Technical Topics > Equipment
LOG Not Performing Well
ultravista:
~SIGINT~, thanks for the feedback. I wasn't aware that the small gauge wire could be the culprit. Interesting.
This is 60 feet. Is it enough to materially affect the signal?
What surprised me was the day/night testing. During the AM testing, the bands were quiet on the LOG but active on the Pixel. I commonly listen between 7-9 AM ET and get a lot of APAC stations. It was as if the LOG wasn't connected, it was so quiet.
The evening however was a different story. The same stations received on 160/80/40m by the Pixel were also received by the LOG. Albeit not as loud, the same stations were present, including Israeli CW @ 4133 Khz.
Day or Night, the LOG at 60 feet is dead to NDBs below the Broadcast AM band. The Pixel does a so-so job < 500 Khz and I can tune a NDB @ 415 Khz. The log received nothing.
ChrisSmolinski:
What receiver are you using?
RobRich:
You are using a beverage transformer designed for 400-500 ohms terminating resistance. You LoG is a fractional wavelength antenna below the 20m band, or perhaps more around the 30m band due to resonance changing as approaching the lossy ground. Either way, your transformer is taking an already low-impedance antenna and lowering the ohms even further as frequency decreases, thus increasing mismatch and losses.
Start with removing the transformer IMO. Wind a 1:1 or whatever if needing common mode current isolation from the feedline, though as for balancing the LoG itself, the antenna already should be rather balanced regarding differential currents.
I only have a few snap-on ferrites on the coaxial feedline at the the feedoint my 148' LoG. I do have a decent RF choke back at the receiver end, but it is not really needed for my particular deployment, either. YMMV.
~SIGINT~:
--- Quote ---This is 60 feet. Is it enough to materially affect the signal?
--- End quote ---
Absolutely as you are dealing with signal amplitudes in the micro volts (uV) range which need to travel down the conductor to the feed point. The smaller the conductor the higher the resistance therefore you will get attenuation along the conductor. You also have less surface area to capture those waves.
Did you remove the insulation on the antenna wire? That as well has an attenuation factor. Then there is also the feedline loss. Every little bit makes a difference because all those little bits add up. Even the quality of the conductor can make a difference. Cheap mix alloy conductors with very little copper content make for poor antennae.
I also looked at the DXE-BFS-1 instructions and they specify:
Antenna wire: You will need a minimum of 3/8 wavelength of wire of any gauge between #8 and #20.
Your current wire is most likely 24 or 26 gage. 3/8 wavelength at 160 metres is 200+ feet of wire. Even at 1/4 wavelength you are looking at 137 feet of wire.
NJQA:
I don’t think you want to remove the insulation from the wire on a LoG antenna.
Although this isn’t the case for you since you just installed your LoG, both LoG and BoG antennas suffer performance degradation if they get subsumed into the ground. These antennas need to be sitting *on* on the ground, not under it, even a little bit.
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