Newcomer fist feedback.

Just about everything about Red Pitaya
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f4hga
Posts: 10
Joined: Thu Sep 22, 2016 10:14 am

Newcomer fist feedback.

Post by f4hga » Mon Oct 03, 2016 2:18 pm

Hello all,

I just acquired the redpitaya board a week ago.
Here is below my first feedback:

First of all I am using this board mostly for HAM radio activities. What conviced me to purchase it is the ability to use it for measurements but also to build and design of my own radio equipments.

- The board and its associated ecosystems of application is very impressive. So far I used the RadioBox, VNA and SDR transceiver. All of them work like a charm. The VNA showed the SWR curves of my various antennas exactly as measured with my MFJ. ( I used an RLB bridge for measurement ).

- Strangely I spent more time seting up the network (Wifi and Eth) than using the applications themselves.
I strongly recommend looking at these URLs for anyone strugling with WIFI and searching for a clear debug approach:
https://wiki.archlinux.org/index.php/Wi ... management
and https://wiki.archlinux.org/index.php/WPA_supplicant

- Regarding the SDR transceiver, I have to use it through ethernet my wifi seems to slow and the audio is hashed. I therefore purchased a wifi router, were I can connect my PC and my red pitaya on the ethernet switch. If I remove the ethernet then the RP connects via WIFI on the network, and it can be used for other apps.
I attached a power meter to the OUT1 output and measure a little less than 10dbm for the power with an FM modulation. Then by attaching a dummy load and approaching the antenna cable of another transceiver I was able to go to transmit mode and hear my voice. The modulation is very good also in SSB modulation.

Now the great fun will begun. I plan to build the additional hardware to get a full operational transceiver:
- receive and transmit switch.
- 45W HF power amplifier.
- LPFs for the various bands.
- Band switcher through I2C commands.

What is really fabulous is that all these missing parts will be developped using the read pitaya as a measurement tool.

Thanks for reading.

F4HGA.

Nils Roos
Posts: 1441
Joined: Sat Jun 07, 2014 12:49 pm
Location: Königswinter

Re: Newcomer fist feedback.

Post by Nils Roos » Mon Oct 03, 2016 4:02 pm

It's always good to hear when things went as intended^^

Thanks for sharing.

pavel
Posts: 542
Joined: Sat May 23, 2015 5:22 pm

Re: Newcomer fist feedback.

Post by pavel » Mon Oct 03, 2016 4:08 pm

Hello Ghislain,

Thank you very much for your kind feedback! I'm glad that my VNA and SDR transceiver applications work well for you.

If possible, I'd be very interested to know more about your comparison of the Red Pitaya VNA application with the MFJ VNA.

Out of curiosity. For your transceiver based on Red Pitaya, are you planning to modify the RF inputs to improve their MDS and IMD3 characteristics?

Best regards,

Pavel

f4hga
Posts: 10
Joined: Thu Sep 22, 2016 10:14 am

Re: Newcomer first feedback.

Post by f4hga » Wed Oct 05, 2016 9:16 am

Hello Pavel,

I have done a few measurements with the VNA.
My MFJ analyzer is not a VNA but the MFJ266 (with tuning knob).

However also have the HF Aduino VNA desgined by my good friend F4GOH (https://hamprojects.wordpress.com/2016/ ... h-version/)
This opensource VNA has a lot of similarities with the mrs MiniVNA version 1. It is based on a AD8302 to measure reflected power and unsigned phase. The sign has to be deducted after data acquisition.

What I did yesterday is a comparison of my homebrew multi dipole fan antenna that is based in my attic.

Description of the multi dipole antenna:

It is designed as such:
- One shorted dipole for 40M
- One dipole for 20 M
- One dipole for 17 M
- One dipole for 15M

I was not able to add 12 and 10 M due to not enough room space.

Here is what the antenna look like in 4NEC2:

Image

The theorical swr graph is this one:

Image

Here is the swr graph measured with Red Pitaya VNA:

Image

Here is the swr graph measured with HF Aduino VNA:

Image
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f4hga
Posts: 10
Joined: Thu Sep 22, 2016 10:14 am

Re: Newcomer first feedback.

Post by f4hga » Wed Oct 05, 2016 9:23 am

Next to m my previous posts, here are the smith charts measurements on 40 M band , between 6.5 Mhz and 7.5 Mhz.

With Red pitaya:

Image

With HF arduino VNA post processed with Zplots for phase sign correction:

Image

All this to say that the red Pitaya VNA is performing extremly well, the smith chart curve is a pure beauty.
I also want to insist on the HF arduino VNA along with Zplots that is able to give a good result for sign correction.

Best regards to you all.

F4HGA / Ghislain.
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pavel
Posts: 542
Joined: Sat May 23, 2015 5:22 pm

Re: Newcomer fist feedback.

Post by pavel » Thu Oct 06, 2016 8:21 am

Hello Ghislain,

Thank you for all the information about the analysis of your antennas and about the Arduino VNA! Very interesting!

Best regards,

Pavel

F4HHS
Posts: 5
Joined: Sat Apr 23, 2016 8:31 am

Re: Newcomer fist feedback.

Post by F4HHS » Sat Oct 15, 2016 1:41 pm

Ghislain,
Thanks for sharing your experiments on VNA/SWR measurements. Great !
I also use a RP since a few months , mainly on Rx and I'm now trying Tx part.
When I check my transmision, the quality of audio is always very bad with many noise and "craks".
I use PowerSDR mRx and also Quisk on Windows and the results are always the same (tests with different microphone....).
Did you experiment audio transmission (SSB) with your configuration ? If yes, did you do some particular setup on PowerSDR (or other) for Tx audio ?
Thanks in adavance,

Denis / F4HHS

f4hga
Posts: 10
Joined: Thu Sep 22, 2016 10:14 am

Re: Newcomer fist feedback.

Post by f4hga » Mon Oct 17, 2016 10:43 am

Hi Denis,

So far I didn't TX that much. All what I did was simply attaching a dummy load to OUT1 then use a standard tranceiver for listening with a wire connected to the antenna connection.

The audio was very good with no distorsion.
My PC is an old laptop DELL 630.

But beware I have to get my PC connected to the RP with an ethernet cable. It doesn't work with WIFI as my bandwith is too small. I am using the ethernet switch part of my wifi router.

BR.

Ghislain/F4HGA.

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