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Author Topic: New Antenna Not Working  (Read 2309 times)
AB1TS
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Posts: 14




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« on: August 22, 2013, 08:42:05 PM »

I just put up a G5RV antenna that I bought because I didn't want to hassle with trying to make it myself. I thought I would save myself some time. However, when I hooked it up today I was getting a high swr as in above 4 on all frequencies but 20m and that one wasn't great. I have the antenna about 35 feet up, maybe a bit higher and it is connected to about 100 ft. of RG-8, which is connected to my antenna tuner.
Here is my guess as to why my swr is so high that not even my tuner can correct it. I think that it is my pl-259 connectors. I soldered them on, but never felt comfortable with them. I struggled to get the solder to flow into the holes so I did the best I could.
Does anyone think that this is probably my problem? Could a bad solder job cause the problems I am having?
Any help is appreciated!
Sean
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K7KBN
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Posts: 2753




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« Reply #1 on: August 22, 2013, 08:56:53 PM »

Very well might.  Did you check continuity end to end and for open circuit center to shield?

What are the specs on your iron?  (It IS an iron, not a gun, right...?)
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73
Pat K7KBN
CWO4 USNR Ret.
KI4DSC
Member

Posts: 65




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« Reply #2 on: August 22, 2013, 09:09:47 PM »

If you have question about your feed line I would start there.  First use an ohm meter and put one side on the center and the other on the shield.  You should have an open.  If you have a closed circuit (the shield and center are connected) you found your problem.

Next check that you have connectivity between the center on both ends of the cable and then the shield.  (assuming you can get the antenna end and the radio end of the cable in hand at the same time.  

connect the cable to a 50 ohm dummy load and check the swr.  If it is way off still you have a cable problem.

You can over heat the connectors when you are trying to solder them.  Don't use cheep connectors!  I use Amphenol connectors and have had no trouble.  They cost about $4-$5 each.  

I don't know your background in soldering but I will give you a few quick tips.
1. Use flux
2. Use 60/40 solder not 40/60.  The 60/40 has more tin and a much lower melting point 360 degrees vs 460 degrees.
3. Use nice thin solder and don’t over heat your connector.

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WH7DX
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Posts: 1029




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« Reply #3 on: August 22, 2013, 09:15:43 PM »

I just put up a G5RV antenna that I bought because I didn't want to hassle with trying to make it myself. I thought I would save myself some time. However, when I hooked it up today I was getting a high swr as in above 4 on all frequencies but 20m and that one wasn't great. I have the antenna about 35 feet up, maybe a bit higher and it is connected to about 100 ft. of RG-8, which is connected to my antenna tuner.
Here is my guess as to why my swr is so high that not even my tuner can correct it. I think that it is my pl-259 connectors. I soldered them on, but never felt comfortable with them. I struggled to get the solder to flow into the holes so I did the best I could.
Does anyone think that this is probably my problem? Could a bad solder job cause the problems I am having?
Any help is appreciated!
Sean

Buy a cheap volt ohm meter for $15 and do a ohm check on both sides.  Check center and shield.  I had one coax I made short at connector.  That God I checked that one first.   It was on 160m dipole going in tree!   I accidentally grounded it.   It might be bad connection or short.   Either way it will show up.  Should be same resistance touching probes as center to center etc.
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NY7Q
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Posts: 16




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« Reply #4 on: August 23, 2013, 07:14:00 AM »

This situation is exactly why we need the NOVICE ticket brought back.
It is pitiful that an extra class cannot solder a pl-250
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N0IU
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Posts: 1235


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« Reply #5 on: August 23, 2013, 07:45:42 AM »

It is pitiful that an extra class cannot solder a pl-250

...or preview their posts and proofread them before posting!
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W5DXP
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« Reply #6 on: August 23, 2013, 08:01:58 AM »

... I was getting a high swr as in above 4 on all frequencies but 20m ...

