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Author Topic: Antennas  (Read 4262 times)

Offline zackers

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Antennas
« on: February 04, 2013, 1803 UTC »
I am curious what some of you are using for antennas, particularly in the AM broadcast band and LF ranges. I have several amateur radio antennas that perform fine in the shortwave spectrum. I also have a 20-turn 5-foot square loop (with taps every 5 turns) that I thought would be a decent performer on MF and LF frequencies, but it just hasn't done what I expected for some reason.

I live in a house on a lot approximately 50 X 100 feet. There is a tree to the east on the neighbor's property that is about 50-60 feet tall. I can't use that as an antenna support.

I just finished building the AMRAD active whip antenna. I will probably get this up about 25 to 30 feet but there''s no way I can get it up 60 feet to clear that tree. So I don't know how well it will perform yet. I guess I'll know in a couple days. I hope it does well in this location as an LF antenna.
East Central Illinois
TS-850S, 40 meter full-wave loop, various dipoles

Offline BDM

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Re: Antennas
« Reply #1 on: February 05, 2013, 1625 UTC »
For me with limited room, I'm using a Pixel active loop. It outperforms my 80m dipole on the MW and especially the low bands (LW). Works very well in my situation. Low noise also compared with any wire but again I'm in an urban area. Height will have little to no effect for the low bands except if it gets the antenna away from noise sources.
« Last Edit: February 05, 2013, 2226 UTC by BDM »
Radios -- Perseus SDR // Icom IC-7410 // Tecsun PL-660 // Panasonic RF-5000A --Antennas-- Pixel Pro 1B loop - 82' fan-dipole at 40' - tuned MW/BCB 40" loop and 100' receive only dipole
-Brian--North of Detroit--MI-
1710/KHz the MW Pirate Clear Channel (not so much anymore "sigh")

Offline desmoface

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Re: Antennas
« Reply #2 on: February 06, 2013, 1607 UTC »
Im very happy with my full wave horizontaly polarized loop tuned for the 80 meter band, ~ 275 ft long.  You can see how it performs by checking out some of my pirate/numbers video's on youtube under "desmoface."

73's
Kenwood TS-870SAT & Afedri SDR
Full Wave 80 Meter Horizontal Loop ~ 260 Ft Long
Pse qsl to desmoface @ yahoo . com
NE Ohio

cmradio

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Re: Antennas
« Reply #3 on: February 07, 2013, 1050 UTC »
Living in downtown QRMville, a loop was a no-brainer for me.

Peace!

Offline Rafman

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Re: Antennas
« Reply #4 on: April 23, 2013, 1620 UTC »
Full wave 40M loop [~140'] hung like a picture frame [vertical] with ends up @45' & fed in bottom, center, with 450 ohm ladder line. I then tune the ladder line with an old Johnson Matchbox [275w version], then feed that through [an optional] Mizuho SX59 Preslector...
I intend to replace the Matchbox with binocular 9:1 xformer but not likely to happen until next fall. No point in doing it so the lightning gods can melt it over the summer!!!

That is my main DXing antenna, living in rural area means I already have a low noise level & I use this setup pretty much exclusively with my Perseus SDR...

It's a Grand Setup!!! ;)

Rafman
~
Rafman
Onion Flats [Baskerville] VA USA
[All QSLs greatly appreciated: WIFIDX@gmail.com]
Elad FDM-S1&S2 / SDRplay1 & SDRplay2
Mizuho SX59 & SX3 preselectors / JPS ANC4 Noise Phaser
41m EU beverage / 40m loop / 75m CF Zepp / 41m Sloping Dipole
The "Real FCC" http://bit.ly/2lQDNYm

Offline ChrisSmolinski

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Re: Antennas
« Reply #5 on: April 23, 2013, 1653 UTC »
I use my 670 ft sky loop. It works great at the upper end of MW where it is about a wavelength, as you would expect. I get excellent reception from TIS stations and the like.

