700 MHZ DIY Double Biquad/Moxon Antennas

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Hi all, just wanted to share my DIY double biquad and Moxon antennas that I've been experimenting with. Would love to hear any comments or suggestions if you have any.

This started because I had some free time over the holidays and remembered someone on here experimenting with DIY antennas. I searched for a while and never couldn't find the specific post/type of antenna, but that's when I ran across several sites mentioning biquad/double biquad antennas so I figured I would try one of those. I used the websites below to design and build my first antenna, the double biquad.

https://martybugs.net/wireless/biquad/double.cgi
https://buildyourownantenna.blogspot.co ... lator.html

Using CellMapper, I knew I was mainly getting B12 and B25. B12 seemed to be the most consistent so I stuck with that and plugged 700MHz into the double biquad calculator. Turns out, that low of a frequency requires a fairly large antenna (at least for the calculator's optimization). I plowed ahead anyways and built the 24" wide element with 6AWG bare copper wire. I just used whatever scrap metal I had laying around for the reflector and attached an N-type connecter to it.

After I built the double biquad, I finally ran across the post on here talking about another DIY antenna, [url=http://www.wirelessjoint.com/viewtopic.php?t=1732]DogTho's post on the Moxon antenna[/url]. I plugged 700MHz into the Moxon calculator (link below) which resulted in a much smaller antenna so I built one of those too. You can enter the wire diameter into that calculator so I used a much smaller 14AWG wire. So much easier to build...

http://tippete.net/cgi-bin/moxgen.pl

Below are some pictures of the antenna setup. Sorry for the low quality.. I can post some better pictures later if there's interest. The first image is the "jig" that I built to bend the wire. The next picture is of both antennas hanging in the attic. The Moxon is stuck on a piece of carboard for now ha.





Next are the AT!GSTATUS? results from my modem. I did a baseline comparison with generic 4dBi flat omni antennas, shown in the first image. I was getting occasional service using those. Second image shows the results from the double biquad/Moxon combo. I've been using it for about a week now and have been getting very reliable service.





I made another double biquad antenna yesterday to see if I could improve my connection with two of them. I used the same element design but used an old fluorescent light shroud for the reflector ha. However, I got worse service whenever both were connected. Any thoughts? I'm guessing that I don't have enough power to drive both of those massive elements? I'm currently using an externally powered modem enclosure with a EM7455. If power is the issue, it's possible that using a single biquad for the aux antenna may work.

Last notes, the biquad design website recommended hanging the antennas vertically. Right now, I have mine hanging at ~45 deg. I plan on playing around with the orientation some more to optimize it. I had also planned on placing these outside once I got them working, but I probably won't do that now since I'm getting good service as-is. Plenty of room in the attic and would like to avoid weather/lightning issues.

Thanks for looking! Pretty new here.. got a ton of help when setting up my modem/router. Hope someone can get some use out of this in return!

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Played around with it a little last night and realized that I was getting a much worse signal on B25 but my download speeds were still a lot better. So next step, I'm going to build a B25 double biquad centered on 1900MHz to see how well it works. May even try a triple biquad... should be much easier since it'll use 14AWG wire instead of the 6AWG for B12. And 9" wide instead of 24"...

[Didneywhorl]

How is the element attached to the light shroud? You may be getting noise from the metal shroud reflecting at odd angles? The first one has a 20dbi increase, that's fantastic! Single band antennas do tend to have high gain.

You may also be getting crosstalk, try rotating them 90 degrees from each other. The rotation pattern depends on how the signal radiates from the antenna. You basically want them at different polarizations so that the signal waves cannot get received from and by each other.

The antenna size doesn't really take more or less power based on its size. Your modem should be fine on anything you can build.

[chunk]

How is the element attached to the light shroud? You may be getting noise from the metal shroud reflecting at odd angles? The first one has a 20dbi increase, that's fantastic! Single band antennas do tend to have high gain.

You may also be getting crosstalk, try rotating them 90 degrees from each other. The rotation pattern depends on how the signal radiates from the antenna. You basically want them at different polarizations so that the signal waves cannot get received from and by each other.

The antenna size doesn't really take more or less power based on its size. Your modem should be fine on anything you can build.

