Sunday, August 13, 2017

W6LVP Loop Trial

After reading many reports about some of the "new" broadband, amplified loops and having had considerable experience with large unshielded tuned loops, and also having a vacation coming up to a coastal area, I thought it might be a good time to spring for one of them and give it a try,  especially given the increasing and intermittent high noise floor in my neighborhood.

For ease and quick shipping and a somewhat lower price,  I chose to go with the W6LVP loop after seeing several good reports among the Facebook DX groups that I have been frequenting.

I will say that the customer service, method of secure  payment and swift  delivery was very good and the antenna arrived in short order, well packed and of apparent good construction. Assembly, such little of it that there was, was very simple and intuitive.  The antenna is very light and is attractive.

I fired it up inside the shack only a couple feet off the floor and fed it into the R-75 only a few feet away.  the power supply was very quiet and there appeared to be no noise coupling from it even with the close proximity that I found it to be to the loop in the initial test.

Noise inside my house is a bit high due to multiple cell phone chargers, wifi, televisions, cable boxes and computer power supplies,  but with judicious rotating of the loop, noise was lower than the vertical out in the yard and considerably lower than the sloper.  Comparing signal strength of WWV and CHU showed about three S-units down from the outside forty foot vertical over 60 buried radials, but due to the reduced noise, they were all at least as readable on the loop inside.

Noise on the MW broadcast band and Low  Frequency band was comparable to the vertical. To be totally fair, rotating the loop inside the house showed noise coming from various locations,  with two of the main sources just about 90 degrees apart, so nulling both would be just about impossible no matter how good the loop would be.

The next day,  I mounted the loop on a temporary mast in the back yard about 20 feet from the house.  It was up about fifteen feet  above ground in the same general area of the yard as my vertical ( about ten feet away) and about 20 feet east of where the sloper traverses the yard.

Firing it up at that location gave it a much better chance of showing off its performance. In fact, it was a whole different world from when it was inside.   Nulling the major noise source was much easier, though there seemed to still be a secondary noise source whose null would require a position mutually exclusive to the position for nulling the worst noise source.

The first test run was done in the MW broadcast band at 0000 GMT July 23. This is over an hour before dark at my location in Woodway, on the west side of Waco, Texas.  To get an idea of just where I am, if you look at a map of Texas, look on the west side of Waco along Highway 84, a couple miles west of its intersection with Loop 340/State Highway 6. The following signals were logged as ground wave signals on the loop feeding the R-75:
XEMU     580 kHz   5 kw  Piedras Negras, Mexico  S-5 and steady
KLIF        570 kHz   5 kw Dallas, Tx S-9+10 db
KLBJ        590 kHz   5 kw Austin, Tx  S-9 + 20 db
KTBB       600 KHz  5kw  Tyler, Tx  S-5
KILT         610 kHz   5 kw  Houston, Tx S-7
KESB       620 kHz    5kw  Dallas, Tx S-8
KSLR       630 kHz    5 kw San Antonio, Tx S-7
Unk          640 kHz     1 kw  Norman, Oklahoma S-5
KSKY       660 kHz   20 kw  Dallas, Tx S-9+20 db
KKYX      680 kHz   50 kw  San Antonio, Tx S-8/S-9
KSAH       720 kHz   10 kw  San Antonio, Tx S-8
WBAP       820 kHz   50 kw  Fort Worth, Tx S-9 + 40 DB
KONO      860 kHz     5 kw  San Antonio, Tx  S-7
Unk           930 kHz     5 kw San Antonio, Tx S-7
WOAI      1200 kHz   50 kw  San Antonio, Tx S-9
KRZI        1660 kHz   10 KW Waco ( local) full scale

These were logged in a quick sweep mostly of stations I could identify by presence to get a quick idea of what was going on via groundwave before too much night effect prop would begin.