It's OK in the middle of the band, and pretty bad on lower MW and LW due to being so short, relative to the wavelengths.
Chris Smolinski
Westminster, MD
eQSLs appreciated! csmolinski@blackcatsystems.com
NRD 545 / netSDR / AFE822x / AirSpy HF+ / KiwiSDR / 670 ft horizontal loop / 500 ft northeast beverage / 270 ft west-south-west beverage / 300 ft south beverage / 43m / 20m / 10m  dipoles / Crossed Parallel Loop

Offline fpeconsultant

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Re: Antennas
« Reply #6 on: April 24, 2013, 0118 UTC »
You guys are mind readers. I was going to post & ask for opinions on a new antenna - I have a 300' tuned longwire at about 30' and would like to try something new.  My lot is about 330'x330' so I can get some wire in the air.  I see Chris's note about his skyloop and I'm considering one but I like chasing beacons sometimes so maybe the skyloop aint' for me.  What can you guys suggest?  Im a SW Clandestine, HF Pirate, general SW, WEFAX, Beacon, MW enthusiast (phew..).
Thx in advance for any ideas - and bear in mind before you answer that I'm a fire protection engineer NOT aN electrical type at all (water & electricity thing....) so I might have 99 more questions if you don't mind giving the help.....
Near Chicago, IL USA.  Drake R8, Ten-Tec RX340, JRC NRD545, Watkins Johnson HF-1000, Wellbrook loop at 28', 40m inverted vee.  Please QSL to fpeconsultant@aol.com thanks.

Offline BoomboxDX

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Re: Antennas
« Reply #7 on: April 25, 2013, 1440 UTC »
I don't DX Longwave, so I don't know about that.  I mainly DX MW and tune around on SW when MW season's done.

Most of my MW DXing is done with spiral loops when they're needed.  I have a Radio Shack loop, Select-A-Tenna, and also a box crate loop that works well.  The box crate has a bit more gain than the other two antennas.
An AM radio Boombox DXer.
+ GE SRIII, PR-D5 & TRF on MW.
The usual Realistic culprits on SW (and a Panasonic).

Offline Token

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Re: Antennas
« Reply #8 on: April 25, 2013, 1616 UTC »
Hmmm…I use whichever of my antennas work best at the time, I often switch through them until I find the one that is best, and that can sometimes be one that does not make a lot of theoretical sense.  Sometimes that might be an antenna that produces a much lower signal amplitude but a better signal to noise ratio.  Keep in mind that out here in the desert I am in a pretty low noise area, RFI really is not a regular issue for me.  I do have some light RFI, but not much at all.

Not going to run through all the antennas, but here are the ones that typically work best on MW and LW.

I have three Rhombic antennas for HF work.  Two of them are 450 feet apex to apex and the other is about 310 feet apex to apex.  Via vacuum relays at the terminated end of the Rhombic all three of them have three modes of operation, terminated, open, and shorted.  In the terminated mode they are directional, towards the terminated end.  In the open mode they are bidirectional, through the long axis of the antenna.  In the shorted mode each becomes similar to a large horizontal Sky Loop slightly squished, the two larger ones are about 1000 foot loops, and the smaller is about 700 foot.  This basically makes them full wave Sky Loop, although much lower than optimal, for about 1000 kHz and about 1400 kHz.  Typically one of these three antennas results in the best SNR on MW and LW.

Surprisingly my 160 meter half wave dipole, despite being a bit too short for the frequency range, does well on MW, and fair on LW.

I also have two loop antennas.  One is a home brew passive mag loop, I forget the number of turns right now but on about a 3 foot box.  The other is a Wellbrook ALA1530S+.  Both of these antenna perform well on MW and LW, with the Wellbrook being the nicer to use of the two.  The advantage to these antennas, naturally, are that they can null offending low angle or groundwave stations, sometimes making it possible to pull out a station that the other antennas might have lost in other noise/QRM.

