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Receive Antennas (below 30MHz) - For all topics related to receive antennas used on HF, MW, LW, etc. For transmit antennas use the Amateur Radio Antennas forum.

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Old 12-02-2018, 8:11 PM
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Default Mini review: W6LVP active loop

Got one several days ago, where has this thing been all my life? So far there is nothing that my 130ft offset center fed 80-10m dipole can receive that the W6LVP loop cannot and the loop picks up lots of things below the AM BCB that the dipole cannot.

I have the loop on a rotor and have played with nulling AM stations, which it does better than 30dB, otherwise I mostly leave the loop pointed in an E-W direction and enjoy it. I'ts now my main HF/VLF antenna for an Icom R-8600 and a perfect complement to this high end receiver. The W6LVP loop is replacing a trapped sloping wire off the top of my tower, which was sharply tuned to a couple of amateur bands but would also pick up over 10W of energy when I light up my main HF antenna with 1,200W. Under the same conditions the loop just saturates the preamp and no dangerous levels reach the receiver and the maker of the antenna runs 1kW very close to his own loop with no damage to the loop preamp.

Prior to getting the W6LVP, I had made a 3ft dia passive shielded loop with a 4:1 balun interface that had a great null but otherwise was a bit numb on sensitivity. I tried a 15dB gain low noise HF preamp on the home made loop with some improvement, but was not thrilled with it. The W6LVP loop is a little down in level on most HF bands from my 130ft OCFD but the signal to noise seems a little better on the loop with its quieter noise floor.

I also have a high end AMRAD active 1m whip but at my location it picks up too much noise in the VLF range to be useful. In contrast the W6LVP loop is picking up lots of VLF beacons and WWVB just fine with a nice low noise floor and the loop is doing a much better job over the entire HF band compared to the AMRAD due to my noisy location.

Right after I ordered my loop the seller contacted me with some concern of a 50kW AM station near me that he researched on his own and suggested I might benefit from a notch filter for that frequency. I did some measurements on the AM station with my passive loop and OCFD and sent the results to W6LVP and he recommended the notch filter, which he installed for free. The antenna was on my roof about 10min after opening the package and I've been enjoying it ever since.

For anyone looking for an HF receive antenna of any kind I suggest you look at the W6LVP loop. Overall it works better than any passive wire SW antenna I have used like the PAR SW end fed, Alpha Delta SW sloper and full size 80-10m OCFD and it has the ability to null out noise or offending high power stations. So far I have not experience any overload of the antenna, so the preamp is plenty beefy for an urban location with lots of high power transmitters in all directions. I just can't say enough good things about this antenna and its about half the $$ of its nearest competitor.

I was so impressed with the antenna I bought the W6LVP experimental setup for travel, which is the loop preamp and power inserter and you supply your own wire for the loop. I found repeat customers get a hefty discount on the next purchase.

Last edited by prcguy; 12-02-2018 at 8:16 PM..
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Old 12-03-2018, 5:11 AM
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Thanks prcguy!

Is the notch filter applied before the lvp preamp (attaching loop to the filter first), or does it follow the preamp?

And, how much current does the amp draw in your setup? As a battery freak, every milliamp counts here.

Thanks again for the real-world review.
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Old 12-03-2018, 10:55 AM
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The filter is before the preamp. I'll have to measure the current and the loop came with a big 1.5A linear wall wart. Its good if it draws a lot of current, that means the preamp is a high level beefy thing.

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Originally Posted by hertzian View Post
Thanks prcguy!

Is the notch filter applied before the lvp preamp (attaching loop to the filter first), or does it follow the preamp?

And, how much current does the amp draw in your setup? As a battery freak, every milliamp counts here.

Thanks again for the real-world review.
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Old 12-03-2018, 12:09 PM
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You think it's on-par with the Wellbrook or is it better? Also, I tried my PAR HPF at the Wellbrook interface hoping it'd help HF noise floor but it wound up killing all signals across HF.
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Old 12-03-2018, 12:36 PM
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The W6LVP is the only active loop I've tested but the maker has compared to Wellbrook and Pixel and says they all work about the same, whatever that is worth. One thing W6LVP offers is custom notch filters before the preamp for your local blowtorch AM station and that can make it rise above the other brands if IMD is a problem. He can also add a 40 something MHz low pass if local FM stations are causing IMD. Ridgescan could probably benefit from both.

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You think it's on-par with the Wellbrook or is it better? Also, I tried my PAR HPF at the Wellbrook interface hoping it'd help HF noise floor but it wound up killing all signals across HF.
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Old 12-03-2018, 1:28 PM
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I've been using a Pixel loop for several years with my Perseus and ELAD SDRs. Much better for receive in terms of S/N ratio than my Cushcraft R8 vertical up at 35 feet for overall HF/MW/LW listening. Starts to approximate performance of vertical at about 16-18 Mhz.
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Old 12-03-2018, 4:08 PM
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Using a very crude meter I see about 90ma at 14v. That's a good sign for me as something in the 50ma or less range would indicate a very low IP1/IP3 amp that is easy to overload.

