[Lowfer] RX Loop Tuning

[Bill Ashlock]

Paul,

>Using cat 5 wire to bring in the antenna provides one with a certain 
> >measure of noise immunity from feedline pick up. It also gives one 3 
> >addition pairs of wire to things like motor control.

Yes, the twist in the cat 5 line should help in the immunity factor. What 
kind of loss can be expected at say 200kHz for 200ft? One time I tried using 
twisted cable (not cat 5) for sending a square wave to the loop final and 
found the losses to be high.

I'm a bit partial to the flexibility of the RG-59 coax with F connectors and 
use it for all TX and RX Lowfer antenna connections. From one of the Hams 
fests I ended up with a ton of free F connectors and male-male connectors 
(which also work nicely as panel mounted connectors) Very easy to try out 
any new antenna ideas, make quick line extensions, burry the line where 
required, leave it lying on the ground in the woods for months, etc - and 
the line is very low in loss, including 185k square wave transport.

Thanks for the input.

Bill


>
>The isolation between the motor control and antenna leads is superb.  There
>has has never been a time whe I can hear the brush noise from the motor
>turning the cap.  Actually I wish I could hear it a little it would help in
>the tuning of the ant at imes.
>
>The other pairs are great for headphones, preamp power, etc.
>
>
>Paul C
>W1VLF
>
>
>
>----- Original Message -----
>From: "Bill Ashlock" <ashlockw@hotmail.com>
>To: <lowfer@mailman.qth.net>
>Sent: Thursday, May 01, 2003 10:43 AM
>Subject: [Lowfer] RX Loop Tuning
>
>
> > Jay/others,
> >
> > I've been experimenting with my motorized trimmer cap over the last few
>days
> > and it seems to be working fairly well. In review, this is a 2"x4" box
> > containing a small Jameco gearmotor and 3/4" square compression mica 
>that
>is
> > located below the loop. (The gearmotor voltage is provided via the coax
> > leadin).
> >
> > Last night I changed the control box at the receiver so that the 
>receiver
>is
> > connected at all times - not disconnected when either UP or DOWN buttons
>are
> > pressed. Used a couple of shockty diodes and 100 ohms of series 
>resistance
> > to protect the receiver's input (and ears). This appears to work fine.
> >
> > Pictures and schematic to follow after a more thorough check. Next idea 
>is
> > to replace the push buttons with a 500 ohm pot connected to the + and -
> > voltage sources. This will allow a slow motor rate for fine tuning and a
> > fast rate for large frequency changes - IE: from 137k to 185k.
> >
> > Bill
> >
> >
> >
> >
> >
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