Need a external antenna

30 posts in this topic

Posted

I have an Icom A6 handheld radio. I need to install an external antenna. Can you guys suggest what did and didn’t works for you?  

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Posted

Quarter wave centered on your turtle deck or metal belly pan will work real good. I have one of those Cessna type slanted back somewhat aero but not the lightest possible weight antenna you can have if you want. It will perform well.

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Posted

Unless ur turtle deck has a big window in it.

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Posted

Is there an antenna mount on the airframe just behind the turtle deck?

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Posted

I bought a well used 24" blade on ebay and it works like a charm, about $35. and this guy makes high quality BNC coax cables to order, don't buy the black Chinese ones, they are junk - I had a dead transponder for months because a brand new back cable was dead. https://www.ebay.com/itm/BNC-Male-to-BNC-Male-50-Ohm-RG316-Coax-Low-Loss-RF-Cable/272908120318?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

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Posted

Good point about paying attention to the coax. In my first avid the builder used 90 ohm coax in a setup similar to what you are doing with a handheld. It received pretty well but I could not get out. Once I figured out the coax was the wrong impedance and installed 50ohm, it changed everything. That little hand held icom worked like an in dash radio!

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Posted

Thanks Chris and nlappos, My turtle deck is all metal with no windows. It is also comes apart in the center. I'm sure is does not matter if it sets to one side. I planned on making a star ground plane out of foil tape on the underside. The battery is right there so I also plan to ground it well. I'm not sure about there being an antenna mount aft of the turtle deck because the storage compartment was already installed when I got this project. I'll check it out.

Nlappos I will get a cord ordered today. Thanks for the outlet.  :BC:

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Posted

I took nlappos's advise and ordered one of these cables. They make a better dual shielded version called RG-400. It's 50 Ohms and suppose to block out all ignition noise. The RG-316 has good reviews but it still a single shielded coax. I do like the fact it is small as the RG-400 is much heavier. 

Attached is a good little article I found that helped explain this subject for Dummies like me. 

XCOM Aerial Dummies Guide.pdf

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Posted

Hi Vance,

You will not need to do any additional ground plane under the antenna if mounted on the TD. Do not do additional grounding to the battery as part of the antenna system! That can have potential unintended consequences. The turtle deck will be a superb ground plane so you will not need to do anything for additional grounding.

I would mount the antenna as close to the center of the turtle deck as practical both front to back and side to side.  That will help ensure your antenna radiation pattern is omnidirectional. You will only need to verify continuity between antenna ground and turtle deck and that usually happens automatically with the antenna mounting screws depending on the antenna.

This is the antenna I have laying around. You can have for price of shipping if you think you will use it. Its a good antenna. It was under my fat Avid when I got it so the builder bent the stainless radiating element so it wouldn't hit the ground. it can be left bent or straightened. let me know if you want it.

Chris

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Posted

Got it. no ground plane needed, don't ground to the battery, close to the center as possible, and yes I can use the antenna. I'll PM you my address and we can go from there.

Thanks Chris

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Posted

I've been fighting radio issues myself lately, and I think the antenna is the problem.   I have  a never used ELT antenna, would that work to try to check and see if I really have an antenna problem?  Electronics is not my strong suit by any means.  Thanks,  JImChuk

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Posted

Jim an ELT antenna might work for general communication but it would be a good idea to sweep it with an antenna analyzer first to make sure SWR is decent over the entire com band. Is that what you are wondering?

 

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Posted

I have a beautiful ELT antenna. I was going to use it (thinking it was a VHF) but was told it would most likely transmit ok but would not receive well on certain frequencies. 

But like I said......I know little about this stuff. 

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Posted

Jim an ELT antenna might work for general communication but it would be a good idea to sweep it with an antenna analyzer first to make sure SWR is decent over the entire com band. Is that what you are wondering?

 

My thoughts were this.  (and I'm probably wrong)  The ELT is set up to transmit at 121.5  The channels I use are 122.7 -123.0  Not really very far from 121.5.  Would it likely be good enough or at the least not do any harm to my radio if I tried it?  JImChuk

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Posted (edited)

It SHOULD not do any harm to try. Will probably work just fine. If it doesn't or you want to know what the SWR is over the whole com band, if you pay shipping both ways I will check SWR across the entire band for you.

