitters, used for radar. And in the Gunn Diode.

Be careful Simen with the "saver" R+jX chart, there is never negative values for R. The R scale (red) is on the vertical left side of the chart, and for this example with a range from 0 to 2000 ohms. Negative to positive values apply only to X (reactance) and are shown on the right scale (cyan) of the chart.

I suggest you to have a look to stub circuits behavior. I have put below a capture of data provided by W4RNL at which is a good summary.

Red marker in "saver" capture is the short circuit situation equivalent to a RLC series circuit with R=0 and LCw = 1/Cw (cancellation of reactive part) at 27.075 MHz.
Green marker in "saver" capture is the highest impedance situation equivalent to a RLC parallel circuit with high R (theorical infinite value) and LCw = 1/Cw (cancellation of reactive part) at 54.050 MHz

You can also check that L and C have not the same values for these two situations. Green marker behavior is equivalent to add a lambda/4 stub to the first one. The first provides the short circuit situation (red marker) which is the load value for the second lambda/4 stub. Finally you get the high impedance situation at the end of this second stub (green marker).

I hope it is enough clear as english is not my native language ! Please note that I don't succeed in downloading your s1p files from this message (file format probably unknown from the website).

Jean-Roger

Full set of plots for my current setup I am pretty sure they show the gypsy antenna is not that good now to find a way to improve it.

Here you go

Brent,
My NanoVNA has a couple of circuit pads at that location (VDD and BOOT0). When shorted together at power-up, they cause the NanoVNA to enter DFU mode for firmware update. I suspect your unit has a switch provided to provide that function without an added jumper wire.
--John Gord

I'm a new user to the group. I did a search on the topic but was unable to discover what the small momentary push button switch in the center of the right edge of the nano VNA does. None of the online videos, etc. seem to know this control is there. It doesn't seem to do anything when I press it. Any ideas?
Thanks.

The following files have been updated in the Files area of the [email protected] group.

• //NanoVNA PC Software/NanoVNA-App.rar

By: OneOfEleven

Description:
NanoVNA-App PC software v1.1.109 bug fixes and updates to V2 support

Thanks for the responses. The nanoVNA I have now I managed to break the s11 connector off the circuit board but I did repair it successfully. Then I 3D printed an enclosure to help protect the connectors but it only works for BNC which is a pain to remove because I find myself using the SMA more. I'm hoping the h4 will have found a way to relieve stress on the connectors. Also I do work with crystals so I'm also looking for that extra resolution which hopefully it will have. Also extended frequency to 3 gigahertz frankly I have no use for that right now because primary interest is qrp work mostly on the low bands.

On 11/3/20 10:22 AM, ERNEST AEC-RADIO wrote:

Bruce:
You might have caused the AD602 devices to open, as they have almost zero
protection, aside from a capacitive input.
The level of R.F probably killed them.
The devices are readily available, and not costly,
There should be 3 devices, all identical.
SA602AD, 8 pin D.I.P packaging

There's 20dB of attenuation between the external port and the mixer. More likely a overpower situation would blow up the resistors in the attenuator before it cooked the mixer. The series resistance might also limit the current through the mixer inputs.

Sure, putting 100W into it probably would blow it up - The 50 ohm load resistor would cook first from the 70Vrms, then the 250 and 50 ohm resistors in the attenuator. And if the 250 ohm survived, then the mixer sees it.


It's a Gilbert cell mixer which is basically a differential amplifier pair, and the RF inputs go to the bases of the transistors (see Fig 3 in the datasheet) with a 1.5k resistor to ground. A negative voltage will reverse bias the BE junction, but that's probably "volts" max Vbe-rev. Too much positive voltage reverse biases the mixer transistors.

On Mon, Nov 2, 2020 at 6:43 AM BruceN <k4tql@...> wrote:

Did a stupid. I was measuring an antenna and left the VNA connected to
the feed line while I went off and did something else for a bit. My
automatic message system kicked off and transmitted from a different
antenna pouring 100 watts into the aether. The antennas were close,
parallel in fact.

When I came back to the VNA, I found that I couldn't calibrate it. The
display showed traces all over the place instead of the nice straight lines
you get after calibration. I guess I may have bricked it but would
re-loading the firmware correct the issue? I hate to dig into it because
it is a "real" nanoVNA-H with the nice plastic case and kinda tough to
break into. I suspect that repairing it wouldn't be worth the trouble
since a new one is so inexpensive.

Moral of the story: turn off all RF sources while using the VNA and
disconnect it if you walk off to do something else.

--
*"To invent, you need a good imagination and a pile of junk"* -- Thomas
Alva Edison (1847-1931)

Bruce:
You might have caused the AD602 devices to open, as they have almost zero
protection, aside from a capacitive input.
The level of R.F probably killed them.
The devices are readily available, and not costly,
There should be 3 devices, all identical.
SA602AD, 8 pin D.I.P packaging

correction? email is DOT NET? ?as? ?n8cdw@... not . c o m

*Sent:* Tuesday, November 03, 2020 at 10:51 AM
*From:* "Ed March" <shop101@...>
*To:* [email protected]
*Subject:* [nanovna-users] NanoVNA-H4 for sale $52
I'm posting this for my Friend Carl who has a

nanoVNA-H4 for sale

$52 Shipped Conus

n8cdw@...

815-703-9472

Pictures on linke below



Contact him for details....

The nanoVNA H4 is in stock at R&L Electronics as of today, 11/03/2020. I just ordered it along with the $7.95 test kit (circuit board with connectors, etc.)

Ted, KX4OM

I'm posting this for my Friend Carl who has a

nanoVNA-H4 for sale

$52 Shipped Conus

n8cdw@...

