Mark
Tell us more about the transformer? My own experience is that core
material and impedance matching at the frequency of interest often pays off.
I have a 200' BOG (N-S) and a 460ft� x 6ft Beverage (E-W) . Both
antennas work very well for what they are comparing them to what I hear
on the Xmit antenna. In the "development " phase I found that measuring
the actual feedpoint impedance and then making sure that the impedance
matching� ratios are "close" resulted� in very predictable and
repeatable results. I dont have my notes handy , and both my antennas
are essentially "Reversible" coax antennas. One transformer turned out
to be 3:1 and the other 5:1. I get performance on 160-40, noticeable
poorer performance 30M� and� very poor signal signal 20M and above. I
attribute this to the matching transformer design which favors the lower
frequencies.
Everything for the moment was done using� cheap RG-6. But I will be
replacing all of that with a RG-58 construction in the fall.
Dave
NR1DX
On 6/30/2020 2:56 PM, Mark Lunday wrote:
"Beverages just want to work" is what I have heard.
Not having much luck with that here. I suspect operator/installation
error.
I did a lot of reading and I must be doing something wrong.
* 250 feet of insulated wire strung out in 030 degrees direction
toward EU, pretty straight, varying in height from 4 to 6 feet,
running through thick brush with no metal objects or artificial
elements along the run.
* 9:1 transformer at feed point with ground rod
* 300 feet of coax, mix of RG-8, MMR-400 to get to the edge of the
woods from the house
* No terminating resistor
On bands 160-40, the signals are very weak. I am monitoring WSPR, FT8.
I can hear signals on 160-40 but they are way down compared to dipoles
and inverted L on the same bands. Like 20-30 db down. From what I
read, I should NOT need an HF pre-amplifier, right?
Signals on 30 and 20 seem to be better and I can copy some DX from EU
on FT8.
I will try installing a new ground rod, the old one is 10 years old
and perhaps not making a good ground connection at the feedpoint. The
transformer is brand new, so that's not an issue. The coax has tested
out fine. Soil is central North Carolina clay, a bit dry at this time.
I am guessing performance is poor on 160-40 because of the short
length and that it's bi-directional (no terminating resistor), which I
am seeing on 30 meters. But I did not think it would be THIS bad on
160-40....
Mark Lunday, WD4ELG
Greensboro, NC FM06be
wd4elg@arrl.net<mailto:wd4elg@arrl.net>
http://wd4elg.blogspot.com
SKCC #16439 FISTS #17972 QRP ARCI #16497
_________________
Searchable Archives: http://www.contesting.com/_topband - Topband
Reflector
--
Dave
Manuals@ArtekManuals.com
www.ArtekManuals.com
--
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus
_________________
Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
|