[Top] [All Lists]

[TowerTalk] Improving the 402-CD (was Weatherproofing for copper coils?)

To: <>
Subject: [TowerTalk] Improving the 402-CD (was Weatherproofing for copper coils?)
From: (
Date: Sat, 1 Sep 2001 10:07:10 -0600
On Sat, 1 Sep 2001 10:29:45 -0400 (EDT) Steve Miller
<> writes:

> > Why re-invent the wheel?  
> Because I want a better wheel.
> I plan to use large 4'5" diameter coils (sic)

        I don't think the elements will support 4 FOOT 5 INCH
        diameter coils !   N4KG  :-)

> CC 402-CDs work fairly well, but they can be improved.  

        How far below a FULL SIZE 2L Yagi is a 402CD
        in gain?  Maybe 1 dB?

        How much improvement can you expect from
        a shortened (loaded) Yagi, even with Lossless coils?
        My guess is you might get close to 1 dB more gain
        but you will still have limited bandwidth due to loading.
        Have you considered plating the coils?

        Note that F/B and GAIN typically do NOT peak with
        the same tuning / spacing of the elements.  To achieve
        peak F/B, gain is usually reduced by around 1 dB.

        The exceptions to this rule of thumb are for 3L Yagi's
        on a 0.25 WL boom or 4,5,6L Yagi's on a 0.75 WL boom
        where gain and F/B tend to peak at the same frequency.

        If F/B is a major concern, the best solutions are to either
        stack a pair of 2L Yagi's or go to a 3L Yagi, optimized
        for F/B (typically 7.0 - 7.5 dBi free space gain) on a 
        35 ft boom for 40M.  Going to a 48 ft boom (0.35 WL)
        will yield another dB of gain at somewhat less F/B.

        Tom  N4KG
> My design started with the CC-402 and used AO to optimize a better 
> design
> (not just better coils) that fits within the 402-CD turning radius.  
> Using 
> high Q coils, it has about 1 dB more gain and 5 dB better 
> front-to-rear 
> on CW compared to the original CC-402CD assuming 402-CD coil Q of 
> around  200. A slightly lesser improvement is seen on SSB. 
> Hope this helps,
> Steve

Juno offers FREE or PREMIUM Internet access for less!
Join Juno today!  For your FREE software, visit:

List Sponsored by AN Wireless:  AN Wireless handles Rohn tower systems,
Trylon Titan towers, coax, hardline and more. Also check out our self
supporting towers up to 96 feet for under $1500!!

FAQ on WWW:     
Administrative requests:

<Prev in Thread] Current Thread [Next in Thread>