815-703-9472

Pictures on linke below



Contact him for details....

Im just posting this for a friend

Carl has a VNA for sale Contact Him for Details

*Sent:* Tuesday, November 03, 2020 at 2:23 AM
*From:* "Simen Tobiassen" <simen@...>
*To:* [email protected]
*Subject:* Re: [nanovna-users] Real/Imaginary vs R+jX (Ω) Charts #features #general_vna #learning #manuals #measurement #nanovna-saver #nanovna-v2 #training #charts
Thank you, Jean-Roger, for taking the time for an extensive answer! I had to lay down flat on my bed with this one ;)

This response got long. I tried to get it all in there, not necessarily expecting you to answer them all ;)

RESISTANCE IN YOUR COAXIAL CABLE STUB

Your antenna has R = 0 Ω.
The R+jX (Ω) chart allows for positive and negative R values.

1) What is the significance of R = 0 Ω in your “antenna”; Is there an “RR-resonance” (one +R Ω
and one –R Ω meeting and cancelling at = 0 Ω) – in the same way the LC meet in resonance at ±jX = 0 Ω?

This would be like the Negative Resistance Oscillator type amplifier in the old reflex Klystron microwave emitters, used for radar. And in the Gunn Diode.

+R and –R SPIKES

The attached Touchstone file “Coil L3 - 11-32 Mhz –66154.1 Ohm Negative Spike.s1p” shows a negative resistance in the R+jX (Ω) Chart: R = –66154.1 Ω.
On the same frequency the |Z| Chart shows a 67785 Ω spike.

The attached Touchstone file “L3 Coil in series - How do I move –R up.s1p” shows a negative R in the R+jX (Ω) Chart: R = –18141.3 Ω.

2) How is this Resistance being created, incl these Resistive spikes, while the resistance in the wire is close to 0 Ω?

I have tried to correct these negative resistances using resistors, and only got them up to about –800 Ω.

3) Any ide on how to move -R’s up into 0 Ω?

SERIAL C (F) AND SERIAL L (H)

The Serial C (F) is explained to be a measurement of a capacitor in series with a resistor, and the Serial L (H) an inductor in series with a Resistor. Regardless of this, I do not find instructions on how to actually connect the NanoVNA to a coil to get the values right in the Serial C (F) and Serial L (H) Charts.

I either connect one end of my coil to the S11 center terminal, or I connected in Parallel to the S11 port.

On the Serial C (F) Chart I typically get curves with large, abrupt “Spikes” at frequencies where the Reflection Coefficient is in resonance and the Phase Angle is 0°, falling steep.

The Serial L (H) Chart usually shows a curve almost identical to the SRF curve on the R+jX (Ω) Chart, on the same frequency.

I then thought I could use the C value at the Marker on the Serial C (F) Chart and the H value for the same Marker in the Serial L (H) Chart, to calculate the +jX and –jX values on that frequency. I expected to get two different reactance values, but NanoVNA Saver always give me the same but opposite reactance values.
I expected the same reactance values only when the R+jX (Ω) Chart shows ±jX = 0 Ω = LC resonance.

4) How do I connect to get the Serial C (F) and Serial L (H) Chart values right?

5) Is the NanoVNA not able to measure/show the true L and C values
and their actual, separate +jX and –jX values?

6) At an ordinary LC resonance point the XL and XC are cancelling, resulting in 0 Ω.
At a coil’s or a capacitor’s SRF point though, is there actually no L and C as the NanoVNA suggest?

? WAVE + PHASE ANGLE 0° + SRF – AT ONE FREQUENCY?

Your coaxial cable stub has

Red Marker: 27,0275 MHz
Phase Angle Chart: 0° (where it actually crosses)
Real/Imaginary Chart: REAL = -0.95, IMAG = 0 (short circuit situation)
R+jX (Ω) Chart: 0+j0 Ω (short circuit situation)

Green Marker: 54,0050 MHz
R+jX (Ω) Chart: Approximately SRF

Will there be some kind of better resonance if we get all the following to resonate at the same frequency?

A Reflection Coefficient Resonance --> Length related
Open or Closed = Standing waves

B Phase Angle 0°, with Steep change --> Length related
- as in your ? wave cable stub

C Self-Resonant Frequency --> Length related
David KNIGHT, PhD in Microwave Spectroscopy, concludes that
the SRF is mostly related to length, in his “self-res.pdf”


The attached Touchstone file “L3 Coil in series - How do I move –R up.s1p” shows at 13.36 MHz:

a) Real/Imaginary Chart: REAL = 1, IMAG = 0 (open circuit situation)
b) Phase Angle Chart: 0°
c) Serial C (F) Chart: At “SRF” point C and L is zero
d) Serial L (H) Chart: At “SRF” point C and L is zero
e) R+jX (Ω) Chart: R = –18141.3 Ω, +jX = 967 Ω

7) What would be the significance of a) – e) being on the same frequency,
incl - R+jX (Ω) Chart: R = 0 Ω, ±jX = 0 Ω?

Is it cold enough? Remember, the performance of an antenna is inversely
proportional to the temperature at the time it was erected.

73, Zack W9SZ


<>
Virus-free.
www.avast.com
<>
<#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>

On Tue, Nov 3, 2020 at 12:57 AM John Nightingale via groups.io <if455kc=
[email protected]> wrote:

On 2020-11-02 4:04 p.m., deadman1966@... wrote:

... Flurries and high winds here so hopefully i get a nice day in the

future to get it higher in the air.

Tsk. That's not ethical, OM; right now is the time. In the ham radio

tradition procrastination in antenna work is to continue until there is
no choice by which point the weather /has/ become wet and windy!

John

at radio station VE7AOV

--