[ADXA] grounds and antenna 1 and 2 split ideas...

Thu Jan 21 13:05:43 EST 2016

Dennis.
   Make sure you  have diode protection on the antenna receive inputs, (1) the one in the main TR relay (for isolation impovement) , and (2) if an RCA type phono antenna input for receiver (non coaxial) then it usually hooks back into the coax receive side of the TR relay and can couple into that via the ground portion, especially if no diode there either. If you have, as Dave says, TWO Coax Ant outputs (ant 1 and ant 2) on the back just program in Ant 1 for transmit in VFO 2 and antenna 2 programmed to VFO 2 for receive That way you have good TR isolation on transmit, like for your normal receive line for TR relay function. Most are diode protected, especially for lightning protection.
    Despite this, I always unplug ALL coax cables or anything connected to the equipment during a storm. Often I also unplug the AC line, as years ago I had 20 equipment pieces fused/welded at the neutral of all the AC plugs to the female wall neutral. That in itself produced other internal PS and caps issues, not involving the receiving coax line.  If I’m gone, always unplug ALL connections. The only thing I leave attached is the Ground wire, and sometimes THAT ground is also an entrance way to the radio for transmit antennas close to ground or requiring a LOT of ground radials close by ..  RF does couple into the ground radials ( that’s 1/2 the antenna ) and those ground currents do spread a significant distance to the station and house ground at times. Good to never ground a station ground to an immediate ground radial system under the tower if that ever has to be the situation. A 1/2 wave vertical is no problem since a ground is not needed, only perhaps a short counterpoise system elevated a few feet to coax integrity. The 1/2 wave vertical is a voltage feed, not current fed, as I often used to forget. 
   Good to have banter back and forth on these issues thru the adxa site!
San YY

From: Dennis Schaefer 
Sent: Thursday, January 21, 2016 11:26 AM
To: David Norris 
Cc: hamop1 ; Joel Harrison ; adxa 
Subject: Re: [ADXA] receive antenna port on back

Thanks to all - I'll be careful if I get an Icom rig but right now the only Icoms I have are an IC-7000 for portable use and an IC-703 QRP rig.  My main HF rig is a Kenwood TS-590S and it does have a separate receive antenna port.   That's the only one I'd use with a  receive antenna.  It does have two antenna ports, and also an RCA Jack that is for the RX ANT.   I don't think I can transmit on ANT 1 and receive on ANT 2  but I'll look that up.

Of course, the main goal is something for quiet receive on 80 and 160 meters.    For starters, I'm thinking about a beverage on the ground with a preamp.   I also have noise problems on the higher bands, mainly 12 and 17 meters because of where the WARC antenna is located.  I haven't been able to isolate it yet, so a receive antenna out in the woods for those bands would be helpful.

73,
Dennis, W5RZ

On Jan 21, 2016, at 10:49 AM, David Norris <k5uz at suddenlink.net> wrote:

  Don't use the RXV ant jack on Icoms.  Use one of the other ant jacks.  You can set most of the newer radios to RCV on one jack and XMT on another.  No chance of blown relays. This works fine on the 7700 and the 7800/7850.

  73 

  David A. Norris, K5UZ 
  Director, Delta Division

  Sent from my iPhone

  On Jan 21, 2016, at 8:39 AM, hamop1 <k5yy1 at cox.net> wrote:

    Icom rigs have been known to blow thru the receive antenna only phono jack input, getting RF THRU the internal TR relay for the main antenna. Much is strict RF overload of that one ‘receive only’ line ..... I would disconnect any long wire close to the ground and reconnect, perhaps an old “throw switch”?..  I have no problems if putting a dipole in that “receive only” antenna input, for some reason. It should overload too , if too close to the transmit antenna...
    73
    San

    From: Dennis Schaefer 
    Sent: Thursday, January 21, 2016 8:05 AM
    To: Joel Harrison 
    Cc: adxa 
    Subject: Re: [ADXA] VP8STI 160 Meters - A Wild Night!

    Joel,

    We appreciate the updates and it is good to see messages on the ADXA list.

    I don't work 160 much, but my 130 foot horizontal dipole works fairly well for transmit when the feedline conductors are tied together and fed against ground.   I need a receive antenna and my rig has a receive antenna port.   I see receive antenna protectors, but I have not really seen much about when one is needed.   If I am running 100 watts on 160, what are the possibilities that I will blow my receiver due to RF on the receive antenna port?   I assume a relay or other circuit in the rig  removes the antenna from the circuit when I am transmitting, but I'm not sure.   I can ask the question on the Kenwood TS-590S reflector, but I knew there was a lot of knowledge here also.  

    So - just for educational purposes - does using a separate receive antenna increase chances of blowing the receiver front end at 100 watts?   At 1 kw?

    73,

    Dennis, W5RZ

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