[TowerTalk] Xm 240

[Lux, Jim]

On 11/27/22 11:08 AM, john at kk9a.com wrote:
> I just watched a couple of NanoVNA H4 youtube videos.  That looks like a
> nice little antenna analyzer that is overly complicated if you just want to
> see the SWR curve.
>
> John KK9A

It's as simple or complex as you want to make it. You don't even have to 
do the calibration if you don't want to, and you're happy with moderate 
accuracy measuring S11.

What's useful about it is not only can you display the match (either as 
SWR or return loss) and measure resonant frequencies.

But you can also do useful stuff like check your feed line for changes.  
The TDR function sweeps a wide band and calculates what a time domain 
reflectometer would show. You'll see every kink and connector as a small 
reflection. But what's better is you can measure the loss of the coax, 
in situ.  So all those "did that connector fail?" or "did water get in 
to the coax where the animals ate it".  Not only can you see it, but you 
know how far it is from the end, so if you have to repair it, you know 
where to go.

If you're looking to adjust a tuner, the VNA is your friend.

If you're looking to check a filter (say you've got band by band 
filters, or a low pass anti TVI filter), a minute with the VNA and 
you'll know if you fried that capacitor or the inductor got bent when 
you dropped it.

It's cheap. Compare $80 for the NanoVNA to $360 for the MFJ-259D, and 
I'll bet it can do everything the MFJ can.  And if you drop it or blow 
it up accidentally, it's another $80 to get a new one.


FWIW the other cheap tool these days is a TinySA - $60 for a spectrum 
analyzer that goes 20 kHz to 960 MHz. Wondering if your Tx is 
splattering? Wondering where that RFI source is?

The TinySA also can serve as a signal generator with limited capability 
- really nice for giving you a signal to radiate, so you can check your 
antenna, feedline, etc. all the way down to your receiver.


>
>
> Lux, Jim wrote:
>
>
>
> Or get something like a NanoVNA, which has a narrow band receiver.
> Although, I suppose you could saturate the mixer if you have a strong
> enough signal. But you'll know it if that occurs, because the S11
> magnitude will look pretty wonky (spikes where a harmonic of
> interference happens to mix with a harmonic of the LO).
>
> The NanoVNA H4 (with the 4" screen) is $80 from R&L.
>
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