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Author Topic: Airband Yagi antenna designs  (Read 67898 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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« 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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« 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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« 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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KSFO NORCAL App Rwy 28L/R
KSFO Tower/Ground
NORCAL Approach (KOAK)
NORCAL Departure (KSFO/KOAK)
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ZOA Oakland Center (35/40/41)


RJTT App/Dep
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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
dave
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« Reply #15 on: December 05, 2008, 06:37:03 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!

The DPD Productions antennas are great.  30m of RG-58 has a little over 4dB of signal power loss.  That means you will losing a little more than half of the received signal power in the coax.  Depending on the received signal strength at your location this may not be an issue.  If it is, you want to put an amplifier out at the antenna. 

Your amplifier choices are inexpensive broadband amplifiers and more expensive narrowband amplifiers.  If you live in a strong RF signal environment then you have to be a little careful - you could saturate the amplifier if you are close to strong transmitters.  This can cause unintentional interference to your airband reception.  In that case you may want to add a bandpass filter for airband. 

Try with the longer cable first.  You will know pretty quickly whether you need a lower loss feedline or an amplifier.

I am not familiar with sources in Europe but I can definitely recommend one of our partner sites, ScannerMaster, for all your needs:

Scanner Master

Hope this helps.

-Dave


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vicosh
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« Reply #16 on: December 07, 2008, 07:59:43 AM »

Thank you very much, Dave!

I accesed scannermaster.com but right now they don't have any preamp/pass band filters for the air band. Searching on Internet, i found this:
http://www.garex.co.uk/vhf_accs/ap-3.htm
Should i consider this solution in case of poor reception over the 30m RG-58 cable?
And another question (hope i'm not annoying): i've noticed you're using uniden and radio shack scanners and the quality of your feeds is.... ubelivable Smiley Because i don't want to use my handheld scanner for feeding LROP, i'm thinking to buy an Uniden BC350C scanner. What do you think about it? It's very cheap and the specs are pretty good. Or maybe I should buy a radio shack PRO-163 ?

Thanks a lot, Dave!
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« Reply #17 on: December 07, 2008, 05:44:11 PM »

I have a pro-95 handheld from Radio Shack.  I've had really good success with it, so I'd go with the radio shack model.

Chananya
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« Reply #18 on: December 11, 2008, 08:40:03 AM »

Thank you very much, Dave!

I accesed scannermaster.com but right now they don't have any preamp/pass band filters for the air band. Searching on Internet, i found this:
http://www.garex.co.uk/vhf_accs/ap-3.htm
Should i consider this solution in case of poor reception over the 30m RG-58 cable?
And another question (hope i'm not annoying): i've noticed you're using uniden and radio shack scanners and the quality of your feeds is.... ubelivable Smiley Because i don't want to use my handheld scanner for feeding LROP, i'm thinking to buy an Uniden BC350C scanner. What do you think about it? It's very cheap and the specs are pretty good. Or maybe I should buy a radio shack PRO-163 ?

Thanks a lot, Dave!

That unit should work fine.  Not sure if that unit is weatherproof, but if it can be mounted right at the antenna you might get better results.  But I would try it indoors first.  Outdoor preamps can be a hassle.  At a minimum, you would have to change the 9V battery every now and then, at least on this particular unit.

Bearcat 350C's are decent - we use BC-350A and 350C units on a lot of the many feeds that we run ourselves.

I have never used a PRO-163 so I can't comment on that.  Let your budget determine the preferred approach - by far the antenna and feedline are the most important elements.

-Dave
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« Reply #19 on: December 11, 2008, 11:09:26 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!

30m on RG58 is quite lossy.  Almost to the point you lose the efffort you put into installing the antenna high up.

Can you get RG8 class coax?  If not, can you put the receiver closer to the antenna and just run the audio lines down to your PC?

Beware of amplifiers as they may also amplify FM radio signals to the point where your primary receive channel  is no longer 'clean'    Amplifiers without proper filters to pre-select sections of the radio spectrum create move havoc than good.

Think of you in a room full of people.  Everyone is talking low.  You can hear the person near you just fine.  Now you add an amplifier. (Everyone in the room now speaks louder).  So hearing the person in front of you now becomes difficult.

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« Reply #20 on: December 11, 2008, 06:19:27 PM »

Thank you very much, guys!

For T210 Driver: I'm seriously thinking to use RG8 coax cable  smiley. I just read about it yesterday. Its specs are much better than the RG58's specs.
Regarding the AMP: of course i should be very careful with the other channels that are stronger than the air band channels. But together with the amp i will put a pass band filter for the air band. A quick solution could be this one:
http://www.garex.co.uk/vhf_accs/ap-3.htm
What do you say about it?

Dave, thanks a lot for the answer. I've chosen the radio shack PRO-163. I've read many good things about it and at radioshack.com it's a super promotion until Saturday: only 149$ !!! (normally: 219$)

So... on december 23rd the guy from usa will arrive in romania with my station and my antenna  cheesy Not later than January 15th my feed should be online. I'll put the pics on the forum smiley
« Last Edit: December 11, 2008, 06:22:40 PM by vicosh » Logged
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« Reply #21 on: December 11, 2008, 09:35:46 PM »

Thank you very much, guys!

For T210 Driver: I'm seriously thinking to use RG8 coax cable  smiley. I just read about it yesterday. Its specs are much better than the RG58's specs.
Regarding the AMP: of course i should be very careful with the other channels that are stronger than the air band channels. But together with the amp i will put a pass band filter for the air band. A quick solution could be this one:
http://www.garex.co.uk/vhf_accs/ap-3.htm
What do you say about it? 

This looks like this is a 50 pound investment for this preamp purchase.   With no documented information mentioned about 'true' preselection for the aviation band, I would avoid this aquisition.   

And yes, stick with Rg8  or Belden 9913 cable if over a 10m run from the antenna to the receiver unit.

I undertstand someone is importing material for the this installation and I am hopeful what has been imported in will work for your application

Feel free to ask questions if you like.

Paul

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« Reply #22 on: December 18, 2008, 09:11:00 AM »

Hello everybody. I need some help again  smiley
I bought this antenna from dpdproductions: http://www.dpdproductions.com/page_vhf_air.html (UHF/VHF Air Omni Model Antenna)
My question is (maybe someone who already operates with this antenna knows the answer):
does this antenna connect to the ground through the mast? It's very important for me because the place where the antenna will be placed is pretty isolated and even if there is another tree that is higher than the antenna's mast i'm still worrying about the lightning strikes.
In the technical specs it is written that the vertical support is made out of a very resistan plastic so... there is no metal contact betwen the mast and the antenna, is that right?

Thanks!
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« Reply #23 on: December 18, 2008, 11:26:48 PM »

Mt personal opinion is that no, it does not need grounding of any sort.  I have my antennas (4 ) simply clamped with the provided clamps to the supporting pipe.   

Excellent results.


Paul
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« Reply #24 on: December 19, 2008, 12:37:49 AM »

I have my DPD Airband antenna mounted on the balcony using a couple of wall mount brackets. I didn't have any pipes to clamp it to using the supplied clamp. There is no metal contact between the antenna and mast in the DPD antennas. Excellent results here too. Ken
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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
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