I have a Penetrator 500 base antenna that I am trying to get a good swr for 27 mhz. I put the antenna together just like it says to do with the directions but when I check it with my antenna analyzer it has a 1.1 swr on 28 mhz. But a 2.5 or 3.0 swr on 27 mhz.so I moved the top element of the antenna up and down with no results any suggestions?
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Base Antenna Help
- Thread starter 225inthegreatlakes
- Start date
I believe they made two different Penetrator antennas. Can you describe the one you have.
One shows a length of 193.125" length and the other shows 196".
I got my doc's from someone else and he noted on the documents that one was for 23 channel and the other was for 40 channel. The way he has it marked the shorter one is marked 23 channel version. I would figure that the center of 23 channels would require a bit longer element, so I'm not sure he knew what he was talking about.
They both show different kinds of hardware and they may be matched differently, but not sure on the matching thing.
The only thing I know is that there are two different sets of docs for this model 500 from Hy-Gain.
One shows a length of 193.125" length and the other shows 196".
I got my doc's from someone else and he noted on the documents that one was for 23 channel and the other was for 40 channel. The way he has it marked the shorter one is marked 23 channel version. I would figure that the center of 23 channels would require a bit longer element, so I'm not sure he knew what he was talking about.
They both show different kinds of hardware and they may be matched differently, but not sure on the matching thing.
The only thing I know is that there are two different sets of docs for this model 500 from Hy-Gain.
As far as answering your question..... This antenna was designed for the CB band. The longer antenna would have been centered around 27.105 (23 channel) and the later antenna around 27.205.
As we see from Jay above, the only difference was in the length of the main element.
You analyzer is telling us the antenna is too short. I can only assume that you have all the right lengths of tubing. The only part you can tune on this antenna is the main element. Double check all tubing lengths.
The next issue would be (what I call) the hairpin. Is this part original? If it has been altered, then we have a problem Houston! This hairpin replaced the original printed circuit boards that Jay spoke about above. It needs to be the correct size to operate correctly!
Make sure all the elements and the hairpin are making a good electrical connection! I highly recommend using 3M plastic ScotchBrite pads to clean the joints! You can get the industrial ones at Home Depot. Steel wool is BAD!
I did a re-install of an I-10K for Snoop Dog's neighbor in Long Beach, CA. He swore up and down that all the measurements were right on. When I couldn't get it to match up, I took the antenna down and found that the top element was 10" too short. Double check all your measurements!
Also, try another piece of coax. Yours might be bad causing the bad reading.
As we see from Jay above, the only difference was in the length of the main element.
You analyzer is telling us the antenna is too short. I can only assume that you have all the right lengths of tubing. The only part you can tune on this antenna is the main element. Double check all tubing lengths.
The next issue would be (what I call) the hairpin. Is this part original? If it has been altered, then we have a problem Houston! This hairpin replaced the original printed circuit boards that Jay spoke about above. It needs to be the correct size to operate correctly!
Make sure all the elements and the hairpin are making a good electrical connection! I highly recommend using 3M plastic ScotchBrite pads to clean the joints! You can get the industrial ones at Home Depot. Steel wool is BAD!
I did a re-install of an I-10K for Snoop Dog's neighbor in Long Beach, CA. He swore up and down that all the measurements were right on. When I couldn't get it to match up, I took the antenna down and found that the top element was 10" too short. Double check all your measurements!
Also, try another piece of coax. Yours might be bad causing the bad reading.
Thanks for all the history on the antenna etc.I am sure I put all the elements together correctly,after all I am getting a good swr for 28 mhz. although that is not what we want ,Is there anyway this antenna was modified before I bought it or do you think the antenna needs cleaning if it is put together correctly?
It is always possible that the antenna was modified. Hopefully Jay will chime in here with the correct measurement of the "hairpin".
