7 Antenna

[Bartman]

The last couple of flights have been in light rain and solid IMC and I have very poor reception with lots of noise.  Basically the brand new IFD 440 sounded like crap with lots of static even when we did get reception. Today we had to push the volume button and listen to a lot of noise just so we could hear center so we didn't miss a call. Anyway,  I have two of the 7 antennas on top of the cabin and the rear one looks like it is brand new. The front one has taken a lot of abuse over the years with the cabin cover and just over the past two years now looking really bad. I'd say it has been sanded and painted in the past too. I really like the retro look of the 7 antenna, but the Comant CI-196 looks like it is a drop in replacement and we can run new RG 400 Coax while we are at it. At this point I assume the front antenna is connected to the IFD 440, but we will confirm. 

Any comments on the CI-196 or other options ?

 

 

[McMooney]

I'm having the same problem lately.  at certain times, the radio becomes so filled with static i can barely make out atc.

one place it's common is when i'm about 3 to 4 miles from my home field and abeam the tower.   total static.

[Marauder]

10 minutes ago, Bartman said:

The last couple of flights have been in light rain and solid IMC and I have very poor reception with lots of noise.  Basically the brand new IFD 440 sounded like crap with lots of static even when we did get reception. Today we had to push the volume button and listen to a lot of noise just so we could hear center so we didn't miss a call. Anyway,  I have two of the 7 antennas on top of the cabin and the rear one looks like it is brand new. The front one has taken a lot of abuse over the years with the cabin cover and just over the past two years now looking really bad. I'd say it has been sanded and painted in the past too. I really like the retro look of the 7 antenna, but the Comant CI-196 looks like it is a drop in replacement and we can run new RG 400 Coax while we are at it. At this point I assume the front antenna is connected to the IFD 440, but we will confirm. 

Any comments on the CI-196 or other options ?

 

 

That’s the way I went. When I had my interior out for renovation I pulled all of the RG-58 for Com and Navs and ran new RG-400. I also replaced my 7 antennae with a new CI-196. Make a noticeable difference.

BTW - unless they switched them, the front antennae is on Com 1.

 

[Marauder]

And the CI-196 is a direct replacement for the 7. The hole for the BNC is offset on these antennas. 

[Bartman]

I'm about ashamed to show just how bad this thing looks, but here goes. It didn't look bad 10 years ago, but I think it has been sanded and painted in the past, and years of putting the cover on and off has taken its toll. 

[Marauder]

19 minutes ago, Bartman said:

I'm about ashamed to show just how bad this thing looks, but here goes. It didn't look bad 10 years ago, but I think it has been sanded and painted in the past, and years of putting the cover on and off has taken its toll. 

Holy cow Batman. That is really rough looking. I thought mine was bad but you have taken it to a new level.

This is what I found with the RG-58. They used a clip to hold it onto the steel tubing and it compressed it badly. 

[Hank]

If you're gonna redo your antennae anyway, move them back out from under the cover. Makes travel so much simpler!

The front location is now my GPS puck, and the canopy cover just touches the edge of the first antenna.

Edited April 26, 2018 by Hank

[MB65E]

1 hour ago, bluehighwayflyer said:

+1. We did this not too long ago on our C for this same reason but even more so just for aesthetics, and another unexpected benefit was a noticeable reduction in noise. 

Wow, just from the wind noise of the antenna? That’s great. I guess the top antenna is literally less than a foot away from the backseater’s head.

 

[carusoam]

This sound like the second discussion related to antenna grounding issues mentioned this week... somebody else had ice bridging the antenna to ground...

If updating your antenna, look up spacing and grounds and doubler plates... I think this is the usual conversation for antennae...

PP thoughts,

-a-

[Mooney in Oz]

If none of the above works then it might be worthwhile adding static wicks. 

Worked for me years ago when I had a similar problem.  

My antennas were in good shape with no need to change.

[jlunseth]

Adding wicks to the antenna, or adding them somewhere else?

[Mooney in Oz]

28 minutes ago, jlunseth said:

Adding wicks to the antenna, or adding them somewhere else?

To the trailing edges of the airframe such as elevators, rudder and ailerons.

[jlunseth]

Thanks.  I get some static, particularly on my newer 430AW, but I already have wicks all over the airframe.

[bradp]

I don’t think there’s an easy path for adding wicks to non wicked airframes.  They are riveted to the control surfaces which I’m sure would require rebalancing. Not a simple slap on type of job. 

[jlunseth]

What I speculate is a problem, particularly for turbos at high altitudes, is having the antennae on the roof at all.  The body of the aircraft casts a big “shadow.” Where I run into difficulty is two things.  First, any frequency in around the 125 range is often a problem.  Most of western MN is 125.5 or something like that, and flying west I always hate it when I have to listen to the static out there for about an hour.  The other is high altitude operations with weather around, especially out in the western states or at night when there is not much radio traffic anyway, so if you have not heard a broadcast from ATC in awhile you don’t necessarily think something is wrong.

