Since they were on sale before New Year’s at HRO @$450, I thought I might give it a try to see how it might work with my SteppIR MonstIR
I must admit to being quite skeptical about small antennas particularly when mounted in the vertical plane when HF is usually horizontally polarized. Further it’s a magnetic loop so it receives at 90 degrees to the Electrical Field. The receive lobes are end to end on the loop rather than broadside as you would expect from an electric field antenna. The loop only weights 3 lbs and is 1meter in Diameter. The loop has a preamp at its base and uses RG-6Quad to carry both power to the Preamp and signal back to the radio.
I finally had some time today (@Burt I am far to busy experimenting to rag chew) so I built a 5’ antenna base
in the backyard out of 1 1⁄2” PVC, installed a small TV rotor and the mounted the
loop onto a 5’ piece of 1 1⁄4” EMT galvanized pipe as a temporary test
stand. The loop was 10’ from the ground albeit the backyard hill rises
50’ vertical right near where the stand was installed.
First Impression.. it actually hears things.
More important it actually hears very different signals than the MonstIR. Noise spikes that was quite dominant on the MonstIR were absent on the Pixel Loop. Noise spikes that were heard on the Pixel Loop were not present on the MonstIR. They are clearly hearing very different things.
Surprise, surprise.. a few signals were actually much louder (10-20 dBm) on the Pixel Loop @10’ than on the 4 Element MonstIR @85’ even when both were oriented for maximum signal.
Diversity was quite interesting.
1. In some cases, it made no difference.
2. In some cases it made things much worse as one or the other antenna was not hearing the signal.
3. However in many cases, the diversity reception was significantly more intelligible than the non-diversity by either antenna.
The 2 SCU's on the 6700 made it very easy to test different configurations for diversity.
I have not spent any time making detailed measurements yet... but I could see in dBm on DDUTIL (I really wish the S Meter in SSDR read out in dBm) that there were significant differences in relative received signals for each of the 3 different cases.
I must admit to being rather surprised that the Pixel loop actually worked and especially since it was only at 10’.
A few months ago we removed the top 30’ of a tree on the backyard hillside. But we left the bottom 20’ of the tree trunk..
So I now have a perfect natural antenna tower which should not need a building permit for the pixel loop and which once installed on the tree, the loop should clear the hillside.
I will report back once it’s at planned height with proper measurements
(I really wish the S Meter in SSDR read out in dBm)
I know you know that I known you know this... If you hover the cursor over the s-Meter it will display signal in dBm.
By the way, the 6700 (and perhaps the other 6000 units) will read out in dBm. It's easy to do, just click the signal strength bar with your mouse and then leave your mouse over the readout bar. The signal in dBm will pop up over the bar and will update, if you leave your cursor on the spot.
Brief instructions for DIV SPLIT. To use this feature there is a simple rule:
- Define splits on the slice pairs, main and split, starting with A: split one on A/B, split two on C/D, etc.
- After defining split slices, enable DIV on the main slice, where desired: slice A, C, etc.
- Enable Split by right-clicking the Slice frequency box.
- "Mute all but active" is enabled by default.
- An additional option, "Split follows TX slice" is available on the Radio tab.
- DIV is only supported on the main slices, not the splits.
- Note that "Mute All But Active" understands DIV splits.
- Note that "Split Follows TX Slice" also understands DIV splits.
I have also been using the Pixel Loop for about 6 months now. I have nothing but praise for this little wonder. It definitely needs the preamp, but since using it my home grown QRN is no longer any problem -- even the A/C varispeed motor on the roof, while it still shows up, is no longer the +24 dB killer that it is with my Tx 40m doublet nearby on the roof.
While these things are mildly directional, I didn't bother putting mine on a rotator. It is mounted about 5 ft off the ground in my back yard, about 50 ft from the house, and aimed toward Europe. The lobes are broad enough that I easily pick up South America and Alaska, along with Europe and Japan and Australia / NZ along the main direction. QTH here is Tucson, AZ, in the extreme SW of the USA.
As for diversity vs dual receive (one Rx in each ear), I hardly notice any difference between the dual Rx and true diversity, except sometimes when working CW. I did a test comparing the two approaches the other day, with one antenna being the Pixel Loop and the other antenna being my 40m doublet about 50 ft apart. I tuned to 5 MHz WWV and switched between true diversity (phase locked receivers) and two different receivers, both frequency calibrated to a Rb standard at 29.9 MHz. You really could not distinguish true diversity from dual Rx. Both had the audio image shifting left and right. Phase coherent reception would really seem to be necessary only when trying to accomplish interferometry. Phase coherence should not be confused with frequency coherence - it seems to be more stringent than required for most on the air use.
73 de Dave, N7AIG
I gather that noise immunity is a big factor with the Pixel Loop. However I'm in a rather low noise location. Do you think in this situation a Pixel Loop will outperform the 43' vertical, or should I just stay with what I have?
