Multiple Antennas - Best Practice?

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Just put up the 40M beam, so now i have three antennas - 20/10M, 40M and 160/80M.  I have one amp.  What's the best practice to connect the antennas so I can work one band and monitor other bands on a 6700 with 2 SCUs?  How does this tie in with loggers that think slice A/B are "special"?  I'm looking at an Array Solutions SIXPAK as a matrix switch, but Array Solutions also recommends receive bandpass filters to protect the receiver front ends which is another bank of switching.  My 40M and 20/10M antennas share a tower and are close enough together that I expect there'll be some coupling.  Preferably a bandswitch is just a single mouse click and the logger follows to the active band.  Pointer to an app note, powerpoint or white paper would be great!
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Asher - K0AU

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Posted 4 years ago

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Jerry W4UK

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1. For receiving wide-band, use a wide-band rx antenna like the pixel loop on the rx antenna port.

2. For tx, next time you upgrade your amp, consider getting one with multiple antenna ports. My Yaesu Quadra has 4 ports and they automatically switch in line as the band changes (which, BTW, is also automatic with DDUTIL controlling it). When you "dedicate" a port to a particular band/antenna, it also makes it easy to add a stub cut for a troublesome harmonic of that band if running SO2R

If I change bands on the flex, within about one second the amp changes bands, the antenna port changes to whatever ant I used there last, and any Quadra ATU presets changes also to whatever I used there last (the Quadra has a 3:1 capable ATU built in).

3. Don't know about the loggers.

4. Flex engineers have published allowable rf inputs and have mentioned that the flex is pretty well protected from reasonable voltage levels from nearby antenna coupling. I don't remember the details, but you could look them up, then measure your actual RF voltage levels before deciding if you need additional protection.

Jerry

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ka7gzr

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I have two Pixel Loops (now Inlogisinc) phased 90 degrees from each other. I use the RXA and RXB inputs on the Flex 6700. I have my PTT output wired to the power supplies of the Pixels and it shorts the loops and removes power to them to prevent damage when transmitting. I also have the same setup on my Icom IC-7850. The pixels are a wonderful broad band antenna and are really a 'quiet" antenna.

Jim

ka7gzr  

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Asher - K0AU

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Did you consider feeding the Pixel Loops through a 2:1 broadband combiner?  Looks like coverage would be close to omni.  I don't have enough coaxes for separate runs to each and don't have enough space to rotate one.
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Ken - NM9P, Elmer

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With the 6700 he can use them for diversity reception, which would be more effective than simply combining them.
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ka7gzr

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Ken is correct that the ultimate goal is a diversity mode. Currently the Flex 6700 and the Icom IC-7850 only run the individual receivers to a single side of a headset. QSB signals will sometimes be louder in one side of the headset and then will switch resulting in a swirling phenomenon in your head. Kinda of like Led Zeppelin's "Whole Lotta Love" but that's another story.

Hopefully Flex will develop a more sophisticated diversity mode. I don't see Icom doing this. However , the recent update from Icom for the IC-7850 enabled tracking of the 2 receivers. This resulted in allowing the two receive only channels to track, but I do not expect much more than that from Icom.

Jim

ka7gzr  

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Andrew Russell

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Asher,

I have a 6500 with Pixel loop on RXA, 80m full wave loop on ANT1 and 160m inverted L on ANT2. So the three are available for RX and two for TX.

Andrew de VK5CV

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Lee, Elmer

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I use a Wellbrook ALA 100M loop http://sdr-w9oy.blogspot.com/search?q=loop
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Ken - NM9P, Elmer

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He Lee, nice recording of our rag-chew group on 3.820!  I have been thinking of a loop like this.  I am currently just using a homebrew tuned shielded magnetic loop using 20 ft. of RG-11 and a varactor diode remotely controlled by a variable voltage injector.  It seems to work well, but I need to turn my preamp on +20 dB on 80 & 160 meters to get acceptable signal strength. It tunes from about 1.540 Mhz to about 4.600 Mhz with the diodes I am using.   

