[Elecraft] 40M Tx Alignment Hi Current Concerns

Sun Jan 12 19:00:01 2003

Hi Gil,

The 0.13V drop in the power cord corresponds to 4 or 5 feet of #18 cable. Is
that about what you have? That's a pretty small drop at 2.2Amps (change in
current between Rx and Xmit). Even going to #16 wire would only reduce it to
about 2/3 of that value.  If you can't make the cable shorter, then it's
probably ok as-is.

The difference you see on the LCD voltage readout is about right considering
the Schottky diode and the fuse, plus the power line drop.  With your DMM
you can check on both side of the diode, D10 (RF board) and both sides of F1
(the resetable fuse). The diode drop should be less than 0.6V at 2.4A and
the drop across the fuse should be less than 0.2V.

73/ Bob - AG5Q

----- Original Message -----
From: "Gil Stacy" <[email protected]>
To: <[email protected]>; <[email protected]>
Sent: Sunday, January 12, 2003 4:44 PM
Subject: Re: [Elecraft] 40M Tx Alignment Hi Current Concerns

> The power source may have been part of the problem..  I had been using a
2.9AH gel cell (12.4 volt charge) and a power cord that came with an SWL 40
kit.  I just hooked up a RS 13.8 3A power supply with some power cord from
RS for DC use.  Paired cord with postive marked with white stripe.   May not
have been quite 18 guage, but close.  With power up to the radio, rx on, the
power supply at the connectors read 13.78 volts with a DVM.  At the LCD on
the radio, the voltage was 13.1 with the RX on at 7100.  With a setting of 5
watts on receive, the LC D read 13.1 with a drain of .22.  The DVM read
13.78.   In TUNE mode, the first time I tested, the voltage dropped to 12.4
with a drain of 1.4 amps. Happy dance.  Ten minutes later, 1.8 drain.  DVM
read 13.69 or a drop of 0.09 at the connectors.    The set had been turned
off.  On 10 watts, LCD read 13.1 voltage, with a drain of .22.  DVM read
13.78 at the connectors.  In TUNE mode, voltage drop on LCD read 12.2 with a
drain of 2.4 amps.  DVM at the connectors showed 13.65 or a DVM drop of .13
volts.  Would it still be the power cord??  I can always cut some lamp cord
when no one is looking. Thanks
> 73/Gil