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First off, thanks to everyone for all the helpful responses! It made me
realize just how loaded my question actually was. It also help unjam the gears
in my head. That said, there's a lot of stuff here to respond to, so hopefully
I don't forget anything I wanted to discuss.

To clarify, I intend to operate at a fixed frequency, no modulation,
preferably somewhere in the 900MHz ISM band, driven by an amp operating at
less than 5W. Each run of the experiment should only last a few minutes at
most.

Probably due to me not knowing any better, I'm leaning towards making my own
amp along with bypass filtering. The amp section would be based on modules
such as:





@Jim Lux & Andy G4KNO
Your references to the FCC requirements and the given examples are very
helpful. It provides a better perspective of what I'm dealing with here. It
also shows me how much I still have to learn.

Regarding the monolithic filters in that band, I suspect they're a lot less
common than they once were. I see reference to a lot of discontinued items.
That said, some can still be found which is plenty for my needs as long as
they provide sufficient performance. The datasheets for some of these leave a
lot to be desired. I didn't hear of minicircuits until you mentioned it. It
looks like they may have a viable solution.

@Roger Need
I actually had both the rf-tools page and that digikey part (along with some
others) already opened in a browser tab. I made the mistake of making a really
sharp 1st order bandpass without realizing how ridiculously tiny either the
capacitor or inductor was. After widening the band enough to allow for more
realistic components, the roll off was much more shallow, in turn requiring
higher order filters. By that point, I became a bit more concerned regarding
the complexity of the filter.

@OneOfEleven & John Gord
Thanks for the hardware suggestions (I'm actually considering a TinySA to test
filters and amps), but since a critical aspect of my experiment is getting
phase angle information, I either have to use the nanoVNA to generate the RF
signal, or I don't use the nano at all and instead buy an old so-called
"vector voltmeter" along with all the other hardware I'd need. I can't help
but to think it should be possible to sufficiently attenuate frequencies
outside the nano's 5th harmonic much easier and cheaper than to purchase a
bunch of additional equipment.



So one thing that's not clear to me, particularly when it comes to
dielectric-type filters, is whether they could be cascaded to increase Q
without using amp inter-stages.

Hello everyone!

RF newbie and first time poster here. Recently purchased a NanoVNA-H for a
specific experiment I'd like to perform. Without going into the unnecessary
details of the experiment itself, what I'd like to do is use the nano as a
fixed RF frequency gen, probably in the ~900MHz ISM band, to be fed to an amp
and transmitted via an antenna. A probe on S21 will then be used for obtaining
relative phase angle measurements.

I know the nano generates a square wave output, thus the dominating
frequencies are the fundamental and odd order harmonics, along with some even
order and spurious frequencies. I also know that the nano will rely on the 5th
harmonic of some fundamental in order to reach my desired fixed frequency.
Since not only would it be irresponsible to transmit those various other
frequencies, but I also think my experiment would be better served by having
as spectrally pure signal as is reasonably possible. To avoid any confusion,
my intended TX signal chain is as follows:
nanoVNA S11 -> bandpass filter (probably LC?) -> RF amp -> antenna

So my question is this: how sophisticated does the filter realistically need
to be? Would a 1st order LC bandpass do, or do I need something else? Are
there any common "gotchas" that trip up newbs that I should be aware of?

Thanks!
Mark

On Wed, Oct 6, 2021 at 09:01 AM, Jim Lux wrote:

Saver, in general, doesn't have a lot of error recovery built in - it's
a nice program, but there's plenty of places where if something is
wrong, it just dies, and leaves it up to you to go look at the source
code to figure out how to fix it.

The original author of NanoVNA Saver, Rune, developed a very nice program
and graciously shared it with the user community. He was very responsive
to comments in this group and corrected bugs quickly and added many user
requested features.

Sadly he became quite ill and was no longer able to work on this project.
He graciously allowed his project to be taken over by Holger Müller
(zarath) and he has released several new versions but is not active in this
group. Bugs and new features requests can me made on the NanoVNA Saver
github page.

Roger

Hi Norman
Yes, CE and the FCC would consider that sweeping signal a Transient during any compliance testing.Might even get it declared Spread Spectrum hihi.? ?(That's what Lorawan is doing)? Certainly a Quasi Peak test would take it virtually to zero.? ?Just last week I had to do some patterns on an occupied frequency and had to run +37 dBm vs my usual +13 dBm to get a good plot.? ? Kept the source antenna close the ground and only had it on for a few minutes.??Yes, had some experience with OFCOM.? ?Hold 2E0VAA and G8EMY licenses.? ?I know, an 8, but it is a full license.? Kent


On Wednesday, October 6, 2021, 11:01:09 AM CDT, Norman_G8EYM <brycek.fs@...> wrote:
Hello Kent,

Mark introduced himself as an 'RF newbie' and I was, somewhat clumsily,
trying to point out that transmitting RF is not an unregulated activity.
I understand that very low power CW transmissions might not be noticed.
But adding an RF Amplifier could change the game.

Cheers,

_Norman._

Sent from my GNU-Linux ThinkPad.

