Comm Antenna location

I'm planning my VHF comm install on my 9A. In general where are -A owners putting this antenna - TOP or BOTTOM. VHF is basically line of sight - a TOP mounted allows for better comm when on the ground (terminal area, etc) - at altitude I can see the benefits of a bottom mounted antenna. Theorically these diploes are omin directional so the radiation pattern should not be affected by top or bottom location - depends more on the ground plane . . . any comments??

Yes, the top mounted antenna works better when on the ground. But, when you are on the ground, you are usually close range. Generally bottom is better for com but top or bottom will work fine. Further aft is better on bottom to get away from gear legs.

Bottom mount works very well

FWIW: During my build I could contact the tower from inside my garage (3 miles away) with my bottom mounted antennae. Most times I would get a 'loud and clear' although I did get 'scratchy but readable' a couple of times. Good luck.

I've been planning on mounting mine on the belly right under the pilot's legs and up against the center section bulkhead covers. This would allow me to easily hook up my handheld to the antennae if necessary and it would make running the ant. cable under those panel covers and up to the panel easy. Possible interference from the gear legs is something I hadn't thought about though (but now will).

I mounted my -9A comm antenna forward of the spar inside the web of gear leg tubes. It's out of the way of my size 12s yet quite accessible. The xpndr antenna is in the same position on the right side of the fuse. Another option to consider is mounting the antennas just aft of the firewall.

Steve

wing tip?

Anyone use the antenna that mounts in the wing tip?

Looks like it is made out of aluminum strips about 1" wide.

It would seem there may be times when the fuse would blank out the signal, if so, how bad a problem is this?

Or do they work just fine?

Mike

Anyone use the antenna that mounts in the wing tip?

Click to expand...

Lots of info on this question in the forum archives which is available via the "Search" feature .

Sam, I already tried that, found 8 hits for "Bob Archer antenna", in the last year. All seemed to be in regards to the nav antenna, not comm.

I just bought a project that already has the wingtip comm antenna, installed, and was looking for feedback on the performance.

If they have problems, now is the time to replace it, not after the plane is flying.

Dan C., a google search picked up your setup, how happy are you with the wingtip setup?

Thanks all, Mike

Rule of thumb

A COM antenna should be mounted vertically for best results, a NAV antenna can (or should?) be mounted horizontally. That's why the Bob Archer design works best for VOR's . A good drawing of this type can be found in Bob Nuckolls Aeroelectric Connection book, very easy to make. Or you can buy one at Spruce.

It would not be that hard to change later.

Mike S said:

Sam, I already tried that, found 8 hits for "Bob Archer antenna", in the last year. All seemed to be in regards to the nav antenna, not comm.

I just bought a project that already has the wingtip comm antenna, installed, and was looking for feedback on the performance.

If they have problems, now is the time to replace it, not after the plane is flying.

Dan C., a google search picked up your setup, how happy are you with the wingtip setup?

Thanks all, Mike

Click to expand...

Adding the antennae later should be easy. Granted I have not done it but don't think that it would be more then a one day job at most.
I have both a Bob Archer comm and a bent whip belly mounted comm antennae. (I have two radios). So far I have not noticed any big difference in performance between the two antenna's.

Kent

Thanks

Kent, thanks for the answer.

This is just the kind of info I am looking for--------theory is just fine, but actual usage reports are what I was hoping to get.

Mike

Belly

Mike,
Mount it on the belly but at least three feet from the transponder antennna. We put our transponder antenna just ahead of the spar and out of the way of stomping feet messing up the connector and coax. Plus it's very accessible. We mounted the bent whip in the center under the baggage compartment where it's easily accessible and has the distance from the transponder. The center strip that's removable allows access to the connector.

Guys have complained at times that the Archer comm can be blanked by the airframe when the control tower is on the opposite side of the wing with the antenna. Besides, the nice flat belly acts as a great counterpoise to aid signal radiation.

Regards,

Thanks

Pierre, thanks for the reply.

I am leaning in the direction you suggest, but as the prior owner already had installed the Archer unit in the wing tip, I was wondering if, and how much,the saving in time and $ to just leave it alone was going to cost me in the radio performance end.

Mike

I am leaning in the direction you suggest, but as the prior owner already had installed the Archer unit in the wing tip, I was wondering if, and how much,the saving in time and $ to just leave it alone was going to cost me in the radio performance end.

Click to expand...

Mike, I've never used the Archer com antenna (I have the Archer nav version and it works great) but from the numerous reports I've seen over the years, and from Bob's recommendations, the wingtip com antenna is not a stellar performer. I suggest you go ahead and install a whip antenna on the bottom of the plane so you will get the radio performance you expect. The installation shouldn't take more than an afternoon and then you can be confident the radio is performing to its potential. The wingtip antenna and coax can be left in place in case you ever want a second com antenna.

Mike,

I'll throw my thoughts in just to stir the pot a little.

I think you need to consider your "mission." If you aren't going to be spending enormous amounts of time talking to center, Ken'ts reply would seem to indicate the in-tip antenna is good enough. Granted, I am sure it is not optimal. But probably good enough for unicom/local tower/local approach.

If you go with the Archer antenna that you have, and it doesn't work well enough for your personal preference, then at that time you know it is worth the time/$ to install a belly whip antenna ala Pierre.

Here's what I would do if I were in your position. I think the time/$ to install the whip antenna now is small and worth it. Once you're flying, you can audition both antennas. Then decide if you prefer the performance of the whip, or if you would rather remove it and go with the sleek and stealthy in-tip.

Or just get a second com and use them both.

But what do I know. I am at least 3 years from installing radios.

Good luck,
Robert