Again, the analyzer is telling us the antenna is too short. If there is excessive corrosion, the top element may be "insulated" from the rest of the antenna, although this is not very likely! Since it is working on 28MHz, it leads me to believe that the problem is something other than corrosion. Have you tried a different piece of coax yet?
If I was having this problem, I'd tear it all apart, measure each piece for correct length, clean, and reassemble. I'd also make sure I cleaned the hardware that connects the hairpin to the feedpoint and the element!
Again, the analyzer is telling us the antenna is too short. If there is excessive corrosion, the top element may be "insulated" from the rest of the antenna, although this is not very likely! Since it is working on 28MHz, it leads me to believe that the problem is something other than corrosion. Have you tried a different piece of coax yet?
If I was having this problem, I'd tear it all apart, measure each piece for correct length, clean, and reassemble. I'd also make sure I cleaned the hardware that connects the hairpin to the feedpoint and the element!
On my Penetrator I could not get any better match than 1.4 on the MFJ. I removed the factor Beta match ( the thing that looks like a water bottle holder hair pin thingy ) and constructed an adjustable matching circuit similar to what Jay did on the 10K. After that my match is 1.0 swr, 49 ohm , X = 0 with 99% antenna efficentcy.
ok I went through and checked all the measurements and they are all correct length m2 with expose of 52 1/8 m3 with expose of 49 3/8 m4 with expose of 44 1/2 and top radial assy of 50"
and the ground plane elements are r2 expose 30" and r3 exposed at 50. I did noticed it looked like one of the ground plane elements broke before it was a inch or so short so i just made it longer so it would be the right length if the ground plane elements have anything to do with the swr. I also noticed today it looked like one of those wires on the bottom of the antenna that looks like a coat hanger connected to one of the ground elements bolt to another bolt where the other coat hanger thing connects was broken before and the wire rebent to connect to the bolt. but everything else looks ok. still no luck with the swr. I took the top radial and lengthing it and shorten it but was unable to get a good swr for 27 mhz.
and the ground plane elements are r2 expose 30" and r3 exposed at 50. I did noticed it looked like one of the ground plane elements broke before it was a inch or so short so i just made it longer so it would be the right length if the ground plane elements have anything to do with the swr. I also noticed today it looked like one of those wires on the bottom of the antenna that looks like a coat hanger connected to one of the ground elements bolt to another bolt where the other coat hanger thing connects was broken before and the wire rebent to connect to the bolt. but everything else looks ok. still no luck with the swr. I took the top radial and lengthing it and shorten it but was unable to get a good swr for 27 mhz.
smalltiredart said:
How were you able to measure the efficiency of your antenna? Since approx 12" of the main radiator is inside the base clamp (ground), how did you compensate for the losses there?
Both the Avanti Sigma 5/8 and I-10K use an elevated feed to help minimize losses and I don't believe either of these two antennas are 99% efficient.
If I remember correctly (and I do), the I-10K was a significant upgrade over the original Mastadon 5000 concept which was nothing more than a Penetrator with an improved feed system like you used.
Master Chief, undoubtedly he would have had to build a whole new base setup as well as the tuner and just use the stinger. He would even have to redesign something to hold the ground radials.
You're exactly right he could not have just simply built a tuner like Jay and added to the antenna. Sounds like someone's been partyin’ too much. I sure would like to see a picture of that booger since I'm from Missouri.
You're exactly right he could not have just simply built a tuner like Jay and added to the antenna. Sounds like someone's been partyin’ too much. I sure would like to see a picture of that booger since I'm from Missouri.
Master Chief said:
Thats basically what I did is created a Mastadon 5000. Jay would not do it for me.
Marconi said:
I just took a piece of 3/8 alum. tube, with a piece solid alum. 3/8 o.d stock and bent a U shape. Attached it to the same points that the stock Beta match attached to. The top of the U slides on the solid stock and clamps with worm gear clamps. When on the MFJ and I slid the device up and down it gave me a different ohm and swr reading.
I have no clue what you are talking about re-designing the ground radial holder ? It uses the same one it always has.
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