Pete: Sorry I read some of your numbers incorrectly. A cable with 0.3
ohms resistance and 20 amps of current will have a voltage drop of 20 x
0.3 for 6 volts. This can't be correct. More like 20 x 0.03 for 1.2
volts. Still too much.
Don't try to measure resistance with a DVM, as point contact and lead
resistance will be too great. Just measure voltage drop across the
various components which will be more accurate. That's what is important
anyway.
73
Bob, K4TAX
On 4/26/2020 11:34 AM, N4ZR wrote:
Aside from my decimal point problems.... The cable measured 0.3
ohms, with my DMM, but in retrospect, its measurement could not have
been correct. However, the measurement on the 4005i is about right,
because that was done by comparing the voltages at its input and
output, and was at 100 watts key-down. The 4005i's *voltage drop* at
100 watts was 0.08 *volts*, which strikes me as not bad at all.
73, Pete N4ZR
Check out the Reverse Beacon Network
at <http://reversebeacon.net>, now
spotting RTTY activity worldwide.
For spots, please use your favorite
"retail" DX cluster.
On 4/26/2020 12:11 PM, Bob McGraw K4TAX wrote:
The power cable at 0.03 ohms on each side, a total of 0.06 ohms
resistance. The 4005i, per his measurements, has 0.08 ohms
resistance. The power distribution strip contributes more than 50%
of the voltage drop. Actually more than the power cables.
The power cable contributes 1.2 volts of drop. The 4005i
contributes an added 1.6 volts of drop for a total of 2.8 volts.
The calculation is simple: E = I x R current multiplied by
amps equal voltage.
73
Bob, K4TAX
On 4/26/2020 10:53 AM, Leroy Buller wrote:
40 inches of power cable. In my experiences, that could be an issue
depending on the gauge of the wire. I used a long cable 12 gauge
and had
issues. Went to 24 inches number 10 gauge and voltage drop
significantly
improved. The resustace does not have to be large to cause a
voltage drop
Lee
On Sun, Apr 26, 2020, 9:47 AM N4ZR <n...@comcast.net> wrote:
I've had an e-mail exchange with West Mountain Radio. Measured the
voltage drop inside the 4005i at only .08 volts at 100 watts key down.
My power cable from the 4500i to the K3 measures 0.3 ohms on each
conductor, which at 20 amps should only yield a 1.2 volt drop,
right? I
don't know where the other volt plus of drop is coming from. The cable
is 40 inches long, and only minor shortening is possible. It is about
the largest wire that will fit in the Powerpoles on both the K3 and
the
4005i.
Suggestions welcome
--
73, Pete N4ZR
Check out the Reverse Beacon Network
at <http://reversebeacon.net>, now
spotting RTTY activity worldwide.
For spots, please use your favorite
"retail" DX cluster.
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