Re: Testing a helix antenna?
Send me the dimensions and I'll have a look.
While it may have a good Return Loss at 3.4 GHz, that does notmean the radio waves are going out the front of the antenna!? hihi
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On Wednesday, November 4, 2020, 1:08:46 PM CST, <aleatorii.yg@...> wrote:
Thanks for the reply, but what's confusing me is that, looking at the results of the VNA, this appears to be a 9cm antenna.
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Re: Testing a helix antenna?
Thanks for the reply, but what's confusing me is that, looking at the results of the VNA, this appears to be a 9cm antenna.
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Re: 50Mhz 3 element Yagi SWR results quite different from NanoVna predictions!
Hi Marco,
your measured file looks like measured directly at the antenna. But running antenna with you rig, you need a cable with connectors. So take a look at that cable and connectors and make a vna-plot with this cable. Maybe there are faults in the cable / connectors.
73, G¨¹nter, DK5DN
Am 04.11.2020 um 18:40 schrieb I0MOM via groups.io:
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Hi,
just received my nanoVNA H4 and after a few satisfactory tests, decided to use it to fix my 3 element 50Mhz yagi which presents a little too high SWR on FT8 frequency (50.313Mhz).
The SWR reading at the radio was around 2.8 and that put in protection the rig.
To have an idea of how work on the antenna I run a scan with NanoVNA (after a calibration from 48 to 54 Mhz) and the results can be seen on the attached NanoVNA saver file..
The SWR at 50.313 Mhz were 2.6 quite similar to the 2.8 measured on the rig , but when I moved to 51.450 Mhz , the predicted lower SWR frequency, SWR jumped to infinite!
Quite shocked I resort to the old usual way of tuning an antenna and sampling with the transmitter a range of frequencies, found that the SWR trend was the opposite way from the predected and the real SWR minimum (1:1) was between 49.6 and 49.7 slowly rising to 2:1 at 50.1 Mhz. and then higher and higher as the frequency increase.
I did the measurements a couple of time before writing and I wont to believe to NanoVNA but instead of helping was misleading, and I have no idea of what I did wrong.
Have a nice evening,
73 de I0MOM Marco in sunny Rome
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50Mhz 3 element Yagi SWR results quite different from NanoVna predictions!
Hi,
just received my nanoVNA H4 and after a few satisfactory tests, decided to use it to fix my 3 element 50Mhz yagi which presents a little too high SWR on FT8 frequency (50.313Mhz).
The SWR reading at the radio was around 2.8 and that put in protection the rig.
To have an idea of how work on the antenna I run a scan with NanoVNA (after a calibration from 48 to 54 Mhz) and the results can be seen on the attached NanoVNA saver file..
The SWR at 50.313 Mhz were 2.6 quite similar to the 2.8 measured on the rig , but when I moved to 51.450 Mhz , the predicted lower SWR frequency, SWR jumped to infinite!
Quite shocked I resort to the old usual way of tuning an antenna and sampling with the transmitter a range of frequencies, found that the SWR trend was the opposite way from the predected and the real SWR minimum (1:1) was between 49.6 and 49.7 slowly rising to 2:1 at 50.1 Mhz. and then higher and higher as the frequency increase.
I did the measurements a couple of time before writing and I wont to believe to NanoVNA but instead of helping was misleading, and I have no idea of what I did wrong.
Have a nice evening,
73 de I0MOM Marco in sunny Rome
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Re: Testing a helix antenna?
OK, having the first turn near the reflector is one technique to get a 50 Ohm match.
?You may try moving it a bit closer to the reflector while watching 2.4 GHz response.?
Next is that boom??? When we put a 50 Ohm trace on a circuit board, the dielectric?
slows down the waves.?? The now travel about 60% the speed of free space.
When that boom touches the helix, or to a smaller amount, simply gets near it,
you get a similar effect.??? Now the Turns/Diameter ratio of the helix is altered.A few pieces of styrofoam supporting the helix might help.
So you might try moving that first turn in an out a bit.? And you often see quite a??
change when you snip a few millimeters on the end.?? But I just don't see a lot of
hours in it's engineering, if you know what I mean.? .Good luck with your project. Kent
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On Wednesday, November 4, 2020, 12:03:20 PM CST, aleatorii.yg@... <aleatorii.yg@...> wrote:
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.
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Re: Testing a helix antenna?
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.
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Re: Testing a helix antenna?
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.
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On Wednesday, November 4, 2020, 11:33:47 AM CST, <aleatorii.yg@...> wrote:
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?
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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?
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Re: Mystery Push Button Switch on the Side
"...you CANNOT brick the Nanovna..."
Hold my beer!
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On Wed, Nov 4, 2020 at 10:32 AM Larry Rothman <nlroth@...> wrote: 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
On Wednesday, November 4, 2020, 9:21:44 a.m. EST, Brent W Baum <
baumbr53@...> wrote:
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.
--
Carey Fisher
careyfisher@...
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Re: Mystery Push Button Switch on the Side
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
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On Wednesday, November 4, 2020, 9:21:44 a.m. EST, Brent W Baum <baumbr53@...> wrote: 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.
|
Re: Mystery Push Button Switch on the Side
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.
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RESISTANCE IN YOUR COAXIAL CABLE STUB Your antenna has R = 0 ¦¸. The R+jX (¦¸) chart allows for positive and negative R values. 1) What is the significance of R = 0 ¦¸ in your ¡°antenna¡±; Is there an ¡°RR-resonance¡± (one +R ¦¸ and one ¨CR ¦¸ meeting and cancelling at = 0 ¦¸) ¨C in the same way the LC meet in resonance at ¡ÀjX = 0 ¦¸? 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
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Re: Help reading Antenna plots
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.
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Re: Help reading Antenna plots
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Re: Mystery Push Button Switch on the Side
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
toggle quoted message
Show quoted text
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.
|
Mystery Push Button Switch on the Side
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.
|
File //NanoVNA PC Software/NanoVNA-App.rar updated
#file-notice
The following files have been updated in
the Files area of the [email protected] group.
By: OneOfEleven
Description:
NanoVNA-App PC software v1.1.109 bug fixes and updates to V2 support
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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.
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Re: RF from outside - Did I brick my nanoVNA-H?
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)
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Re: RF from outside - Did I brick my nanoVNA-H?
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
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Show quoted text
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)
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schweppe
I0MOM