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Originally Posted by hertzian View Post
Thanks prcguy!

Is the notch filter applied before the lvp preamp (attaching loop to the filter first), or does it follow the preamp?

And, how much current does the amp draw in your setup? As a battery freak, every milliamp counts here.

Thanks again for the real-world review.
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Old 12-03-2018, 4:19 PM
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Thanks for measuring! Got some great feedback immediately from LVP:

The portable that runs off the AA pack draws about 80ma. The standard version uses 130ma. That works for me!

I might have to pull the trigger on the experimenter version once I stop buying other toys.

My loops hinge on the 1/10th wavelength in circumference rule of thumb - that is to maintain the classic directional pattern, you don't exceed 1/10th at the highest frequency of interest - otherwise you lose your nulls and point off into other directions which might be nowheresville.

OR, if you want to maximize signal, then try to approach 1/10th wavelength at the lowest frequency of interest in loop circumference.

That means no larger than about 6.5 feet circumference for 20 meters and below. Or to maximize levels for 40 meters, that would mean using a loop 13 feet in total circumference.

The ARRL uses a slightly smaller circumference than the standard definition for a small loop. I just use 934 / f mhz and divide that by 10 for general work.

Lots of fun. Might have to get more than one to accommodate the low bands and the high bands (if they ever come back. )
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Old 12-03-2018, 4:33 PM
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Not sure you need to go bigger than 3ft on the active loops, they have plenty of signal available on all bands. If you buy one let Larry know prcguy sent you.


Quote:
Originally Posted by hertzian View Post
Thanks for measuring! Got some great feedback immediately from LVP:

The portable that runs off the AA pack draws about 80ma. The standard version uses 130ma. That works for me!

I might have to pull the trigger on the experimenter version once I stop buying other toys.

My loops hinge on the 1/10th wavelength in circumference rule of thumb - that is to maintain the classic directional pattern, you don't exceed 1/10th at the highest frequency of interest - otherwise you lose your nulls and point off into other directions which might be nowheresville.

OR, if you want to maximize signal, then try to approach 1/10th wavelength at the lowest frequency of interest in loop circumference.

That means no larger than about 6.5 feet circumference for 20 meters and below. Or to maximize levels for 40 meters, that would mean using a loop 13 feet in total circumference.

The ARRL uses a slightly smaller circumference than the standard definition for a small loop. I just use 934 / f mhz and divide that by 10 for general work.

Lots of fun. Might have to get more than one to accommodate the low bands and the high bands (if they ever come back. )
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Old 12-03-2018, 7:55 PM
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Will do.

Sure enough, amplified loops where one is chasing s/n, and not trying to bang the s-meter, larger is not always better. His loop sizes seem very reasonable.

I'm thinking of the experimenter version, where I can play with all that - signal vs s/n, more omni vs sharp nulls etc etc.

I like the various choices available. Having a hard time choosing one.
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Old 12-03-2018, 8:13 PM
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Quote:
Originally Posted by prcguy View Post
The W6LVP is the only active loop I've tested but the maker has compared to Wellbrook and Pixel and says they all work about the same, whatever that is worth. One thing W6LVP offers is custom notch filters before the preamp for your local blowtorch AM station and that can make it rise above the other brands if IMD is a problem. He can also add a 40 something MHz low pass if local FM stations are causing IMD. Ridgescan could probably benefit from both.
Thanks
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Old 12-03-2018, 9:16 PM
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One of the things that I've heard pretty much second-hand is that while the LVP Loop doesn't have quite as much gain, it is quieter than the Wellbrook, Pixel or even the MFJ one. As was mentioned earlier, when you work with amplified loops like this, always think signal to noise ratio, not the overall signal strength.

Let's put this into context for those that might not know what this all means. Let's say you've got a signal on 3 Mhz that is fairly strong, but on a wire antenna, it's got noise issues - something that on HF is all to common an occurrence. It can get fatiguing to listen to this station, regardless of what tricks you can use - and there are some - to clean it up. Assume that with the noise included, we're talking about something around S5 or so. Now flip over to the loop - the signal may go down to a S3 level, but the noise is far less. That's a whole lot easier to listen to and there are ways to improve the intelligibility once the signal is cleaned up..

We are now considering the strength of the signal along with the noise on a wire antenna vs. the same signal (less noise) on a loop. The signal to noise ratio is, in its simplest terms, the amount of the signal received along with the noise as a measurement.

And we haven't mentioned the price and Larry's exemplary customer service, both of which are always considerations. The Pixel is almost 2x the price, so if you're on a budget, the LVP line is worth looking into.

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Old 12-04-2018, 6:49 PM
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Update: Today I received my W6LVP "Experimenters Kit" which consists of the same loop preamp used with the other models but with binding posts for attaching your own loop made of anything conductive and the power inserter.