At 0100,  still a bit before sunset and still full sun at the WWV transmitter site,  a quick sweep of time and frequency stations yielded the following:
2500    WWV  S-5
3330    CHU    S-4 ( their transmitter site in darkness)
5000    WWV  S-9
7840    CHU    S-7
10000  WWV  S-9+20 DB
14670  CHU    S-7
15000  WWV  S-9+10DB
20000  WWV  S-7
25000   WWV Just audible carrier

The R-75 in all of these tests was being run with neither pre-amp on. Ambient noise on the loop was about S-1, while on the vertical was S-3.  It should be noted that the vertical had been put up in the quietest spot in the yard by walking a portable receiver around tuned to 500 kHz.

A quick tune around showed the Voice of Greece, a strong evening regular on 9420 at S-9+20 DB. A check of Radio Encyclopedia from Cuba on 530 kHz showed it at S-7, well above the noise and listenable.  On the vertical it usually runs S-9 but with some noise in the background.

A quick test of the low frequencies showed, as expected, it was well too early for the European and African Long Wave broadcasters to be heard. I quickly ID'ed a few non-directional aircraft beacons:
ARM  245 kHz  Wharton, Texas   S-5 ( about 200 miles)
PQF    248 kHz  Mesquite, Texas  S-7 ( about 100 miles...Mesquite is on the east side of Dallas)
ROB   400 kHz  Robinson, Texas  S-9+20 db ( local NDB 10 miles away)

A quick ham band test in the 40 meter cw portion showed:
0227 GMT   OK2RRR   7007 kHz  Czech Republic RST 579
0238 GMT   F5IN          7011 kHz   France               RST 579
0247 GMT   W0LI         7017 kHz   USA                  RST 589
0248 GMT   K9OM        7017 kHz  USA                  RST 599
0249 GMT   W7FW        7018 kHz  USA                  RST 599

Again, these were on the R-75 with no extra preamps on and with 250 hz filters in.

This being at the end of a long day and with other evening chores still ahead, this was the end of the first days testing.

The next day ( July 23, 2017) allowed time for a little more testing under daylight conditions.  Unfortunately my operating set up did not allow quick A-B testing between the loop and the vertical because I have no remote antenna switching and I was actually using the feedline that normally goes to the vertical to feed the loop.  The transmission line is about 100 feet of RG-8 X that is routed in an indirect route along fence lines to allow the shortest run across open lawn to the antennas. The RG-8X is not buried.

In a run beginning at 1436 GMT or about two-and-a-half hours after local sunrise, a run of the time and frequency stations yielded the following:
 25000 kHz   WWV   S-5
20000 kHz     WWV  S-7
15000  kHz   WWV   S-9
14670  kHz    CHU    S-4
10000 kHz     WWV  S-9 ( No WWVH)
7850  kHz     CHU     S-4
5000  kHz     WWV   S-8
3330 kHz      CHU     inaudible
2500 kHz      WWV   Just audible carrier

A run through the 20 meter amateur band resulted in  a logging of showed numerous USA stations at S-9 or better  At 1444 I heard VE2WU calling CQ on 14017 about S-5 followed by XE2AAW in Mexico at S-7.  No Europeans were heard in a quick sweep. WRMI on 9455 was S-9 at 1448 GMT. At about this time, rains were coming in and the loop was taken down from its temporary mast because the connections had not been waterproofed for this quick test.  The next few days saw several periods of thunderstorm activity, so testing was pretty much halted. The rest of the week was also taken up by preparations being made for the vacation trip that would include testing the antenna at the Gulf Coast.

This would be a real test as we were going to the coast in a passenger car rather than our usual Chevy Suburban and would have no room for large mast sections usually carried on the luggage rack on the roof of the Suburban.  The loop would be the only antenna taken.

We arrived at our coastal location about midday July 31. Radio activity would take place in the environment of family activity, so it would not be a full five days of all-out testing but it was hoped that a fair amount of " wringing out" of the antenna would take place.  It was mounted on a camera tripod with a short piece of PVC pipe extending above it to keep the loop away from the metal of the tripod.  The antenna was set up on a balcony about 15-18 feet above the ground and about a hundred yards from the water.

