Re: O S L on antenna side of a balun / choke with stud terminals?
'm not sure I completely agree :) Fortunately (or unfortunately) the transmission line acts as a impedance transformer. Given the length of the transmission line, impedance "shown" on to the TX might be the same as antenna's impedance, or quite different (depends on transmission line length and it's impedance).
Like wise, what TX "presents" to the t-line is not what will be presented to antenna (the same principle where t-line transforms impedance).
I do NOT known if this transformation done by the t-line is reciprocal: let's take a simple example. Take antenna tuner out of picture, so you have TX(50), t-line(100), and antenna (25). By carefully selecting t-line's length, you can transform antenna's 25 to match TX's 50. I think (!?!) that at the same time, on the antenna side, using the same t-line magic, TX's 50 will be now "presented" to antenna as 25!
If this is true (is it?), you can expend to any length of the t-line by adding antenna tuner - whatever t-line presents to TX side (let's call that Zx) will be matched to 50, and like wise, TX side will appear to t-line as Zx, and t-line will transform that to 25 on the antenna side.
If all this holds water, if TX sees SWR as 1:1, that means that SWR on the antenna side is the same!
Two (hand picked) examples of reciprocity:
1) lambda/4 t-line transforms short (0 ohm) to open (>>0). Wise versa is the case as well: >>0 on one side transforms to 0 on the other
2) lambda /12 t-line does magic Z1*Z2=sqrt(Zt) (multiplied impedances from each side are square root of t-line's impedance
If, in generic case (any t-line length/impedance) the following holds true Z1=k*Z2 and Z2=1/k*Z1 ("k" is impedance transformation "factor" that t-line does), it appears that good SWR on one side is good SWR on the other as well, right?
Now, you make an interesting point, if all this magic is happening by "bouncing" waves back and forth, cost of doing it with real t-line with losses might be significant - wave bouncing back and forth will lose some of it's energy in the t-line, and seeing SWR meter showing 1:1 on the either side will NOT indicate that such losses are present. Antenna tuner will make t-line/antenna appear "friendly" to TX, but will not deliver all the power to ether
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Re: O S L on antenna side of a balun / choke with stud terminals?
To directly answer you final question, SWR is the same throughout the length of a transmission line.
Losses in the transmission line will make the SWR higher toward the antenna end, but usually not by much.
I say this because the outgoing power will be slightly weaker at the antenna end than at its source
from the antenna tuner, the reflection back from the antenna feedpoint will be slightly stronger at the antenna end.
Jerry, KE7ER
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On Wed, Aug 19, 2020 at 07:54 AM, Miro, N9LR wrote:
Asked differently, if SWR is low at one end, does it mean it's low on the
other end as well (again, lossless components used!)
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Re: Performance of my nanovna V2 clone - return loss of port 2 seems much too high ?
Hello,
Thank you for your anwer
Ok, please find below the same test but done without any cables on port 1
and only a through cable to connect to port 1 and port 2. I have also used
400 points to get a clean accurate trace with as little noise as reasonably
possible.
=> At 1.5 Ghz; the return loss on port 2 is still significantly too low
(15.5 dB vs 20dB) expected, *so no changes*
=> At 3 Ghz, the return loss has improved significantly, *it is now 14.7 dB
which is a bit better than the 13dB specified officially.*
=> At 2.33 Ghz, the return loss is 11.7 dB is which is much too low, it
should be minimum 13dB according to the specifications
[image: image.png]
*Conclusion*: my measurements and yours simply confirm that the return loss
on port 2 of my nanovna 2 clone is unfortunately not as good as the one
of your genuine nanovna V2 model <> .
This is the confirmation that I wanted to have (thanks for your help). I am
not saying all the nanovana V2 clones systematically under perform on port
2 the return loss, but on the other hand, if I have the issue then other
clown owners may have it too (quite common sense really). It will not
prevent me from sleeping at night, but at least I know....
Kindly note that the quality of the calibration loads and of the SS405
cables that I used for this test are perfectly OK.
Thanks
Regards
Peter
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On Mon, Aug 17, 2020 at 8:47 PM <switchabl@...> wrote: Peter,
I have attached a measurement of port 2 return loss from my NanoVNA V2,
bought from tindie. This one seems to be meet the specs (-20.3dB @1.5GHz
and -15.5dB @3GHz).
