Max Microphone Cable Length

Jeremy - W2JG

Doug - W3UB

K1DLM

If you use a balanced microphone with the XLR input, it can be thousands of feet. How long are you thinking and what type of Mic are you using?

Jeremy - W2JG

Thanks for the quick reply, under 10 minutes!  Do you think a 50ft cable would work?  Did you purchase the cable and from who or did you make it?

Thanks again Doug!

Jim Gilliam

Paul Christensen, W9AC

Doug - W3UB

Jeremy - W2JG

Jeremy - W2JG

Thanks Jim!

Your point about the noise is why I asked the question.  Thanks for your suggestion for iron core clips!

This now raises a second question, are you aware of any double shield cables?  If available, I would think that might help.

Thanks again for your quick reply!

Jeremy
W2JG

Jeremy - W2JG

K1DLM

Paul Christensen, W9AC

The source Z of the RS60F is almost certainly under 1K-ohm.  50 ft. will be fine.

One more point to mention:  The days of strict audio impedance matching have been over for 3+ decades.  Some folks still think that a 10K-om input impedance needs a 10K-ohm microphone when using modern audio equipment. We no longer need to maximize the power transfer function as we did in the days of input and output transformer matching. 

The audio industry has long been using voltage-based audio matching, rather than power-based matching.  That means, even if the rig's input Z is 10K-ohm, the transceiver is simply a bridging termination on the low-Z source. 

A good rule of thumb is to use a low source Z at every opportunity, and a moderately high-Z at the termination in at least a 10:1 ratio.  Excessively high input Z is not always a good thing either, especially when using switched audio systems.   

Paul, W9AC

Jeremy - W2JG

Thanks Doug!

A couple of questions comments...  First, excuse my ignorance, may be lack of sleep, but what do you mean by transporting TX and RX audio to client, isn't that the point of cable?  I also saw from the link that you are only using a 3-pin cable.  I was hoping to use all 8 pins so that I could also use the PTT.  How did you do the PTT with your 35ft cable?

Thanks Again!

Jeremy
W2JG

Paul Christensen, W9AC

Jeremy - W2JG

David,

THANKS!  That is a GREAT comment about using the back panel XLR connector!  I was not aware that the front connector did not provide a balanced/differential input!

Jeremy
W2JG

Doug - W3UB

Jeremy - W2JG

Hi Paul!

I noticed your comment about one of the replies.  I do not want to start a grudge between commenters, but I need to follow up because I am now more confused.  I completely understand your comment about connecting single ended to differential, but I don't know what the M350 uses, I have been searching for specs since starting this post, but have yet to find the info.  I bought the headset with the 8-pin Foster connector, but don't know how many pins the M350 uses.  Do you know?  (My headset is currently in storage, so I cannot look at it)  There was also an implication that the front panel connector was not balanced but the rear XLR connector was.  I went back to the FlexRadio documentation and saw that the front panel uses two pins, +/-, for the microphone.  I would assume that means it is differential, if not what is the difference between the front and rear connectors for the microphone.  I know that the front also has pins for PTT, Up, Down, and Fast.

Thanks so much!

Jeremy
W2JG

Jeremy - W2JG

Mark WS7M

I am running balanced to my radio which is in a shed next to my op position.  I have RFI chokes on both ends but the distance is roughly 30 feet and also no issues.

K1DLM

Jeremy - W2JG

Thank you Dave for all your efforts to help track this down!  I greatly appreciate it!

I would also like to once again thank everyone else for your extremely prompt responses and good discussion of my question.  I really appreciate eveyone's help!!!

Jeremy
W2JG