Marine Radio Installation P337

[mcgeer25]

Does anyone have input on what this entails/suppliers?

[stackj]

Mine is not pressurized but I do have a marine radio installed that I use for the Coast Guard Auxiliary.

In my case, I had my avionics shop install an antenna on the belly and submitted the appropriate Form 337 for that installation.

My radio plugs into the cigarette lighter, so there was no installation paperwork required for that (It is considered portable).

With your pressurized model, you will have to work with someone who is authorized to penetrate the pressure hull if you plan to run an additional antenna cable through it. This requires either instructions from the manufacturer for hull penetration or a DER/FAA approval.

Some of my friends who also fly for the CGAux use an internal antenna and just place it a window. We seem to have pretty good luck with that arrangement.

If your marine radio is 12 volts, you can get a power supply that will still plug into your cigarette lighter and yield 12 volts for the radio. My friends frequently just use a simple motorcycle battery to provide power for the marine radio. (I would recommend a Jel-Cell as they will not leak.) They just have to make sure they remove it and charge it often enough to support their mission requirements. (a six hour mission for us requires 6 hours of receive time and about 10 to 15 minutes of transmit time.)

[mcgeer25]

Jim,
This is great information--I thank you so much!!
Speaking of the CGAUX, my thought is to join myself. The issue I have right now is to find someone to talk to. I submitted a CGAUX form on line last week and have not heard back. I just purchased the 337 and thought it would be a good way to build time and be a part of an exciting org. I will be basing the plane in Rockland,ME.
Anyway, I will do the installation to communicate with my fishing budies.
Dick McGee

[Dave Underwood]

For the extra antenna, and more importantly, the hole required, you will need a DER sign off on an 8110-3 on a P-series.

The science behind the mod is a doubler of sufficient thickness and enough rivets of enough strength. The big FAA/DER concern is hoop stress & thus strength around the hole. The smaller the hole the better.

You might want to call Ray Torres from RT Aerospace as he is a DER and perhaps less expensive than others as well as being one of us.

I have had to do this twice now on the roof area of my P and in the end it is a doubler of the same thickness as the skin and about 12 AD rivets for a 3/4" hole. If anyone is interested in the calculation please let me know. Regardless you still need the DER to sign the 8110-3.

My only advice is to plan the position out carefully and work with the DER.

Regards - Dave

[Ernie Martin]

One other thought (which I wasn't going to voice until I saw the complexity of the antenna install) is to consider either a hand-held marine radio or a standard radio with a short antenna located inside the aircraft.

What I have found is that heigth is a huge advantage. When you're at a heigth of 1000 or 5000 feet (as opposed to 30 feet on a boat), your receive and tranmit distances become very large. A hand-held unit typically has 5 watts transmit output power, but I use one 30 to 40 miles away from our island home to let my wife know I'm approaching, so she can pick me up at the airport. A standard radio, with 25 watts output, could be connected to a short (about 2 feet long) standard antenna inside the aircraft, one that can be removed when you don't need to use it. This should provide nearly the same range as the installation that you're contemplating.

Depends, of course, on how often and how critical is the need for this capability. But you might consider trying one of these two options first to see if the communications quality is satisfactory.

Ernie

[Mark Hislop]

A couple of thoughts on mounting an antenna on a pressurized hull.

A company named Comant makes multi-use antennaes, combining functions such as XM, GPS, and VHF. I would check with them to see if they have an antenna that could replace one of your existing antennaes, using the same mounting point. W would think there would be no paperwork involved in such a switch.

I assume you could mount the marine antenna on the bottom of the aircraft, in fact it might be better to mount it there. The rear half of the lower fuselage is not part of the pressure vessel. There is an access plate (at least on my 73 model) between the main gear at the centerline of the fuselage. Perhaps you could mount the antenna there. Another thought is, if you have an ADF and you are planning on getting rid of it, you could mount your marine antenna where the ADF loop sensor used to be, on the center bottom of the fuselage.

Mark

[mcgeer25]

You guys are all fantistic!! I'm a new member and very recent owner of the P337. I now know I joined an excellent organization and I certainly hope to meet y'all in the neer future.
My location is Owls Head, ME, and if any of you have the chance to visit, you certainly have a place to stay.
Dick

Along the same lines as what Mark was saying about Comant, if you can use one of your existing type antennas for the marine radio, I have had success with using the same antenna for two coms. All that is required is a splitter to tie the two com antennas into the antenna cable.

Keven
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Tv discussion

[mcgeer25]

Kevin,
Thanks, My plane goes in for annual the end of May. Having all of this information means it will come out with one of your suggestions.
I'm serious about the place to stay.
email copterits@comcast.net, cel phone #413-262-1110. The Knox County Airport is less than a mile from the house.
Dick

[WebMaster]

I used to fly into SFM, and B19 frequently. Flew into Limington (63B) when it was gusting over 30Kts, and it was the closest I ever came to crashing.

[mcgeer25]

HI, the coast of Maine is a challange, no matter how you look at it. Winter winds, Summer fog. I'm new to Maine, just now transitioning from W.MA. The guys at RKD are great and I just joined the flying club there. The club is very old and active-- has 75 hangars for instance.
Anyway, you guys have been great with your help and the offer is open to stay at my place anytime.

[stackj]

I tried using an Aircraft Communication VHF antenna for the Marine radio. The radios operate in different frequency ranges.

When I tested SWR (Standing Wave Ratio) using this configuration, the marine radio was sending 25 watts (High Power) with over 23 watts reflected. This can be tough on your transmitter final RF Amplifier.

I tried cutting off a proportional section of the antenna (The marine frequency is higher, requiring a shorter antenna). This didn't work as the antenna has a network in the base further tuning it to the expected frequency range.

I bought the Comant aircraft antenna for the marine frequency range and 25 watts out had a refelction of less that 1/2 watt.

You will probably want to make this decision in advance as the aircraft frequency antenna may have a different footprint than the marine frequency antenna.

My aircraft freq antenna had a 4 hole foorprint and the marine one has a 3 hole foorprint.

[Paul Sharp]

One other thing I didn't see mentioned, and that might work - you'd have to try it to see - is to buy a small antenna tuner and put that between the splitter on the A/C com antenna and the marine radio. There's no free lunch, and the tuner won't work wonders in terms of total efficiency (you can "match" bed springs to a transmitter if you really want to, after all), but it might allow use of the antenna while keeping down the SWR ratio, still permitting enough RF output to communicate well, and not having to mess with another antenna mounting. I had a small one (probably still around out in my garage) that was about 6" x 3" by 2 1/2" with two tuning knobs on it that I used to use in a 4x4 vehicle. It worked fine in terms of making the radio happy and I still had enough of an RF broadcast pattern to make for reliable communications. It was cheap, too (something like $20-30).