There is also significant ripple on your measurement. It looks like your
calibration is bad and you have significant residual source match error (or
possibly your cable is bad, but less likely; since you are calibrating
directly at the port 1 connector, you are measuring the cable as well). So
I would take the results with a grain of salt. Mine is not perfect either,
but it looks a lot less bad.
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Re: O S L on antenna side of a balun / choke with stud terminals?
I'll assume you have 50 ohm coax from transmitter to antenna tuner.
From antenna tuner to 25 ohm antenna is 100 ohm coax.
The antenna tuner is adjusted so the transmitter sees a 1:1 SWR in the coax between transmitter and tuner.
The impedance change from 100 to 25 ohms between the transmission line and the antenna will create
a reflection, some of the outgoing power heads back to the antenna tuner. This creates standing waves
as the reflection interferes with the outgoing power. The job of the antenna tuner is to reflect all of that power
coming back from the antenna, sending it back out to the antenna in phase with the power from
the transmitter. So assuming the 100 ohm coax is lossless, none of the power in those reflections is lost.
But there will be an SWR of 100/25 = 4:1 in the transmission line from antenna tuner to antenna.
Jerry, KE7ER
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On Wed, Aug 19, 2020 at 07:54 AM, Miro, N9LR wrote:
Might appear to be slightly off topic, but I hope it's not :)
Lets assume we have ideal/lossless "everything" from end to end. Source (TX)
is pure 50 Ohm, the same with coax 100 Ohm, antena 25 Ohm. Over simplified,
but will get us going. Reflections everywhere (TX to coax, coax to antenna).
Now, I put antenna tuner between TX and coax (or coax and antenna), make
transition from 50 to whatever impedance coax is now presenting (coax length,
transformed 25 ohm from antenna, ...), get SWR 1:1.
Does it now mean that SWR is 1:1 at the antenna end as well?
Asked differently, if SWR is low at one end, does it mean it's low on the
other end as well (again, lossless components used!)
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Re: O S L on antenna side of a balun / choke with stud terminals?
Might appear to be slightly off topic, but I hope it's not :)
Lets assume we have ideal/lossless "everything" from end to end. Source (TX) is pure 50 Ohm, the same with coax 100 Ohm, antena 25 Ohm. Over simplified, but will get us going. Reflections everywhere (TX to coax, coax to antenna).
Now, I put antenna tuner between TX and coax (or coax and antenna), make transition from 50 to whatever impedance coax is now presenting (coax length, transformed 25 ohm from antenna, ...), get SWR 1:1.
Does it now mean that SWR is 1:1 at the antenna end as well?
Asked differently, if SWR is low at one end, does it mean it's low on the other end as well (again, lossless components used!)
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Re: SWR trace always showing 1:1 as flat line at bottom of screen
I asked a friend to solder me a test load of VSWR 1.5 and now, before measuring, I always check the correctness of the settings and calibration, if something is wrong, it is always and clearly visible!
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Re: SWR trace always showing 1:1 as flat line at bottom of screen
Are you sure you had the proper port selected for the SWR trace? S21 not
S11?
*Clyde K. Spencer*
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On Tue, Feb 18, 2020 at 3:11 AM <nanovnagroup@...> wrote: Hi,
I Ham friend of mine ordered a NavoVNA and he asked me to come over and
help him understand how to check the SWR of his antennas. I am not yet very
familiar with all the operational procedures of the NanoVNA except for what
I could gathered here by reading other posts. But can't seem to remember a
similar issue being brought up and a quick search did not help either. Plus
I still need to order mine, but have not made up my mind between the v3.4
and the 4H, etc, so didn't have any experience at all playing with this
device until now.
What I did first was set the start and stop frequencies (in this case
2-35MHz), then proceeded to make a calibration which included a reset and
then seemed to go well on all three steps, as the markers for open, short
and 50ohm where all showing in the correct position on the smith chart
after the calibration was completed and saved. Afterwards I tried with a
narrower frequency range (2-10MHz) then calibrated again, but the results
where still the same as described bellow.