Ken - NM9P
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Burt Fisher

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The thought occur to Lee to explain what antenna is up at exactly which time?
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Lee, Elmer

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the good s/n is the loop the bad s/n is the vert, or as in the video legend ANT1 is the vert XVTR is the loop
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EA4GLI - 8P9EH - Salvador

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Ken, you might want to look into this Active Amp http://active-antenna.eu/amplifier-kit/ for your RX loop. It has interesting features:

  • 4 remotely switched modes (Loop A, Loop B, crossed parallel loops A&B and dipole)
  • Each mode can be switched immediately
  • Good sensitivity and a flat frequency response
  • High dynamic range
  • Protected input from strong signals
  • High immunity to local noise with balanced amplifiers and balanced feed line
  • Balun transformer coupling for common mode noise reduction
  • Extensive documentation manuals with detailed description how to build your own small antennas
I also like the fact that you can run an ethernet cable (SFTP) and to feed power to the amp, and to receive the RF from the loop. So a single cheap cable runs everything and then you use a short run of cable from the controller to the radio.

I just received mine and I am trying to figure out the best approach with the 6700. Trying to understand the Loop A and B and how to better utilize them.
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Norm - W7CK

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I wonder how the performance would compare with the Pixel or Wellbrook.  I like the concept for sure!   Please let us know how it compares to your other antennas.

I live in a darn hoa and have only been able to put up 2 antennas.  A vertical and a ZS6BKW that is only about 20' off the ground.  The vertical does fairly well on TX but fairly noisy on RX, which is pretty typical.  The ZS6BKW does well as NVIS on both RX & TX.  I sometimes use the vert for TX and RX on the ZS6BKW. It would be nice to use a small loop for RX as long as it outperforms the ZS6BKW I already have up.

I'm done babbling......
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EA4GLI - 8P9EH - Salvador

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I will let you guys know. It is through this forum that I got the clue to start looking into Magnetic Loops. It is just both the Pixel and the Wellbrook are prohibitively expensive to get into Barbados given the size of the package and it is a tough one to get through a friend on the plane. But getting the amp here was easy (small package through regular mail less than $10 to get here), so now it is a matter of trying different loop designs with materials that are readily available here, such as aluminum tubing, flat aluminum or copper tubing.
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Lee, Elmer

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just 14g ant wire should be good enough.  No need for tubing for a RX antenna.  I have my loop long the perimeter of a crossed + pair of fiberglass arms  

73  W9OY
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EA4GLI - 8P9EH - Salvador

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I am reading this document http://active-antenna.eu/tech-docs/3_ActiveAA_Antena_11.pdf
Check this excerpt from the document:

There are two goals when designing a small wideband loop - low inductance and large area. The construction of the loop should be made with the following rule in mind: the ratio of loop area to loop inductance should be maximized. That automatically means that a circular shape with 1 turn is the best choice. The material could be copper or aluminum – actually the loop Q-factor is not important. The important factor is the low loop inductance. The conductor must be as fat as possible to reduce the loop inductance.


What is your take on the inductance aspect Lee?
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Lee, Elmer

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I think you guild the lilly.  "Best" is a very relative term.  In my experience if you increase the loop diameter you over come some of the form factor complaints, unless you are going for very sharp nulls in a discrete pattern like trying to null out a particular local noise source.   Of course the name of the game is experiment, but 20ft of fat copper pipe starts to get very heavy and expensive in terms of mounting and design compared to 2 oz of wire on 2lb of fiberglass.  Just offering my experience.  I think the main point is to have a single loop, and not a multi turn coil.  There are many more than 2 goals.  Size, weight, cost, and mechanical stability are also design constraints.

My present rectangular loop has a  circumference of 22ft on 8x8 crossarms and was very easy to build and was dirt cheap.  The wire stresses the cross arms and is structurally very solid in terms of weather and wind resistance but also very light, and for me this was as much a consideration as getting every last bit of performance from fat heavy costly circular pipes.  Performance is good from 630M to 10M using the Wellbrook amp, but the preferred performance of the system is 10mhz and below.  If you look at my blog (link above) you can see my build here is a youtube demo of the loop as built  improving S/N.  The demo predates the WBN blanker.  I'm very interested in what you come up with.

73  W9OY
(Edited)
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EA4GLI - 8P9EH - Salvador

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Hi Lee,

I am investigating the loops. It is not my text that I quoted there, I was sincerely curious on your opinion about the single 14 gauge cable vs what that document says about the higher inductance. I can see your point about the weight. That makes a lot of sense.

Thanks for your links.

73s
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Chuck - KJ6HT

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Does anyone have any experience with the Wellbrook Model ALA1530LNPro IMPERIUM ? The specs are very impressive and the testimonials indicate that it outperforms the Pixel (DX Eng.) Pro 1B.