I just have a simple quarter wave piece of SS wire through a feed through insulator with coax ground connected to the turtle deck and it works real well without any de-tuning to broaden its bandwidth. SWR is 1:1 in the middle of the band and is less than 2:1 at either end. I don't think an ELT antenna would be any worse.

Edited by Chris Bolkan

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Posted

The turtledeck aluminum makes a perfect ground plane, better than the foil. Let me know how the coax works (how quiet the radio is), I might upgrade.

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Posted

Now you guys got me thinking about redoing my antenna set up. I just need to find a decent antenna now . 

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Posted

Chris,  I may just send you my old antenna.  It used to work just fine, could read people 30 miles away like nothing.  Now, not so good.  It was made by a guy in Michigan, and it didn't need a ground plane.  Don't think they are available any longer.  Thanks,  JImChuk

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Posted

If anyone has a antenna laying around I'll take it . I'm using my rubber one on my radio for now. 

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Posted

I gotta tell you guys, it's great to see everyone jumping in to help each other out with issues.  I love it.

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Posted

I gotta tell you guys, it's great to see everyone jumping in to help each other out with issues.  I love it.

That’s what this site is all about. Good bunch of guys on here. 

 

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Posted

So I’ve been doing some more looking into these cables and it looks like it’s not worth me buying all the wire and tools to make them myself when there are other outlets that will make them at a reasonable price.  Aircraft Spruce as much as I try to support them really bends my prop with what they charge for certain items. They will make you up a RG 400 Coax with dual BNC connectors for just over $50. I found this site that will make the same thing for $38. 

I plan to use the one i ordered online (RG316) until I get it my setup mounted then have the RG400 made to the correct length. I’m convinced after reading up on this subject that the RG400 double shielded coax is a must for our applications. 

Here is the site I mentioned that makes up the cables at a reasonable price. 

https://fieldcomponents.com/BNCM-RG400-BNCM-Length.html?Session_ID=c23b3966041b730045d6a529ea430749&add_BASK

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Posted

eBay has a minimal selection of lengths but if you want a 10 footer they have them at a decent price too. You may be able to contact the seller and request other lengths. 

 

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Posted

UPDATE!!!

I did some testing last night with my new cord and an old antenna. It was a great improvement over the rubber whip but there is still room for improvement. The tower reported loud and clear with my plane setting inside my hangar with the door closed. I pulled the plane outside and started the engine and made another radio call to the tower. They reported loud and clear with a humming sound in the back ground. I laughed because I wanted to tell them "Of course there is a humming sound...it's a 2 stroke". :lmao: There was still some noise related to the ignition. The new RG316 was better than the standard RG58 but not by much. The RG400 has foil and double wrapped shielding over the center core that is suppose to suppress a lot more RF noise. I went to the local Flight School on the way home and looked at their AC7 Champ. It uses the same radio and intercom I use. As I suspected they were using the RG400 double shielded coax. During my flight review last week we were talking to the tower 10 miles out with no problem. 

I ordered a new RG400 cable and it should be here Friday. I think I'm finally on the right path to having a decent radio system using a handheld.

I hope this helps somebody having the same issues. I'll post again as soon as get the new antenna and coax installed. 

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Posted

There are basically 2 ways for ignition noise to get into a radio. (Maybe more than 2 but 2 dominant ways.)

1) Radiated to the antenna and

2) Conducted through the wiring used to power the radio.

If you are battery powering your radio, #2 doesn't matter. If you have the option of running on battery or 12V from the plane and you have ignition noise in the radio, you can unplug the plane power from the radio and see if the noise goes away while running on batteries only. If the noise goes away when unplugged from aircraft power, you can install one of those inexpensive noise filters in series with the power to the radio and it may help reduce ignition noise.

If the ignition noise is still in the radio when running battery power (the most likely scenario), the best way to eliminated radiated noise is to install those metal Bosh shielded resistor plug caps. Those will eliminate ignition noise getting into the radio. The penalty is slightly less spark energy and rise time. I personally never experienced a problem with the reduced spark energy and the handheld (and later panel mount) radio had no ignition noise whatsoever.

Chris

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