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Still glitches/spikes on > 300MHz / NanoVNA-H

 

Despite various firmwares and repeated calibrations I'm getting these spikes when measuring antennas.
In this example it's a 2m Yagi (that's 140-150MHz).

It was suggested that this might simply stem from incoming signals, but I used a handheld radio to transmit to double check and it has no influence on the graph.

I found that the glitches start from anything >300MHz

V_20201206_115704.mp4
V_20201206_115704.mp4
NANO-H1.jpg
NH1.jpg

 

These glitches come from transmitters which signals are received by your antenna.

73, G¨¹nter

Am 06.12.2020 um 13:40 schrieb andrewhege33@...:

Despite various firmwares and repeated calibrations I'm getting these spikes when measuring antennas.
In this example it's a 2m Yagi (that's 140-150MHz).

It was suggested that this might simply stem from incoming signals, but I used a handheld radio to transmit to double check and it has no influence on the graph.

I found that the glitches start from anything >300MHz





schweppe.vcf
schweppe.vcf

 

Your handheld transmitter may not be on the frequency(ies) that are causing
the spikes. The spikes, as previously mentioned, are stemming from
close-by (and strong) RF sources likely in your immediate volume. How far
and at what power levels are your closest AM, FM, police, public service,
VHF and UHF TV, ...... installations? How does rotating your antenna
affect the spikes?

Dave - W?LEV

On Sun, Dec 6, 2020 at 1:24 PM schweppe <schweppe@...> wrote:

These glitches come from transmitters which signals are received by your
antenna.

73, G¨¹nter

Am 06.12.2020 um 13:40 schrieb andrewhege33@...:
Despite various firmwares and repeated calibrations I'm getting these
spikes when measuring antennas.
In this example it's a 2m Yagi (that's 140-150MHz).

It was suggested that this might simply stem from incoming signals, but
I used a handheld radio to transmit to double check and it has no influence
on the graph.

I found that the glitches start from anything >300MHz










--
*Dave - W?LEV*
*Just Let Darwin Work*
 

That is not the case, I wrote in my post that I used a handheld radio to simulate a transmitter ..
 

The spikes are also present with just a 50 ohm terminated coax ..
 

NanoVNA uses si5351 above it's spec and most chips work fine above 200MHz and up to 300MHz, but some are a few MHz short of it.
This has been discussed here before and the key is the point where the vna transfers from fundamental mode to harmonic mixing mode.
Lowering the transition frequency from 300MHz to 296MHz for example fixed the 300MHz spikes for some.

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