Hey OPCOM...............

[RolandSWL]

A while back you started a thread about the Pixel Technologies, RF PRO-1B magnetic loop antenna.

http://amfone.net/Amforum/index.php?topic=32860.0

I have been trying in vain to find some information on the optimum mounting height for such an antenna.

Any insight?

Thanks, RSWL....................

[flintstone mop]

The height of the loop is not critical. I had mine at 10 feet off the ground and now it is 35 feet high on a small tower.
Fred
I have that model.....and WOW the price jumped up a full $100.00 

[W6MQI]

Far as I know height is critical for magnetic loops I would say no higher than one loop diameter above ground.

73,Dave

[W7TFO]

With the way the company shows it assembled, it would be well neigh impossible to mount it within a loop diameter of ground level.  Accounting for provided mast, preamp, and rotor.

They do show it on a pole (pipe mast) in photos, but say it will work at "ground level".

73DG

[RolandSWL]

I'm finding all kinds of "opinions" on line concerning mounting height (ground level to 30feet up) but nothing I can take a ruler to. With the proviso to keep it away from metal objects.

Does mounting height effect the pattern as with a dipole or beam?

RSWL...............

[flintstone mop]

Dave 6MQI, may be a little more tuned in to magnetic loops than me.
I'm building a helical magnetic loop antenna and the designer says that one loop length from the ground is all that is necessary. So, my 6 foot loop need to be elevated 6 feet from the ground.
I do not think the magnetic loop antenna is depending on the ground for reflections or operation.
I had that Pixel receive antenna mounted 10 feet from the ground and there was no change in performance on receiving DX whether 10 feet or 35 feet. Pick your height and mount it. I used good quality RG6 75 ohm cable. A rotor helps a lot!!! You can get some great nulls with a magnetic loop antenna. Null out interference or noise or adjacent stations. Not always a guarantee cuz it depends on the angle they are coming into your RX antenna
Fred

[Steve - K4HX]

Mount it at the height and location where local noise is minimum. Anything else is not worth worrying about.

[RolandSWL]

Thanks for the info. One last question, where can I get a fibreglass mast to mount the loop?

RSWL...................

[W3NE]

My PRO-1B is about 30 ft. above the ground. I live on the third floor of an apartment building where there is a high noise level, and wanted to get the loop away from the noise sources and as clear as possible from the roof. I used the recommended quad-shielded RG-6 cable because of the noise environment here. The loop is rotatable - almost essential.
 
I get 2 to 3 S-Units improvement in SNR on 75 & 40 compared to the best alternative antenna I can erect here. My loop has some value for nulling undesired signals, but it is not great; I use rotation primarily for peaking signals even though it has a broad pattern.

If you have room for a decent "standard" HF antenna and are not affected by local noise, I think that would be preferable to incurring the expense of the PRO-!B and a rotator.

See eHam Reviews for numerous user reports on the -1B.

Bob - NE

[W3NE]

I forgot to mention: DX Engineering has a wide variety of fiberglass tube.
Bob - NE

[W6MQI]

I'm finding all kinds of "opinions" on line concerning mounting height (ground level to 30feet up) but nothing I can take a ruler to. With the proviso to keep it away from metal objects.

Does mounting height effect the pattern as with a dipole or beam?

RSWL...............

 One can mount the loop higher than one loop diameter but, you won't get any kind of extra gain from doing this. Are you using the loop to transmit or receive only? If transmitting watch out for high voltages a 100 watt rig can generate upwards of 10,000 volts at the tuning cap. Also your loop will work best at the highest usable design frequency then drop off as frequency is decreased.

73,Dave

[flintstone mop]

My PRO-1B is about 30 ft. above the ground. I live on the third floor of an apartment building where there is a high noise level, and wanted to get the loop away from the noise sources and as clear as possible from the roof. I used the recommended quad-shielded RG-6 cable because of the noise environment here. The loop is rotatable - almost essential.
 
