Radio Antenna Help

[AR_Hillbilly]

Folks,

I have broken my Comant antenna on my Aeronca Sedan. Had an extension cord hanging down from the ceiling to plug my trickle charger into. Been fine for a couple months now but Saturday it somehow got caught up in it and I didn't notice until it was to late. It basically bent it back right at the joint between the metal base and whatever the antenna material is. It is not completely apart but just crumbled some of the material right at the joint, I can see the wire running from the base to the antenna. I am wondering if I can just secure the top part to the bottom part somehow or do I need to replace the whole antenna. I will try to get a link to the pictures of the break on here soon. I found what looked like the same antenna that is on it on the Chief and Aircraft Spruce site ( Comant CI 121), the antenna on it is a 4 hole and this looks to be the same. I have included the link to the one I'm looking at.

http://www.aircraftspruce.com/catalog/a ... ant121.php

Any advice would be appreciated.

Thanks,
Justin

[AR_Hillbilly]

Here is the link to the pictures.

https://photos.app.goo.gl/CfMT5Xh6XDUymvXQ2

[rkittine]

Is it electrically still connected? Do you have or can you borrow an SWR Bridge or Antenna Analyzer? If the SWR is below 1.6:1 just epoxy it all together. Any Avionics shop will have one and you should be able to find a local HAM Radio club and get someone to check it for you.

Bob

[AR_Hillbilly]

Bob,

Thank you for your quick reply. It appears to still be electrically connected. Looking at the exposed portion it just appears there is a copper wire surrounded by a clear coating running up through the antenna. That doesn't appear to be damaged. I am not sure what an SWR Bridge or Antenna Analyzer is. I am somewhat familiar with testing CB antennas for proper ohms so not sure that is the same thing. Is that an aviation specific device or would maybe a CB radio shop have such a device?

Justin

[rkittine]

Most CB SWR Bridges are made for +/- 27 MHZ, where you aircraft radio goes from 108 or so up through 130+. So the SWR Bridge has to be one that covers that frequency range. They normal come in two to three models. 1.8-55 MHZ, then 60-200 and then 200 t0 500. You need the middle one. Where are you located? Bill Pancake is a HAM and will for sure have one and any avionics shop will.

The antenna is actually a wire encase in something ridged protective cover. A 1/4 wave antenna for the AM Aircraft band will have a radiator of about 21" so as long as it is intact you should be fine with a good repair job on the outer shell. Many Airband Radios jut have a much heavier rod with no exterior casing and work just as good. Many a perfectly fine 1/4 wave vertical antenna have been made out of straightened coat hangers.

Bob

[Paul Agaliotis]

Justin,
My guess is you will need to replace the antenna. Use the time it's still working to find a replacement. It's going to fail you right when you need it the most.
SWR (Standing Wave Ratio) has to do with the resistance to AC current. The antenna is tuned for a specific frequency range to eliminate this resistance. That's why you can't use a GPS antenna for COM usage, they are tuned to a different range.
Paul

[AR_Hillbilly]

Where are you located? Bill Pancake is a HAM and will for sure have one and any avionics shop will.

Bob,

I am in rural Arkansas, close to a little town called Jasper. I have a friend in Little Rock that is a HAM operator and he said he had one if it included the freq that I needed. I'll update him on what I think I need.

Paul,

Thank you for your post. I am thinking I will see if I can find a piece of pvc pipe the right size to slide down over it for support and secure it with some tape or glue for now until I get another solution worked out.

The link I provided for the CI 121 antenna in the original post...Is that the right antenna needed or am I looking for another model? Does anyone know?

Thanks,
Justin

[rkittine]

I used to have responsibility for a Plant in Sheridan, Arkansas years ago and then one in Crossett. I enjoyed visiting Little Rock. My girl friends company did the Clinton Library in Little Rock, so I have been there a lot.

Bob

P.S. - Tell your friend that you need an SWR Bridge that will cover 100-150 MHZ. If he has one for 2 Meters it should be fine.

[Paul Agaliotis]

Roady,
I use the Comant antenna on all of my stuff. Works great and trouble free, tuned for the specific COM frequency. The little wire whips work ok but have a larger frequency range and suffer a little bit.
I called my radio manufacturer and they recommended the Comant antenna, glad they did.
Paul

[rkittine]

Ah, but then Which Comant antenna. They make one like Roady has as well as thick wire antennas with sturdy base as well as the ones enclosed. In reality, the exposed wire antenna can actually be easily cut to an exact frequency. 1.4 wave whips are more broad banded than gain antennas, but much depends on the mounting location. If mounted on the top of your aircraft over metal (needed for a good ground plane) the majority of radiation will be above. There is a lot more then just the antenna that makes a difference. Feed lines, correct connectors, grounds etc. will effect them, but if your electrical parts of your antenna are unharmed and it worked good where it is, just recover it to protect it.

Bob

[AR_Hillbilly]

Thank you for the reply folks. Yea the right antenna is what I'm after. Not sure which one to pick if I go that route. For now I just put a short piece of pvc pipe down over it and taped it up. I haven't been able to do a distance check since I'm all in the boonies but it worked within a few miles of one of the airports I went by yesterday on my to Gastons.

[AR_Hillbilly]

It will be a few days before I can look for myself but what kind of connector is on the Antenna? Will I need some sort of adapter to plug into the meter?
I look at a Comant antenna spec online and it states BNC so I think that is the correct answer but wanted to verify if someone knew.


Thanks,
Justin

[Richard Murray]

Justin-

Typically the antenna lead has a male BNC connector and most SWR meters have an SO-239. That would require a BNC to PL-259 adapter.

So if you are inserting it between your radio and the antenna, and the SWR meter has SO-239 input connectors, your would need two adapters and a coax jumper with BNC connectors on each end. The lead from the radio is a short piece (under 12") with a female BNC connector on it.

[rkittine]

BNC to SO-239 and the reverse are probably one of the easiest adapters to find and most any avionics shop or CB Shop should have them. If you are anywhere near a Ham Store, they will for sure have them.

If you can not find any, drop me a note and I will send you two or a jumper with a BNC on one end and a PL-259 (The male that goes with the SO-239) on the other.

rkittine@aol.com

Bob

[AR_Hillbilly]

Thank you Richard and Bob. Just the info I needed. I didn't understand all of it but the guy that does HAM here did and had all the adapters I needed.

Justin