T!
T!
Mojave Desert, California USA

Offline jFarley

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Re: Antennas
« Reply #9 on: April 27, 2013, 1838 UTC »
I agree with Token's philosophy here.  To ask a single antenna to work optimally over the frequency range of 100kHz to 30MHz is probably a bit optimistic.  This is a 300:1 frequency (and wavelength) range; for an antenna to be the  best possible choice from all types available at every frequency over this range is asking an awful lot.  I have multiple antennas available for the portions of the spectrum which interest me the most; at ID time, being able to select from among them via a switch is a great tool to have in your toolbag.

Given your real estate size, I can't see how you can lose with a skyloop or possibly a rhombic to cover a big chunk of the spectrum.  An alternate antenna could be used to fill in holes in coverage as you see fit, and if the two antennas overlap in coverage in a chunk of the spectrum, even better.

I have a 100x300 foot suburban lot, but right now I have no wire antennas up other than a small EWE; it's not the greatest antenna, but it is a very simple wideband alternate choice.

I acquired a Wellbrook a few months back and am satisfied with its performance.  At LF, I have been able to log most of the NDBs others have posted here, as well as several others.  I do not currently DX MW, and I can't comment on its performance there, but given the number of high power MW stations in Chicago, I would prefer a resonant loop here.  The NRC AA Loop (Alt-Azimuth, 36" box loop) is the best antenna I have ever used for MW... 

For shortwave, the performance of the Wellbrook seems quite good above around 8MHz; I have been able to get reasonably good copy of, for instance, the 27MHz Euro SSTVs and 19M Euro pirates here in Chicago.  I think that an SML is a great choice for a general purpose antenna which can be used to complement another primary antenna.  In my book, the single greatest advantage of a small loop is that one can move it around in a lot to site it away from neighbor's houses to minimize interference pickup, something which is a lot harder to do with a larger wire antenna.  The choice of which one to buy is a matter of personal preference, and there are many reviews of both the loops offered by Wellbrook and Pixel.  A couple of reviews which need to be read if you end up leaning that way are:

"Active Loops, Active Voltage Probe and Wire Antennas; A Statistical Review of the Performance of Six Antennas (Part I)" by Jack R. Smith K8ZOA, Clifton Laboratories

http://www.cliftonlaboratories.com/Documents/Loop%20vs%20Loop%20Final-Final.pdf

"The Pixel Technologies RF PRO-1A and Wellbrook Communications ALA1530 Active Loop Antennas Compared" By Guy Atkins KE7MAV

http://www.wellbrook.uk.com/reviews/ALA1530-vs-RFPRO-1AReview.pdf

My listening is concentrated in the 90 meter to 43 meter range, and for this range my workhorse antenna is a small (20" square 4 turn) resonant loop which tunes from 2500 to 7500kHz.  This is a high Q (around 240) unshielded tunable loop, and being unshielded, it is somewhat like having casual sex without protection.  An unshielded loop does not offer the same degree of QRN protection as do the shielded loops mentioned above.  When local noise here is low (and that's currently about 90% of the time) the resonant loop will almost always exhibit a better S/N ratio and lower minimum discernible signal than the Wellbrook in this frequency range.  It is not unusual to be able to detect a carrier fading up on the resonant loop 10 or 15 minutes before I can detect it on the Wellbrook.

I hope this helps in some small way!
Joe Farley, Near Chicago
SDR-IQ / R8 / R7
Remote Resonant Loops for HF and LF / ALA 1530
Active 60" Whip / PA0RDT
QSLS appreciated to:    jfarley44@att.net

Offline skeezix

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Re: Antennas
« Reply #10 on: April 28, 2013, 0149 UTC »
I use a Wellbrook ALA-1530S+ with the Perseus and does great on LW, MW, and the lower HF bands. As thre frequency increases, it does fine, but not stellar, but its designed for the lower parts.

Also have a 102' G5RV that I used to use for this and the Wellbrook smokes it by a large margin on the lower end, and rotating it down on LW & MW to null out stuff is something the G5RV couldn't dream of doing.

I have a bunch of RFI around the house. For now, the loop sits in the garage and still picks up a lot of RFI. Soon as the ground thaws, going to move it out to the shed that's about 100' away from the house and that should fix the RFI problem, I hope (portable radio indicates its quiet back there).

Minneapolis, MN