OK, thanks for this info.  I just upgraded to General, bought a TS-2000, and
put a an 80-meter loop.  The radio has a built in tuner and I want to see
what it can do, but it only works with a coax connection.  I have a BAD RFI
problem!  I can't put out more than 25W or my audio is really distorted.
Right now I'm externally tuning with a MFJ 949D transmatch. SOmeone
suggested that the problem MIGHT be with the MFJ.

Thanks,
Duane
KD5NFQ

-----Original Message-----
From: pic microcontroller discussion list
[mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Thomas Sefranek
Sent: Thursday, January 22, 2004 3:47 PM
To: PICLIST@MITVMA.MIT.EDU
Subject: Re: [EE]: BALUN


> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Duane
> Sent: Thursday, January 22, 2004 4:33 PM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: [EE]: BALUN
>
>
> Hello everyone,
>
> Does anyone have any experience with making a BALUN to match $%)
                                                               ^^^
                                                               450
> ohm Ladder
> line to 50 coax, something like RG-58? I have an 80-meter loop antenna,
> drive it with ladder line, but want to convert it to coax at the radio.

So why do you believe you have 450 ohms at the end of the feedline
connected to your loop?  (I'll bet you don't!)

Just because you have 450 ohm feed line does NOT mean the termination
impedance IS 450 ohms.

Simple illustration, Short the end of the feed at the loop.
Do you believe you'll have 450 ohms impedance at the radio end?
(There actually is a length of line that may make this happen,
 but lets not go there, it would be a LONG line.)

My experiences with 75 meter loops is: the feed point is ANYTHING from
a few ohms to a few HUNDRED ohms depending on where your feed point is
relative to the corner, and the height of the loop above conductive
surfaces.

You might want to measure the impedance before you get a balun.

BTW: I have built loops that used pulleys on the corners so I could
pull the loop feed relative to a corner to match it to 50 ohm cable!
Works GREAT on one frequency!

>
> Thanks
> Duane
>
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  *
  |  __O    Thomas C. Sefranek  WA1RHP@ARRL.NET
  |_-\<,_   Amateur Radio Operator: WA1RHP
  (*)/ (*)  Bicycle mobile on 145.41 MHz PL 74.4

ARRL Instructor, Technical Specialist, VE Contact.
http://hamradio.cmcorp.com/inventory/Inventory.html
http://www.harvardrepeater.org

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