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Great post William. This board as stated previously needs to be moved to a
forum where we can have sub topics for discussions. There is so much
information flowing through here that much of it gets list in the weeds.
It
can be overwhelming. There are very skilled individuals here with VNA
usage
and RF. If we had it broken down by topics then it would be easier to
source
and direct to the appropriate topics based on need.

Maybe we should look at migrating this over to a free slack community?
===============================

Groups.io allows sub-groups. No need to move.

Cheers,
David GM8ARV
--
SatSignal Software - Quality software for you
Web:
Email: david-taylor@...
Twitter: @gm8arv

On Aug 31, 2019, at 9:45 PM, William Clark <wclark@...> wrote:

nanoVNA Message
There has been some great discussion on nanoVNA reflection and calibration topics. Perhaps the following could be of interest to those who would like to see a drawing or two with coupling instructions for various feed line measurements and db gain/loss calculations. Promise -- no complex math involved. If complex math was taught from secondary school and on after trigonometry, it would be in the long run, much easier for people to understand electricity and RF as really exists. BTW, 'complex math' is in reality not very complex but very intuitive and well worth the time to study it. It makes cabling and RF measurements innumerably simpler to understand rather than the funky single-phase volts and current that most RF techs and Hams are taught.

Compliments of WAVETEK: (800) 851-1198,
<- get a PDF manual here or search for: Wavetek 3ST
(or)
wavetek.org
Create a nickname and a single-use password for these sites to be safe.

Here is a small snippet of information in the WaveTek 3ST RF diagnostic manual (very similar to what the nanoVNA is trying to do) on correct reflection instructions and theory. The manual has a pretty good write up on how these devices like WaveTek 3ST and nanoVNA should be used and hooked up with impedance bridge taps and directional couplers for accurate calculations. The manual is free and available for a download in PDF in its entirety.

2.3 INSTALLATION
Proper installation of the Transmitter is essential to correct operation of the system. The transmitter is typically installed in a headend rack. There are two different options for setting up the system. One entails inserting the sweep at a standard combining network input, with a directional coupler (test point) at the output of the combining network.
Alternately, a directional coupler may be used to insert the sweep at the output of the combiner. A directional coupler is used to sample system signals in the headend, and an additional directional coupler is used to inject the sweep (see figure). The sampling directional coupler (DC a) may be of any value (dB), but higher values are typically chosen to limit insertion loss. The sweep insertion directional coupler (DC b) tap loss must be taken into account when setting the insertion level of the transmitted sweep signal.
[Diagram 2-1 - unprintable here]
The transmitter output level is variable from +20 to +50(1) dBmV in 2 dB increments. The output level will be attenuated by the tap value of the directional coupler. For example, if a sweep signal level of +16 dBmV is desired on the system and the output of the 3ST Transmitter is set to +36 dBmV, a directional coupler value of 20 dB may be used, or the combination of a lower value directional coupler and an attenuator pad.

[Combining Network Diagram did not paste here] Get the manual to see an example.

An alternate method would be to insert the 3ST Transmitter output at one of the combining network inputs, and connect the (transmitter) reference input to the headend amplifier input test point. This method eliminates the need to add directional couplers at the combiner output.

For detailed setup information, see "Stealth Sweep Start-up Procedure", page 4-1.
Hope this helps for those of you struggling to understand these topics. My hat is off to all of you not sitting in front of a TV but using your hands and brains.
--
Prof. Wm. Clark (Ret.) CS, BSEE, BSEET (KE7FO)

On Aug 31, 2019, at 9:40 PM, Reginald Beardsley via Groups.Io <pulaskite@...> wrote:


That's a *lot* cheaper and *much* nicer than the one I'm making. I still need to make the holes. The ones for the switches are pretty scary.



On Saturday, August 31, 2019, 6:41:53 PM CDT, Vince Rooney <vince@...> wrote:


This is a housing I was considering. Will need some machining. Was thinking of putting a larger screen and full size connectors on it.

Thanks Vince

I would really appreciate a copy of your firmware!

Please see the attached photo of my model:

At first glance it looks almost exactly the same as yours.

I have also added a copy of my 'bad' firmware, if anyone wants to take a look ror might find it interesting:

Thanks again

On Aug 31, 2019, at 6:28 PM, Reginald Beardsley via Groups.Io <pulaskite@...> wrote:


I bent up a housing out of 28 gauge galvanized steel (HVAC duct scrap). I tried hammer forming, but was not happy with how that turned out. I might take a crack at hammer forming aluminum, but I didn't want to heat galvanized with a torch and give myself zinc poisoning. So I went with a simple two piece U design.

I got the back cover which holds the connectors 1/16" too long, so I'm going to do it over for the 4th or 5th time. The Harbor Freight 3 in 1 metal machine doesn't have a decent backgauge so it is *very* difficult to set the shear accurately. And to make matters worse, I'm a complete novice at sheet metal. But there's only one way to learn. Keep doing it until you get it right.

I thought about putting N connectors on, but decided to stick with the SMA. I've got an 8753B/85046A. I'm not expecting this to get a lot of use. I bought it more out of curiosity than anything else. If I did use it for serious work, I'd run SMA cables to a fixture.

It's not got enough memory to add much software functionality and I wasn't able to find a pin compatible part with more memory.

Have Fun!
Reg

Try a different firmware version.
Like one of the 2 ch versions

I found that one of the firmware files seems to be an older version with a
new name date

Also when you have yours connected to the computer
Open a terminal window at 9600
And type INFO see if the date matches the firmware version

Also can type HELP

Sorry for the broken typing from my cell phone

73
N7kbc
Dwight




On Sat, Aug 31, 2019, 09:49 <sarelskiet@...> wrote:

Thanks Vince

I would really appreciate a copy of your firmware!

Please see the attached photo of my model:

At first glance it looks almost exactly the same as yours.

I have also added a copy of my 'bad' firmware, if anyone wants to take a
look ror might find it interesting:

Thanks again

One difference I noted between my white unit and my black one: The front and back panels of the white unit are unshielded, painted PC board. The black unit has aluminum front and back panels.

So I wondered if one was better shielded than the other. I laid my 5 watt, 450 MHz handheld antenna on the face of the VNA and keyed the transmitter. Then I moved the HT approximately one foot away and retested. The resulting interference comparison is shown in the attachment.

Short answer: "Nope". No difference whatsoever. My recommendation would be not to key a transmitter in the vicinity when making critical measurements. Practically speaking I think the interference is surprisingly low. And the metal panels make no difference.

WA8TOD

Thanks Vince

I would really appreciate a copy of your firmware!

Please see the attached photo of my model:

At first glance it looks almost exactly the same as yours.

I have also added a copy of my 'bad' firmware, if anyone wants to take a
look ror might find it interesting:

Thanks again