Hi Christos and all Bingo! I solved my pin 1 problem by eliminating all ground connections on one side of the cables from SDR1000 to the pc: microphone, line in/out to Delta 44 and USB cable, leaving only one thick cable from sdr-chassis to pc-chassis. The echoing has totally gone. In order to confirm the method I then removed the previously installed ferrite chokes from USB, Delta-44 and microphone cables: still everything perfect, no echoing / rf interference.
73, Chris HB9AJP (Thank you, Peter, for translating!) > > Eliminating echoing effect on SDR1K (The Pin One Problem) > I am a relatively new sdr-1000 user and since the beginning of > my setup I came across to severe rfi problems thathad to do > mostly with echoing audio during transmition on all HF bands > (even with 5W of output power) > After investigating the sdr1k forums for useful guidelines > dealing with this issue, I decided to common bond the FA-66 > and my computer chassis to the sdr-1000 case with a grounding > braid without any noticeable elimination of the echoing effect > Since the audio cables connecting the rig to the edirol are > homebrew I next disconnected their shield from entering the > edirol. The echo effect disappeared to a degree that was > barely noticeable. After some tests I found out that the > major RF feedback was entering through the shield of inputs > 3 & 4 (those with the RCA connectors) of the edirol. > Now that I found the path of the problem I tried to figure > out a solution. The use of isolation transformers was > rejected because I could not get them on the local market. > Meanwhile I downloaded and read a paper written from Jim Brown > (K9CY) named: "Guide to RFI, Ferrites, Baluns and Audio > Interfacing" witch can be found at: > http://www.audiosystemsgroup.com/RFI-Ham.pdf > > In page 5 Jim states: > The Pin 1 Problem: > The most common way that hum, buzz, and RF interference enters > equipment is via a design defect first widely understood by > the pro audio community thanks to the work of Neil Muncy, > (ex-W3WJE). He named it "the pin 1 problem," because it is a > mis-wiring of the shield of audio cables pin 1 in the XL > connector commonly used for pro audio, but it is just as much > a problem in unbalanced interfaces of all types. The proper > connection for a cable shield to equipment is the shielding > enclosure (chassis), but products with a "pin 1 problem" connect > the shield to the circuit board instead. Nearly all consumer > equipment, including even the most expensive "high futility" > gear, is built with pin 1 problems. Virtually all computer > sound cards have pin 1 problems. So do most RS-232 interfaces > and nearly all ham equipment indeed, almost all RFI problems > we describe as "RF in the shack" have pin 1 problems as their > root cause! > Reading all this I realized that perhaps Pin One Problem applies > also to my case since the ohmmeter measurements and visual > inspection of the inside of the edirol confirmed exactly that. > Then I made adapters which allows the shields of the Tx and > Rx audio cables to connect directly to the edirol case (at > the screw the ground symbol exists) and not through the > connectors first to the circuit board common ground, just to > find out that even with 5 meters long cables no rfi was induced > in my transmit audio. > Jims document is a must reading for every ham as it is very > comprehensive and helps you distinguish and resolve many kinds > of rfi. Ending I believe you will find this information useful > for dealing with rfi issues on sdr1k or other equipment. > > 73 de Christos (SV1FXO) > > ====== other links pa0pvn ======= > http://www.audiosystemsgroup.com/publish.htm > RF Susceptibility of Condenser Microphones > Pin 1 Revisited > Pin 1 Revisited -- Part 2 > Shield-Current-Induced Noise - Part 1 > Shield-Current-Induced Noise - Part 2 > http://stason.org/TULARC/entertainment/audio/pro/index.html > 3.4 - Which is it for XLRs? Pin 2 hot? Or pin 3 hot? > 3.5 - What is phantom power? What is T-power? > 3.6 - How do I interconnect balanced and unbalanced components? > 3.7 - What are ground loops and how do I avoid them? > 3.8 - What is the "Pin 1 problem" and how do I avoid it? > http://www.tvtechnology.com/pages/s.0071/t.1589.html > http://www.rane.com/note165.html > ================================== > _______________________________________________ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ FlexRadio Knowledge Base: http://kb.flex-radio.com/ FlexRadio Homepage: http://www.flex-radio.com/