After connecting the antenna to CH-0 both the Smith chart and return loss
traces seemed to be showing useful indications, but the trace corresponding
to the SWR was always shown completely flat at the bottom of the screen and
the readout for that trace was in fact showing 1:1 as well along the whole
trace. This happened even when the Smith chart clearly was showing a
reading of an impedance that was quite different than 50 ohms, plus
capacitance or inductance. Besides it would be impossible for a single
antenna to have 1:1 on the whole frequency range. Just as a test I
connected a dummy load instead of the antenna and then the return loss
trace would also be flat, and the smith chart would show the marker very
close to where 50ohms would be expected to be.
So my question would be if I am missing to set up something else in order
to be able to make the SWR trace work. I tried disabling all other traces
but that did not solve anything either. Also not being yet very familiar
with practical use of the device, I found that the Scale setting was a bit
confusing as it only has the numbers and then a +1 field. Would this be
used to define the per division dB value of the vertical scale markings?
Thank you in advance for any pointers.
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Re: SWR trace always showing 1:1 as flat line at bottom of screen
-same problem-solution return nano -2nd nano reads 1;1.19 with dips=another return, The dips are at the right freq. but read 1: 1.09
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Re: We started selling SAA2 with N-type RF connector and 4-inch display
Hugen
This is my third nanovna purchase and appreciate the UPS service
Keep up the good work
John VE3IPS
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Re: We started selling SAA2 with N-type RF connector and 4-inch display
Thank you for opening my eyes to the various ways of calibrating for non-insertable devices. Much of what you generously shared is above my paygrade, so to speak. So, I plan to re-read your post several times in the hope of gleaning more knowledge from your information-dense reply. Moving forward, I wish the connector discussion will focus on enabling the nanoVna to live up to the "vector" in its moniker because if the phase measurement of a DUT with same-sex connectors (non-insertable device) is rubbishy, then the usefulness will drop to that the "scalar" level. Furthermore, with true 2-port VNAs in the pipeline by both Gabriel & "a member of the V2 team", developing a non-insertable calibration technique should assume greater importance. .....They are not exclusive to APC7
though. The nicer 3.5mm calkits e.g. tend to come with a matched set of f-f,
m-f and m-m adapters. Even used these adapters still go for a pretty penny The above paragraph startled me enough to make me check at Keysight website. Indeed, as you correctly claimed, the current 85033E 3.5 mm calkit does include options 100/200/300 for matched f-f, m-f and m-m adapters. However, rolling back to just one earlier revision, to the 85033D, these options didn't exist. Instead, APC-7-to-3.5 adapters were included for measuring non-insertable devices. Likewise, the 8753ES VNA was sold together with a N calkit (85032B) that has APC7-to-N (m/f) adapters, explicitly for use with non-insertable devices. My point is, until fairly recently, APC7-based "swap equal adapters" was the dominant technique for sub 6GHz VNA. (digression: subsequently, e-Cal came along and freed us from learning calibration!) :-) If the APC7 equiped nanoVna fails to materialize, my backup plan is coincidentally somewhat similar to your above recommendation - swap between 83059B (f-f) & 83059C (m-f) 3.5mm adapters. I know they aren't phase matched, but judging from their physical lengths, I hope they are close :-) I am interested in non-insertable devices calibration techniques that are suitable for the nanoVna. If you feel the "offline" unknown-THRU cal is doable by dedicated hobbyists, please consider documenting the steps for us to follow. Thanks. Leong, 9W2LC
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Re: Where did OneOfEleven go
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Re: O S L on antenna side of a balun / choke with stud terminals?
Seems the half wavelenth of coax thing would be accurate
only on a very narrow range of frequencies (and harmonics).
Calibrating a VNA through the coax can cover
as much spectrum as you wish.
Jerry, KE7ER
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On Tue, Aug 18, 2020 at 08:02 PM, k4mla wrote:
You can match/measure the feed point of your antenna by using an _electrical_
half wavelength or multiples thereof, between the tuner/analyzer and the
antenna.
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Re: O S L on antenna side of a balun / choke with stud terminals?
You can match/measure the feed point of your antenna by using an _electrical_ half wavelength or multiples thereof, between the tuner/analyzer and the antenna.