73 ED W2RF
After all the reviews I've read I finally ordered a Pro-1B for myself. Had a great conversation with Doug at Inlogisinc regarding powering the preamp. I am full time in my motor home and have been working to get rid of as many wall-wart power supplies. I asked Doug about powering the preamp with 13.8 volts DC. As we chatted, Doug recommended just putting the DC input right to the Pre-Amp and let it pass through the bridge rectifier and all the filtering. I have a very short run of cable so he felt the battery voltage would be plenty. The original PS is set to provide 20 Vdc to the Pre-Amp to compensate for any voltage drop over long cable runs.
Great solution and I have been able to meet my goal of using battery power at the radio compartment including a 12Vdc Netgear 1 Gb LAN switch. My radio is under the seat of my dinette, right by where we like to charge our cell phones and such. I found a very nice 12Vdc to 5Vdc USB power hub that is totally clean to do our phone and tablet charging.
All my LAN stuff and personal device use along with the Flex 6500. Solar panel charging puts me off grid completely.
Looking forward to installing the Pixel.......
I am interested in the loop's performance primarily on 40-160 meters. You have mentioned some actual signal gain over the StepIR, but how about signal to noise ratio? I have built a simple shielded loop for 160 meters...no preamp, and no matching transformer yet... And I still see S/N improvements of 3-6 dB over my offset fed dipole at 38 ft. The base of my loop is about Six feet off the ground with an "arm-strong" rotator. I plan to add remote varavtor tuning and a 50:5 turn matching transformer before the 160 contest and hope it improves things.
I have considered the Pixel, but for my budget $500 isn't exaclt "inexpensive." Would the improvement over my loop be worth it?
Funny how price pain thresholds are relative to individual circumstances.
Frankly I did no comparative product research whatsoever. I just saw Stu K6TU post about how well his pixel loop worked for him, they had one in stock at Ham Radio Outlet, it was $50 off and most important less than the price of a pair of shoes for the XYL so I did not need to ask for a hall pass.
Had the grandkids yesterday so no time to test. Yuma Hamfest tomorrow but I will try it on low bands when I get back from Yuma.
I have never seen a completely satisfactory explanation for the virtues of the magnetic loop antenna, but the best I can come up with is to note that most home grown QRN is from harmonics of fast edge switching, and is near field structure, not far field. So the locally generated electromagnetic field exhibits a mix of EM wave and static field behavior.
We know that static E fields die away as 1/R while static B fields are dipole in nature and fall away as 1/R^2. Couple that with the very small dimensions of the loop compared to the wavelength of the receiving frequency, and you see that the E-field, while stronger than the B field, cannot couple very well to the small antenna. And the local B field is very much smaller than the local E field.
Meanwhile the B field of distant radio waves (far field) is changing very rapidly and the area of the loop is much larger than its linear dimension, so the rapidly changing magnetic flux contained is very much larger than the E field difference between top and bottom of the loop. We know that a loop of wire containing a changing magnetic field generates a voltage where the loop is broken, proportional to the rate of change of the B field and the area of the loop. At MHz frequencies this changing B field has a very large rate of change, despite the field strength being 1/c of the E field strength in the wave.
The end result is that these magnetic loops show much greater immunity to local EM field disturbances and respond quite well to MHz B field changes of the incident radio waves. But the small size, and the relative weakness of the B field compared to the E field of a radio wave (1/c), makes a 30-40 dB preamp a necessity to get comparable voltage levels at the antenna connector.
The above explanation should be further specified as for a loop mounted vertically. It's linear counterpart would be a small vertical antenna, also often used as Rx antennas. Both are polarization sensitive for vertical polarization.
I have no idea whether home grown QRN is preferentially polarized, but if it is, or in any event, some of it is vertically polarized, I'd expect the magnetic sensitivity of the loop and the weakness of near B fields to give the loop a better local noise immunity than a small vertical Rx antenna. But this is just a conjecture on my part. I have never directly compared the two options.
If most local noise is horizontally polarized then perhaps a small vertical would perform just as well. Anyone have experience with both kinds of Rx antennas?
Gives me shivers to remember that experience. The only one that aced that course, from a thickly Chinese accented English of Dr. Chang, was Marco Jarich, from Yugoslavia -- he was thumbing madly through a little grey English-Yugoslav dictionary trying to follow along, while Dr. Change filled 3 blackboards with equations. Every one of us always failed the first 1 hour midterm exams, except Marco, who became the class grader. All the rest of us always had to take a 4 hour make up midterm in Dr. Chang's office. .... as I said, it brings back shivers.
I had to live in the library and translate from the French the Theorie Electrostatique from E. Durand, to make it through the first semester.
I sure wish I had a much better grasp of E&M than I do...
73 de Dave, N7AIG
By contrast the 5000 had much more sophisticated diversity with the ability to steer the phase and gains of the two signals. So it would appear that Flex understands some of the possibilities.
I suspect that more sophisticated diversity will likely be a V2.+ feature
If far enough away from metal sources (and high enough off the ground?), the antenna may be mounted horizontally with the nulls facing straight up and down. Has anyone tried this orientation and compared it to their experience mounting the loop vertically?
One day I will get an opportunity to redeploy the Pixel Loop, and I could benefit from your experiences.
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