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Author Topic: Airband Yagi antenna designs  (Read 45161 times)
dave
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« on: May 13, 2008, 12:11:59 AM »

These designs are reprinted with the permission of Kent England WA5VJB.  They appeared in the March 2008 issue of Popular Communications.

For those of you looking to get good airband reception in a particular direction, these antennas should work wonders for you.  And they are very inexpensive to build.

Enjoy - and you can find more designs and info at http://www.wa5vjb.com (currently in the process of changing DNS so try tomorrow).

-Dave

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KSYR-pjr
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« Reply #1 on: May 13, 2008, 12:41:21 PM »

Dave, how do you suppose these antennas compare with a custom j-pole?  Would it be worth my time and energy to replace my current j-pole with one of these or would the difference in reception be minimal?

I quickly scanned the article and saw an impressive increase in signal strength over a discone antenna, but I didn't see any mention of a j-pole.
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Regards, Peter
ATC Feed:  Syracuse (KSYR), NY
dave
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« Reply #2 on: May 13, 2008, 12:49:14 PM »

The difference would likely be noticeable, but might come at a cost.  If you are having trouble with ground-based transmissions and are trying to improve those, this will help.  The biggest difference is that this is a directional antenna and the j-pole is an omnidirectional antenna.

So let's say the airport is north of you and therefore this antenna was pointed north to maximize reception from the airport.  Off the sides (east and west) and the back (south) signals might be weaker on this antenna than on the j-pole.  This antenna will have a more compressed vertical lobe which makes the problem potentially worse (j-pole has a better high-angle response).  On the other hand, the airborne signals are typically much stronger since they are typically line of sight.  So it might not matter that much.

I think the best summary is that if one can get away with an omni antenna (like a j-pole), then stick with it.  If one is in a real fringe area and not very close to the airport, then the beam could make the difference between hearing and not.  In your case, I think you're fine...feed sounds great all the time.

Hope this helps.

Dave

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KSYR-pjr
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« Reply #3 on: May 13, 2008, 12:58:13 PM »

Thanks, Dave - Appreciate the input.  I was indeed thinking about the ground activity since that is often weak on my feed.  However, I don't want to give up any air/ATC reception for ground.

My plan all along had been to get one of the FBOs there at SYR to host a ground/clearance feed, but I haven't had the time to negotiate that with them yet. 
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Regards, Peter
ATC Feed:  Syracuse (KSYR), NY
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« Reply #4 on: May 14, 2008, 09:50:53 AM »

Built one last night just to try out the design.  See attached pictures.  Have it running right now phased with a wire j-pole (the usual antenna serving the KMHT and KASH feeds).  I can't mount the beam outside right now so it is near an external wall facing toward Manchester and Nashua.  I am about 10-11 air miles from Manchester and about 6 air miles from Nashua and a little higher in altitude than either airport.

The first tests were done with the beam antenna sticking out the window.  It definitely has a typical pattern for a 3-element Yagi.  If you get the dimensions correct these antennas just work.  I was able to pick up the Manchester ATIS transmission very clearly; with the wire j-pole I can't hear it at all.  The Yagi also allows pretty clear and reliable reception of Manchester Tower; with the wire j-pole I can only hear Manchester Tower on certain days, usually when the power line noise is low.

Phasing antennas takes a little bit of work.  I just "tee-ed" the antennas together (using a BNC T connector) just to see what the two of them would sound like, and hoping that I would get more constructive than destructive signal enhancement.  So far so good...but with the correct length coaxial phasing lines I should be able to do a little better.

I currently have the beam antenna on a mast indoors (on the 3rd floor) pointed toward Manchester.  Nashua is close enough that it comes in well anyway.  I can hear most aircraft on the ground at Manchester with this setup.

For those who are handy with a soldering iron and might like to have fun with a small project, this is a great way to enhance reception, especially when you are far from an airport.  And especially if you can get the antenna outside and in the clear, away from obstacles.  The only way to see how well you can do is to experiment.

Have fun.

Dave

« Last Edit: May 14, 2008, 09:53:16 AM by dave » Logged
KSYR-pjr
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« Reply #5 on: May 14, 2008, 10:38:37 AM »

Phasing antennas takes a little bit of work.  I just "tee-ed" the antennas together (using a BNC T connector) just to see what the two of them would sound like, and hoping that I would get more constructive than destructive signal enhancement.  So far so good...but with the correct length coaxial phasing lines I should be able to do a little better.

I am VERY interested in trying this.  I was always curious if one could connect two different types of antennas via some type of splitter to the same scanner in order to get the benefits of both.  If I am reading your post correctly, it seems that it can be done and as simply as using a BNC T connector?  Are there any pitfalls I should be wary of?

I realize that you stated experimentation is key here but if you don't mind, I would like to learn from your experimenting.  Smiley   As you know I am on the road 4-5 days every week so time is very valuable to me when I am home. 

That mentioned, though, I would still like to try this myself, since I have the same characteristics of a feed (9 miles from airport, cannot get ground aircraft unless they are the big jets, sometimes experience weaker tower, etc) and it seems that this may really be an incredible improvement.

My neighbors are going to hate my antenna farm that is growing on the corner of my house!  But then again given what some of them are doing to their backyards, eff 'em.  (The next time I move it will be to a farm with 1/2 mile between me and the next house,  but that is a story for another day.)

