Topband: RX PREAMPS

[Tom W8JI]

>I  have used the HI Z rx system and also the DXE ones.  HI Z said in the 
>past no need for a sequencer to get power off the amps if the xmit ant was 
>close to the rx system antennas.  Close I would say 60 foot.  DXE has 
>always suggested using a sequencer to get power off the amps during xmit. 
>I am going to be forced to move a DXE system within 65 ft or so of my 160 
>vertical and wonder if anyone has had any experience of using the DXE 
>without a sequencer close to their xmit antenna.  Just hate to install one 
>more thing I could get around but will if absolutely necessary.  I know 
>moving it closer is not an ideal situation but you do what you have to. 
>Any input?  73 Mike K4PI
> _________________


You actually have to try it and see. Interaction depends on the very fine 
details of the system, including cable lengths and the transmitter system 
does to the feedline when on RX and how the RX antenna couples to the TX 
antenna. As such, there will never be one universally true answer, so asking 
others won't really tell you how it will work with your system.

I do know that what Hardy said is basically correct. It models that way, it 
works the way he described.

If I place any RX vertically polarized antenna around my 160 TX antenna, 
even if the RX antenna is 250 feet or further away, I can always see a 
substantial interaction with certain termination changes in the TX antenna 
array when receiving. The only exception is if the RX antenna design nulls 
coupling to the TX antenna.

An RX antenna cannot be designed to be immune at such close spacings, unless 
it places a pretty deep null in the direction or in the polarization of the 
TX antenna.

So you have multiple things affecting how it will work:

1.) How your system terminates your TX antenna when on RX

2.) If the RX antenna nulls the TX antenna, either by pattern and/or by 
polarization

3.) What level damages things or affects things

4.) What else is around

5.) What people call good enough

and so on.

Since no two systems are identical in every single way, you just really have 
to try it.

73 Tom