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added calculation for added length.
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user9425
user9425

First you don't necessarily have to do anything. The SWR is below 3 for the bands and most transceivers can handle that OK.

If you want to try to get the resonate points inside the bands you will need to lengthen the wire. it is usually a good idea to start with too much wire and trim the length to bring the resonance down, but in your case it look like the wire is too short.

Ideally solder additional wire on the end and cover it heat shrink, then cover that with water proofing sealant. However you could get very similar results with a simple crimp splice or even just mechanically connecting the wire. If you don't provide some protection from the elements the connect will eventually corrode.

In theory you should be able to calculate the exact length of wire you need. In practice it is difficult to account for all of the factors. Everyone I know of doing wire antennas makes them long and trims them as need to get the resonance.

Currently the antenna is resonate at about 7.7 Mhz. You would like it to be resonate at 7.1 Mhz. Take the old resonate frequency divided by the new resonate frequency and multiply by the original length, (7.7/7.1)*65 = 70.5 or so. The result is about 70.5 feet which would have you adding 5.5 feet to the existing antenna.

I would probably add about 7 feet and trim as needed to get the resonates where i want it.

First you don't necessarily have to do anything. The SWR is below 3 for the bands and most transceivers can handle that OK.

If you want to try to get the resonate points inside the bands you will need to lengthen the wire. it is usually a good idea to start with too much wire and trim the length to bring the resonance down, but in your case it look like the wire is too short.

Ideally solder additional wire on the end and cover it heat shrink, then cover that with water proofing sealant. However you could get very similar results with a simple crimp splice or even just mechanically connecting the wire. If you don't provide some protection from the elements the connect will eventually corrode.

In theory you should be able to calculate the exact length of wire you need. In practice it is difficult to account for all of the factors. Everyone I know of doing wire antennas makes them long and trims them as need to get the resonance.

First you don't necessarily have to do anything. The SWR is below 3 for the bands and most transceivers can handle that OK.

If you want to try to get the resonate points inside the bands you will need to lengthen the wire. it is usually a good idea to start with too much wire and trim the length to bring the resonance down, but in your case it look like the wire is too short.

Ideally solder additional wire on the end and cover it heat shrink, then cover that with water proofing sealant. However you could get very similar results with a simple crimp splice or even just mechanically connecting the wire. If you don't provide some protection from the elements the connect will eventually corrode.

In theory you should be able to calculate the exact length of wire you need. In practice it is difficult to account for all of the factors. Everyone I know of doing wire antennas makes them long and trims them as need to get the resonance.

Currently the antenna is resonate at about 7.7 Mhz. You would like it to be resonate at 7.1 Mhz. Take the old resonate frequency divided by the new resonate frequency and multiply by the original length, (7.7/7.1)*65 = 70.5 or so. The result is about 70.5 feet which would have you adding 5.5 feet to the existing antenna.

I would probably add about 7 feet and trim as needed to get the resonates where i want it.

Source Link
user9425
user9425

First you don't necessarily have to do anything. The SWR is below 3 for the bands and most transceivers can handle that OK.

If you want to try to get the resonate points inside the bands you will need to lengthen the wire. it is usually a good idea to start with too much wire and trim the length to bring the resonance down, but in your case it look like the wire is too short.

Ideally solder additional wire on the end and cover it heat shrink, then cover that with water proofing sealant. However you could get very similar results with a simple crimp splice or even just mechanically connecting the wire. If you don't provide some protection from the elements the connect will eventually corrode.

In theory you should be able to calculate the exact length of wire you need. In practice it is difficult to account for all of the factors. Everyone I know of doing wire antennas makes them long and trims them as need to get the resonance.