Thanks for the tips! I had no idea if a larger antenna drew more power so I'm glad to know that. There's definitely something wrong with the second antenna. I hooked it up with the Moxon like my other setup, and it had really bad signal.
It probably has something to do with the connection to the shroud like you mentioned. My first antenna shroud is bare metal so no issues getting a connection there. The second one has a coating which I must not have done a good job of removing at the connection. I've shelved it for now.. waiting for some N type connectors to come in the mail so I can make some B25 antennas. Planning on trying a double and maybe triple biquad since its going to be a good bit smaller than the B12 antenna.

[terryjett]

Played around with it a little last night and realized that I was getting a much worse signal on B25 but my download speeds were still a lot better. So next step, I'm going to build a B25 double biquad centered on 1900MHz to see how well it works. May even try a triple biquad... should be much easier since it'll use 14AWG wire instead of the 6AWG for B12. And 9" wide instead of 24"...

Never stop learning! Try and try again

I have had epic failures through the years and some very successful builds. Back about 18 years ago had a wifi company buy a design I made (was in a HAM magazine). Not talking big money, but sure felt good...

The biquads are excellent antennas. Friend of mind took my last two ( https://wirelessjoint.com/viewtopic.php?f=24&t=765 )out into the woods of E. Texas and hits a tower about 12 miles away in piney woods. He tried some other antennas and never got about 12 mbps, but with biquads he get 25-30 all the time.

Main thing is get your bends tight as possible, always use the correct diameter wire and keep your spacing correct between radiating elements and reflector.

[terryjett]

Finally got to a desktop and looking at your design a little closer. If I may offer some tips...

Pay close attention to the original design @ https://martybugs.net/wireless/biquad/ . It is very important to get the radiator and reflector connected to coax / coaxial connector. Looking closer at your design, thing you could improve performance. Yours are like:

K631bkV[1].jpg

ullMPUE[1].jpg

The center conductor of cable or connector should be soldered to one side of radiator and other side of radiator is to reflector:

tOTNFpo[1].png

It is very important to maintain the correct distance between:

Fds5nHT[1].png

Using a connector to mount the radiator to reflector and help you in big ways. I use whatever is in my stock or junk box. N-Type panel mount is a great choice. They will help you maintain spacing and impedance. For example: https://amzn.to/35zJD65

I use SMA panel mount mostly because have coffee cans full of them:)

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Never stop learning! Try and try again

I have had epic failures through the years and some very successful builds. Back about 18 years ago had a wifi company buy a design I made (was in a HAM magazine). Not talking big money, but sure felt good...

The biquads are excellent antennas. Friend of mind took my last two ( https://wirelessjoint.com/viewtopic.php?f=24&t=765 )out into the woods of E. Texas and hits a tower about 12 miles away in piney woods. He tried some other antennas and never got about 12 mbps, but with biquads he get 25-30 all the time.

Main thing is get your bends tight as possible, always use the correct diameter wire and keep your spacing correct between radiating elements and reflector.

Appreciate the tips! I was afraid someone was going to zoom in on those connections haha. I'm using the exact N-type connectors that you had linked. I fought for a while trying to solder the 6 AWG wire and realized that it wasn't going to happen. It's just too big of a heat sink... of course, I could be doing that wrong too. That's why I used the screw-on lugs on the second antenna with smaller wire going to the N connector.

And that's all why I'm trying out B25 on the next attempt.. it'll be centered on 1900MHz like the one you built in your link. The 14AWG wire will be much easier to work with and solder. I'm going to be a little more meticulous with the next one and am planning on routing out a template from a piece of wood to help get better, more accurate bends in the wire. Just waiting on some parts to get here before I can get started!

Did you have any guidance on how far apart to space the antennas? Was the vertical orientation the best for your signal? I know that Marty's site mentions vertical is best, but mine get better signal at 45 degrees. I've got it mounted indoors and my build isn't exactly optimal either, though.

[terryjett]

Don't worry about closeups, we all been there:)

Soldering irons are fine for the smaller connections, but to work with large diameter wire and sheet metal a soldering torch is best: https://amzn.to/2LIoa3N You got to be careful and not melt the dielectric material in wire / connectors though.

Try to "tin" everything before putting altogether. Meaning use some fine sandpaper to ruff things up and place a small amount of solder on things. This will help as it does not take as much heat at final assembly.