I get 2 to 3 S-Units improvement in SNR on 75 & 40 compared to the best alternative antenna I can erect here. My loop has some value for nulling undesired signals, but it is not great; I use rotation primarily for peaking signals even though it has a broad pattern.

If you have room for a decent "standard" HF antenna and are not affected by local noise, I think that would be preferable to incurring the expense of the PRO-!B and a rotator.

See eHam Reviews for numerous user reports on the -1B.

Bob - NE

My .01 cents worth.
A magnetic loop antenna or a long beverage antenna is nice to have in a  Ham's arsenal of listening antennas. If a sudden problem pops up, like a bad electrical insulator on a cold night and the power company is going to be slow to fix, the extra RX antennas will help and a magnetic loop antenna will reduce the "electrical noise" that rides along with an ELECTRO Magnetic Wave we call RF.
Fred

[RolandSWL]

I moved from an electrically noisy town to a REALLY electrically noisy town about 7 years ago. I put up three new antennas recently(at no small expense) two slopers and one random with a 9 to 1 matching device. The slopers are terrific noise grabbers while the random is quieter with a slightly lower sensitivity. I'd all but given up on listening due to the electrical noise.
I'm hoping the magnetic loop is a solution.

RSWL.............

[Opcom]

The loop is about 3 FT above the roof of the shack. It proper is mounted to a 24" piece of thick gray PVC pipe of the largest size accommodated. It's not perfectly rigid but being short it works fine. 5 FT flopped around, beware. That sits on the rotor, and the rotor is on a TV pole mounted to the side of the metal building.

The performance is good for nulling out noise and other slop, more than peaking up a signal. If the other party will blab for a while, it is possible to find the setting that gets rid of the most noise while letting them through nicely. The direction will be different for different bands and even specifically noisy frequencies. The additionally bought radio shack TV rotor has good positional accuracy but the 'readout' is a not-so-pointy pointer. I am considering a small dot of paint on the knob, and then at each good place, a small dot of paint on the scale. If I were OCD I would label each one and print out a spreadsheet for call sign, city, time of day, and frequency. The loop only has to go through 180 degrees, not 360.

I planned to raise the height by 10 FT more, but when I transmit at the limit, the loop, despite being far away from the wire dipole, picks up a fantastic amount of my RF.
With the loop turned off, it still does pick up a lot as though the RF is powering the thing, which might be true to some extent if it uses rail to rail protection and a clamp, I have not asked the maker.
The warning about it being left on during TX, and due to its high gain and high tolerance for overload, making enough RF to blow up a sensitive receiver input should be heeded. There is a connector that can be used to turn it off for TX. That can hook to the TR switch bus of the shack.

I am very satisfied with the performance and have also done some AM BC band DX at night. It could be put up by one person but was easy with two.

[W6MQI]

I moved from an electrically noisy town to a REALLY electrically noisy town about 7 years ago. I put up three new antennas recently(at no small expense) two slopers and one random with a 9 to 1 matching device. The slopers are terrific noise grabbers while the random is quieter with a slightly lower sensitivity. I'd all but given up on listening due to the electrical noise.
I'm hoping the magnetic loop is a solution.

RSWL.............

RSWL
 That sucks about the noise I feel for you I too suffer from noise like plasma TV’s, computers etc. I’ve done the loop thing and they do work but, I found my present system to work a little better plus its real fast to switch directions. My system which I use mainly for 160-80 meters incorporates three 23’ tall verticals spaced 1/8 wave at 160 meters in a triangle shape. Each antenna has its own pre-amp with equal lengths of coax running back to a switch box. The switch box has relays which steer the three verticals in six different directions by inserting a delay line to create a null. Various length delay lines will change null height and width there is also a 180 deg phase inverter so all phasing tracks right for 80 meter use. You can read about these types of antennas in low band dxing by ON4UN a great book but, not for antenna beginners. I hope the loop does the trick for your needs living in the urban environment with all its noise pollution just plain SUCKS!

