Is my antenna broken?

[longhaireddwb]

I'm sure it is but I want someone to agree with me.
Here's whats up.

I have an A-99 and I've ran it for about 14 months. I took it down and took it apart then moved to the other end of town. I thought I was careful with it. I put it in the garage for 2 weeks while I got the house together.

I went out today and put up my mast and put the A-99 on top. Ran my coax and put it threw the wall into my new radio room. I put an end on the coax so I could hook it to a radio and give it all a test. But before I plugged the coax into the radio I thought I'd do a continuity test on the end I just put on the coax. Big time continuity! I cut the end off and checked between the braid and the center lead of the coax and I still got continuity.

I went back on top of the roof and pulled the coax off the antenna and checked the coax from that end and no continuity. I checked the antenna its self where the coax screws on and I got continuity. I took the top and second stage off of the antenna so I was only checking the main shaft of the antenna and I got continuity!


So before I order another antenna someone please tell me I'm right about this just to confirm what I think is true. That my antenna is broken inside somewhere and not repairable.

 

[Robb]

1) Did you try the antenna at all?
2) I think these antennas are ground/'shunted'; so of course they will show continuity.
3) Hook up the antenna and check the match.

What did you find?

I'll bet it is fine...

 

[longhaireddwb]

I didn't try it Rob. I had cut the PL259 off the end after I put it on and it was my last one. I'll see if I can get another one tomorrow and give it a try. It dont make sense to me to have continuity from the center conductor to the threaded part of the antenna where the coax threads on but I also can't think of any reason that the antenna would have been damaged.

Anyone else have any comments on this?

 

[Marconi]

I didn't try it Rob. I had cut the PL259 off the end after I put it on and it was my last one. I'll see if I can get another one tomorrow and give it a try. It dont make sense to me to have continuity from the center conductor to the threaded part of the antenna where the coax threads on but I also can't think of any reason that the antenna would have been damaged.

Anyone else have any comments on this?

Robb is right. You just jumped the gun cutting the connector off.

 

[mackmobile43]

I didn't try it Rob. I had cut the PL259 off the end after I put it on and it was my last one. I'll see if I can get another one tomorrow and give it a try. It dont make sense to me to have continuity from the center conductor to the threaded part of the antenna where the coax threads on but I also can't think of any reason that the antenna would have been damaged.

Anyone else have any comments on this?

Yes, connect the coax and start talking.

 

[Beetle]

Whatever it was that you used as a continuity tester was DC powered, right?

RF is not DC, right?

What might appear as a direct short with a DC ohmmeter may not be anything of the sort when you test with RF at the proper frequency.

Some antennas, like a plain vanilla dipole, won't have continuity at the feedpoint. Other antennas, like the A99, have an impedance-matching system built in. It has a coil across the feedpoint, which at DC will read a very low resistance.

Luckily, not knowing these things only cost you a PL-259 and the time to install it. Grab an antenna book and check some of the basic antennas. Learn how they work.

 

[BOOTY MONSTER]

LOL ........ when i researching how to build my home brew 5/8 it became apparent that something was wrong with the plans and what folks were telling me be cause it was obvious there was gonna be a short caused by the tuning . LMAO .

RF can be a funny critter .

 

[longhaireddwb]

Wow! Thanks guys!

I guess I did just jump the gun. I never did give it a try because I didn't want to take a chance on damaging a radio. Thank you all for straightening me out.

Now if I only had another pl259! I guess I'll have to contact a couple locals with my mag mount and see if anyone has an extra. If not then radio shack here I come.

 

[jazzsinger]

Whatever it was that you used as a continuity tester was DC powered, right?

RF is not DC, right?

What might appear as a direct short with a DC ohmmeter may not be anything of the sort when you test with RF at the proper frequency.

Some antennas, like a plain vanilla dipole, won't have continuity at the feedpoint. Other antennas, like the A99, have an impedance-matching system built in. It has a coil across the feedpoint, which at DC will read a very low resistance.

Luckily, not knowing these things only cost you a PL-259 and the time to install it. Grab an antenna book and check some of the basic antennas. Learn how they work.

What he said.

many antennas both base and mobile show dc shorts,more often than not to allow static a path to ground,but as beetle points out,rf isn't dc.

as for your pl plug,heat the tip (and solder holes if you soldered the shield) and yank the coax out,then holding your fingers over the solder holes in the body,reheat the tip and blow through the other end,making sure you have something to catch the solder that will come flying out otherwise it will go all over the carpet,(my ex used to love that part,pmsl),you then have a pl plug thats as good as new to reuse.

 

[Beetle]

Radio Shack PL-259s are generally a bit less than good. They might work in a pinch (which seems to be where you are at the moment ), but look for genuine Amphenol 83-1SP (the SP stands for silver plated).

Generally, look for a dull surface finish - that's how silver looks. If it's bright and shiny and pretty, it's probably nickel plated. Nickel doesn't solder worth beans. If your connector is shiny, do yourself a two-step favor:

1) Wire brush the areas you'll be soldering to. Brush them until you see the brass underneath. Brass solders nicely.

2) Find a source for Amphenol connectors and lay in a good supply. If you use smaller coax, like RG-8X, don't forget the adapters. They need to be silver plated as well as the main connector.

I've heard a rumor that Amphenol is using a tin plating on some of their PL-259s instead of nickel. Tin isn't as good as silver, but it's much better than nickel (and tin is already an ingredient in the solder you should be using).

 

[mackmobile43]

Radio Shack PL-259s are generally a bit less than good. They might work in a pinch (which seems to be where you are at the moment ), but look for genuine Amphenol 83-1SP (the SP stands for silver plated).

Generally, look for a dull surface finish - that's how silver looks. If it's bright and shiny and pretty, it's probably nickel plated. Nickel doesn't solder worth beans. If your connector is shiny, do yourself a two-step favor:

1) Wire brush the areas you'll be soldering to. Brush them until you see the brass underneath. Brass solders nicely.

2) Find a source for Amphenol connectors and lay in a good supply. If you use smaller coax, like RG-8X, don't forget the adapters. They need to be silver plated as well as the main connector.

I've heard a rumor that Amphenol is using a tin plating on some of their PL-259s instead of nickel. Tin isn't as good as silver, but it's much better than nickel (and tin is already an ingredient in the solder you should be using).

Yes unless it's silver I lay a flat bastard mill edgewise and take it down to brass especially where you solder through to the shield area of the pl-259 and if you have a small drill bit run it through those same holes for an extra added feel of confidence.

Make sure to cut your shielded portion of the coax as closely to the end of the end of the insulated area as possible to insure that you maintain the coaxes 50 ohm status, I also sweat the shielded area of the coax prior to inserting it into the pl-259