Sandbagger
Administrator/The Boss
Posts: 6,250
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Post by Sandbagger on Jan 30, 2022 17:41:39 GMT -5
I just came Across this very same antenna. I cannot get the SWR lined out and I’m thinking the coil is bad at the bottom. I cannot find a manual for this but I’ve been told that the radiator length is 22.6 inches like the penetrator 500. It has been hanging since the 80s when I found it so I had to do a lot of scrubbing to get the oxidation off. Do you happen to have a manual for this antenna? If not, have you ever had experience replacing or rebuilding the coil? Thank you If the antenna's dimensions are correct, what is the SWR? Is it "slightly" off like 2:1 or less, or is it way off like higher than 4:1? Slightly off, and you could conceivably tune it by changing the length of the radiator. If the SWR is way off, it's likely that there is a problem with the matching coil. It could have been damaged by pushing too much power through it, or it might have taken a lightning strike, or maybe corroded from age. I have never dissected that particular antenna, so I don't know if the matching circuit is an etched PC board helical coil, like the older RS "Colinear" 5/8th wave, or whether they used an actual wire coil. The only way to know for sure is to drill out the rivets in the base and look inside.
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Post by 550ozarks on Jan 31, 2022 2:07:13 GMT -5
Just found a brand new Radio Shack CrossBow .64 wave ground plane. Over 22ft long with 4-9ft radials. Best antenna I owned back in the day. Was looking for quite some time. And one turned up. ;D That antenna looked very much like a Hy-Gain Penetrator, same basic dimensions. The big difference was that the Penetrator used a Gamma match while the RS used a coil in the base. That coil will probably limit your maximum power to 400 watts or less. Still it was a decent performer.
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Post by 550ozarks on Jan 31, 2022 2:08:22 GMT -5
That antenna looked very much like a Hy-Gain Penetrator, same basic dimensions. The big difference was that the Penetrator used a Gamma match while the RS used a coil in the base. That coil will probably limit your maximum power to 400 watts or less. Still it was a decent performer.
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Post by 550ozarks on Jan 31, 2022 2:10:45 GMT -5
I’m checked the coil with an ohm meter and it showed continuity from the coax connector to where the bolt secure the radiator to the coil. If it has continuity, does that mean the coil should be good? Or can it show continuity and the coil will be bad? The SWR is just passed three in the red. I’m not sure on the length of the main radial. I was told 22’6”.
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air1
Ratchet Jaw
Posts: 70
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Post by air1 on Jan 31, 2022 9:52:50 GMT -5
I have one of those in the air. The center vertical is 22' 7" long. I have never been able to find a manual. In 1978 when they came out I helped my friend put his up and I'm sure it had a manual. Not much to them though. Just put the screws in the holes, and it's good to go. The coil was gone in mine when I got it, so I used the matching rod, it's two rod supports and the beta rod and from a Penetrator 500. Just had to drill 2 holes for the screws to hold the supports to the vertical element. Then another one through the bottom insulator to install a bolt to connect the rods on the outside and the wire on the inside from the antenna connector. You may be able to purchase the parts as this antenna is still being produced. The upper insulator, if needed, and lower insulator (base assembly) will both fit the RS .64 antenna. Just look at a manual for the P500 to see how it is put together. Or you could fab up your own like others have done. A coil can show continuity and still not work correctly. That happens to transformers sometimes. The important thing is to know what the resistance is supposed to be and probably the only way to find out would be to have someone measure a known good one. Could be crud under the lower insulator causing a problem, or the screw that contacts the vertical element is not making good contact. Might just require a good cleaning, especially on the inside and outside of the joints of the elements. There are compounds that can be used to coat the joints to help prevent oxidation and allow them to slip together and come apart easier. I put some window/door 50 year silicon on the bottom of the base insulator and around all the element joints and screws when I put it together to keep out the moisture.
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Sandbagger
Administrator/The Boss
Posts: 6,250
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Post by Sandbagger on Feb 1, 2022 16:47:46 GMT -5
I’m checked the coil with an ohm meter and it showed continuity from the coax connector to where the bolt secure the radiator to the coil. If it has continuity, does that mean the coil should be good? Or can it show continuity and the coil will be bad? The SWR is just passed three in the red. I’m not sure on the length of the main radial. I was told 22’6”. An ohm meter will only tell you a small portion of the story. Yes, if it showed an open circuit, that would be a big red flag. But showing continuity does not mean that the coil's inductance is correct. You should also see a DC short to ground as well, as the "coil" is actually an impedance transformer, so there will be path to ground, usually fewer turns than the path to the radiator. Still, your best bet would be to take the base apart and visually inspect the matching coil to determine if it's intact or is suffering from some "ailment".
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