73,Dave

[W8VG]

I love my loop.  There are times in the evening on 75 meters where I can't operate AM without it--have one particular noise source that's really offensive.  Sounds like a nearby appliance with a really noisy switcher or something.  The loop is quieter overall but is particularly useful if you need to null out a particular source that is bad--the 30db null really works well there--with careful movement of the rotor--it just disappears in the noise. 

Just mounted it out in yard on top of small tripod with some conduit and cheapie TV rotor (from home depot) and run the cable across the patio over to shack window.  When it's time to mow, I can just move it over on to the patio--closer to house.  Height doesn't seem to be critical for receiving solid 75/40 signals and I can null out the neighbors hash to point where I can't tell it's in there anymore. 

When I first connected it up to my R-390, though it wasn't working until I put it on 7293 and heard the AZ gang jump right out of the noise.  When I shut off the power supply feeding the preamp at the loop--they all went away. 

Only real constraint for me was keeping it about 20' away from any significant wires or metal conductors.  My XYL took the attached photo shortly after I erected it--has been out there for about a year without problems.  Was going to move it farther out in yard--beyond the trees--but it works well where it is and the trees hide it from neighbors. 

Best 73's
Geo W8VG

[RolandSWL]

Thanks for the input all. I have a birthday coming up in October and my beautiful bride has been looking over my shoulder for a gift idea. I may get careless and leave the Pixel Tech site open, accidentally.

RSWL......................

[W3NE]

A photo of my antennas on the third floor balcony of a life care complex is attached. They include a PRO-1B and rotor, an Arrow 2m/70cm J to the left of the loop mast, and a HamStick dipole on a strut to the right. Talk about compromise! I wanted to run a 170 ft. wire from my balcony to a tree but management refused permission.

The PRO-1B improves reception as described in a previous post but it is still too close to horrendous noise sources in other apartments to obtain a really good null, although its immunity to electromagnetic components has made a big improvement over other antennas I've tried. Plans are for the HamSticks to be replaced with an improved loaded dipole, and if that works, maybe a big investment in a screwdriver dipole to facilitate QSY.

Bob - NE

[W7TFO]

A good cheap source of stout fiberglass sections is surplus military camo net supports.

Some were aluminum, but the others are all over hamfests out here.

There are enough in a kit bag to go up some 30 feet, usually for less than $75.

73DG

[wa3dsp]

The military fiberglass poles are meant to be heavily guyed. They have no lateral strength at the joints and will break apart easily. On the other hand if you can get them the military aluminum 5 foot sections are really nice. PVC conduit in larger sizes 10 foot lengths would be fairly stable but not great. You could possibly find two sizes that would fit inside one another and make it stronger or you could fill it with concrete! I don't think there is any requirement that the supporting pole be non conducting.

[W7TFO]

Indeed, it would be too tall without guys at any real height.  Especially with camo net poles (not to be confused with AN/GRA-6 poles) that have have less insertion length than real antenna poles.

I meant you could get a whole bunch of stuff for mounting a loop, using one or two sections for cheap.  It would be plenty to hold up that lightweight loop, stiffer than PVC conduit.

73DG

[wa5ddz]

 I picked up five nice fiberglass poles from the local university track and
 field. The pole vaulters often have old, damaged ones or need the latest thing. Same with the high school. Some as long as 14 feet. They are light weight and very strong. And some don't bend so easy. Different diameters,
thickness, with and without taper.  Good post for bird feeders.

[Opcom]

The "2.5 FT" (plus the insertable section) military aluminum sections of one kind come with a base insulator and the 40FT full height of the thing takes three sets of 4-rope guys. I have no doubt it is rugged but do not know how long the guys will last in the elements. I have put them up many times.
It's a soldier A and soldier B job.. One to lift the free end overhead to get it started, the other to pull the ropes until it is erected upright.


There's a nice topic about AB-86 and AB-56 aluminum type masts here.
http://amfone.net/Amforum/index.php?topic=16442.0
The attachment is the TM with all the part numbers, handy if you collect one piece by piece or need a certain item.