|
Hi My 50 ohm cal load failed that I got in the kit,
has anyone had this happen to them ?
Thanks Dave 2E0DMB
|
the load I got happens to have bad contact internally too, reacts when shaking or knocking at the table. Recommend use of better SMA-Loads for calibration.
See RF-Parts or other dealer
|
thanks for the info, I did not think I would be the only one
Thanks Dave 2E0DMB
|
50 ohm cal load failed SMA connectors are fragile, and provided load spins in nanoVNA female socket. Some folks reduce CH0 SMA connector wear by adding male-female adapter. For frequent recalibration and BNC-equipped DUTs, I and others buy BNC cal kits, which are IMO more durable and convenient, e.g.:
|
at RFPARTS to buy for 3,95$
Had recently gained bad experiece with cheap SMA-load baught via ebay (aro 1$ a piece), none of them had 50ohms,
so I discarded them, contacted the ebay dealer for replacement, got it, but they were no good either
|
Mine failed also - a piece of junk. Bought my own online.
|
On Sat, Nov 2, 2019 at 06:50 PM, @arnoh wrote:
at RFPARTS to buy for 3,95$
It looks like cheap Chinese SMA-terminators. If so, they have bad performance. Try to measure it with multimeter, does it have 50.0 ohm? Most of all it has high error, something like ¡À5 ohm.
|
On Sat, Nov 2, 2019 at 09:56 AM, QRP RX wrote:
It looks like cheap Chinese SMA-terminators. If so, they have bad performance.
Try to measure it with multimeter, does it have 50.0 ohm?
Most of all it has high error, something like ¡À5 ohm.
---------------------------------------------------------------------------------------------------------------- As QRP replied, there is a difference between a 50 ohm termination and a good quality 50 ohm calibration load. That is why commercial calibration kits cost so much money. Using an un-characterized termination, your OSL calibration will look correct but you will be referencing all your measurements to however good the termination is. For example if you use a poor termination for performing your OSL calibration and then measure a good quality load. The load will look poor. Checking the termination with a multimeter only tells you what its DC characteristics are. You need to measure the termination against a known good quality load to verify its characteristics. It might prove worthwhile to construct your own 50 ohm load using the methods presented by other members of this group. Herb
|
I have a set of SS SMA PCB mount male connectors that I soldered 4 200 ohms
0603 resistors around the clock, 12,3,6,9 and it measures very close to my
HP SMA termination.
Mel, K6KBE
toggle quoted message
Show quoted text
On Sat, Nov 2, 2019 at 10:38 AM hwalker <herbwalker2476@...> wrote: On Sat, Nov 2, 2019 at 09:56 AM, QRP RX wrote:
It looks like cheap Chinese SMA-terminators. If so, they have bad
performance.
Try to measure it with multimeter, does it have 50.0 ohm?
Most of all it has high error, something like ¡À5 ohm.
----------------------------------------------------------------------------------------------------------------
As QRP replied, there is a difference between a 50 ohm termination and a
good quality 50 ohm calibration load. That is why commercial calibration
kits cost so much money. Using an un-characterized termination, your OSL
calibration will look correct but you will be referencing all your
measurements to however good the termination is. For example if you use a
poor termination for performing your OSL calibration and then measure a
good quality load. The load will look poor.
Checking the termination with a multimeter only tells you what its DC
characteristics are. You need to measure the termination against a known
good quality load to verify its characteristics. It might prove worthwhile
to construct your own 50 ohm load using the methods presented by other
members of this group.
Herb
|
On Sat, Nov 2, 2019 at 10:46 AM, Mel Farrer, K6KBE wrote:
I have a set of SS SMA PCB mount male connectors that I soldered 4 200 ohms
0603 resistors around the clock, 12,3,6,9 and it measures very close to my
HP SMA termination.
---------------------------------------------------------------------------------------------------------------- Mel, I used a commercially made HP 50 ohm termination as my standard until David Taylor pointed out that even though it was manufactured by HP its s-parameter specs were lukewarm at best. My S11 measurements on known devices were slightly off, but that was because my NanoVNA OSL calibration was made with a load that was slightly off. Changing to a Mini-Circuits 50 ohm load with known s-parameter specs up to 18 GHz solved the problem. To my point, what you have observed may not reflect accuracy unless your HP termination is well characterized. Of course if you are just using the NanoVNA in a hobbyist environment where measurements within 5 - 10% are acceptable, then pretty much any 50 ohm load or termination assembled using good rf techniques should do. - Herb
|
Well, my HP was calibrated decades ago before I retired. and like you say
for fun stuff it is good enough. I prefer to roll my own now. Close
enough is good for me.
Mel, K6KBE
toggle quoted message
Show quoted text
On Sat, Nov 2, 2019 at 12:57 PM hwalker <herbwalker2476@...> wrote: On Sat, Nov 2, 2019 at 10:46 AM, Mel Farrer, K6KBE wrote:
I have a set of SS SMA PCB mount male connectors that I soldered 4 200
ohms
0603 resistors around the clock, 12,3,6,9 and it measures very close to my
HP SMA termination.
----------------------------------------------------------------------------------------------------------------
Mel,
I used a commercially made HP 50 ohm termination as my standard until
David Taylor pointed out that even though it was manufactured by HP its
s-parameter specs were lukewarm at best. My S11 measurements on known
devices were slightly off, but that was because my NanoVNA OSL calibration
was made with a load that was slightly off. Changing to a Mini-Circuits 50
ohm load with known s-parameter specs up to 18 GHz solved the problem. To
my point, what you have observed may not reflect accuracy unless your HP
termination is well characterized.
Of course if you are just using the NanoVNA in a hobbyist environment
where measurements within 5 - 10% are acceptable, then pretty much any 50
ohm load or termination assembled using good rf techniques should do.
- Herb
|
Mine's only good to a couple hundred megs and then becomes reactive. On 02 November 2019 at 11:43 "davebb123456 via Groups.Io" <david.browne7@...> wrote:
Hi My 50 ohm cal load failed that I got in the kit,
has anyone had this happen to them ?
Thanks Dave 2E0DMB
Nigel A. Gunn, 1865 El Camino Drive, Xenia, OH 45385-1115, USA. tel +1 937 825 5032 Amateur Radio G8IFF W8IFF and GMRS WRBV701, e-mail nigel@... www
|
Mel,
I used a commercially made HP 50 ohm termination as my standard until David Taylor pointed out that even though it was manufactured by HP its s-parameter specs were lukewarm at best.
[]
- Herb
=======================================
Herb,
It wasn't me who commented on your HP termination. Must have been another David!
Cheers,
David
--
SatSignal Software - Quality software for you
Web:
Email: david-taylor@...
Twitter: @gm8arv
|
No problem. Mel, <> Virus-free. www.avg.com <> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2> On Sun, Nov 3, 2019 at 3:45 AM David J Taylor via Groups.Io <gm8arv= [email protected]> wrote: Mel,
I used a commercially made HP 50 ohm termination as my standard until
David
Taylor pointed out that even though it was manufactured by HP its
s-parameter specs were lukewarm at best.
[]
- Herb
=======================================
Herb,
It wasn't me who commented on your HP termination. Must have been another
David!
Cheers,
David
--
SatSignal Software - Quality software for you
Web:
Email: david-taylor@...
Twitter: @gm8arv
|
Arno DK3SS
Oristo
David J Taylor