Adjusting Cushcraft R10 for 11 meters?

[Spirittalk]

I picked up a very cheap Cushcraft AR10 on ebay.

I would like to know the best way to adjust it for working on 11 meters band.

I have the ATU MFJ904 but wonder if there is another way of adjusting it from the antenna end ?

A half wave length vertical for 11 meter band is 17:3 feet, the cushcraft measures 17:5 feet.

How much power PEP am I likely to loose from an umatched antenna tuned via a tuner?

Should I cut 2 inches from the top of the antenna or is there another method to make adjustments antenna end ?

I am studying for my M3 callsign at the moment so wouldn't want to cut the antenna too much antenna end, rendering it useles for when I finaly get licensed to use 10 meters.

Will the MFJ904 tuner , tune 11 meter band and then allow me to use it on 10 meters when I have passed the associated radio amateur ticket?

I have even managed to tune a G5RV on to the 11 meter band with this ATU and that is miles out length wise?

 

[Master Chief]

A half wave length vertical for 11 meter band is 17:3 feet, the Cushcraft measures 17:5 feet.

Should I cut 2 inches from the top of the antenna or is there another method to make adjustments antenna end ?

I am studying for my M3 callsign at the moment so wouldn't want to cut the antenna too much antenna end, rendering it useless for when I finally get licensed to use 10 meters.

Will the MFJ904 tuner , tune 11 meter band and then allow me to use it on 10 meters when I have passed the associated radio amateur ticket?

First off, the LOWER the frequency, the LONGER the antenna. So, you will need to LENGTHEN the top element to make it work on 11-meters. The ring should also be longer (of a larger diameter) and you will have to move the tap in order to match the antenna to the feedline.

I don't know where you got that "17:3" number but the electrical length of an antenna depends on the diameter of the tubing or wire and the "step schedule". In other words, an electrical half wave of 14 guage wire will be physically LONGER than an electrical half wave of 1" tubing. A stepped element (varying sizes of tubing that slide inside of each other) will fall somewhere in between.

I don't have the specific measurements for you, but I'd start with a top element that is at least a foot longer and start experimenting. The amount of overlap (tip inside of the next larger element) will not matter. The only important number is the "exposed length".

Once the antenna is built and working correctly, make a mark on the top element where it meets the next size element, measure 4" down, and cut of the excess. This will reduce weight at the top of the antenna (I do this with the I-10K antennas I install, although this does prevent me from ever using this on a lower frequency).

A tuner will work fine, but you loose efficiency.

 

[Spirittalk]

Thanks, I got 17:3 from an online antenna calculating system that gave 27Mhz frequency as 17;3 feet re-occuring as the hlaf wave length on 11 meters.

The measurement calculated was 17:333333333 feet.

 

[W5LZ]

Spirittalk,
The figure you got from the calculator is correct, as far as it goes. What most calculators don't ask you make that calculation only a close approximation. One of the things they don't usually ask is the diameter of the conductor used, which can make a difference. That 17.3~ figure also leaves a bit of 'playing' room so that the antenna can be trimmed for resonance, which means that the length is just a bit too long. (Much easier to cut it off than to add to, you know?)
The 'exact' length for the antenna can change from one location to another. Not huge changes, just fairly small ones, which depends of course on where you want the thing to work 'best'. It really isn't all that complicated, just not as 'simple' as it's made out to be at times .
Until you do get that license I think I'd leave the thingy as is and just use the tuner. A tuner usually means a small loss of power, but in most instances it isn't enough to worry about at all. If what you are trying to 'tune' is ~really~ unreasonable, sure, there can be a noticeable loss in power. But, power isn't everything!
Good luck.
- 'Doc

(Understand the UK has made licenses good for 'life' now. They still have to be 'renewed' periodically, so it sounds like just the 'price' has changed?)

 

[Spirittalk]

Thanks all

I am studying for the exam at the moment and will be taking the M3 part of the exam in the next couple of moths when the examination date is organised ty