[Lowfer] Testing material for losses

[Paul Daulton]

What you are suggesting is a Q-meter. I have two, a Heathkit and a 
Boonton 260. Nice instruments but
Qmeasurements can by had with a signal gen and a rfprobe or scope. 
Measure the peak and then tune either side and record the freq at the 
.707v point. q= Fc/ BW. 

Working on a qrp design by and Indian Ham , the bitx-20, where the 
designer used nylon faucet washers for torroid forms I encounterd the 
following. The washers I used were black plastic(only type I could buy 
locally). My rec was dead. Measureing the q I found the coils on the 
black plastic washers had a q of 40, replacing these with coils wound 
on red t-50 coils I had a q of 160 or better. Rec jumped several 
sunits, not db but sunits. 

The variometer Bill Bowers built for me has a Q of 302 at 1.968uh and Q 
of 457 at 3.185 uh. Goes to reason that the minimum bucking inductance 
should be used. My coil was trimmed to a nomonal inductance of 2200uh 
with the variiometer coil about 20degrees from meshed. I started with 
an ant current meter of a ft37coil of 40t 28awg on the secondary in 
series with a 1n914 and a 50ua meter. I had 10% deflection. After 
trimming the coil I now have 90% deflection with 19turns. 

When I have the time I will set up and try the measurements you suggest. 

73 Paul

Quoting "J. B. Weazle McCreath" <weazle at hurontel.on.ca>:
> Hello Lowfers,
>
> I've read a number of posts lately where the losses of various possible
> coil or antenna forms has been mentioned.  We're all aware of using
> the domestic microwave oven to test material for RF suitability, but
> wouldn't a better test be at the frequency of the intended use?
>
> I've been thinking of winding a self-supporting coil out of 1/8 copper
> tubing with a diameter large enough for test specimens to be slipped
> into it.  A basic oscillator circuit like the Hartley could be whipped
> together using (gasp) tubes so that 10's of watts or more could be
> generated. 
>
> 73, J.B., VE3EAR - VE3WZL
> Solar and wind powered
> Lowfer " EAR"  188.830
> EN93dr
>
> http://www.hurontel.on.ca/~weazle
>
>
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Paul Daulton K5WMS
beacon WMS 187.492 khz qrss30/slow 24/7
Jacksonville,Ar 72076
em34wu