TheRadioBoard

I have exhausted the possibilities for putting up more stranded wire in my small back garden so I was wondering if changing to litz wire might be worth the effort and expense.

A search of this site reveals a few postings suggesting that litz makes for a superior antenna but more opinions would be very welcome. Is there anything to be gained?

The physical strength of wire is a limiting factor as anything too thin will obviously be likely to break in a blow. Is there a useful compromise?

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John

John,

I don't see any advantage to using Litz for an antenna. The advantages gained by using it in LW and lower-MW inductors would be lost in a random-length antenna. I don't think the stuff would stand up well outdoors, either. For LW and MW reception I would try large-circumference tuned loop antennas, assuming you can turn them. Remotely tuning them can be challenging, but we can talk about ways to do it if you decide to build one. Over there, where the MWBC band is less crowded than here in the States, you could make use of the sensitivity of a large (4-6 ft diameter) loop.

73,

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http://kr1s.kearman.com/
http://qrp.kearman.com/

Thanks Jim

As it happens i have a convenient flat roof just above my listening den ( corner of a bedroom). This would be good for locating a loop.

I imagine a vertical loop would be the thing on something like a ham radio remote rotating device. If you have some specific ideas I'd be very grateful. I am a beginner in this area.

There is masses on loop antennas so a few pointers to essential reading would be a great help.

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John

John,

Start reading here: http://www.am-dx.com/ThePVCLoopOverallArticle.pdf

Nine-foot loops are probably overkill, but the construction methods will give you some ideas. If you plug the bottom of the vertical support column with wood you can clamp it into an antenna rotator. It's 0338 local time here so we'll talk about tuning methods later.

73,

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http://kr1s.kearman.com/
http://qrp.kearman.com/

There is a german manufacturerer of litz wire having also a dedicated, rugged antenna litz wire for sale. This litz wire has a special PVC cover for long lifetime (specified with 20 years). I had asked some time ago about the construction of this litz wire which is 125 x 0.125 mm. In 2009, pricing was 1.90€ per meter.

You can find more informations here (only in german - did not find the english product site):
http://www.pack-feindraehte.de/de/news/aktuelles_folgeseite.html?news_id=12
http://www.pack-feindraehte.de/beverage-antenne.pdf

You can ask those guys also directly, in the past I bought a reasonable part of my litz wires used in my crystal radios from this company.

Brösel

I have had a litz antenna up for over 4 years now ,its 440 /40 litz in in teflon tubing . It does make a differance in rececption .

I love to see birds land on it and slip , their feet cant grip the slick suface .

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Mark

I'd be interested in knowing on what frequencies, and how you determined that.

73,

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http://kr1s.kearman.com/
http://qrp.kearman.com/

Kris,
The only difference I can imagine is the loss resistance of the wire, and without any calculations, I bet that 100ft of 10 gauge wire has less resistance than 100ft of 440/40.

Does anyone know how to calculate the AC resistance of 10 gauge wire and 440/40 wire at 1 Mhz?

I'm in an airport or I'd grab some info and muddle through it with my limited algebra ability.
Mikek

I have strung up two different litz wire antennas at two different locations . The first one was at Josh Young's house at the crytal fest .
With the same lenth of wire and the same hight , the voltage produced at the diode double from 6 volts to 12 volts + mesured with a Fluke 87 III meter, was measured on a strong local in springfield MO . At my house , with the same length of wire and hight , just replacing the 16 gauge wire with the 440/40 litz the tank voltage at the diode went fron an average of 8.4 volts to over 13+ on KMOX 1120 , receiving on the entire brodcast band was inproved , more so from the midband down .

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Mark

FWIW.

Just resonated a 6"coil of 440/39 litz (close wound) for Q's across the MW BC band of between +500 (@1700kHz) and +700. (HP Q meter.)

Q @ 1MHz (320pF) was ~725.

Yes, it is a low uH coil.

.................................

Just resonated a 6"coil of 14AWG solid wire (double spaced) for Q's across the MW BC band of between +600 (@1700kHz) and +350 (@530kHz). (HP Q meter.)

Q @ 1MHz (440pF) was ~500.


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With a Q of 725 @ 1 Mhz, that is 0.69 ohms of (ac) resistance.
Let's make a guess that we could get it off the coil and bring that
down to 0.4 ohms of ac resistance.
I'm making a guess that your coil has 40 ft of wire.
I gleaned skin effect info from here,
http://www.allaboutcircuits.com/vol_2/c ... factor.tbl
40 ft of 10 gauge wire has 1.1 ohms of (ac) resistance at 1 Mhz.
Now let's scale these to make a 100ft antenna. 100/40 = 2.5 scale factor.
Litz resistance 2.5 x 0.4 = 1 ohm
12 gauge 2.5 x 1.1 = 2.75 ohms.
We have an additional 1.75 ohms with 10 gauge wire.

The standard BC antenna according to Ben tongue,
http://www.bentongue.com/xtalset/20MeaAGs/20MeaAGs.html
In the last paragraph, it says "25 ohm antenna and 15 to 50 ohm ground."
So, I'm picking a reasonable 50 ohms for the antenna/ground system.
With Litz we might drop that to 48.25 ohms.

I don't see where we pickup more than 5% in signal strength.
Note: I used big wire, 10 Gauge, but I figured if you can buy litz you can buy
10 gauge wire.
I'd be happy to see someone rework my numbers if they see a different answer.
Thanks, Mikek

The actual surface area is greater on , litz 440 /40 than number #10 , i got the litz on ebay for very low price primmarly for a loop ant . Other members of the forum where also witness at the crystal fest .

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Mark

Hey All,

I used the litz antenna at Josh's house. We figured it was roughly 1/3 better than solid wire. Don't remember how we got that figure though.

K

Yes, I remember putting that antenna up at some where around 2:00 in the AM. That was really cool indeed. What a fun time that whole experience was. Like Krystallo, I remember a 33% perceived increase in volume over the 16 stranded I had up before. The Litz wire seemed to help the crystal set come alive a bit more than with the old stranded. Other than the voltage measurements that Mark mentioned, no other testing was done in regard to increase in antenna capacitance and all. I wish we would have taken more time to do that, but we were all just excited to have much better performance from a simple antenna swap. I've got to admit, I miss that antenna and location. Hopefully my large Litz loop will get me back in that reception ballpark. FWIW.

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-Josh-
http://www.youtube.com/user/josh8loop?feature=mhee