gelcells for MFJ xcvr

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From: klaudon@PICA.ARMY.MIL
Date: Tue Oct 05 1993 - 15:59:08 EDT


Joe:
Glad to hear that you're getting this rig! I enjoy mine (30m version) and
want to get something for 20m. I responded to your inquiry a while back
about this rig, and how to power it. I had suggested a 1.3 ah gel cell.
However, after I wrote this to you, I started to pay attention to what
others were doing who were already using gel cells (I am not, at present)
and I started to see that they were talking about using larger ones,
like 4 ah or thereabouts. I have heard Jeff Gold AC4?? on this group
mention his 4 ah cell setup. Sorry, Jeff, I can't remember your call
as I am typing this!

I believe that I heard, or read, somewhere, that one should only use a
lead-acid (gel or wet) cell for use at approx. C/4. I had suggested to
you the 1.3 ah model because the MFJ draws approx 1 amp on transmit.
Since this is fairly intermittent, I had thought that 1.3 would do, especially
from a portability standpoint. These smallest of gel cells are really compact,
light, and inexpensive! Much more so than 4 ah ones. But the C/4 rule
would put the number at Jeff's 4ah rating, or the 3-6 ah rating you have
arrived at (by consensus, I assume?)

For the net members out there:

Anyone care to comment on how to SELECT the required ah rating for a gel
cell application, taking into account tx/rcv duty cycle for CW, and
their respective current requirements? What does C mean, when expressed
in the "20 hour rate", in ah units? Perhaps this has been hashed over
before, but I wouldn't mind hearing about it again w/r to gel cells.

Joe, if you select your gel cell correctly, perhaps that 300ma xformer
should be used instead as the front end of a charger for your gel cell.
That way, you could operate from DC all the time, and recharge the gel
cell when necessary. I personally like the idea of operation from a
pure clean DC source, even when at home. If you are only on the air for
"while" each day, the rest of your time spent in non-ham activities,
then you should have plenty of time to recharge the cell.

BTW, as far as mods go, I know that MFJ has done mods for the audio and
QSK relay in the new rigs they are shipping. But I just use cans and I
seem to have sufficient volume. The relay dosen't bother me but then I
haven't yet tried cranking down the "vox delay" to something that resembles
a reasonably fast "semi" break-in.

72,
Kalman WD6CZI <klaudon@pica.army.mil>


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