[TowerTalk] CUSHCRAFT R7000+

[Bill Coleman]

On 12/4/00 12:55, JORGE DIEZ - CX6VM at cx6vm@adinet.com.uy wrote:

>    Only one problem, some aluminium tubes are so short to be adjusted to
>our 40 mts cw portion of the band (7.000-7.025), so only few inches are into
>the other section, so I am afraid in the future, with some winds, the
>vertical will be damage at this point.

Cushcraft may not tell you this, but there are several versions of the 
R7000.

The earliest versions had three identical BD tubes of 12" in length. This 
was a little short to tune the bottom end of 40m. So in late-1996, 
Cushcraft substituted a 18" tube for the top section. This made it much 
easier to tune.

In Mid-1998, Cushcraft changed the design again, going to slightly 
different traps. The main reason for the trap changes was to reduce 
manufacturing variability. With this change, the one BD tube went to 5" 
and the two BE tubes became 16". The BE tubes go on the top two traps, 
and the BD tube between the lower two traps, changing the dimensions of 
the antenna. Cushcraft also added the reinforcing BH and BI rods around 
the bottom CT1 trap. Previously, this modification had only been part of 
the 80m kit. But, due to some failures in the field, this reinforcing was 
added to all antennas.

Cushcraft made some hardware changes in mid-1999, but no substantial 
physical changes.

>    Now I have at my garake the 80 mts kit and have a question:
>
>    the manual says that I must modify all the dimensions of the R7000 when
>I add the 80 mts section.

Follow the manual. Adding the 80m section changes the loading of he 
antenna slightly. Also the given dimensions may be more optimal for the 
design.

>    I tought that I not need to modify the 10-40 mts R7000 and only add the
>80 mts kit up the final section.

Follow the manufacturers recommendation.

The R7000 resonance is primarily controlled by the trap frequencies. The 
actual dimensions of the antenna make only a small difference.



Bill Coleman, AA4LR, PP-ASEL        Mail: aa4lr@arrl.net
Quote: "Not within a thousand years will man ever fly!"
            -- Wilbur Wright, 1901


--
FAQ on WWW:               http://www.contesting.com/FAQ/towertalk
Submissions:              towertalk@contesting.com
Administrative requests:  towertalk-REQUEST@contesting.com
Problems:                 owner-towertalk@contesting.com