Looks interesting. Was wondering if anyone ran one of these. Any thoughts? http://www.lightningantennas.com/mobile/
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Lightning Antennas GR45
- Thread starter Blackcat630
- Start date
Good reviews according to the site testimonials. I'm not in the financial situation where I can drop 100+ on ANOTHER mobile antenna. Especially right after Christmas. Guess I'll stick w my trusty 108 whip for now.
630, I use to rave about this mobile antenna based on my daddy's use on his trucks in the Texas valley running his field services business crews.
I recently got one of my dads antennas from my brother, and I tested it by replacing the 102" whip at the ground plane part of my Marconi 4x. The antenna was new/old in the box. I set it up and attached it to a 25' foot push-up pole. I also compared it to a 102" whip on the same GP setup.
Click here: http://www.worldwidedx.com/attachments/gr-45-on-marconi-5x-ground-plane-2-jpg.11272/
Dx was dominate back then, but I tested them with local signals when I could. I saw a little advantage with the 102" whip much of the time, but it was close. Since I had to physically change antennas...the testing was not quite like switching...using a switch.
IMO, the antenna works well for what it is but I have not tested it mobile.
I have been told and Signal Engineering use to claim that the GR45 antenna responded exceptionally well to horizontal signals suggesting this was an advantage. I was not able to confirm any evidence of this...and I tried comparing the GR45 to an A99 I could install about 40' feet away.
IMO, as the antenna comes from the factory the large top hat will not work dependably as a mobile unless modified. My antenna was static and the top hat repeatedly came loose at the hub and the wires slipped disturbing the match. My brother told me that daddy use to spot weld these parts...so he could run them on his field equipment.
Just my two cents.
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I've never used or seen one in person but they've been available it seems for 35+ years.
All I noticed from the pic is it seems to violate one of the rules of loading an antenna, the capacity hat appears to be too close to the coil.
I would expect less local vertical performance than a Whiskey still type mobile antenna.
If I had one of these I'd add 12"-18" between the coil & cap hat and remove a winding or two.
Seems a bit pricey for an oddly shaped mobile antenna, even if it does have almost 1/2 the amount of magic Antron9.9 gain
All I noticed from the pic is it seems to violate one of the rules of loading an antenna, the capacity hat appears to be too close to the coil.
I would expect less local vertical performance than a Whiskey still type mobile antenna.
If I had one of these I'd add 12"-18" between the coil & cap hat and remove a winding or two.
Seems a bit pricey for an oddly shaped mobile antenna, even if it does have almost 1/2 the amount of magic Antron9.9 gain
630, attached below is a set of Eznec models, comparing the results for the GR45 to a 1/4 wave using 5 x 102" ss steel whips. I also added an overlay for a pattern comparison.
Well NB, like I've said before...CB'rs tend to take a technical article that suggest issues of one sort or another and make a mountain out of a mole hill out of it...just like this extensive article by W8JI. He even gives us a big red warning rant about this very thing concerning folks that misrepresent his work (his words).
http://www.w8ji.com/mobile_and_loaded_antenna.htm
Well the Whiskey Still idea covers a big field of different antennas with big coils...and I'm not too sure they are all effective. If you give me the full dimensions for your favorite WS model I would be glad to try and model it for comparison. Below is an article comparing big coil antennas among others. I don't vouch for this article, but it does present mobile antenna comparisons, and may be worth reading.
http://www.copperelectronics.com/articles/big_coil_antennas_exposed.php
NB, I might try this idea on my model of the GR45 below. You could be right.
NB, I agree here...the antenna is not worth the money to me.
According to this model it does not look like the coil and top hat being close together doesn't hurt at all...unless the design can be even better with space between the coil and top hat.
Click on the PDF attachment below for the model results I get comparing a standard 1/4 wave vertical with 5 x 102" ss whips to a GR45 on top of a suitable ground plane, and elevated to 36' feet.
