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Author Topic: Antenna Analyzer needed  (Read 3772 times)
KD3RA
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Posts: 9




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« on: August 21, 2012, 06:26:13 PM »

Is there anyone around that would be willing to measure my antenna with an analyzer. I'm getting back into HF and haven't used my HF beam and VHF antenna's for almost 20 years. I would love to test the antenna first. I'm located in Levittown, Pa.

267-795-7704

Charlie
KD3RA
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N4JTE
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Posts: 1158




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« Reply #1 on: August 21, 2012, 10:24:50 PM »

Well welcome back, nothing basic you cant do at your radio, swr, etc.
The analyser thing just saves a lot of walking on simple antennas.
Bob
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KC4MOP
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Posts: 750




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« Reply #2 on: August 22, 2012, 04:40:07 AM »

Levittown, Pa, Sorry can't help. You are on the flip side of Pa. We are in Western Pa.
Hopefully someone closer can help.
I am guessing you want to fire back up your station and see what happens?? Equipment and antennas sitting for 20yrs?
Start with a dummy load to check out the radio(s) and do some sort of visual inspection of your coax. Give it a quick try. If you see extreme high SWR and very low power out from your radio then you will know that there is some maintenance needed on your antennas.
You might be lucky, but 20 yrs is a long time. Weather and time may have done its damage.

Fred
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W5DXP
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« Reply #3 on: August 22, 2012, 05:02:17 AM »

Is there anyone around that would be willing to measure my antenna with an analyzer.

I would first reduce power to a minimum, e.g. 10w, and using an SWR meter, see what the SWR on CW is. After that, you might or might not need an antenna analyzer.
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KD3RA
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Posts: 9




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« Reply #4 on: August 22, 2012, 06:39:21 AM »

Right now I have my old tower with a Hygain TH3MK3 and VHF beam at the top. The install is over 20 years old. I cut the wires at the base of the tower years ago to do work on the house. I reattached the Ham IV rotor box to the remaining cable at the bottom of the tower and low and behold the rotor still moves. Next moved on to putting a PL259 onto the coax. It was dark last night and I couldn't climb the tower. I only have one coax cable at the base of the tower. So I don't know if it going to the VHF or HF beam. I lowered the output of the FT-857D and tried the transmitter using both the VHF and HF antenna outputs. The FT-857D would not deliver any output. I measured the coax from ground to the center pin before anything and it measures open. So I'm assuming that the FT-857d is seeing such a high SWR that it will not transmit?

So my next move is to replace the coax to both beams and neww wire to the Ham IV rotor and start there.

Does this sound resonable?


Thanks,

Charlie
KD3RA
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KD3RA
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« Reply #5 on: August 22, 2012, 12:49:57 PM »

Well after some research I found the answer to the HF antenna. The TH3MK3 uses a beta match. Meaning that the match is connected to both driven elements and gets grounded to the mast at the other end. If you measure the DC resistance of the antenna it should show up as a short. I'm presently measuring an open. So somewhere the feedline or antenna is open. I already ordered new rotor cable and new coax to rewire. I jsut hav eot get up the nerve to climb a tower again. Hi HI.

Charlie
KD3RA
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W5DXP
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« Reply #6 on: August 22, 2012, 02:07:15 PM »

I jsut hav eot get up the nerve to climb a tower again.

Apparently you get nervous just thinking about it.Smiley
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K5KNE
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Posts: 65




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« Reply #7 on: August 22, 2012, 10:57:25 PM »

An antenna analyzer is what you need to find out what the antenna is doing. Can you hear anything on the receiver? If the hf antenna is working you should hear some signals on 40 or 20 meters. If the coax is going to a vhf antenna, you won't get very good signals on hf, but should be able to hear some repeaters on 2 meters.

Is the transmitter in the CW, FM or AM position when testing for output? If you have an swr meter it should read something foward if the transmitter is working. Then try reflected and see if it is lower than the foward reading. If it is the same you do have either an open coax connection, short or something wrong with the antenna. Keeping the power low a cheap dummy load will work fine to check the transmitter. It should put out something on transmit.

Coax does go bad especially if it gets water in it. Small coax like RG-58 and RG-59 can deteriorate so that no signal will go thru it. Assuming that you have RG-8 and it was just cut off and laid on the ground for years - it probably has had water in it unless you taped up the cut off.

Putting some new coax to both antennas would be a good idea as old as your existing coax is. If that doesn't solve the problem - you still have improved your antenna situation and won't have to wonder if the coax was pretty bad. Taking the beams down is a big deal, but would certainly be a good project. There are a number of connections that probably corroded and need cleaning up for the antenna to work right. Again, a clean antenna should work as good as when it was new.