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Regards, Peter
ATC Feed:  Syracuse (KSYR), NY
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« Reply #6 on: May 15, 2008, 03:35:06 PM »

One issue with a straight splitter (BNC T connector, for example) is that you are connecting two 50-ohm antennas in parallel.  This will load down the standard 50-ohm input of the scanner and reduce signals a bit due to the impedance mismatch.  But this is only a receive application, and the gain due to signal enhancement provided by the Yagi may overcome the loss.  So it's worth a try.

Phasing identical antennas is easier than phasing dissimilar antennas.  Each of the individual antenna patterns is different.  It can be done, but takes a little design work to get it right.  Signal amplitudes, phase control, and antenna spacing all play a role.  Without access to an antenna test range it becomes hard to evaluate.  So for hobbyists the "try the best design design you can come up with and see how it does" approach is better.

I ended up sticking the beam out the 3rd floor window.  Hopefully the neighbors won't complain.  smiley  Reception is much better than with it indoors.

-Dave
 


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FlyGuyAlex
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« Reply #7 on: May 17, 2008, 12:21:25 AM »

Hello Dave,
I would like to know how many Db's of gain will you get with this 3 element YAGI Antenna.
Also is it possible to make an 4 or 5 element Yagi Antenna for airband? If this is possible how?

-Alexander
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« Reply #8 on: May 17, 2008, 07:07:42 AM »

This seems to be a very interesting project, I have another question as well. Is there a maximum distance one can have between the mast and the 1st element? if its too large a gap will it affect performance of the antenna?

Thanks
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Feed provider for YPPF
dave
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« Reply #9 on: May 17, 2008, 07:51:38 AM »

Hello Dave,
I would like to know how many Db's of gain will you get with this 3 element YAGI Antenna.
Also is it possible to make an 4 or 5 element Yagi Antenna for airband? If this is possible how?

-Alexander

About 6dB of gain.  Going to 4 or 5 elements would not be a huge change, about another couple of dB. 

We'll be publishing some more designs soon.

Dave

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saint11528
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« Reply #10 on: September 07, 2008, 06:04:56 PM »

Hi Dave ,

First of all thanks for the kind help by giving us the Airband Yagi antenna design. I will be working on this project in few hours.

I have made several types too including the discones for VHF & UHF air bands but still couldnt find the best type for UHF .

Now a days I am testing a Coaxil Collinear designed for VHF air band but the nosie leve goes to high I think it is because I have directly connected the antenna with feed line - it will be kind of you to guide me on this .

I have also made 6 element  LPDA for VHF & 9 element UHF but I got disappointing reception results even though on VHF LPDA I am still able to hear ground / twr comm about 40 Mi away.

I didnt use 4:1 balun on LPDA instead I used a TV balun at the antenna feed point of radio .

It will be nice to hear yours and other friends comments , we can discuss to have better reception..

Shehzad
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chefnoel
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« Reply #11 on: September 19, 2008, 04:14:56 PM »

Don't know if this is the correct place to ask my question - but >  > > >
I have just recently obtain a RADIO SHACK PRO-2018.  What kind of an antenna should I get?  The little one on top of the radio does not do much.
Thanks
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dave
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« Reply #12 on: September 20, 2008, 07:54:10 AM »

Don't know if this is the correct place to ask my question - but >  > > >
I have just recently obtain a RADIO SHACK PRO-2018.  What kind of an antenna should I get?  The little one on top of the radio does not do much.
Thanks

You have a bunch of alternatives:

Base Antennas from ScannerMaster

I highly recommend these folks - if you call them they are very helpful - tell them you came from LiveATC.net (we are an affiliate).

VHF Airband Antennas from DPD Productions

These antennas are great if you really want to focus solely on airband reception.

Just remember, you will get best results when you mount your antenna as high and clear of obstructions as possible.

-Dave
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Squawk 7700
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« Reply #13 on: September 20, 2008, 10:58:15 AM »

Using the VHF Air Vertical Outdoor Model Antenna from DPD Productions that Dave mentioned above.
I'm happy with it and it performs well. Significantly improves reception on the Airband Frequencies.
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Feeder:
KHWD Ground/Tower
KOAK Del/Gnd/Twr
KSFO NORCAL App Rwy 28L/R
KSFO Tower/Ground
NORCAL Approach (KOAK)
NORCAL Departure (KSFO/KOAK)
KSJC NORCAL Approach #2
ZOA Oakland Center (35/40/41)


RJTT App/Dep
RJTT Tokyo Control
RJTT Twr/TCA
vicosh
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« Reply #14 on: December 05, 2008, 05:29:56 AM »

Sorry for being a little bit off topic. Dave, i want to ask you something: i'm from Bucharest/Romania and I want to feed Bucharest APP and LROP Twr. The place where the feed will be located is at 10-15 miles away from the airport. The reception is very good if I place the antenna at 5-6 m height (even using a hand-made antenna). I want to buy this antenna: http://dpdproductions.com/page_vhf_air.html.
The problem is that the provided feeder is much too short. In this case, it's ok if i will extend the feeder via an n-male connector to bnc-male connector adapter and a 30m RG-58 cable? Or is much too long? Should I buy an amplifier? If yes, what amplifier would you recommend?

THANKS A LOT!
« Last Edit: December 05, 2008, 05:36:46 AM by vicosh » Logged
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