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I got prettty peed off with an eBay seller. I bought a NanoVNA, which he
shipped 3 weeks after getting my money. It arrived yesterday, but when
powered up, all I get is a white screen, and a couple of LEDs on. When
powered off, one of the LEDs stays on for about 30 seconds or so. Anyway, I
can't get anything out of this. The seller offered me a refund or a
replacement. I said I would take a replacement if he could ship by DHL.
FedEx or UPS, rather than their normal slow postal service. I suspect he is
not actually going to use one of those couriers, but he has said express
mail, so hopefully it wont be too long before I have a working one.

--
Dr David Kirkby Ph.D C.Eng MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, CHELMSFORD,
Essex, CM3 6DT, United Kingdom.
Registered in England and Wales as company number 08914892

Tel 01621-680100 / +44 1621-680100

Two bad clones have been found, they have failed to understand the role of bridge and shielding, and made some bad modifications to facilitate manufacturing.

My unshielded black clone just arrived, 16 days after ordering.
White text is less bold than on shielded black units,
and front bezel is held by 4 black screws,
while others appear bright riveted(?)
eBay seller onemoredeal (Jonna) had explained that delivery was
delayed from eBay estimate (based on speedpak shipping service)
by using alternate (Chinese post) that allows battery,
which was indeed included and charged.

Adding an SMA "protector" to TX did not appreciably impact calibration;
even a BNC adapter does not much affect readings below 100 MHz

Not sure whether description as "bad clone" is entirely accurate;
2017 nanoVNA by edy255 also lacked shielding...


FWIW, shippers crushed outer corrugated box by about 1/3,
but inner nanoVNA box wrapped in foam was intact.

Also perhaps 'Donate@ it to the world and take the duff one apart see what is really in one of them ... obviously nit just a dummy load as i suspected or you would have that nice big dip for 70cms

cheers

Tim M0THM

Makes you wonder how many people buy something like this and just plug it in expecting it to have been tested etc beforehand ... then damage thier TX.

Here are the images: Sorry for the bandwidth.

________________________________
From: [email protected] <[email protected]> on behalf of alan victor <avictor73@...>
Sent: Friday, July 12, 2019 3:50 PM
To: [email protected]
Subject: Re: [nanovna-users] Narrow band filters and LO phase noise/jitter?

Here are some home made roofing filters. The bandwidth, center frequency and transition to the noise floor are a reasonable challenge for the casual measurement. In these measurements I see no issue with good agreement with other measurement systems. One filter is a 4 pole and the other a 6 pole at 70 and 25 MHz. Yes, the return loss on the 25 MHz filter looks pretty good. I would challenge that number based on the calibration but suspect its probably at least 20 dB! Alan

Here are some home made roofing filters. The bandwidth, center frequency and transition to the noise floor are a reasonable challenge for the casual measurement. In these measurements I see no issue with good agreement with other measurement systems. One filter is a 4 pole and the other a 6 pole at 70 and 25 MHz. Yes, the return loss on the 25 MHz filter looks pretty good. I would challenge that number based on the calibration but suspect its probably at least 20 dB! Alan

Very nice. Thanks for sharing. Nice example of taking a 2 pole monolithic crystal filter and sweeping it first in a 50 ohm system and noting that it is not properly terminated. Then adding series resistors to provide a reasonable termination and obtaining a proper frequency response.

The challenge I was chasing is to be sure fidelity of the response was correct without access to analyzer IF bandwidth or sweep speed. Filter measurements can be distorted. It appears the nanoVNA handles the issue(s) well.

________________________________
From: [email protected] <[email protected]> on behalf of Oristo <ormpoa@...>
Sent: Friday, July 12, 2019 2:07 PM
To: [email protected]
Subject: Re: [nanovna-users] Narrow band filters and LO phase noise/jitter?

Here is an article about crystal filter analysis by nanoVNA:

Great. Happy to hear success. There are further improvements that can be accomplished in the cal process. However, will see if they make sense and provide enough improvement to warrant posting.

Alan W4AMV

________________________________
From: [email protected] <[email protected]> on behalf of sites.online@... <sites.online@...>
Sent: Friday, July 12, 2019 1:29 PM
To: [email protected]
Subject: Re: [nanovna-users] Calibration of the 4 track nanoVNA

Thank you Alan W4AMV,

Finnally I have my nanoVNA correctly calibrated. I am happy now with the measurements!

Cheers and 73

Luís, CT2FZI

Here is an article about crystal filter analysis by nanoVNA:

Thank you Alan W4AMV,

Finnally I have my nanoVNA correctly calibrated. I am happy now with the measurements!

Cheers and 73

Luís, CT2FZI

There is a filter spurious on the high side of the skirt. This shows up as a spike on the VNA display. There is none on the low side skirt, despite what appears to be a spurious on the VNA display. I put together a 4 pole 77 MHz crystal filter and its swept response on the nanoVNA as well on another analyzer are in excellent agreement. This filter has a reasonable transition BW compared to its center frequency; 1800 Hz at 77 MHz. At this point I would say there is no issue. I will capture its response and post. Alan

________________________________
From: [email protected] <[email protected]> on behalf of alan victor <avictor73@...>
Sent: Thursday, July 11, 2019 6:19 PM
To: [email protected]
Subject: Re: [nanovna-users] Narrow band filters and LO phase noise/jitter?

