[BC] [TZ] TALL ANTENNA

[Phil Alexander]

Don,

This thread belongs better in either [TA] Tech Assist or the [TZ] TechZone
because it is one of "them" cantankerous technicalwhatamos things, and I
suspect we will wander into technical waters at least as deep as we did
a week or so ago chasing the bunny down the ground wire hole. 

For that reason I'm going to post this in the [TZ] TechZone and request
Barry divert other replies there because that it a better place to chase
this rabbit.

For those of you who want to participate and are not members of the [TZ]
list, I suggest you go to <www.radiolists.net> and join in on the TechZone
that was your posts won't have to wait for special non-member approval.

Items we must cover are:

          ATU "tuning" or set-up in general
          How Pi networks are similar to the more common Tee type (mostly same)
          and how they differ (not much).

The short answers are you probably have everything you need to make this thing
work except for one or two caps of the correct values because you have moved a
long way frequency-wise.

-----Original Message-----
>From: donroden at hiwaay.net
>
>Opps ..... change of subject......
>
>Here I go chasing another bunny down the hole......
>
>ex-930khz tower ( ahem.... *assuming* it was a 1/4 wave when built )
>
>then it would possibly be 250 feet tall.
>
>Currently on 1240khz and the previous ( deceased ) engineer matched it with a
>  C/L/C pi-network.
>
>This antenna has been operating fine for over twenty years.
>
>A kilowatt SX-1A won't null on the Phase Null position ... .40 is as  
>low as it will null.  Seems strange, because I've seen SX-1As null at  
>40 through 60 ohms.
>
>Lots of fold-back or pdm kill  under modulation peaks.
>
>A dummy load at the ATU will Phase Null to ZERO, and SX1 will modulate fine.
>
>A OIB-3 shows 52+10 indicated when I took power down to under 50 watts  
>just to keep the SX-1 making a solid carrier with no modulation.
>
>All three C/L/C components are fixed with no markings.
>
>I can faintly see a .002 on one of two stacked output caps to  
>ground.... maybe the second cap is also a .002 ( ?? )
>
>At 1KW no modulation, the antenna current meter ( WOW they actually have one )
>  reads around 1.5amps which equates to 440R.
>
>The OIB-3 never found a good null for either R or j on the antenna feed.
>  but there was  a broad semi-null around 450R.
>
>I'm thinking the taller tower might be +200j but I couldn't find it.
>  Maybe interference from the 950 a mile away. ( maybe not ).
>
>I've always trusted the OIB-3, and will test it tomorrow .... never seen it
>  do like this afternoon.
>
>Don R