The location was at Crystal Beach, Texas on the Bolivar Peninsula about 12 miles east of Galveston, Texas.

The first listening came late in the afternoon of the first day and was a short one due to other activities including unpacking,  running errands to a local grocery to stock up on supplies and the first steps into the salt water ( priorities!!!)

A quick check at 2300 GMT showed our old favorite, the Voice of Greece on 9420 at S-9+20 db.
WWV on 10 MHz was S-9 with QSB and on 15 mHz was S-5 with QSB. A quick check of a few Medium Wave stations  showed WTAW on 1620 KHz, 10 kw,  from College Station, Texas ( about 160 miles) S-9 + 10db. KRZI on 1660 from Waco, also 10 kw was S-9, and while they were still on daytime power, there was some evidence of night effect as there was some QSB. KOGT 1600 from Orange, Texas with 1 kw about 75 miles away was S-9+10 db, but it should be noted that it is almost a water path from that location.  Thus ended the first evening of testing with swimming and dinner taking over!

With testing the next morning some disappointments began to show up. It was obvious that there was difficulty in nulling noise and many signals were just not what they should be. particularly signals to the north were poor. It was then discovered that the reason for this is that the beach house had been built with metal studs in the walls and the wiring for lights on the balcony were running within a foot of where the loop was set up. Tilting the loop to get it away from the walls of the let it " see around the house" as it were and to get it away from the house wiring helped considerably. Signals via groundwave from medium wave stations to the north and east of us jumped 20-25 db or more and the noise was nullable. This would appear to be a consideration for anyone planning to use one of these loops made by any manufacturer.  Metal framing might be a bit of a problem, though other testing with the loop inside and near windows without metal screening outside showed fine results in the direction of the opening.  Turning the lights off on the balcony where the wiring ran so very close to the loop took care of  most of the noise problem. It would appear that the antenna will work very well inside if some care is taken with placement.  No antenna can perform miracles if not given a chance!!

After the antenna rearrangement, reception on the low frequencies was quite good.  The dial was full of low frequency non directional beacons,  with dozens heard very well beginning the next morning about 1600 GMT ( 9 a.m. local time) with many heard from all over Texas, Louisiana and a few from Mexico.  The noise floor after antenna rearranging and nulling was about S-2.  The carrier for the WWV station on 60 kHz was even heard.

Daytime reception on medium wave was quite good. A sampling of more " interesting" MW loggings that mid morning ( starting about 9:30 a.m. local):
KTSA  550  5 KW  San Antonio  S-7
KLVI   560   5 kw   Beaumont, Tx S-9 + 30 db
KLIF    570   5 kw   Dallas, Tx  S-5
KJMJ   580    5 kw  Alexandria, Louisiana  S-4
XEFD  590    5 kw  Reynosa, Mexico S-9
XEGH  620    1 kw  Reynosa, Mexico S-7
KSKY  660    20 kw  Dallas, Tx  S-6
KKYX  680   50 KW San Antonio, Tx  S-9 + 10 db
WQNO 690   10 kw  New Orleans, La S-5
KEEL   710    50 KW Shreveport, La  S-5 ( a loooong way for daytime groundwave!)
KSAH  720     10 kw  San Antonio, Tx  S-9
KTRH  740     50 kw  Houston, Tx  Full scale.

Rotating the loop seemed to indicate a pretty broad main lobe but a fairly deep and narrow null.

I ran through 31 meters about mid afternoon, at a time I thought would be before the night time enhancement of those frequencies with a later run through the same band near sunset. Here are a few samples with the sweep beginning at 2000 GMT, or 3 p.m. local time ( actually 2 p.m. local sun time given that we are on daylight savings time...something easy for me to forget!)  This was with the loop attached to a eight foot long piece of PVC pipe and extended out from the balcony to get it away from the metal in the walls and the wiring in the  ceiling.

