Base Antenna Help

[Marconi]

Ok STD, I understand what you are saying now. You just made a device that replaced the fixed wire tuner with one that had some adjustment capability in it. It is generally better to be able to tune an antenna rather than have one fix-tuned. I guess that would work to tune out some reactance the manufacture did not count on. Good business if the position (location) of the original parallel tuner did not play a resonant role in the design.

Couldn't you just as well have opened the wire tuner at the top and add some extra length and used an adjustable strap across it to tune up and down a bit to do the same thing? Or is that basically what you did with your u-shaped loop?

In the case of Jays I-10K, I have the feeling that the spacing relationships of all tuner elements in and around his tuner are important. In particularly the relationship the tuner has to the ground plane radial where it is ultimately attached.

 

[Jay in the Mojave]

Hello 225 in the Great Lakes:

It sounds like the Top Hat Radials are not installed, this will make the antenna work at a higher frequency. Or as Master Chief mentioned the vertical element is too short.

The Top Hat wires where made from aluminum rod about .12 inches in dia, and where 10 inches long. And there where 4 ea of them. I have used false ceiling hanging wire avialable at home improvement stores as the wire, made them 20 inches long, made into a 90 degree cross, and soldered to a flat washer.

The Mastadon 5K was a prototype antenna, only 12 where made and tested. Some prototype testers where paid to test and compare the antenna with other antennas as I did, and the data was compared. This justified the cost of starting up the production of the Interceptor 10K Antenna.

So no parts for the Mastdon 5K are avialable, and would be really expensive and time consuming to make again.

Hope this helps.

Jay in the Mojave

http://www.a1antennas.com

 

[Marconi]

Hello Jay. If the description that STD gives us for his Mastdon is pretty close to what you did with your's, then you ultimately changed the antenna quite a bit to come up with the I-10k, right?

Is that basically what you did in desiging your Mastdon, change the tuner to make it tunable?

 

[Master Chief]

If I may, yes the I-10K is MUCH different from the M-5K!

As I have said in the past, a 5/8 is a 5/8 is a 5/8, electrically speaking. If you choose to use a 14ga wire or 1" tubing, once the correct electrical lengths are worked out, they will perform about the same.

Mechanically speaking, the use of different materials and "stepping" the elements correctly will make a HUGE difference with the ability of an antenna to survive the elements.

Therefore, the "magic" is in the matching section! You need a way to match the feedpoint of the antenna to a 50-ohm coax feedline. Some matching networks are more efficient than others. Jay realized that the M-5K system was still a bit lossy and came up with a better design!

The more signal you can get into the antenna, the better it will perform! Jay's antenna does this exceptionally!

To better clarify this point, we have a local here who's I-10K is 500' from his shack. He is using Heliax to feed the antenna. Although Heliax has less loss than regular coax, it is still lossy at those lengths! We are going to do some tests to feed it with a balanced line (almost ZERO loss) instead of the long run of heliax. The military has been using balanced feedline to feed MEGAWATT antenna systems for years!

Since a 5/8 is a 5/8, we only need to modify the matching network to feed it with balanced line instead of unbalanced coax and still have the excellent performance of this 5/8 antenna.

If you want a ready to go antenna that is both electrically efficient and mechanically strong, the I-10K is the way to go! If the M-5K was available, it would have been less efficient and not performed as well as the I-10K.

 

[225inthegreatlakes]

Hello, Jay in the Mojave
Yes you are right the very top four hat radials are missing on the antenna so this exsplains why the antenna was not matching up correctly even though I had everything else at the correct length etc. We will either try your suggestion with the false ceiling hanging wire or maybe try and find a longer top element to bring the swr down on 27 mhz. as long as the antenna will work properly without the top four hat radials?