Topics

Antuino and SWR


Michael Aiello
 

Has anyone experimented with the Antuino as an SWR meter?
I have noticed it reads consistently high, even after repeated return loss calibrations.

Using a set of calibrated dummy loads, I get these readings:
1:1, 50 ohms  - Antuino reads 1.0
2:1, 100 ohms - reads 3.0
5:1, 250 ohms - reads 8.7
100:1, 5000 ohms - reads 99.9

So we have good agreement at each end of the scale, not so much in the middle. Using my commercial SWR analyzer, these loads read exactly as marked.

Anyone have a similar experience?

73,
Mike N2HTT


Ashhar Farhan
 

Mike,
This is unusual. Do you have a signal source that can be used to provide variable level signals such as a step attenuator or an amplitude controlled signal generator?
It could be that the frequency calibration is off. Have you checked the frequency calibration too?
What frequency are you using for swr measurement?
- f

On Wed 12 Jun, 2019, 6:23 AM Michael Aiello, <n2htt.mike@...> wrote:
Has anyone experimented with the Antuino as an SWR meter?
I have noticed it reads consistently high, even after repeated return loss calibrations.

Using a set of calibrated dummy loads, I get these readings:
1:1, 50 ohms  - Antuino reads 1.0
2:1, 100 ohms - reads 3.0
5:1, 250 ohms - reads 8.7
100:1, 5000 ohms - reads 99.9

So we have good agreement at each end of the scale, not so much in the middle. Using my commercial SWR analyzer, these loads read exactly as marked.

Anyone have a similar experience?

73,
Mike N2HTT


Michael Aiello
 

Hi Ashhar,

I do have a fixed and step attenuators, so I could use my KX3 as a signal source to get a signal down into the -10 to -40 dbm range. I have not attempted the frequency calibration. I was testing the SWR at 7.1 MHz.
I have done the return loss calibration - how do you perform the frequency calibration?

Thanks
Mike


Ashhar Farhan
 

Mike,
The procedure is documented on hfsignals.com. You hold down the tuning knob while switching on the unit, this puts it into calibration mode. Choose Frequency Calibration, and set the output (as measured on a receiver or freq counter) to exactly 10 mhz, tap the button once more to save it and restart the unit.
- f

On Wed 12 Jun, 2019, 4:47 PM Michael Aiello, <n2htt.mike@...> wrote:
Hi Ashhar,

I do have a fixed and step attenuators, so I could use my KX3 as a signal source to get a signal down into the -10 to -40 dbm range. I have not attempted the frequency calibration. I was testing the SWR at 7.1 MHz.
I have done the return loss calibration - how do you perform the frequency calibration?

Thanks
Mike


Michael Aiello
 

HI Ashhar,

I was able to get reasonable SWR values after calibrating the frequency using an ancient but apparently still fairly accurate Fluke frequency counter (hamfest find a few years back.)  I wasn't successful in trying to zero beat it, couldn't pick up enough signal. 

The SWR still reads a bit high compared to other SWR measuring tools I have, I'm thinking of just modifiying the table in the code a bit to compensate.

Thanks for the help, it is an awesome diagnostic tool

73
Mike


David Wilcox <Djwilcox01@...>
 

Farhan,

I just re read the limited instructions on the Antuino and it only addresses the “return loss” calibration. You left out a sentence about the “frequency calibration”.  No where does it say to calibrate at 10 MHz.  Please add this for those who need to know.

Dave K8WPE

David J. Wilcox K8WPE’s iPad

On Jun 12, 2019, at 7:47 AM, Ashhar Farhan <farhanbox@...> wrote:

Mike,
The procedure is documented on hfsignals.com. You hold down the tuning knob while switching on the unit, this puts it into calibration mode. Choose Frequency Calibration, and set the output (as measured on a receiver or freq counter) to exactly 10 mhz, tap the button once more to save it and restart the unit.
- f

On Wed 12 Jun, 2019, 4:47 PM Michael Aiello, <n2htt.mike@...> wrote:
Hi Ashhar,

I do have a fixed and step attenuators, so I could use my KX3 as a signal source to get a signal down into the -10 to -40 dbm range. I have not attempted the frequency calibration. I was testing the SWR at 7.1 MHz.
I have done the return loss calibration - how do you perform the frequency calibration?

Thanks
Mike