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| | |-+  Airband Yagi antenna designs
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Author Topic: Airband Yagi antenna designs  (Read 48718 times)
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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Chananya Freedman
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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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Chananya Freedman
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dave
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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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vicosh
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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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vicosh
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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
vicosh
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« Reply #25 on: December 19, 2008, 04:41:53 AM »

Ok, understood! But I wasn't referring at the reception quality. I just wanted to know how the antenna will react at a lightning strke. A lightning strike.. this is the worst case. But in stormy/snow conditions the antenna could be loaded with some statical charge that could be discharged into the receiver. Does this antenna have any system to 'route' the statical charge to the earth?
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Biff
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« Reply #26 on: December 19, 2008, 09:25:50 AM »

You're still going to run your coax through a grounding block, right?

Ground the mast and the coax, and you'll probably be ok. 
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« Reply #27 on: December 24, 2008, 08:12:44 AM »

You can use a lightning protection system by grounding the antenna mount. 

But from experience ( I have 114 antenna sites operational), no matter what sort of of lightning protection you have, it will not prevent a lightning strike. 

If its your time....its your time.   shocked
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« Reply #28 on: January 24, 2009, 02:14:02 PM »

Here are some photos of the Airband Yagi antenna. The elements were made from copper tubing which were soldered with a short length of brass tubing since the copper tubes were sold in 3' lengths. The boom was made from wood, the box was a project enclosure from Radio Shack. Chassis mount Coax F connector, epoxy, heat shrink tubing, screw protectors on the element tips, and paint completed the project.
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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
dave
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« Reply #29 on: January 24, 2009, 03:10:30 PM »

Awesome construction job!
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