A comparison of the DA100E with the AmRad active antennas.

A friend bought a DA100-E active antenna and brought it over
for me to evaluete. I compared it to a AmRad and "North Country"
active antenna. The AmRad and NC are both built from
published diagrams.

The DA100-E is rated for operation from 500KHZ through 30MHz.

I live about 3 miles from a 1KW MW on 770KHz and within about
5 miles there is a station on 1250KHz(1KW) and on on 1380KHz(2KW).

These provide a realistic test for IM. Antennas,a nd receivers,
that suffer from IM will give products at:
770+1250
770+1380
1250+1300
1250-770
1380-770
1380-1250

The last is a good indicator of LF performance.

The AmRad has excellent IM charactoristics and I receive no mix
products.
The North Country is barely acceptable and gives weak MW and HF mix
products
with bad LD products.
The DA100-E falls in between.
The DA100-E goes deaf very rapidly as I tunee below 500KHz and by
the time I reached 242KHZ, a 25W NDB about 7 miles way, was virtually
deaf. I couldn't pick up the 100KHz LORAN C at all. The lousyville DGPS
on 290KHz is S4 on my wire antenna, S9+10 on the AmRad adn lost in IM
on the
NC antenna. It was just detectable on the DA100-E.
I could just detect the 770+ mix products with both other MW outlest.
But I could not detect thier mix products. There was no 2nd or rd
harmonic with the
DA100-E, but theire was a weak 4rt and 5 harmonic. These are produced
inteh antenna and are not actaul "real world" signals. The AmRad and my
wire antenna
do not have them.

Above ~5MHz the DA100-E and the AmRAd are very similar and roughly
equal to
my 70' wire antenna. The AmRad is a better deal, but requires modest
tech
skills to construct. The DA-100E is an acceptable MW and good HF
antenna, but it is a very poor LF antenna. Compared to my ~$20 wire
antenna, I use commercial Mini Cirucits transformers, the ~$180 seems
to be a bit steep.


The "North Country Radio" antenna
http://www.northcountryradio.com/index.htm#anc506 plans were
published
in PE magazine several years ago. My copy was based on the published
plans
and may not reflect the current product. I made no effeort to select
devices for optimal performance. I would rate the version I built as
only suitable
for locations far from MW stations. Above ~5MHz it was an acceptable
antenna.
Nothing to set the world on fire, but very workable. The North Coutnry
site
does list a LF extension modification that worked, but given the
proximity
to 3 MW stations, the LF mod onlyh added more noise mix products.

The AmRad antenna is reported to have some LF noise issues when
operated
from the stock power supply.
See: http://www.pacificsites.com/~brooke/LF-Ant.shtml
And the stock power supply was reported to produce some nasty spikes
from
the un-bypassed diodes. I don't and have never, operated from the stock

supply.

Terry