Re: Testing a helix antenna?
On 11/4/20 9:13 AM, 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?
The "natural" impedance of a multiturn helix is about 100 ohms. One either does some sort of matching transformer, or, you adjust the spacing of the turn closest to the ground plane to essentially make it a broad band tapered transmission line transformer. With a VNA, it's pretty easy to see the changes. If it's a quad helix or something other than the classic axial radiation, then I don't know what the normal Z is. FOrtunately, you can find the book by Kraus, "Antennas" on line as a pdf, and it is literally the book on helicals. In neither axial nor other radiating modes is the helical a "shortened antenna" - it's a totally different design.
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Re: Testing a helix antenna?
Remember, resonance is not defined by lowest SWR, but at the frequency at
which the complex portion of the impedance goes to zero.
Helices are traveling wave antennas, not shortened 'rubber ducks'. \
Dave - W?LEV
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On Wed, Nov 4, 2020 at 5:30 PM <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?
--
*Dave - W?LEV*
*Just Let Darwin Work*
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Re: Testing a helix antenna?
Because of the nature of a helix, I found the precise measurement of the inner diameter open to error, so I'd ignore that.
The conductor gauge is 4.85mm.
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Re: Testing a helix antenna?
Oh I see, I didn't realise this group was for SAA2 versions only. I chose here as it seemed the best place to ask as it's an actual practical application (the frequency range here is irrelevant here really, as the query is for a helix antenna in particular, rather than about the V2 Plus4 itself). Other NanoVNA groups here appear to largely be firmware related posts, from what I've seen.
As for 13cm, it's worth experimenting with, as is the 5.6GHz range (for radio amateur use), thanks to the very cheap drone FPV gear available from China. It's a shame that the latter range isn't presently catered for with any of the NanoVNA range, but hopefully it will be in time.
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Re: Testing a helix antenna?
The diameter is about right, but 10 mm conductor is certainly out of the range forall of my charts.
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On Wednesday, November 4, 2020, 2:47:44 PM CST, aleatorii.yg@... <aleatorii.yg@...> wrote:
Thanks again.
Details here: Loop spacing: 21.5mm
Loop diameter (inner): 36mm
Loop diameter (outer): 46mm
19 turns
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Re: Testing a helix antenna?
Thanks again.
Details here: Loop spacing: 21.5mm
Loop diameter (inner): 36mm
Loop diameter (outer): 46mm
19 turns
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Re: File /NanoVNA PC Software/NanoVNA-App.rar uploaded
#file-notice
Many thanks! I should have thought of that, hindsight 20:20, etc.
--
Best Regards,
Tom, VA7TA
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Re: File /NanoVNA PC Software/NanoVNA-App.rar uploaded
#file-notice
You need update firmware on NanoVNA for work (nanoVNA-App need new format for data exchange)
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Re: File /NanoVNA PC Software/NanoVNA-App.rar uploaded
#file-notice
Greetings,
I decided to give NanoVNA-App a spin for the first time and I am impressed with the appearance of the GUI. But it runs OK with my TinySA but not with either of my nanoVNAs.
My attempts to run NanoVNA-App under Windows 10 Pro 64b with my two versions of nanoVNA's failed - just a blank screen. When I click SCAN I get a water drip sound every few seconds and the USB data command stream flows but reports a frequency step error - the NanoVNA-app is set to 101 steps. Screen capture works normally, battery voltage is reported, etc.
I decided to try it with my TinySA and it appears to be fully functional with the baseline noise floor trace shown clearly.
I wonder if I am doing something wrong?
--
Best Regards,
Tom, VA7TA
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Re: Testing a helix antenna?
Well, gentlemen......... ( um, and ladies)
This might not be technically the correct forum. The frequency of discussion is above 3ghz, which is out of the range of all the nanovna devices which are not of SAA2 architecture.
Whinge over. I am delighted to see some reports of the V4 device in use, as I am an almost exclusive V2 owner (of four), and considering the possibility of investing in a V4. I wish the forums had not spread into so many different branches, as it is more difficult to pick up and follow interesting threads, which might start in another group; this particular topic being an excellent example.
I am sorry I cannot offer any support regarding 13cm aerials. BUT this post might encourage me to do some ¡°play¡± in this frequency band, not just because of this post, but because the kit to experiment is suddenly within my budget.
Carry on playing, ladies and gentlemen. It helps to keep the brain of a 70 year old geriatric alive.
Steve L. G7PSZ
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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.
|
schweppe
I0MOM
