[TowerTalk] Relay Box Measurements

[K8RI]

On 8/26/2012 1:27 PM, Jeff DePolo wrote:
>> when you do the measurements (using some form of VNA, I
>> presume), do you
>> cal with a set of standards with UHF connectors, or something else?
>
> You're better off using lab-grade test cables with constant impedance
> connectors (N, SMA, TNC, etc.) and a precision cal kit to do the cal, and
> then use a high-quality adapter to get to UHF to connect to the DUT.  Unless
> you're dealing with short wavelengths, the added electrical length of the
> adapter (maybe 3/4"?) isn't appreciable (3/4" is only a little over half a
> degree at 10m), but if you're a purist you could always offset the complex Z
> accordingly (Smith Chart or electronic equivalent thereof). Insertion loss
> of a quality N to UHF adapter is negligible at HF.

For myself I'm really not interested in reaching lab grade accuracy.
If line loss is within a few tenths of a db of the manufacturers specs, 
I'm happy.  That lets me compare coax cables as well.

If I can find discontinuities within a few tenths I'm also happy.

My primary interests are SWR, finding resonance, and bandwidth.
Using the TDR function it's finding those discontinuities such as coax, 
coax connector, or relay problems.


73

Roger (K8RI)
>
> 				--- Jeff WN3A
>
>
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