For SDR users

Sun Jun 9 20:03:32 CDT 2013

I played with the Ham-It-Up upconverter a little more this evening.  Once again, I confirmed that there is no such thing as a free lunch.

In order to prevent RTL front-end overlod, I had to run the RTL gain at no higher than 20dB.  Otherwise, I get overload from AM broadcast stations during the day, and HF broadcasters at night.  For example, right now, I am seeing HF broadcast stations both just above and just below the 40M ham band that are overloading the dongle’s front end if the gain is above 20dB.  What I see is a jumping of the spectrum floor (apparently being modulated by the station of interference), and a LOT of additional spurious signals on the panadaptor, like every kHz.

At a gain setting of 20dB, amateur signals on 40M are not nearly as strong as they should be.  On a particular SSB QSO at about 7.132MHz, I can barely hear a guy using the RTL/upconverter combo, but he is S9 on my Elecraft K3.  If I run the RTL gain up a little, he would come in better, but the RTL overloads and that’s the end of that.

Filters might help a little bit, but you run into the same old problem on 40M, there are high-level signals from HF broadcasters just above and just below 40M that would be hard to filter out without a really good BPF.

Eight-bits A/D is eight-bits A/D, you get what you pay for.  For $70 for the dongle & upconverter, it’s an interesting toy, but an actual Softrock receiver is probably money better spent, at least for HF.
Terry, WB4JFI

From: wb4jfi at knology.net 
Sent: Sunday, June 09, 2013 12:39 AM
To: Karl W4KRL ; tacos AMRAD 
Subject: Re: For SDR users

I quickly checked the Nooelec Ham-It-Up upconverter board tonight.  Mine came with a 125.0MHz oscillator, not a 100MHz one.  It works fine with one of the RTL dongles that I have.  I think the dynamic range is only about 60dB, but I need to do some real testing.  I needed to bump the dongle’s gain up quite a bit.  Note that there are no input filters on the board, so EVERYTHING is upconverted.  I need to see how well it works with nearby high-power signals on MF and HF.
73, Terry, WB4JFI

From: wb4jfi at knology.net 
Sent: Friday, June 07, 2013 6:59 AM
To: Karl W4KRL ; tacos AMRAD 
Subject: Re: For SDR users

I have one of these boards, I haven’t had time to test it yet.  Maybe over this weekend.  I saw a ham on a Yahoo group say that it didn’t do very well.  He replaced the 100MHz oscillator with a 125MHz oscillator to get around some local FM radio station interference.  It may be that the oscillator module provided has some issues.  The board does seem well built.
Terry, WB4JFI

From: Karl W4KRL 
Sent: Thursday, June 06, 2013 5:55 PM
To: tacos AMRAD 
Subject: For SDR users

Just got this advertisement from an eBay vendor I have dealt with successfully. I have no knowledge of the product or its quality but it looks interesting. 

73 Karl W4KRL

Description from vendor:

Converts signals in the MF and HF Bands to signals in the VHF Band (specifically 100.5MHz to 150MHz). Intended for use in receiver applications with projects like RTL-SDR/SDR#/FunCube Dongle, or to listen to AM radio using an FM receiver. 

The design files can be found in SVN or downloaded as an archive. The board was designed using the Free Open-Source Software KiCad and QUCS. All design files are Open Hardware and released into the Public Domain under Creative Commons CC0. 

Now available from NooElec Online or eBay. 

KS4JU at HamRadioScience has a review of the board and has posted a tutorial video. 

Questions or comments? Visit the Opendous Google Group! There is also a FAQ and additional testing results. 

Design

The Upconverter is a passive Double-Balanced Mixer with RF switches at input and output to allow a Passthrough mode. Power is sourced from a standard USB-microB connector to allow powering via mobile device chargers. The switch controls the signal path, Passthrough or Upconvert, and mirrors the board layout. Switch towards the SMA connector is Upconvert, towards PCB edge for Passthrough. 

http://www.ebay.ca/itm/Ham-It-Up-v1-2-RF-Upconverter-For-SDR-Funcube-RTLSDR-MF-HF-Converter-R820T-/161039905660?ssPageName=ADME:B:FSEL:CA:1123

http://code.google.com/p/opendous/wiki/Upconverter

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