Use a Dremel and get the paint off everything before soldering. You can get solder to stick to most sheet metal but it must be ruffed up and clean. Takes some experimenting. Get some scraps and practice.

"Did you have any guidance on how far apart to space the antennas? Was the vertical orientation the best for your signal?"

LTE signals arrive at your antenna in an "X" pattern. That is the reason for recommended 45 deg angles. Your biquads are already slanted at 45 deg by design. But, every situation is different. What works good for one locations might not be best for another. Experiment. Have always used biquads in vertical position.

What I have found is things change depending distance from tower. Rule of thumb is at least one wavelength apart. A 700MHz wavelength is 42.9 cm (16.8897638 in). Again, this is just a starting point. In the lab things are perfect, in the field many rules change. Start out about 24 inches apart.

Please forgive my spelling and grammar, on a small screen and have 12 fat fingers

[terryjett]

Forgot: if you really want a professional job, do not forget your flux: https://amzn.to/38DU2j5

After you ruff things up and clean the surfaces of all soldering points, apply the flux to really get the solder flowing!

[OptimusPrime]

Anyone bold enough to try one for B71/b71 632-678 MHz?

Another good Moxon reference:
https://gitlab.com/cbowman/uv-moxon-yag ... /readme.md

[terryjett]

Anyone bold enough to try one for B71/b71 632-678 MHz?

Another good Moxon reference:
https://gitlab.com/cbowman/uv-moxon-yag ... /readme.md

Never gave them a try for 600MHz. The wire gets pretty long at this lower frequency and would require lots of extra support. Wavelength's become longer the lower the frequency, so the longer the antenna must be. But, bet this type of antenna would be pretty good performer.

Keep in mind the cbowman moxon yagi would have to be recalculated for frequencies. It is setup for HAM radio bands 2M and 70CM:

2M = 144 MHz to 148 MHz

20CM = 420 to 450 MHz

[OptimusPrime]

Never gave them a try for 600MHz. The wire gets pretty long at this lower frequency and would require lots of extra support. Wavelength's become longer the lower the frequency, so the longer the antenna must be. But, bet this type of antenna would be pretty good performer.

Keep in mind the cbowman moxon yagi would have to be recalculated for frequencies. It is setup for HAM radio bands 2M and 70CM:

2M = 144 MHz to 148 MHz

20CM = 420 to 450 MHz

Yeah, will need new dimensions but using this calculator it seems it isn't as large a size:
https://i.imgur.com/FeJSLFV.png

[terryjett]

Guess I am confused. "Anyone bold enough to try one for B71/b71 632-678 MHz?"

Was talking about the size and supports for the double biquad.

Pay no attention to me, I am very amateur at all this stuff.

[OptimusPrime]

Guess I am confused. "Anyone bold enough to try one for B71/b71 632-678 MHz?"

Was talking about the size and supports for the double biquad.

Pay no attention to me, I am very amateur at all this stuff.

No, sorry for the confusion. I was referring to the moxon. Seems it has better gain than the double bi-quad?

[terryjett]

Theoretically the double biquad antenna has around 13-14dBi. Even one thrown together should have about 10dBi.

Do not have the 4nex2 software (https://www.qsl.net/4nec2/) on this computer, but it can help you determine some antenna designs gain.

Not that familiar with the UV moxon design, but be very interesting to try out. Does not look hard to build, just need to pay close attention to measurements and spacing of drilled holes.

[OptimusPrime]

This looks interesting. I'll see if the person can do one for the B71/n71 frequency:

https://www.thingiverse.com/thing:3584713

I've also asked about a moxon to another poster.

In the end, it would be great to optimize these band but will probably want more full spectrum (panel, lpda, parabolic)

[terryjett]

This looks interesting. I'll see if the person can do one for the B71/n71 frequency:

https://www.thingiverse.com/thing:3584713

I've also asked about a moxon to another poster.

In the end, it would be great to optimize these band but will probably want more full spectrum (panel, lpda, parabolic)

Yagi's are great for long distance reach out and give me some signal. They are extremely hard to build by hand. Alignment is the key. Have built a few but found it best to buy if looking to optimize signal.

If you are experimenting, by all means so for it but if you are looking to improve your reception, look at some of The Wireless Haven offers.