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Hmm... interested to know what's going on with the void in the PCB. Likely to do with the directional bridge, but what?
/ Gerry

There was still a small error in slide 25 in the English version.
The drawing was correct, but in the text I mixed up the meaning of NODE and ANTINODE.
Now corrected, without changing the version number.
Thanks to Hans DJ7BA for finding it.
73,
Luc ON7DQ

There is almost no difference in the amount of commenting between the various nanoVNA branches.
You can easily do on github a comparison between branches to find out.
But all are fairly easy to understand

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NanoVNA Wiki: /g/nanovna-users/wiki/home
NanoVNA Files: /g/nanovna-users/files
Erik, PD0EK

This one looks satisfactory... 1500mAH

Yet another "off the beaten path" , and very polite request.
Feel free to ignore it.

The NanoVNA is "open source" - hence many "dupes" exist.
I would be very grateful to hear from some experienced software hacker to tell me which code
is the MOST commented one.
I am basically looking for C/C++ code implementing Smith chart.
So far I found two and since I have not look in details in NanoVNA code
I could use some suggestions.

Thanks
73 AA7EJ

As long as this topic is being addressed, how about links to suitable products?

This confused me as well at first. I was expecting to see impedance expressed as something like 10 + j240 ohms on the smith chart mode. Actually these are the resistance and reactance values, not real and imaginary (how NanoVNA refers to it, anyway)
.
You have to switch on the Reactance plot to see the "j" number.

What Jean-Roger said!

It was very definitely the cable. After buying a new cable, windows recognised the device automatically, no messing with drivers was needed, and NanoVNA Saver worked first time.

Apparently some sellers of clones are cheaping out on the accessories, and the cable is junk (maybe it's intended as a phone charging cable only).. mine was missing a "short" and "open" cal standard as well.

Thank you.

this is slightly off topic but the ne602 is prone to overload. I recently built an upconverter and I used one of these that works quite well
.ADE-1-24 ADE-1-24+ DOUBLE BALANCED Frequency Mixer RF
I found that its lack of gain made no difference in the 1 -30mhz area. I see them on ebay

Hi nanovnauser;

A couple of more or less encouraging comments for you. Your VNA antenna measurement results indicate the following:

1) You did well... You are using the VNA and interpreting the results correctly in the context that you have described for its use. You clearly have done a fine job matching your antenna. It looks spot on and well matched.

2) Anything that gets you on the air is a good antenna, and I applaud your effort in that regard. 20 dB below 100W puts your EIRP (very isotropic in your case BTW) at the 1W level. Time of day (interpret this as night), prevailing ionospheric conditions, and persistence can render you surprise and enlightenment. WAS has been achieved at considerably lower power levels on 80 meters, and I have personally copied a 10 mW beacon at 340 mil on 80 meters, so I'm not going to rag on your antenna. I rag on those who whine about HOA's and the like for keeping them from operating. Do a Google Earth fly over of N2PK's QTH... He manages to keep the hostile HOA police in the dark. Then take a look at his DXCC record on 160 meters, and his position on the honor roll. I've tuned up the metal roof of a brick storage building in order to QNI into our 80 meter net. The Tx performance was awesome... but whoa!!! Definitely not as desirable as a Beverage on Rx.

3) Maybe this is obvious to everybody, but I'll comment on the array of VNA photo's you attached. The Smith Chart pretty much tells the whole story, and all that follow are simply different ways of displaying exactly the same information. VNA's measure reflection coefficient; the displays are simply computational results of the same measurement.

Bottom line... I'm convinced of your ability and knowledge of using a VNA to correctly and accurately tune antennas. Getting yours tuned precisely where you wanted it is certainly a bigger challenge than tuning up a cook book design. Try getting on the air an hour or so after dusk... and especially on weekends.... when hams actually make their presence known. Try answering a few of the stronger CQ's. You may be surprised at the gems that are borne out enthusiastic dumpster diving. LOL!



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73

Gary, N3GO

Hi Roger,

Thanks for the suggestions, I have the attenuator shown in the picture and did wonder if I could use this but was not sure about the calibration procedure. I will try this as well, currently I have my NanoVNA connected directly to the transformer and have been testing various winding combinations to get a good match. So far I have got a 1.5 to 1 VSWR at 7.15MHz but the circuit is still on a breadboard so I expect the numbers to change a bit when I solder it up on a veroboard.

As kb1gmx mentioned above, the NE602 has a very good gain at 40m and I am sure that what I have now would work quite well but I am quite curious if I can make a really good match now I have a VNA to work with. The other radios I have built for 40 and 20 meters have all been quite successful and I did not have a VNA for these - now I do have one I am finding it very interesting to experiment and really see what the changes I make actually do.