Larry, K4MLA
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On 8/16/2020 2:39 PM, KENT BRITAIN wrote: The wire may be non-resonate without your home brew matching network,but with the network it has to be.??? To be an efficient radiator, you haveto resonate.???? Kent WA5VJB
On Sunday, August 16, 2020, 1:34:08 PM CDT, David Eckhardt <davearea51a@...> wrote:
How many hams actually match *at the feedpoint* to a 50-ohm coaxial line?
I'll bet very few.? At VHF and UHF, yes, at the antenna match is practical
and usually accomplished, but not at HF.
That's why I use open wire feeders where SWR losses are *far* less than in
coaxial cable and the feedline is not stressed even with SWR at full
power.? And......I use a single set of wires for 630 through 6-meters with
that system with home brew matching network.
Antennas do not require being resonant to do a good job of radiating.? My
system is not resonant (¡À jX = 0.00, the definition of resonance) in any of
the HF ham bands, but it does very well, both in practice and in the 4NEC2
model.? It's lowest 1/2-wavelength resonant frequency is 950 kHz, the lower
1/3 of the AM BC band.? I seriously doubt I'd do any better with resonant
dipoles for all the individual bands.
Dave - W?LEV
On Sun, Aug 16, 2020 at 6:07 PM Chris Wilson <chris@...> wrote:
Hello David,
? Sunday, August 16, 2020
? Without? knowing what impedance the antenna itself presents, how do I
? know the best way to match it to the coax impedance?
Best regards,
? Chris? ? ? mailto:chris@...
DE> What's important is the load the antenna plus feedline present to our
DE> modern transceivers.? So, why the concern for 'at the antenna'
DE> measurements?? Sure, its nice to know, but the coax contributes it's
own
DE> impedance transforming properties.? If you must, make the measurement
at
DE> the shack end of the feedline, and use a tool such as SimSmith to take
out
DE> the impact of the coaxial line.
DE> Again, what is important is the load presented to the transmitter, not
DE> necessarily what the antenna impedance is at the feedpoint.? One must
STILL
DE> consider the transmission line between the transmitter and the antenna
DE> feedpoint to obtain this result.
DE> Dave - W?LEV
DE> On Sun, Aug 16, 2020 at 5:31 PM Jerry Gaffke via groups.io <jgaffke=
[email protected]>> wrote:
Roger wrote:
? You can clearly see that the two plots are nearly identical. What kind of coax?
I bet it isn't RG174.
I have seen significant differences when checking out an HF antenna over
100 feet of RG8X.
I have a 20M dipole with a current balun attached to it which for this test I consider to be the "feedpoint" of the antenna.
Not totally clear which side of the balun you consider to be the
feedpoint
of the antenna
I assume this means you leave the balun attached to the antenna, and
only
calibrate out the coax.
Jerry, KE7ER
On Sun, Aug 16, 2020 at 09:47 AM, Roger Need wrote:
I have a 20M dipole with a current balun attached to it which for this test I
consider to be the "feedpoint" of the antenna. 55 feet of coax runs
back
to
the shack. First measurement with NanoVNA Saver was made at the feedpoint and
stored as an s1p file. The coax was then "calibrated out" and a second Saver
measurement made back in the shack. The first s1p file was then loaded and a
comparison was made. You can clearly see that the two plots are nearly
identical.
Roger
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Re: Phase of very high quality N short
On Wed, 19 Aug 2020 at 00:04, Dana Whitlow <k8yumdoober@...> wrote: I couldn't figure out who from the morass of comments,
but somebody wrote
"It¡¯s not that important that the phase of the open and short are exactly
180 degrees apart".
This is true only if the calibration routines know about this! Otherwise
all bets are off. And the only way for the routines to know about this is
through the cal stds definitions table for that physical set of standards.
Dana Even if the standards are 180 degrees apart in phase, the calibration routines need to know the exact phases at each frequency. +100 degrees and -80 are significantly different from +110 degrees and -70 degrees, yet both differ by exactly 180 degrees. In any case, it is impossible to keep the phases 180 degrees apart at all frequencies. A polynomial is used to express the fringing capacitance of the open and sometimes the inductance of a short too, although the inductance of the short is a significantly smaller effect. -- Dr. David Kirkby, Kirkby Microwave Ltd, drkirkby@... Telephone 01621-680100./ +44 1621 680100 Registered in England & Wales, company number 08914892. Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United Kingdom
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I have been gone for a few weeks. Where did the downloads for OneOfEleven go? I went to he old GitHub link and it is broken.
