PR-781 to Flex 6500 (again...)

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  • Updated 1 year ago
Hi all
I would like to straight this up once and for all...
1/ Is it true or is it not true that a connexion with an XLR-Y and/or XLR-YBal cable on the FRONT end is subject to RFI ?
2/ What is the difference between these 2 cables ?
I have just phoned Heil, and they recommend the balanced cable (orange), again for front end connexion (they do not really know about the rear end)
3/ If it is really preferable to use the rear end (XLR-type plug on the rig itself),then a standard XLR to XLR cable is fine. But what is required to include a PTT in the system ?

Thank you all
73
Paul F6EXV
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Paul F6EXV

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Posted 1 year ago

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Mike Hoing

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I use the XLR in the back for my PR781 with a foot switch to the PTT RCA for keying. That's leaves the front mic connection for my RadioSport headset

Mike
N9DFD
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Tim - W4TME, Customer Experience Manager

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1/ Is it true or is it not true that a connexion with an XLR-Y and/or XLR-YBal cable on the FRONT end is subject to RFI ?

All wired connections in an RF environment are subject to RFI (anything metal can be an antenna).  The front 8-pin Foster connector is a pseudo balanced interface whereas the 3-pin XLR is a true balanced audio interface.  A true balanced interface will be less susceptible to RFI due to the differential signaling.

2/ What is the difference between these 2 cables ?

How they are wired is different since the connectors are different, but essentially they are wired in a balanced configuration (+, - and ground).  The 8-pin Foster connector converts to unbalanced just before the signal enters the codec.

I have just phoned Heil, and they recommend the balanced cable (orange), again for front end connexion (they do not really know about the rear end)

That is what I would expect.  They want to sell you a $25 cable when you can get a balanced XLR microphone cable for less than half that price.

3/ If it is really preferable to use the rear end (XLR-type plug on the rig itself), then a standard XLR to XLR cable is fine. But what is required to include a PTT in the system?

I exclusively use the rear XLR connector for audio.  For PTT, I use a foot switch because my mic is on a boom and I want to be "hands-free" when I operate so I can control a mouse or type on the keyboard for logging.
(Edited)
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Rob G6EIH

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Use the same setup here and get great audio reports.
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Jeffrey Kerber, N3VE

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xlr to the rear and a foot switch is the way to go

Jeff

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W9YU

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I too use the mike in this configuration and get great reports.  I would recommend a boom too.
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Bob G W1GLV

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Tim, are these toroids that clip to a wire all made of the same material. I read somewhere that different materials are effective only for a certain types of RFI.
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Tim - W4TME, Customer Experience Manager

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No.  The materials the ferrite beads are made from are different giving them different properties.   http://palomar-engineers.com/ferrite-products/ferrite-cores/ferrite-mix-selection

And if you need to put chokes on your mic cable, you should work on removing the RFI (primarily common mode currents) from your shack.  Chokes on the mic cable are a band-aid.
(Edited)
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Paul F6EXV

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Thanks guys for the replies.
Next (and hopefully last) question is : where do I connect the foot switch ?
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Tim - W4TME, Customer Experience Manager

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To the PTT RCA connector on the back of the radio
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Mike Hoing

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There is a white PTT RCA connector on. Back. Plug it there your all set


Mike

N9DFD
(Edited)
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Rick WN2C

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I use the PR-781 on my 6300 and the mic cable actually runs within 6 inches of my SB 220 and I have no RFI. It is most likely not the mic cable but off the antenna feed line (or possibly a tuner?)
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Paul F6EXV

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Thanks !
73
Paul
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K2CB Eric Dobrowansky

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To answer Paul's original question #2 -


The difference between the Heil XLR-Y (yellow) and newer XLR-YB (orange) microphone cables is that the wiring on the 8-pin radio connector is different.


On the newer YB cable, the XLR pin 1 shield is connected to foster plug pin 5 (chassis ground). XLR pin 3 ( mic -) is connected to foster plug pin 7 (mic ground). Thus the audio ground and switching grounds are fully isolated.


The newer Yaesu radios, along with the Flex radios, use a pseudo balanced input at the 8-pin mic jacks, with a separate mic audio ground, isolated from the chassis and switching ground. The newer YB cable has the proper matching wiring scheme to avoid stray rf issues and ground loops.


The older Y cable had the shield ((XLR pin 1) and mic - (XLR pin 3) both tied together and connected to both pins 5 and 7 at the 8-pin radio end foster connector.


The yellow cable is fine for the older Yaesu 8-pin radios, such as the FT-1000 and earlier, where only one common ground was used, and available on multiple pins of the 8-pin radio foster connector (pins 2, 5, and 7). But for the FT-2000 and newer radios, and the FLEX radios, (where pin 7 is an isolated mic audio ground), the orange style cable is necessary to avoid issues such as stray RF into the transmitted audio.


If necessary, it is easy enough to convert an older XLR-Y cable to an XLR-YB cable, by making the aforementioned changes.
(Edited)
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Jim Runge

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If you need an XLR microphone cable go to the Guitar Center and get one for around $6 depending on the length you need.
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K2CB Eric Dobrowansky

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Yes, but like anything else, you get what you pay for. Believe it or not, the wire Bob Heil uses in his XLR cables, and also sells in bulk lengths, is very good quality.
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Jim Runge

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I have a 6700 and two 6500 and use the Guitar Center xlr cables on all 3 while running 1500 watts 160-6 Mts.