Thank you Mike for your summary. I might point out that the Un-Uns that
Mike used are the precursor to what has become the Mini-StackMatch, and
the "Stackmaster" he speaks of is actually the StackMatch made by me.
To see some of Mikes towers look on my website in the User's group
section.
It was a fun project, and now he has some competition, N5CQ put up 6
C3+C4 Tribanders, and uses the same products to feed the 6 C3s, and a
StackMatch to pump power in the 3 C4, 40meter sections. This all on a
199 ft rotating tower made by Dick Weber K5IU of RTS.
Jay, WX0B
ArraySolutions www.arraysolutions.com
Michael Lamb wrote:
>
> ----------
> From: Henry G Chapoton[SMTP:chapoton@smtp-gw.gdls.com]
> Sent: Wednesday, July 22, 1998 9:39 AM
> To: kq2m@eci.com
> Cc: towertalk@contesting.com; n4kg@juno.com
> Subject: re: [TowerTalk] Stacking dissimilar antennas - correction
>
> Hello All: I am sorry, but I think I have come into this thread at a late
> date, but I wanted to weigh in anyway.
>
> I have played the stacking game for many years, especially on VHF. I started
> using the standard 1/4 wave RG-11 70 ohm Wilkinson power dividers for up to 4
> yagis on an H frame. I have since used the M2 4 port power dividers that
> work great on VHF.
>
> When I decided to stack six tribanders on a 190 ft. rotating tower, obviously
> I could not use the same old power divider technique because what is a 1/4
> wave on 20 meters is a 1/2 wave on 10 meters! First, I used the SAME yagis
> spaced the same 30 feet distance apart all the way up the tower. Then I
> divided the antennas into pairs; an upper, middle and lower pair. I used
> exactly equal lengths of RG-213 coax from each antenna of a pair to a 25:50
> ohm UNUN physically located between the pair of antennas. I now had three of
> these UNUNs on the tower. I brought equal lengths of RG-213 coax to a
> centrally located "Stackmaster" switch box that allows me to select any
> combination of pairs of antennas. That is accomplished using a 22 2/3 ohm
> UNUN for matching all three or any two pairs to nearly 50 ohms. The UNUN is
> bypassed for any single pair.
>
> So, if you are careful to keep the feedlines the same length (either
> measure the same physical length off the same reel, or better yet,
> measure with an antenna analyzer) and use broadband UNUNs, you can
> even stack tribanders.
>
> My inspiration for the triband stack was an article by Dean Straw and Fred
> Hopgarten (sp?). For HF operation, I simply would not consider using the
> 1/4 wave matching sections anymore because like someone already
> pointed out, the match will be different at one end of the band from the
> other.
>
> 73/Mike, N7ML
>
> PS Does anyone have an idea of how I can reformat my Microsoft
> Exchange e-mail? It looks fine on my end, but I understand that
> it does not word wrap properly when it is sent out?????? Please
> respond directly so that we don't take up space on the reflector.
> Thanks.
>
>
> Bob:
>
> Change those references to "1/4 wave multiples" to "ODD multiples of
> 1/4 wave". Usually a good place to put a 1/4 w. of 75 ohm (or
> whatever) for matching, along with equal lengths of 1/2w. multiple 50
> ohm for the balance of length req'd to the switch box. If you don't
> require the impedance transformation, just use odd 1/4 w. mults of 50
> ohm.
>
> Greg
> na8v
>
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