Gary
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Re: Source for H4 Padded Storage Case?
On 8/18/20 5:02 PM, Jim Lux wrote: On 8/18/20 4:10 PM, AA7US wrote:
I¡¯ve searched for hours and so far come up empty handed...
Does anyone have a suggestion for a soft, clamshell style, padded storage case that'll fit a NanoVNA-H4 with enough extra room for typical accessories?? It needs to have a separate inner zippered compartment to store the calibration fittings and coax jumpers so they won¡¯t rattle around and rub on the NanoVNA's screen.
I've seen multimeter storage cases which are close, but they're either way too big or lack a zippered internal storage compartment.? A portable hard drive case might work also, but again, every one I've encountered lacks an internal zippered storage compartment.
Ideally being able to buy from Amazon or eBay would be best.
In addition to the suggestions in my last email...
There are a wide variety of soft sided cases made for portable games (your Nintendo Switch, for instance) with pockets for adapters, games, etc.
-=- or a portable hard drive case: zillions of cases in every size and configuration you can imagine... You can have it tomorrow in most cases.
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Re: Source for H4 Padded Storage Case?
On 8/18/20 4:10 PM, AA7US wrote: I¡¯ve searched for hours and so far come up empty handed...
Does anyone have a suggestion for a soft, clamshell style, padded storage case that'll fit a NanoVNA-H4 with enough extra room for typical accessories? It needs to have a separate inner zippered compartment to store the calibration fittings and coax jumpers so they won¡¯t rattle around and rub on the NanoVNA's screen.
I've seen multimeter storage cases which are close, but they're either way too big or lack a zippered internal storage compartment. A portable hard drive case might work also, but again, every one I've encountered lacks an internal zippered storage compartment.
Ideally being able to buy from Amazon or eBay would be best.
In addition to the suggestions in my last email... There are a wide variety of soft sided cases made for portable games (your Nintendo Switch, for instance) with pockets for adapters, games, etc.
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Re: Source for H4 Padded Storage Case?
On 8/18/20 4:10 PM, AA7US wrote: I¡¯ve searched for hours and so far come up empty handed...
Does anyone have a suggestion for a soft, clamshell style, padded storage case that'll fit a NanoVNA-H4 with enough extra room for typical accessories? It needs to have a separate inner zippered compartment to store the calibration fittings and coax jumpers so they won¡¯t rattle around and rub on the NanoVNA's screen.
I've seen multimeter storage cases which are close, but they're either way too big or lack a zippered internal storage compartment. A portable hard drive case might work also, but again, every one I've encountered lacks an internal zippered storage compartment.
Ideally being able to buy from Amazon or eBay would be best.
Check out Pelican cases, they have some fairly small ones. Another source is Cabela's (or Walmart, perhaps) - a small gun case might work. Both of those will typically have foam inserts that you cut as you need. The Pelican ones are prescored as 1/2" cubes, so you just pluck out the ones to make the right size holes. Those are likely to be hard sided. The softer sided ones - The ones I've used have been for things like CDs or headphones. You might try something like Guitar Center's online store in the accessories. Or an auto supply place like PepBoys, Kragen, AutoZone. They often have cases of various sizes to store stuff in. And finally, places lie U-Line sells all manner of shipping and factory organizing stuff, and some of it is storage containers. (You might find something for the medical industry, but it will be wretchedly expensive)
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Re: Source for H4 Padded Storage Case?
Not soft, and you'd need to provide your own padding.
But if interested in that retro look, search for "empty cigar box" on ebay.
If not considered appropriate for a nanoVNA,
could use it for your grid dip meter.
I'd probably just steal some tupperware-ish thing out of the kitchen.
Jerry, KE7ER
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On Tue, Aug 18, 2020 at 04:23 PM, AA7US wrote:
Does anyone have a suggestion for a soft, clamshell style, padded storage case
that'll fit a NanoVNA-H4 with enough extra room for typical accessories?
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John
RandMental
Dr. David Kirkby, Kirkby Microwave Ltd