Well NB, like I've said before...CB'rs tend to take a technical article that suggest issues of one sort or another and make a mountain out of a mole hill out of it...just like this extensive article by W8JI. He even gives us a big red warning rant about this very thing concerning folks that misrepresent his work (his words).
http://www.w8ji.com/mobile_and_loaded_antenna.htm
Well the Whiskey Still idea covers a big field of different antennas with big coils...and I'm not too sure they are all effective. If you give me the full dimensions for your favorite WS model I would be glad to try and model it for comparison. Below is an article comparing big coil antennas among others. I don't vouch for this article, but it does present mobile antenna comparisons, and may be worth reading.
http://www.copperelectronics.com/articles/big_coil_antennas_exposed.php
NB, I might try this idea on my model of the GR45 below. You could be right.
Seems a bit pricey for an oddly shaped mobile antenna, even if it does have almost 1/2 the amount of magic Antron9.9 gain
NB, I agree here...the antenna is not worth the money to me.
According to this model it does not look like the coil and top hat being close together doesn't hurt at all...unless the design can be even better with space between the coil and top hat.
Click on the PDF attachment below for the model results I get comparing a standard 1/4 wave vertical with 5 x 102" ss whips to a GR45 on top of a suitable ground plane, and elevated to 36' feet.
Forgot the guys numbers but when skips running from here to Hawaii. There's a guy running running one on his pick up that works good for him. He is a regular skip shooter from Honolulu. Great sounding station with a HR 2010 and a helper. Some of you probaly know him too.
I'm impressed and surprised by the plot compared to a full 1/4 wave vert. It is also the heart of the Merlin 55 which is basically what you show in your top plot.
Try it with a foot of mast above the coil & below the cap hat to see if it improves.
Try it with a foot of mast above the coil & below the cap hat to see if it improves.
"Minigrass"?
NB, below are two additional models that I did with this coil located 24" and 36" inches along the GR45 original 48" length instead of at the top and 2" inches below the top hat.
I'm surprised that at the 24" coil location the matching reactance abruptly went high. There may be a tipping-point somewhere, going down with the coil, between the 24" and 36" locations where the theory, not to place a coil near a top hat, comes into play.
IMO, and to be fair, this suggest to me I have to experiment with the coil location near the base too and then make a comparison. To check this out I will have to make the coil work starting at the base, get it working, and then going up toward the top hat as well.
If I can get this model with a top hat to respond well with a coil at the base...then I will raise it up 12" inches at a time and see what happens. Doing this the antenna may then show us more gain at the base and that will change the idea I just posted.
NB I say this, but I predict the first models I did above, which appears to disprove the theory you questioned above, actually reveals to us...within reason there is no disadvantage to placing an inductive coil near a top hat...and this design could be a small advantage instead. I have already proved this for me and presented the evidence, but how do you see it? Just for grins, you touched on the proof in your first sentence above. Go back and check my first GR45 model project carefully, and see if you see where I've already proved what we see in my first models.
No, I meant raising the top hat a foot above the coil but leaving the full height of the coil (5' total), or maybe drop the coil a foot but keep the total height (4' total).
I set the top hat 10" inches higher, and it moved the top hat to 12" above the top of the coil, see wire #64 is 12" inches. This added + reactance to the antenna and the match went bad.
The model I posted above showing wire #1 at 36" inches places the coil 12" below the top hat.
Oh wow, I've just found this post, missed it for a couple weeks.
OK, that settles it, selling everything, getting a Merlin55
I’ve had a SIGNAL ENGINEERING GR-45 more than twenty years.
Really ought to get it back out. Color matches my longbed Dodge diesel with windowless topper.
No antenna you ever use on a roof mount will get more stares.
Just stare back a few beats too long and they get to thinking maybe they DONT want to know what Agency you’re with.
And it’s a talker.
Guess I should mount the STAR-GUN waaay back on the topper (if FourString’ll give it back).
Scatter a few Unity antennas here and there. Maybe a StingRay box or two.
What else?
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