HFU HF Underground
Technical Topics => Equipment => Topic started by: jimbooregon on January 24, 2020, 0820 UTC
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Hi all,
I'm a retired US citizen presently living in Amman Jordan. We'll be visiting Glasgow Scotland in April and I'd like to pick up a Wellbrook FLX 1530LN then. I'm using an Alinco DXR8E (European model 0.004- 35 MHz).
The user supplies the coax for the antenna and Wellbrook indicates 3-5 meters of JMR 400 or RG 58c. The values translate to
3M 9.8 feet 3.1 feet diameter
4m 13 feet 4.1 feet diameter
5m 16 feet 5.2 feet diameter
The cost and size go up with increasing circumference, so is there a difference and in what areas for increasing size...is it worth the larger size/cost? Recommendations?
Also, LMR 400 or RG 58c... and why.
Thanks in advance for your suggestions and input
73's
Jim
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Your post is a little difficult to understand but for receive, you only need RG58.
LMR 400 is a much heavier cable.
When in Glasgow, check out my friends, Celtic Music Radio, on 95 FM.
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Unless you already have a section of LMR 400 for use, I would purchase the RG58 for receive only purposes. RG58 is cheaper as Brian has stated and LMR 400 is regarded as a low loss transmission coax (over 100 ft.) which is not needed in receiver applications.
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Yeh I can't see a diff between the coaxes listed as far as rx performance goes. On the diameter there may be a diff, with larger loops having a bit more input to the amp and better response at lower freqs.
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The antenna he is talking about (FLX1530LN) is a version of the Wellbrook that doesn’t come with a solid metal loop. You hook up a short loop of either RG58 or LMR400 in place of the loop.
Performance (using good quality cable) should be very similar for either cable type. You might find the LMR400 holds a circular shape better though. You can find variants of LMR400 that have either solid and stranded center conductors. The solid will also help hold a circular shape better, but this may not be a big thing. You can always build a simple frame out of pvc pipe to hold the loop.
As far as the feedline between the Wellbrook and the radio, LMR400 will have less loss, but you won’t notice the difference at MF and HF frequencies unless you are using lengths far greater than 100 ft. RG58 will be fine for most cases. Try to stay with name brand coax - there are many Asian knockoffs that have poor braid coverage.
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Yes. I would go with the best coax for the loop since its such a small length to purchase. It seems a bit odd to me that coax would be used for the loop. Why would you want to use something so insulated to receive with? I'm sure theres a good reason, I just don't what it is.
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Yes. I would go with the best coax for the loop since its such a small length to purchase. It seems a bit odd to me that coax would be used for the loop. Why would you want to use something so insulated to receive with? I'm sure theres a good reason, I just don't what it is.
On my homemade loop, the outer braiding is connected to the inner core.
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That makes sense connecting the inner line with the braid. Still not sure I'd want that jacket though. I like my coax to end at the antenna. However I do use insulted wire on my wire antennas, so I guess it's not that much different.
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The big advantage to the FLX1530 is that it is easy to transport and store. I can just imagine him purchasing one of the regular Wellbrook loops and putting it in checked baggage for the trip back to Jordan! Some helpful baggage handler will probably bend it in half to save room.
The regular Wellbrook just uses the entire tube as a conductor. It is not a shielded loop design where the tubing has a small gap at the top to expose the inner conductor. There is no inner conductor.
I’m guessing that the FLX uses the outer braided shield of the short piece of RG58/LMR400 as the conductor and ignores the inner conductor.
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Yes. I would have thought he'd just be concerned with getting the main amplifier portion and build the loop later back home. However I think the Giga parts in Amman closed a couple of months back.... You know, the one next to the old Home Depot.
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Providing your own loop material allows one to play with concepts like these;
http://www.n5ese.com/loop_ant.html
https://ieeexplore.ieee.org/document/1697139
https://electronics.stackexchange.com/questions/71182/is-this-shielded-loop-antenna-balanced
https://www.ahsystems.com/catalog/SAS-563P.php
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FWIW, I use LMR240 for my Wellbrook antennas and have never looked back. It's ideal for HF and is a relatively thin coax.