V. of Greece           9420 S-5
Voice of Turkey    9460  S-7
R. Saudi                 9555  S-8
R. Marti                  9565 S-7 plus jamming...could null the jamming!
Voice of Turkey     9635 S-5
R. Guinea               9650  S-4
R. Saudi                  9675  S-7
R. Saudi                 9870  S-5
V. of Greece           9935   S-5
WRMI                    9955   S-9+10db

The noise floor was about S-2 with the loop extended about four feet away from the balcony.

Another run through 31 meters beginning at 0030 GMT or 7.p.m. local or a little over an hour before local sunset with the loop in the same position as above:

V. of Greece    9420   S-9+20 DB
WRMI             9395    S-9
WBCQ            9330    S-9+10 DB
Strong rtty sig 9317     S-9
WINB             9265     S-9+10 DB
Nauen, Ger.    9450      S-7
WRMI            9455      S-9
CRI Kashi      9470     S-6
Issoudon         9490    S-9+20 DB
R. Transmundial 9530   S-4  (Brazil)
R. Havana       9555     S-9
R. Boa Ven.    9550     S-5 Brazil
CRI/Rom.       9570      S-9+ 20DB
CRI/Cuba       9580      S-9+ 10 DB
CRI SP kasha  9590     S-4
R.Cancoa N.   9675      S-5 Brazil
RRI                 9730      S-9+ 10 DB
V. of Turkey   9830     S-9+ 10DB
VOIRI            9880      S-5  ( Iran)
V. of Greece   9935      S-9+10 DB
These are all on the R-75 with no extra preamp turned on.

Later at 0200 R. Sonder Grense on 3220 from Meyerton, S. Africa was in very solid at S-9 and listenable without objectionable noise.

I hope this is not getting too boring with too much listing, but I figure that this is the best way to show the performance of the antenna, particularly for those in the Central US and hopefully for those elsewhere looking at a map and sort of imagining tuning and listening get some idea what one could get out of this antenna.

Below is a quick run through of the "usual" Mexican  and Cuban MW stations heard nightly, previously on wire and vertical antennas beginning at 0250 GMT just getting into post dusk darkness:
XEX              730         Mexico City  S-9+20 DB
CMBC           890         Cuba              S-7
XEW             900         Mexico City   S-9+20 DB
XEQ              940         Mexico City   S-9+20 DB
XEOY          1000        Mexico City   S-9+10 DB
XEG             1050        Monterrey, Mex  S-9+20 db ( 150 kw)
XEEP            1060       Mexico City   S-9+ 20 DB
XERF           1570        Ciudad Acuna, Mx  S-9+30 db
R Encyc.         530       Cuba                S-9

All of these signals are more than comparable to how well they are received at home on both the vertical and the sloper, again with noise floor measured at 520 kHz of S-2.

The last " acid test" I gave the antenna was the look at the sunrise Pacific/Asian opening the next morning beginning at 1130 GMT or 6:30 a.m. local time, just as light is beginning to appear on the horizon. Noise floor measured at 2800 khz S-2
2850  KCBS North Korea  S-4  very readable
2500  WWV S-8  with WWVH audible in background
3320  Pyongyang BC S-4
3325  Bougainville and Indonesia mixed  S-5 "bouncing"
3480  Voice of the People S Korea S-5
3910  Voice of the People presumed S-5 and jamming
3925  R Nikkei S-5
3930  Voice of the People S-5
3945  R Nikkei S-5
3985  Echo of Hope  S-5 and jamming
4055  R Verdad S-7 QSB ( interesting notably with not as good a signal as at home!)
4212  WLO  CW/SITOR  s-9+10 DB
4735  R. Tarma Peru S-4.

There were some thunderstorms that developed in the area the next couple days and this led to disappointment in doing more low frequency work and I did not hear any of the European or African Long Wave Stations or MW stations.

Overall,  for its size, the antenna performed admirably well.  It was great to have an antenna to take on a trip that was not a huge chore to pack and set up. It might have been good to have some mast sections that could have allowed the antenna to be set up at a distance from the house and more in the clear.