[McMooney]

How many wicks are necessary ?  can i add a few to the non control surfaces portion of the plane ?  wingtips, above below rudder, out side sections of empennage, etc ?

 

[INA201]

My two cents. Just finished an avionics upgrade. I had one 7 antennae that was shot so we decided to go with the modern look of the 196. I had a tremendous amount of not only static but random crackling noises and such that was driving me crazy.  Garmin Remote audio panel, new wiring, and new antennae made everything close to perfect. I liked the reverse 7 look but I like the modern look a little better. I’m no aerodynamic engineer but seems like the new ones look like they would have less drag but I have no data to support this. 

[McMooney]

What could possibly make an antennae go bad?  I do want to upgrade to vhf/gps combo antennaes anyway.  

 

I really need to do something, ATC was alittle upset with me last week.

[Bartman]

We decided last minute to fly to Destin for the weekend. I listened on COM 2 and transmitted on COM 1 no issues. After about 2 hours COM1 reception improved a lot, but still some noise.  At the end of the flight almost back to normal, but not quite 100%.  I had flown thru rain on past flights but this one was severe clear and bone dry so maybe a moisture problem.  Now considering removing the #1 antenna, clean mounting surface and make sure we have good contact.  New RG400 coax too.  If that fixes it I'll keep the 7 and have it painted. If not we get a new 196. 

[Mooney in Oz]

43 minutes ago, Bartman said:

If that fixes it I'll keep the 7 and have it painted. 

Can it be painted? I have seen  GPS antennas with the warning ‘Do not paint’

[Yetti]

16 hours ago, McMooney said:

What could possibly make an antennae go bad?  I do want to upgrade to vhf/gps combo antennaes anyway.  

 

I really need to do something, ATC was alittle upset with me last week.

The ground. ie the ground plane.   To work well antennas need a good ground plane.   The skin of the airplane is the ground plane for your antennas.  Slight corrosion will cause the antenna to lose ground.    Putting myself through college doing two-way radio work the first thing we did was take antenna off and clean the surface.  I have done this to 100s of antennas.  usually the radio would start working fine.  The other fix was to take the transceiver case which was about as big as a laptop and wack it with your hardhat.   While this seems cruel, it made alot of sense.   The high humidity environment along with cement dust would cause the edge connectors in the boards lose contact. Wacking them with a hard hat would make the contacts work again.   Then there was the time we took the old Motracs out and washed and scrubbed them down with a hose.  Left them out in the sun to dry.    Worked great.

[Piloto]

Bartman before replacing the antenna try painting it with Rust Oleum spray paint. Having the metal of the antenna exposed to the airflow causes electrical discharging in the same way as a static wick. 

José

[jetdriven]

On 4/28/2018 at 8:03 PM, Bartman said:

We decided last minute to fly to Destin for the weekend. I listened on COM 2 and transmitted on COM 1 no issues. After about 2 hours COM1 reception improved a lot, but still some noise.  At the end of the flight almost back to normal, but not quite 100%.  I had flown thru rain on past flights but this one was severe clear and bone dry so maybe a moisture problem.  Now considering removing the #1 antenna, clean mounting surface and make sure we have good contact.  New RG400 coax too.  If that fixes it I'll keep the 7 and have it painted. If not we get a new 196. 

I'm not a fan of painting antennas in fact they strongly, like very strongly, advise not to do it because some paint contains metal (TiO2) and that blocks RF. However the paint shop that painted my airplane actually painted the VHF blade antennas with White Imron paint and it did not affect the range at all so there's that. To know for sure paint a big piece of wrapping paper with the paint you want to try and wrap the antenna with it, and then go see if it will transmit and recieve. In this case your antenna might be trashed anyway, so go ahead and  paint it but verify that it works before committing to something that you can't undo like IFR with one good radio or something.

As others have said, make sure everything under the antenna is clean, clean antenna base, especially bosses where the screws pass through, clean aircraft skin, unpainted where rthe screw bosses contact, clean screws, clean star washers under the screws.  the antenna must ground through the screws and the bosses.  That works call it a day and buy a CI 196. I did all these steps in after eight hours of fooling around with it I broke down and paid $450 for a CI196 and it's been great for years..

Edited April 30, 2018 by jetdriven

[markejackson02]

How much of the interior has to be removed to get to the antennas?

 

[Marauder]

How much of the interior has to be removed to get to the antennas?
 

To get to the one up front you need to remove the roof panel and depending on your model, the plenum for the scoop intake.



To get to the rear one, you need to remove the hat rack roof piece.




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