[Lowfer] SIW (WM) in CT

[Michael Sapp]

Garry: Interesting numbers on your variometer.

My 40 turn 18 inch diameter passive rx loop measures about 1.156 mH and 7.5 
ohms DC with 40/42 Litz wire.  The first tap at 10 turns is about 95uH. My 
100kHz cap checker shows 60 ohms across the first tap. The online inductive 
reactance calculator at 66pacific.com shows 59.7 ohms for 95uH at 100 
kHz.....unfortunately the 100kHz cap checker only goes to 100 ohms. I would 
have to get the old ESI impedance bridge out to with a signal generator to 
get higher AC resistance measurements at LF....

What size Litz Wire on your vario ?

73, Mike tts

----- Original Message ----- 
From: "Garry" <k3siw at sbcglobal.net>
To: <lowfer at mailman.qth.net>
Sent: Friday, January 13, 2017 9:13 PM
Subject: Re: [Lowfer] SIW (WM) in CT


> Mike, I notice you mention your normal lowfer antenna current is about 75 
> ma. With 1 W input that implies a quite high net resistance of about 178 
> ohms. Ground resistance is certainly a part of that but I wonder if your 
> variometer to resonant the antenna is an even bigger source of resistance. 
> The first variometer I wound used run of the mill magnet wire and had way 
> too much DC resistance when enough turns were wound to reach the roughly 
> 2mH needed for antenna resonance. I eventually got some decent litz wire 
> and lowered the resistance to around 10 ohms. I don't recall the total 
> system resistance I ended up with but I'm sure the antenna current is at 
> least 150 ma. So I'd suggest you measure the DC resistance of your 
> matching inductor (yes, the AC resistance at 185 kHz will be somewhat 
> different) and if it's high consider working on that first. It's surely 
> much easier to improve than the ground system, at least in the winter, hi.
> -- 
> 73, Garry, K3SIW, EN52ta, Elgin, IL
> ______________________________________________________________
> Lowfer mailing list
> Home: http://mailman.qth.net/mailman/listinfo/lowfer
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Lowfer at mailman.qth.net
> Post must be less than 50KB total for message plus attachment!
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html