Investing in a good analyzer is worthwhile. The MFJ-259B and similar types are easy to operate and will tell the resonant frequency and SWR by simply turning a knob. IT is far better than making a series of tests on different frequencies looking for the lowest SWR.
You might contact someone in one of the radio clubs in your vicinity and they probably have someone who will be willing to help you.

Good Luck.  Walter  K5KNE
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KC4MOP
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Posts: 750




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« Reply #8 on: August 23, 2012, 04:33:24 AM »

Do NOT climb the tower if you feel a little shakey. Try to find a professional or a fellow Ham who will have to inspect the tower for safety before climbing. Many bad things happen when exposed to Ma Nature, and 20 yrs to boot!!
I was hoping you would fire the radio into a dummy load before throwing power to a questionable load. It lets you know that the radio survived 20 yrs of sitting and that the transceiver is in good health.

Fred
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KD3RA
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Posts: 9




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« Reply #9 on: August 23, 2012, 05:45:15 AM »

Walter and Fred thanks for the great advice.

1. I'm not afraid to climb just making fun of it. I have good safety equipment and went up the tower two weekends ago to replace all of the guy wires with new cable. I wanted to get the tower back in shape first.
2. Next test was to splice the Rotor control box back into the cable at the base of the tower. Rotor turned and position meter worked fine.
3. Resoldered a new PL-259 on the RG-8 coax after cutting a few feet off the old end. Measured the continuity to make sure there was no short (Measured open). Later found out that since the TH3MK3 has a beta match and this should really measure close to zero ohms. (Zero ohms plus the coax cable DC resistance for 80 ft).
4. Set the FT-857D outpuut for the lowest output (5W). Measured the SWR with a Daiwa dual hand SWR meter.
5. No output from the FT-857D. I'm assuming it thinks it was seeing an open circuit.
6. Just ordeder some resistors to make a dummy load.
7. Ordered new coax and new replacement rotor cable.
8. Made a work platform for the tower.
9. The radio is a new Ft-857D Yaesu.


I should have the wire and cable this weekend. I'll keep you posted.

Thanks,

Charlie
KD3RA

 
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KC4MOP
Member

Posts: 750




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« Reply #10 on: August 24, 2012, 04:05:53 AM »

OK Charlie
Welcome back. Amateur Radio is still going strong.
It reads that you have had a plan in place for a while now and the new radio was a good choice.
I still have my TS440 from 1987 and I know there is better and more whistles and bells. I like my simple radio.

Fred
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KD3RA
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Posts: 9




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« Reply #11 on: August 24, 2012, 04:18:47 AM »

Fred,

I'm excited to get back into the hobby. I started 30 some years ago but an auto racing hobby took president until 4 years ago when I got out of the hobby. I've always kept the tower waiting for a good time to get back into Amateur radio.

I used a TS-820 in my early years but these new rigs are really nice. I just got the CAT cable for the FT857D and HRD software. What a difference working the radio from the computer screen.

I just finished making a antenna tower work platform and look forward to getting the coax and rotor wires replaced this weekend.

Charlie
KD3RA
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KD3RA
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« Reply #12 on: August 27, 2012, 08:38:18 AM »

Just to give everyone an update. I climbed the tower over the weekend anf had great success! First I removed all the old coax and rotor cable. Rotor cable was replaced and a new run of coax was installed on the beam. It took some manuvering to get to the wire connections on the beam. I welded up a new work platform and installed it right below the beam. While I was there I took down an old 2-meter beam. It was really too close to the HF beam anyway. Once I got it down I could see the PL-259 was all corroided anyway.

Late last night I was able to get the coax and rotor cable installed in the radio room. As soon as I turned the radio on I could hear signals. 20 meter was good and I made ny first contact on HF in over 20 years with KH6LC (Hawaii).

Next up is something for 40 and 80 meters.

Charlie

KD3RA
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K5KNE
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« Reply #13 on: August 30, 2012, 03:28:25 PM »

I am glad that you found the problem and are back in business.

Have Fun   K5KNE
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WA8UEG
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Posts: 388




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« Reply #14 on: August 31, 2012, 05:00:55 AM »

Good to see your back on the air again and the antenna is working. Your just a bit to far from me I believe, I am in Tannersville (near Stroudsburg). I have a Autek which is not the best on the market but gets the job done and is great if your going to trim dipoles. If your up in this area I would be happy to loan it to you for a few weeks as I'm in good shape on antennas. It is HF only and does not cover the VHF bands.
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