Welcome to the new FlexRadio Community! Please review the new Community Rules and other important new Community information on the Message Board.
If you are having a problem, please check the Help Center for known solutions.
Need technical support from FlexRadio? It's as simple as Creating a HelpDesk ticket.

EMP protection using loop circuit.

N9VCN9VC Member ✭✭
edited February 2019 in FLEX-6000 Signature Series
Hi Tim,

To make sure I understand it right. A preselector added in between the RXA input and RXA
output will have EMP protection or do I have to have protection added myself. This is only in
the single antenna, one receiver situation. Only using single SCU.

73, Jim N9VC

Completed · Last Updated


  • George KF2TGeorge KF2T Member ✭✭✭
    edited February 2019
    Unlikely that a preselector would provide meaningful EMP protection. For true EMP, about the only thing that gives you a chance is disconnection and isolated, shielded storage. For lightning protection, also unlikely the preselector will save you from a direct strike. It might be the "sacrificial" component in some cases, it I wouldn't count on it for any protection.
  • Tim - W4TMETim - W4TME Administrator, FlexRadio Employee admin
    edited May 2017
    The EMP protection for the 6700 is done in the SCUs.  There are sacrificial ESD diodes before and after the preselector filters.  There is also a disconnect relay to ground the RF input signal path if the input signal threshold approaches the damage point of the SCU.  All of this is after the antenna switching matrix.  So any device in the RX Loop is before any of the the ESD protection.
  • N9VCN9VC Member ✭✭
    edited May 2017
    Hi George,

    I am aware of that and I am not worried about the preselector although I
    will add protection before the input. I am worried about the radio.

    73, Jim N9VC
  • N9VCN9VC Member ✭✭
    edited May 2017
    Hi Tim,

    That is what I was looking for in your answer. Rest assured I disconnect
    whenever I am not using the 6700. I just did not want to leave the 6700
    at risk when I would be using the setup. I plan on protection before the
    input of the preselector. But I will not be doing full-duplex or such. I use
    it as a single SCU so when I transmit that should be removed from the
    circuit by relays internal to the 6700. Some might wonder why did I get
    rid of my 6500 and get the 6700 since I do not use the features. Simple.
    The prestige of having the best instead of second-best :-)
    And I might not even do the preselector as I have yet to encounter any
    problem where I thought It would help. It would be the MFJ 1046 mainly
    for help on 160 or lower. I like to listen for the 472 KHz beacons.

    73, Jim N9VC
  • N9VCN9VC Member ✭✭
    edited May 2017
    You can close the thread if you wish. I think I have the answer.
    Thanks again.

    73, Jim N9VC

Leave a Comment

Rich Text Editor. To edit a paragraph's style, hit tab to get to the paragraph menu. From there you will be able to pick one style. Nothing defaults to paragraph. An inline formatting menu will show up when you select text. Hit tab to get into that menu. Some elements, such as rich link embeds, images, loading indicators, and error messages may get inserted into the editor. You may navigate to these using the arrow keys inside of the editor and delete them with the delete or backspace key.