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Comm antenna

Dan Gervae

FRIEND
Upper Peninsula of Michigan
I’m looking for a comm antenna for my Flightline 760A....recommendations desired...I have this laying in the hangar....what is it?
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If you want an ID on that antenna, you'll need a part number from the base.

If you want an antenna that mounts with the 'standard' four hole base, use a Comant CI121. Make sure it's mounted with a good ground plane and NO gasket. Seal with RTV after install. Get a new RG400 coax cable made up with crimp on connectors, to hook the antenna to the radio.

Web
 
Just for info, here; all stick type antennas look about the same. Either three or four screw holes for mounting. Tear drop shaped base. Fiberglass rod. This describes VHF, FM, and Loran antennas. The only visible difference is the length of the rod and then they would have to be side by side to see.

So ALWAYS go by the part/model number on the base of the antenna as an incorrect choice will insure that the radio never works correctly.

Web
 
LORAN thread drift...I flew a C-185 with an ARNAV R-40 and that antenna for years. Problem was some of the lakes, rivers, and mountains in central Alaska kept moving around. Junk coverage for us.

Gary
 
LORAN thread drift...I flew a C-185 with an ARNAV R-40 and that antenna for years. Problem was some of the lakes, rivers, and mountains in central Alaska kept moving around. Junk coverage for us.

Gary

Years ago a pilot told me that he wanted to see just how inaccurate a Loran was. He flew from ANC to Bethel using his Loran as his nav. When the Loran said he was over Bethel, he looked out a window and saw that the village was about thirty miles to the side. It was the last time he used it.

For a long time I kept a Loran antenna on the shelf. It was a cheap dummy load when working on comm's in the shop.

Web
 
Yea the LORAN A-C system was designed for specified coverage, primarily marine but some continental. See pics of useable: (https://www.navcen.uscg.gov/pdf/loran/handbook/APP-B.pdf) The receptions was always degraded by poor localized S/N and subject to sunset or sunrise multi-path signals.

Enough drift but had to get this LORAN port hole closed forever. The users of GPS today have no idea what lonely charts and NDB's played in our flying lives.

Gary
 
I have a brand new stainless straight antenna with insulators on it...anyone use one of these....do you just strip the coax and wrap it around between the nuts to capture it? Of these work ok for com radio....it says that’s what it’s for
 
I have a brand new stainless straight antenna with insulators on it...anyone use one of these....do you just strip the coax and wrap it around between the nuts to capture it? Of these work ok for com radio....it says that’s what it’s for

Make sure it's mounted correctly with the insulators and tabbed washer in the correct order. On your coax cable (tan colored RG400) strip approximately 1" of the outer covering and braided shield off from the center conductor with white covering. Attach a 20 gauge pig tail wire to the outer braided shield with a Sumitomo L-C-5 solder sleeve. Crimp a ring terminal onto the center conductor and install the ring onto the threaded base of the antenna. Finally, solder the pigtail wire to the tab on the tabbed washer.

As long as they are installed properly, with a good ground plane and connected correctly, these antennas work very well.

Web
 
Make sure it's mounted correctly with the insulators and tabbed washer in the correct order. On your coax cable (tan colored RG400) strip approximately 1" of the outer covering and braided shield off from the center conductor with white covering. Attach a 20 gauge pig tail wire to the outer braided shield with a Sumitomo L-C-5 solder sleeve. Crimp a ring terminal onto the center conductor and install the ring onto the threaded base of the antenna. Finally, solder the pigtail wire to the tab on the tabbed washer.

As long as they are installed properly, with a good ground plane and connected correctly, these antennas work very well. Web

Show some pics if available for those that aren't familiar with the parts? Describe ground plane and size?

Gary
 
Here's a pic of the parts and the order of assembly. Note that the upper and lower insulators are usually ceramic, so they are prone to cracking/breaking until installed. I never install the nameplate and the star washer and large solder lug may be a single star washer with a solder tab attached. The small solder lug may be replaced by a crimped on ring terminal.

When any antenna is installed on any non conductive surface (and for all intents and purposes, carbon fiber is non conductive) you'll need to fabricate a ground plane at the base of the antenna. On an aluminum skin, the aluminum area around the base of the antenna forms the ground plane. It's important to know that the term 'ground plane' means the AREA of a conductive surface all around the base of the antenna, NOT just a ground wire hooked to the base.

When installing this antenna on a fabric covered aircraft, fabricate a mount to mechanically hold the antenna in place. Make a hole in the fabric big enough to install the upper and lower insulators. Install aluminum or copper tape in the shape of an asterisk, or stainless screen, for a ground plane, on the inside of the fabric, so that it is sandwiched between the antenna mount and the fabric. Then complete the installation of the antenna as per the picture

Connect the center conductor of the antenna coax to the threaded antenna base and the coax shield to the large solder lug.

As for the size of a ground plane, the ideal is to make it a CIRCLE that has a diameter 2X antenna length. Since that never happens on a small aircraft, try to make it as reasonably large as you can. A circle is the best shape and keep the plane as parallel to the ground as possible (i.e. don't have half of it on the fuselage back and the other half vertical down the fuselage side.

Web
 

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