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Re: Topband: Receive ant question

To: Rik van Riel <>
Subject: Re: Topband: Receive ant question
From: Eddy Swynar <>
Date: Thu, 27 Oct 2011 10:47:18 -0400
List-post: <">>
On 2011-10-26, at 5:32 PM, Rik van Riel wrote:

> With the RX antenna a reasonable distance (>100ft) away
> from the TX antenna, would an RF limiter (like the one
> ICE makes) be an acceptable substitute for a front end
> protector with relays?

Hi Rik,

I can only share my own personal experience here with you, for what it's 

First-off, I use TWO old transceivers for 160-meters, i.e. a Yaesu FT-980, & an 
Icom 751A. I use them (separately, of course!) to drive a pair of 813s, for 1 
kilowatt input. I also use SEPARATE receiving antennas on the band, to cut-down 
on noise.

All was well with the Yaesu, utilizing the separate receive antenna jack at the 
back of the transceiver...however, on those occasions when I used the Icom, my 
observed signal on the scope looked absolutely HORRIBLE. Obviously RF was 
getting back into the rig when I used QRO, this despite the fact that the 751A 
has a separate receive antenna jack at the back, as well. 

A look at the schematic of each rig told the tale: the receive antenna jack in 
the Yaesu is AUTOMATICALLY GROUNDED when the transceiver transmits---in the 
Icom, however, there is no such safety feature: the jack "floats" at all times, 
inviting RF to get into the transceiver, playing havoc with it.

The ultimate "fix" was an outboard, separate grounding relay that is activated 
whenever the Icom transmits---it grounds the separate antenna jack, and I have 
had no further problems along this line. Check the schematic of your 
transceiver: if the auxilliary antenna jack grounds in transmit, you should be 

~73~ de Eddy VE3CUI - VE3XZ

UR RST IS ... ... ..9 QSB QSB - hw? BK

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