I have had a look around for the BN73-202 binocular cores you mentioned and have found them at the same place I buy my FT37-43 cores - I will order a few of these and try them out - hopefully they will arrive in a day or so.

On Tue, Mar 10, 2020 at 02:55 PM, Dragan Milivojevic wrote:

Any plans to release a review of the prototype unit that you got?
========================================================
Erik has experience his own VNA design and provided Gabriel with helpful suggestions during her SAA-2 design. I have not seen any issue reports from him to Gabriel regarding his pre-production unit, so I assume that it is performing up to its advertised specifications. That is encouraging to members of this group who value Erik's technical insight.

- Herb

Also on tindie.
Any plans to release a review of the prototype unit that you got?

Battery spec is in the spec doc in this thread

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NanoVNA Wiki: /g/nanovna-users/wiki/home
NanoVNA Files: /g/nanovna-users/files
Erik, PD0EK

Looks like an interesting way to get on 80 meters which is not something
everyone has the airspace to do. If you want to play with it try moving
the two whips away from each other with a copper pipe in the middle. Even
four feet will make a difference as that is where this antenna needs to
radiate the most.
NE7LS

Hello Herb,

thanks for the reply. I was thinking that the designer probably designed V2 with a specific model of battery in mind, and could maybe provide a hint. (if he's reading this)
For me, the Nano is primarily a portable field instrument, with emphasis on being completely self-contained, so a battery is a high priority.

The standards supplied with the old nano are not bad - I checked them on a HP analyzer, and up to 3GHz they are very good. Of course, I could just have had luck, and other sellers sell crappy ones.

RG174 is more of a problem, but if you don't chase tenths of a decibel, such short pieces are quite "usable" up to 3.

Marko Cebokli

If you want a low cost spectrum analyzer (SA) that goes from a few kHz to 2 GHz. buy an SDRplay RSP1A SDR receiver for around $100 US. Then download the free Spectrum Analyzer program, written by a 3rd party, from the SDRplay downloads section. This program has a lot of standard SA features but you will need some good attenuators because the RSP1A needs to have a maximum signal input below 0 dBm.

Another way to describe two 8ft whips as a dipole... A HF rubber duck antenna.
Or an Electrically small antenna (under .1 lambda , for 80m thats 8M long)
and the loading coils or matching scheme will contribute inefficiency.

Its efficiency is typically under 5% maybe worse. Also likely lower HF antennas
less that very high (at least 20M or more) is also a hit to performance as most
of the RF radiate due to ground bounce is straight UP.

Also it has a very small Aperture, so it intercepts a significantly smaller part
of the incoming signal.

NOTE: a full sized dipole at 10ft (3M) height would greatly outperform that
antenna for distances under 300miles (`500km). It can be bent to fit available
space with some reduction in performance.


Allison
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No direct email, it goes to bit bucket due address harvesting in groups.IO

Hi Dave,
Those results look really nice. If you want to try a direct approach with only resistors, here is the formula -
Make a new board, using 2 SMA to PCB connectors, one for signal in (pin 1) one for signal out (pin3)
From the center pin on both SMA connectors, go though a 56 ohm R to ground.

From the same center pin node, go from each in series though a 300 ohm R to pins 1 and 3 of the filter socket. On the output (pin3) use a 10 pf cap to ground before the 300 ohm R. That's it.

This arrangement yields (close to) the proper load for both 50 ohm in and out ports, as well as 330 ohm load for the filter itself. The actual loads seen by the filter are 326.4 ohms.
You can experiment with the 10 pf cap, it is always shown in the Murata recommended test fixture. My results show it becomes less important on wide (280 kHz) filters, and more important, especially for filter top response slope and group delay "side saddles" for narrow filters (150, 180 kHz).
So, here is another circuit adjustment than can be added to an in-situ ceramic filter, in addition to output load R, to adjust response in circuit for best performance (usually lowest distortion). These adjustments are needed as not all circuits / components used in existing gear are perfect, and no one has an unlimited supply of ceramic filters.
BTW, if anyone needs 10.7 filter data, join the FMtuners group here, there is quite a bit there in the files, which go back to 2001. It probably makes no sense to re-post it all here.
Bob

Your two EXTREMELY short whips configured as a horizontal dipole will have very high losses and low efficiency? because they are physically short. Even though the whips load the elements to achieve resonance their efficiency is going to be horrible. This is the price you pay for "convenient" short antennas at low frequencies. Remember SWR has nothing to do with how well an antenna can radiate or receive an RF signal. A 50 ohm resistor will give you a 1:1 SWR but it will be useless as an antenna.

I generated a very quick & dirty model of your antenna and for NVIS signals arriving from straight overhead the difference between a full-sized dipole and your two short whips at 12' is on the order of >20 dB. This is a huge difference so when you say it works like rubbish it is in fact working as it should.

Gedas, W8BYA EN70

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