Topband: Low Dipole for RX

[Milt, N5IA]

----- Original Message ----- 
From: "Hardy Landskov" <n7rt at cox.net>
To: "GALE STEWARD" <k3nd at yahoo.com>; "topband reflector" 
<topband at contesting.com>
Sent: Thursday, October 01, 2009 8:46 AM
Subject: Re: Topband: Low Dipole for RX


>I put one up here in AZ and it was a waste of time & energy. But Robin (he
> has a 6 call but I can't remember what it is) used one at XZ and said it
> worked fantastic.
> I guess you need to try and see.
> 73 Hardy N7RT
>
>
> ----- Original Message ----- 
> From: "GALE STEWARD" <k3nd at yahoo.com>
> To: "topband reflector" <topband at contesting.com>
> Sent: Thursday, October 01, 2009 8:06 AM
> Subject: Topband: Low Dipole for RX
>
>
>> Anyone using a low dipole on 160 for RX? By low, I mean 8-10ft. I could
>> install one of these until some of the foliage dies off and I can install
>> my two-wire beverage.
>>
>> Would this be useful or a waste of time? Also, if anyone is using one of
>> these, did you attach the feedline directly or use some type of matching?
>> Since the Z is pretty low (a few ohms), I thought a 9:1 xfmr might be
>> appropriate.
-------------------------------------------------------

I was with Robin (WA6CDR) at XZ1N in 1998 when I first suggested the low 
dipole.  I installed it in the jungle and it worked to get some Qs that 
otherwise would not have been worked.

So, when we went to XZ0A in 2000 the low dipole was in the arsenal.  About 
the 2nd evening we were lamenting that we could hear lots of low level 
signals but could not pull them out of the mud.  The next day I installed a 
low dipole across the heliport area with the ends into the jungle.

Bingo!!!!!!!!   For the balance of the expedition the low dipole was used 
during the first 2-3 hours after sunset with great success.  The Beverages 
were not hearing the signals during that time period.

Then, like a light switch being operated, the high angle skew signals coming 
from the southeast suddenly became audible on the Beverages to the 
northeast.  The skew path changed in just a few minutes to the normal 
direction short path.

As far as we have been able to discern, this is a phenomena associated with 
being in the tropics near the equator and working signals from stations 
7-12K miles distant at sunset.

The physics associated with a low dipole say that the antenna will respond 
primarily to high angle signals.  It has nothing to do with being in AZ or 
anywhere else.  If you have signal arrivals that are high angle, the low 
dipole will out perform the Beverages, Loops and phased short verticals.  If 
the signals are coming in "normally" at low angles, the low dipole is a 
dummy load.

You never can have too many antennas.  You just have to know when to use 
each one.

BTW, I fed the antennas in both these cases with the RG-6 tied directly to 
the legs of the dipole.  The few dB of loss from mismatch at the feedpoint 
means nothing.

Mis dos centavos.

73 de Milt, N5IA