I quickly cut some #14 wire and made a loop about 3ft dia and attached to the preamp and hung it on my wood fence about 4ft off the ground and 10ft directly below the overhead AC power feed to my house. I connected this to the RX ANT input on my Icom 7610 and did some quick comparisons of signals with my 130ft long 80-10m horizontal OCFD that sits about 20ft above my roof.

Listening to signals in the 40m amateur band, many signals were similar levels on the loop as with my big OCFD but the noise floor was an S unit or more lower, meaning the loop had more signal to noise than the OCFD. That's significant, especially when the OCFD is up in the clear away from everything and the loop is underneath my AC power line feeder. A lot of signals were lower to much lower on the loop than the OCFD but they could be coming from the null side of the loop, or they were mostly ground wave where height above ground would have a big effect. There were no signals I could hear on the OCFD that I could not hear on the loop.

Moving to the LW and MW range, most signals in the AM broadcast band were equal to or higher on the loop than the OCFD and with a slightly lower noise floor. I could not find any identifiable beacons in the LW band but signals I did hear were generally stronger on the loop with a much lower noise floor. Again, that's nuts considering the loop is right under my AC power wiring.

There were some SW stations starting to come in this early afternoon and the loop also did great in the 5, 6 and 7MHz range with great signal levels and a low noise floor. Some were weaker than the OCFD and some were about equivalent, but nearly all had a lower noise floor on the loop. There were no SW stations in in this quick test that the OCFD heard that the loop nearly on the ground could not hear about as well. I'll be testing more SW bands tonight with the low mounted loop.

All in all the W6LVP series of loops are making me really happy. I had not expected them to work this well and under what I consider compromised locations as I've seen so far. I'll be taking the W6LVP experimenters kit and my RSP2pro the next time I travel.
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Old 12-04-2018, 7:37 PM
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Must.....keep.......................wallet........ ..........................
shut................................arrrrrrrrrrrrr rrrrrrrrrrrrrrrrrrrrrrrrrgh.
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Old 12-04-2018, 11:41 PM
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Oh, and he's in CA so shipping will be very quick to you. Instant gratification! I would also use your R8600 with S meter in the dBm mode and send Larry the frequencies of any AM station over about -40dBm. Since you have that big tower nearby you might benefit from the 40MHz low pass filter. The single freq AM BCB notch filter is free, not sure about the low pass.

I can hear your 8600 begging for a new antenna friend to play with.

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Must.....keep.......................wallet........ ..........................
shut................................arrrrrrrrrrrrr rrrrrrrrrrrrrrrrrrrrrrrrrgh.

Last edited by prcguy; 12-04-2018 at 11:50 PM..
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Old 12-05-2018, 1:01 PM
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Quote:
Originally Posted by prcguy View Post
Oh, and he's in CA so shipping will be very quick to you. Instant gratification! I would also use your R8600 with S meter in the dBm mode and send Larry the frequencies of any AM station over about -40dBm. Since you have that big tower nearby you might benefit from the 40MHz low pass filter. The single freq AM BCB notch filter is free, not sure about the low pass.

I can hear your 8600 begging for a new antenna friend to play with.
Perhaps next year. Christmas presents, interval maintenance on both vehicles,
and the purchase of my R8600 all mean I blew my radio cookie for a while

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Old 12-06-2018, 12:18 PM
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Default W6LVP Loop

I ordered a W6LVP Loop yesterday and I did mention Prcguy to Larry when I ordered. I ordered the standard kit and hope to get it by the weekend. I have researched everything I could about beverages and asked a zillion questions on how I could set up a receiving antenna in my small yard and I think this is the best I option out there for my situation.
Will let everyone know how things turn out when I get it.

Mike
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Old 12-06-2018, 3:26 PM
   
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I have a question (sorry, I'm a bit new at this): does this antenna have any gain at all, and if so how much? If it has gain, which side would I have to point/aim if I know the general direction of the frequencies I'd like to catch? Thanks so much for reading!
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Old 12-07-2018, 12:46 PM
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Default W6LVP Loop

The loop does not have gain so to speak, but in saying that the benefit is that it does have directionality. Also another benefit of a loop system is that the noise levels are much less than other types of antennas along with the ability to null out even more noise as you turn the antenna to find the quietest position.

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Old 12-07-2018, 12:57 PM
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The preamp in the W6LVP loop has gain but its also there for impedance matching. The difference in receive levels from a passive loop to the W6LVP is a lot and signals at my location from the loop can be on par with a large 130ft dipole or better at some frequencies.

The loop is somewhat directional off its ends but not as severe as I expected. The sharp null is looking through the loop like looking through the hole in a doughnut. The cool thing about this antenna is you can be in an area with very limited space and receive signals that are usually reserved for big antennas that take up a lot of property. The loop can also work well indoors where other types of antennas would be much more susceptible to noise generated in the home.

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I have a question (sorry, I'm a bit new at this): does this antenna have any gain at all, and if so how much? If it has gain, which side would I have to point/aim if I know the general direction of the frequencies I'd like to catch? Thanks so much for reading!
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