This 500 Hz bandwidth filter is problematic. Upon further measurements with another instrument there are issues.

I will find another baseline network and report findings again.

Alan

________________________________
From: [email protected] <[email protected]> on behalf of dk1vi <dk1vi@...>
Sent: Thursday, July 11, 2019 4:09 PM
To: [email protected]
Subject: Re: [nanovna-users] Narrow band filters and LO phase noise/jitter?

In crystal factories crystals are measured in a 50Ohm system with a pi-network on both sides as per enclosed picture.
Don't know if the resistance values are readable in the compressed picture so here the are:
Input R1=159 ohms to ground, R2=66,2 ohms in series and R3=14,2 ohms to ground. On the outputside the network is mirrored.
Please do not ask me where this strange resistor values come from.

Never one to back away from a puzzle, the resistive pi network for crystal testing reverse-engineers to a 50 to 12.5 ohm matching pad with just under 15 dB loss (14.774).? Probably trying to "match" the series resonant resistance of the crystal.
Bob C

It was tested with a small ground plane. Tried other configurations too, but with only very small changes.

This antenna was bought on eBay for US$0.99 with free shipping. So it was probably a poor rip-off.
If someone just needs a 430 MHz band antenna it might work out.

Anyway, it's nice to know that the Nano worked well enough to find the missing band problem.

Does it require a ground plane? I would put an SMA connector centered on a plate of PC clad card. Then feed the cable thru back to the VNA.

________________________________
From: [email protected] <[email protected]> on behalf of George <steber@...>
Sent: Thursday, July 11, 2019 7:12 PM
To: [email protected]
Subject: [nanovna-users] SRH508S Antenna SWR with NanoVNA

Decided to test this SRH805S wide band antenna. They claim it covers 144/430/1200 MHz.
While the nano doesn't cover 1200 MHz, it does handle the lower two bands.

Clearly there is a problem as 144 MHz band is not showing any reasonable SWR.

By the way, my graph shows the SWR (left scale in red) and reflected power in percent (right scale in green).

As for the SRH805S, I must have gotten a bad one. One band missing!

Decided to test this SRH805S wide band antenna. They claim it covers 144/430/1200 MHz.
While the nano doesn't cover 1200 MHz, it does handle the lower two bands.

Clearly there is a problem as 144 MHz band is not showing any reasonable SWR.

By the way, my graph shows the SWR (left scale in red) and reflected power in percent (right scale in green).

As for the SRH805S, I must have gotten a bad one. One band missing!

"Have searched the net, but did not find a copy of the QEX 2017/05. Do you know any source for this reference?"

Try searching for, or emailing, the author. Often they will provide a copy to you as a courtesy.

Also try searching for related material to FA-VA5 antenna analyzer. It should be easy to find on web.

He has also written material showing how to connect his unit to DG8SAQ VNWA software.
(Very powerful software but with a steep learning curve.).

This 500 Hz bandwidth filter is problematic. Upon further measurements with another instrument there are issues.

I will find another baseline network and report findings again.

Alan

________________________________
From: [email protected] <[email protected]> on behalf of dk1vi <dk1vi@...>
Sent: Thursday, July 11, 2019 4:09 PM
To: [email protected]
Subject: Re: [nanovna-users] Narrow band filters and LO phase noise/jitter?

In crystal factories crystals are measured in a 50Ohm system with a pi-network on both sides as per enclosed picture.
Don't know if the resistance values are readable in the compressed picture so here the are:
Input R1=159 ohms to ground, R2=66,2 ohms in series and R3=14,2 ohms to ground. On the outputside the network is mirrored.
Please do not ask me where this strange resistor values come from.

QEX is a magazine published by the ARRL for communications experimenters. The articles and papers in it are much more technically-oriented than most of what is in the QST ARRL magazine. One must be an ARRL member to access the QEX files and maybe even a QEX subscriber (I am one - I don't know if an ARRL member can access the QEX files without having a QEX subscription).

I haven't tried to access any QEX papers in a while. The papers as published in the physical magazine are limited in length and so, make available more technical details, software, schematics, etc., etc., there are a bunch of additional files for many of the papers on the ARRL/"QEXfiles" web pages. It appears that the original text of the published papers is not available but the supplemental files referenced above are.

Remember that the magazines published by the ARRL are all copyrighted and so it is not strictly lawful to pass PDF copies of them around, at least to non-subscribers. I'm guessing that that is the reason that one cannot just download PDF copies of the articles.

I will look to see if I can find my paper copy of the 2017 May/June issue of QEX. I think I unpacked my QST and QEX magazines a while back.

As an aside, QEX is a pretty good technical publication.

DaveD

In crystal factories crystals are measured in a 50Ohm system with a pi-network on both sides as per enclosed picture.
Don't know if the resistance values are readable in the compressed picture so here the are:
Input R1=159 ohms to ground, R2=66,2 ohms in series and R3=14,2 ohms to ground. On the outputside the network is mirrored.
Please do not ask me where this strange resistor values come from.

Have searched the net, but did not find a copy of the QEX 2017/05. Do you know any source for this reference?