Hi Everyone,
W0CP writes,
>
> Before last weekend i would have advised you to turn on ur attenuator
> whenever possible to protect the frontend. however, we managed to
> blow out the 10 and 20 db attenuators in one of the m/s rigs in cqwwcw.
> 73 w0cp
>
We have experienced this problem (many times) at Georgia Tech with our
two TS940's. We finally just went in there and took out the 1/8 watt
(or whatever) puny resistors and put in 1 watt and 1/2 watt (man-ly)
resistors. You have to do this before the resistors burn up the
circuit board traces or there will be a bigger problem - rewiring
the board - as we had to do with our IC735 which wasn't so lucky.
Anyway, the problem hasn't surfaced again in 2 years of m/s operation.
73 de Dave, K0DI
gt5830b@prism.gatech.edu
>From zs6nw@leclub.co.za (Jan Zs6Nw) Thu Dec 1 22:01:00 1994
From: zs6nw@leclub.co.za (Jan Zs6Nw) (Jan Zs6Nw)
Subject: RYRYRYRYRYRYRYRYRYRYRY
Message-ID: <12f.8871.400.0CAF26DD@leclub.co.za>
Remember the CQWW RTTY contest ?
Today is the last day for postmarking log entries.
ZS6NW CQWW RTTY 1994 Score
Single op single band unassisted high power
Band Zones Countries QTHs QSOs QSO points
15m 22 67 35 418 1247
124 x 1247 = 154,628
73
Jan Zs6nw
---
* KMail 3.00t ®® LeClub Bulletin Board ¯¯
>From John W. Brosnahan" <broz@csn.org Thu Dec 1 16:10:34 1994
From: John W. Brosnahan" <broz@csn.org (John W. Brosnahan)
Subject: No subject
Message-ID: <199412011610.AA02233@teal.csn.org>
The following paragraph is typical of a number of questions that I have
received about the Autek bridge and whether it can measure R + j. Because
of the interest I felt that a general response might be in order.
>Can you determine R+j with the Autek RF-1 and some arithmetic???
>Since it gives composite impedance, how do I calculate the resitive
>and reactive components. SWR is only good to one decimal place.
>I want to plug the R+j values into my L-net/T-net/Pi-net programs.
Well, yes, sorta! The unit does not give R + j per se. But if you measure
Z at resonance (ie where j = 0) you have R. And if you move off frequency
a little bit the R changes very slowly compared to j so the new Z is
mostly due to j. So by squaring and subtracting the resonant R (j = 0)
from the square of the off-resonance Z (which differs mostly by the
reactance) and taking the square root of the difference you (sorta) get the j
component and by knowing which way you moved and knowing which way the sign
should go for what you are measuring you can determine the sign. All pretty
messy and not accurate enough for anything except a first cut on component
values for L (etc) networks.
And not very useful at all if what you are trying to measure is far from
resonance and highly reactive, unless you know, a priori, that the Z is
mostly reactive such as in the case of a SHORT (much less that a 1/4 wave)
vertical. In this case the Z is almost all capacitive reactance and the
Autek's Z measurement is virtually all due to -j and the Autek has the
capability of switching to the L scale and giving the value of inductance
required to resonate the vertical.
But nothing beats a good old GR-1606 (or the older 916) bridge (or a GR-1602
swinging arm bridge for VHF/UHF). I once bought a cherry 1602 in the wooden
case for $5 at a flea market, so they are out there.
BOTTOM LINE: The Autek is a slick little tool that can do many interesting
things and is well worth the price, but isn't a generic R + j sorta beast.
73 John W0UN broz@csn.org
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