[Premium-Rx] OT-Dressler Active Antennas

[Brooke Clarke]

Hi Tracey:

You're comparing apples and oranges.  The OP was about Dressler Active Whip 
Antennas, not loops.  I've read very good things about Wellbrok loops and my 
experience with loops is positive.

When I was started using the BR RCS-5A chirp receiver the results with a McKay 
Dymec DA-100 active whip antenna the results althoug good, were not what I 
thought they should be.  After a lot of web surfing I installed the B&W 90 foot 
T2FD and it made a HUGE improvement.  The B&W 1.8 - 30 antenna has a closed DC 
path and so has lower noise that single wire antennas.
http://www.prc68.com/I/RCS-5A.shtml#Ant

I think a chirp sounder is the ideal method of testing an H.F. receive antenna. 
  That's because you get to choose the station you want to listen to and that's 
all that gets displayed on the CRT.  Everything else is part of the noise. 
Since there are chirp transmitters all over the world you get a reasonable 
selection of paths.  Of course the CRT is showing you the ionosphere along the 
path.  So now when you switch between antennas you can easily see how each is 
performing across the 2 to 30 MHz range for that particular path.  There is 
also a bar graph that displays s/n or a path quality metric at the top of the 
CRT.  Sometimes you can see both the short and long paths are active and once 
in a blue moon paths that go around the world twice.

The HP 4395A in Spectrum Analyzer mode has it's place.  For example looking at 
the signal/noise on the AMRAD active whip around WWVB showed that it has poor 
power supply noise compared to the DA100 active whip.  It's also good for 
testing transmitters using an outside antenna remote from my test bench.

I've made a number of spectrum plots just to get an idea of what activity is in 
a band.  The 1 Hz RBW is fantastic for finding small signals.  It's amazing 
what you can do with a 12 MHz wide IF channel fed into a digital receiver.
http://www.prc68.com/I/4395A.shtml

Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.precisionclock.com



Tracey Gardner wrote:
> Hi Brooke
> 
> Take a look at John Wilson's review from the April 2001 edition of Short 
> Wave magazine, under the heading "Signal Or Noise?" where he does a 
> comparison between a 15m long wire antenna and a Wellbrook loop.
> You might find the results interesting especially as he uses spectrum 
> analyser shots to support his findings.
> 
> http://www.wellbrook.uk.com/reviews/SWM2001.html
> 
> Tracey
> 
>>
>> At L.F. and lower active antennas can provide decent signals.  But at 
>> H.F. an active antenna will perform much worst than a wire antenna.
>>
>> Have Fun,
>>
>> Brooke Clarke
> 
> 
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