On 06/10/2021 16:37, KENT BRITAIN wrote:

? Hi Norman
On this side of the pond the FCC does recognize the need to radiate signals during testing.
I have an antenna range and commonly transmit on many commercial frequencies.
I am expected to minimize radiated signals per "Good Engineering Practice" and are responsible for any interference I cause.? ? ? The NanoVNA certainly falls into this category.? ? Just leave it on long enough to get a good reading and you meet FCC guidelines.? ?In the real world you would probably leave it on for a week and no one would notice.? ? ?Kent
? ? ? On Wednesday, October 6, 2021, 09:45:24 AM CDT, Norman_G8EYM <brycek.fs@...> wrote:
? Good afternoon Mark,

In most parts of the world, transmitting a radio frequency signal is a
carefully regulated and licensed activity, whether for experimentation
or any other purpose. Holders of transmitting licences are required to
adhere to the local regulations concerning frequency, power, mode of
transmission and harmonic content, to name but a few.

Assuming that you can conform to the required standards and conditions,
the appropriate filtering methods are well documented.

My initial assessment of your planned experiment is that it wouldn't be
legal as, for starters, the 'bare foot' Nano-VNA doesn't have the
capability to be modulated and provide your station ID.

I could be wrong, of course.

Regards,

_Norman, G8EYM_

Sent from my GNU-Linux ThinkPad.

On 06/10/2021 11:36, msat via groups.io wrote:

Hello everyone!

RF newbie and first time poster here. Recently purchased a NanoVNA-H for a specific experiment I'd like to perform. Without going into the unnecessary details of the experiment itself, what I'd like to do is use the nano as a fixed RF frequency gen, probably in the ~900MHz ISM band, to be fed to an amp and transmitted via an antenna. A probe on S21 will then be used for obtaining relative phase angle measurements.

I know the nano generates a square wave output, thus the dominating frequencies are the fundamental and odd order harmonics, along with some even order and spurious frequencies. I also know that the nano will rely on the 5th harmonic of some fundamental in order to reach my desired fixed frequency. Since not only would it be irresponsible to transmit those various other frequencies, but I also think my experiment would be better served by having as spectrally pure signal as is reasonably possible. To avoid any confusion, my intended TX signal chain is as follows:
nanoVNA S11 -> bandpass filter (probably LC?) -> RF amp -> antenna

So my question is this: how sophisticated does the filter realistically need to be? Would a 1st order LC bandpass do, or do I need something else? Are there any common "gotchas" that trip up newbs that I should be aware of?

Thanks!
Mark

? Hi Norman
On this side of the pond the FCC does recognize the need to radiate signals during testing.
I have an antenna range and commonly transmit on many commercial frequencies.
I am expected to minimize radiated signals per "Good Engineering Practice" and are responsible for any interference I cause.? ? ? The NanoVNA certainly falls into this category.? ? Just leave it on long enough to get a good reading and you meet FCC guidelines.? ?In the real world you would probably leave it on for a week and no one would notice.? ? ?Kent
? ? ? On Wednesday, October 6, 2021, 09:45:24 AM CDT, Norman_G8EYM <brycek.fs@...> wrote:
?
? Good afternoon Mark,

In most parts of the world, transmitting a radio frequency signal is a
carefully regulated and licensed activity, whether for experimentation
or any other purpose. Holders of transmitting licences are required to
adhere to the local regulations concerning frequency, power, mode of
transmission and harmonic content, to name but a few.

Assuming that you can conform to the required standards and conditions,
the appropriate filtering methods are well documented.

My initial assessment of your planned experiment is that it wouldn't be
legal as, for starters, the 'bare foot' Nano-VNA doesn't have the
capability to be modulated and provide your station ID.

I could be wrong, of course.

Regards,

_Norman, G8EYM_

Sent from my GNU-Linux ThinkPad.

On 06/10/2021 11:36, msat via groups.io wrote:

Hello everyone!

RF newbie and first time poster here. Recently purchased a NanoVNA-H for a specific experiment I'd like to perform. Without going into the unnecessary details of the experiment itself, what I'd like to do is use the nano as a fixed RF frequency gen, probably in the ~900MHz ISM band, to be fed to an amp and transmitted via an antenna. A probe on S21 will then be used for obtaining relative phase angle measurements.

I know the nano generates a square wave output, thus the dominating frequencies are the fundamental and odd order harmonics, along with some even order and spurious frequencies. I also know that the nano will rely on the 5th harmonic of some fundamental in order to reach my desired fixed frequency. Since not only would it be irresponsible to transmit those various other frequencies, but I also think my experiment would be better served by having as spectrally pure signal as is reasonably possible. To avoid any confusion, my intended TX signal chain is as follows:
nanoVNA S11 -> bandpass filter (probably LC?) -> RF amp -> antenna

So my question is this: how sophisticated does the filter realistically need to be? Would a 1st order LC bandpass do, or do I need something else? Are there any common "gotchas" that trip up newbs that I should be aware of?

Thanks!
Mark

? ?