A G5RV works well only with a wide-range antenna tuner and then only well on 80m, 40m, 20m, and 12m.
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73, Cecil, www.w5dxp.com
The purpose of an antenna tuner is to increase the current through the radiation resistance at the antenna to the maximum available magnitude resulting in a radiated power of I2(RRAD) from the antenna.
KC4MOP
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Posts: 728




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« Reply #7 on: August 23, 2013, 08:16:36 AM »

PL259's are not easy connectors to deal with.
Solder flux and the hottest (300Watt??) Weller gun you can buy is the way to solder very quickly. An ohm meter test will probably show you have a short in the shack or at the feed point.
And I read that the G5RV is not a resonant antenna.Huh? I'm not a guru on antennas and never experimented with a G5RV. I thought it was originally designed for 20M..........dunno... I see you're trying to get the tuner to be happy and it's not!
Here is a link to a credible source about your G5RV and there are several approaches to make it accept RF energy from your radio.

http://www.w8ji.com/g5rv_facts.htm
There shudda (on purpose typo) been information from the company about the complexities involved with a G5RV.
Fred
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K1ZJH
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Posts: 884




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« Reply #8 on: August 23, 2013, 08:43:48 AM »

Some of the less expensive PL-259 connectors are nickel plated, and soldering them can be a challenge!  It takes a lot of heat and patience to get the solder to flow and adhere to the nickel plate. I've had much better luck using silver plated PL-259s. They cost a bit more, but they've kept my blood pressure in check. Regardless, there is a learning curve, and using the right iron makes a big difference.

I've gone over to the crimp style fittings... there is a bit of investment needed for the proper tools, so it may not be practical for a onesy twosy user. 

Pete
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WX7G
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Posts: 5908




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« Reply #9 on: August 23, 2013, 08:50:38 AM »

The connector idea is a Red Herring. UHF connectors either work or they don't and the 4:1 VSWR tells us that your connectors do work.

You have an antenna tuner and that will tune the G5RV and get you on the air.

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KB4QAA
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Posts: 2236




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« Reply #10 on: August 23, 2013, 09:00:51 AM »

This situation is exactly why we need the NOVICE ticket brought back.
It is pitiful that an extra class cannot solder a pl-250
Installation training on PL-259's was never part of the Novice curriculum or tests.  But buying a copy of the ARRL Handbook is quite helpful.
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N3QE
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Posts: 2028




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« Reply #11 on: August 23, 2013, 09:05:46 AM »

It is pitiful that an extra class cannot solder a pl-250

...or preview their posts and proofread them before posting!

I'm actually more disappointed with the fact that PL-259's still exist and that new and old hams have to struggle with them.

Either they don't get the connector hot enough to solder it, or in the process of getting the connector hot enough they completely melt the coax dielectric and end up with a short.

The crimp-on PL-259's are a real advantage but only if the guy has the right crimp tool. A local "new extra" I still have to go over to his house and resolder or recrimp his connectors every time he changes something. I think he feels a little sheepish about asking for help. But really it's not his fault, it's the fact that it's so easy to do it wrong.
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W5DXP
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« Reply #12 on: August 23, 2013, 09:25:48 AM »

Either they don't get the connector hot enough to solder it, or in the process of getting the connector hot enough they completely melt the coax dielectric and end up with a short.

For all my coax needs, I use 0.2" RG-400 Teflon coax with screw-in size reducers for the PL-259s. Teflon used with those reducers make soldering mostly foolproof and they also work with RG-58 and RG-8x. Otherwise, I use ladder-line.
« Last Edit: August 23, 2013, 09:35:30 AM by W5DXP » Logged

73, Cecil, www.w5dxp.com
The purpose of an antenna tuner is to increase the current through the radiation resistance at the antenna to the maximum available magnitude resulting in a radiated power of I2(RRAD) from the antenna.
N6AJR
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Posts: 9879




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« Reply #13 on: August 23, 2013, 12:21:29 PM »

I am an extra and never had a novice, I started as a "2 meter tech" in 1978,   And I hate doing UHF connectors.  I finally went to a complete crimp system because I got tired of fighting the others. The G5RV is a pretty good  antenna that works well on 20 meters and will work in some spots on other bands, depending on frequency. so you may not have a problem at all.  borrow a MFJ 259b and sweep all the bands and see what is really up.
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AB1TS
Member

Posts: 14




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« Reply #14 on: August 23, 2013, 01:55:29 PM »

Well, I took out my coax and put new connectors on and tested the cable and the connectors. Everything is good there, thanks for the tips on soldering them. I have a Hakko soldering iron that allows me to bring the temp up all the way to 900 degrees F. I set it at 775 degrees. I found that things went along much better using a vice to hold the cable and 75mm solder. the smaller stuff was easier to work with.  After  connecting everything again I have found that I did see some improvements on 80, 40, and 20. Everything else is still to high.
I guess I should have mentioned that I am using a IC-706mkII with an Icom AT-180 tuner.  I was expecting that the tuner would do a better job. Even on 20 it seems that it struggles to bring the reading to 2. I am beginning to wonder if there was something wrong with the tuner.

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