I have noticed the same here at home.  While it works well indoors, at least much better than an indoor random wire, it does much better outside and in the clear.  Getting it up fifteen feet or so  really seems to help.  The next plan at home is to put it up on a telescoping mast up about thirty feet.

One observation is that other metal objects very near do seem to affect the ability of the loop to null noise. Dropping the wire sloper at home that had been running near it greatly reduced the noise that apparently was being coupled into it.  If one is using one of these type loops it would proibably be worth the effort to keep it at least a moderate distance away from other antennas,  particularly large wire antennas.  If those other antennas pick up noise where they run,  they could couple that right back into the loop or provide an additional place to be nulled, thus " nullifying" one of the advantages of the loop.

The loop does result in somewhat lower S-meter readings on some signals, but the lower noise floor more than makes up for that.

QSB does seem to be more pronounced than on the larger antennas but that is probably just a result of the smaller aperture and less of a "diversity" effect thereof.

During the test period, I noticed that the antenna did seem to perform better on the lower frequencies, but that might easily have been the result of band conditions,  so consider that a caveat.

I was hoping to hear some DX on 160 meters,  but during the week and during a non contest period there is not a huge amount of activity on that band, so that should not be misconstrued.

All in all,  this antenna has proved worth the expense and for those with limited space or even living in an apartment, I can highly recommend it as a way of getting some reasonable DX.  If you have a balcony, all the better...and if you can get it extended out beyond the balcony, even better yet.  As with any antenna,  giving it an even chance to work by putting it in the best possible location is a given.  If you are in a home with metal framing ( aluminum studs in the walls, etc) do your best to get it at least near a window without metal screening.

I am already planning a way to get the radio and antenna out totally away from wires and walls.  Running the R-75 and the loop both off a 12 volt battery is easily possible.

One note: Despite being in the " hot lobes" of directional antennas from three different 50 kw stations including one that  effectively "pinned" the S-meter on the R-75 ( OK, drove all the lights on...) there were no overload issues.  The Galveston station on 1540 khz runs 2500 watts but its directional had its main lobe right over our vacation location with only salt water between us and  it was not a problem.

There is always a risk in evaluating an antenna over a short period of time given how band conditions can vary.  That goes not only for this report or for any antenna you might try or put up. Poor bands can make the best antenna seem lousy on the first try and listening with extra care on a new one can sometimes give an impression in the other direction.  Always give one time,  and particularly with small antennas like loops,  try different locations and give them an even break to give you what you want.

Again, I hope the station listings were not too boring, but figured it was the best way to show what the thing did. As always, comments welcome.

WWCR                  9980  S-9

1 comment:

  1. One Friday evening I contacted Larry W6LVP and asked a question about the kind of coax that he would recommend for his Magnetic Loop antenna. I was surprised to get a response with technical information within an hour or so. With this kind of customer service I decided to go ahead and order one of his antennas later that evening. I actually received the antenna on Monday afternoon within a couple days.
    I have extreme electrical noise that was S-8 most of the time on my Carolina Windom and made my radio almost unusable. I temporarily installed the Magnetic Loop antenna on a short 5 FT pole in the backyard. With the XYL as the null monitor at the radio I called her on my cell phone and rotated the antenna by hand and was able to get a sharp noise null of about S-1. Very tight null when rotating just a few degrees one way or the other. Went in the house and couldn’t believe the clear signals that were hidden by the previous high noise level. It reminded me of SWLing 50 years ago as a kid back in the good old days before the electrical noise environment turned so bad!
    As I mentioned, the antenna arrived within a couple days and was of high quality construction and packed extremely well for shipment. I had read the previous reviews about Larry’s product quality and customer service and my experience was also very good!!
    I am planning to mount the antenna on a Channel Master rotator one of these days to get the full effect of the excellent directionally of this Magnetic Loop antenna. I even read where Broadcast Band Listeners use this antenna to pick up and select between multiple stations on the exact same AM frequencies.
    I highly recommend Larry W6LVP and his Magnetic Loop antenna to other Hams and SWL listeners. He responds personally to emails within a business day usually just an hour or two. What more could a customer ask for?