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Author Topic: Here's a KX-1, Merry Christmas Donald!  (Read 2094 times)
AE6RF
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« on: December 14, 2006, 10:20:42 AM »


Santa Claus (driving a large UPS truck) is bringing me an KX-1 (pause for engineer happy dance).

Clearly the easiest antenna to use with it is an end-fed random wire.

How readily does the internal ATU tune random wires?

How about (high impedance) end-fed halfwaves?

Thanks in advance...

73 de Donald
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AA4PB
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« Reply #1 on: December 14, 2006, 03:17:37 PM »

The tuner is designed to work with end-fed wires. You should stay away from exact multiples of 1/2 wave in order to have a more reasonable impedance to match.

As with all end-fed wires, be sure you use one or more ground radials or you will find the case hot with RF and it will be difficult to find a match.
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Bob  AA4PB
Garrisonville, VA
AE6RF
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« Reply #2 on: December 19, 2006, 02:46:46 PM »

Well,

I tried a 44' zip cord doublet and it would only match on 10 MHz.

Then I made a 1:1 transformer (BalUn) and it did better, but not "good enough."

Then I tried 28' and a 16' counterpoise.

The 44' doublet with the BalUn was the best of the three. I'll try the 44' doublet BalUn and a couple of tuned counterpoises. That should do the trick.

73 de Donald
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AA4PB
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« Reply #3 on: December 19, 2006, 04:40:48 PM »

A doublet is NOT and end-fed random wire. I would run a couple of radials along the ground, connected to the ground on the radio. Then I'd connect the end of the single wire antenna to the center contact on the radio's BNC connector.

A doublet is a balanced antenna and shouldn't need any counterpoise wires. The doublet should however be fed with a low loss cable like ladder line or perhaps 300 ohm TV twin lead. You'll need a good balun to couple the unbalanced output of the tuner to the balanced feed line. The top section of the doublet should be at least 1/2 wavelength long on the lowest operating frequency.
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Bob  AA4PB
Garrisonville, VA
N8BOA
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« Reply #4 on: January 06, 2007, 07:50:20 AM »

I love that little radio have fun
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N8BOA
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« Reply #5 on: January 06, 2007, 07:53:05 AM »

I love that little radio
 When I go backpacking i have tried endfed with radials but I found a upright V works better. No feed line loss or ground loss
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AE6RF
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« Reply #6 on: January 09, 2007, 05:05:14 PM »

A "non-inverted" V?

Cool, may try that. Tried just about every other shape.

Put's the current node at the lowest height though...

73 de Donald
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VE3WMB
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« Reply #7 on: January 19, 2007, 07:41:41 PM »

The issue with the 44ft doublet not matching on 40m/20 probably has
to do with the length of the feedline portion (ie the unzipped part).
It sounds like you have inadvertently chosen a length that is resulting in an impedance outside the range of the KXAT1. What length is your feedline portion ?  I can suggest some lengths that should work.

BTW I have had very good luck with the KX1 using a 24 to 28 foot mostly vertical wire worked against 5 to 10 radials, each 16 feet long  made from multiconductor computer ribbon cable ( I unzip the individual strands for all but the last couple of feet, and put a piece of electrical tape to keep the rest from unzipping). I find that this is pretty easy to deploy.
What also works pretty well for portable operation is what amounts to a variant of the End-Fed Zepp made from 50 feet of twin-lead, speaker wire, zip cord whatever. Effectively what you want to achieve is to cut off 25 feet of one of the two conductors leaving a 25 foot conductor parallel to a 50 foot one, and then just connect this to BNC jack on the KX1 (I used a binding post to BNC adaptor and banana plugs on the leads).
Surprisingly this antenna matches and performs well on 40m/30m/20m with the KXAT1. Without a balun you will get some "feedline" radiation but the setup works just fine. Practically you can leave both conductors intact and just cut a 1 cm window out at the 25 ft mark on one conductor and cover it with tape. (BTW these are sold commercially on Ebay .. just do a search on 'No Counterpoise').

Best of luck ...

Michael VE3WMB
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