I have assembled my 19 element LPDA with the front 12 elements about 3 feet off the ground and parallel to the ground. The back elements are laying on the ground, but electrically connected in the us
SWR peaks and valleys are part of every LPDA design, but you'll need to get the LPDA well up above the ground for any meaningful results from your VNA. Paul, W9AC I have assembled my 19 element LPDA
3 is really close.... get it up even 2 more and I suspect youll notice a difference. Ideally 6+. Can you point the front of the antenna straight up and test it (up against the side of a tower maybe)?
Doug, You cannot get reasonable readings with the antenna on the ground. You can get more ball park readings by standing it on the back end with the front elements facing skyward. Suggest you place t
The LPDA does not use a parasitic reflector. Pointing it straight up with the low frequency element anywhere near ground level will not give an accurate swept result. The LPDA needs to be raised up i
As others have already posted, the log will show wild SWR curves even when high in the air, altho should show decent freq/SWR response within the band segments it's designed for (in our case, the ham
If I were to get the nose to point up higher, maybe 45 degrees, wouldn't I expect the VSWR to straighten out in the higher frequencies? As I understand the LPDA, as the frequency increases, the short
No, the impedance of the back element so close to the ground could still be upsetting the whole antenna. Get the whole thing up off the ground to try to measure it. David Robbins K1TTT e-mail: mailto
Author: "Roger (K8RI) on TT" <K8RI-on-TowerTalk@tm.net>
Date: Sat, 26 Sep 2015 22:25:05 -0400
I think I'd phrase things a bit differently than a number of posts. What ever the height, the VNA should give accurate SWR readings for "that height" From what I've seen and read, on "the log" all el
Yo, Doug is having fun with tuning a new antenna near the ground. SWR readings are off. Doug and all: I recently helped assemble and install a Cushcraft ASL2010 and we followed the procedure in the m
It is a waste of time checking an antenna near the ground. About the only thing you can determine is if the coax is connected. You need to pull it up at least 30' high. John KK9A I have assembled my
Author: Bill via TowerTalk <towertalk@contesting.com>
Date: Mon, 28 Sep 2015 07:58:22 -0400
Lots of checking of antennas here. Easiest way to check the antenna is to put a pulley on the tower and then haul the antenna up to at least 10 feet or so for 10-20 meters. This will give you a rough
I have assembled my 19 element LPDA with the front 12 elements about 3 feet off the ground and parallel to the ground. The back elements are laying on the ground, but electrically connected in the us
Well, okay, I'm convinced, thanks to everyone's advice, that I cannot expect a VSWR sweep to yield anything meaningful with the antenna on the ground. So I've done everything I can on the ground to e
Author: K7LXC--- via TowerTalk <towertalk@contesting.com>
Date: Mon, 28 Sep 2015 16:15:28 -0400
only thing you can determine is if the coax is connected. You need to pull it up at least 30' high. Yes, 30' high is a truer picture of the antenna resonance (which is probably the number of greates
Make sure the booms are electrically separate. Each 1/2 element should be staggered onto the other boom from the previous one. Some LPDA's have issues with the feedpoint choke, and how the coax is ro
This is really helpful. When I did the plot with the antenna on the ground, all the dips below 5:1 VSWR were below 10 MHz. Then, after 10 MHz, the VSWR saturated at the graph limits of 5:1. The compl
The boom is actually a structural truss, not involved with feeding the dipole elements. All the dipole elements are fed from a linearly tapered coaxial transmission line transformer, the details of w
Itīs probably a LP1005 http://antennas.usantennaproducts.com/item/log-periodic-antennas/-lp-1005aa25-kw-rotatable-hf-log-periodic-antenna/lp-1005aa 73 Peter Make sure the booms are electrically separ
Bingo! Itīs probably a LP1005 http://antennas.usantennaproducts.com/item/log-periodic-antennas/-lp-1005aa25-kw-rotatable-hf-log-periodic-antenna/lp-1005aa 73 Peter Make sure the booms are electricall