Keep in mind the fuse blew because I was Key Down in the CW mode trying to tune an antenna tuner with an antenna that was presenting an high SWR! The current draw exceeded 2 amps.
Under normal conditions with a tuned antenna and normal CW keying very likely the draw would be a lot less than 2 amps and the fuse would not blow.
It is the aberrant condition when you have the uBitx "key down" for long periods of time (in excess of say 30 seconds) and the SWR is off the chart that the fuse will provide some protection to the finals. That is the essence of what was being said and the reason for the fuse protection.
Pete N6QW
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-----Original Message-----
From: Vince Vielhaber
Sent: Thursday, December 28, 2017 8:10 AM
To:
[email protected]Subject: Re: [BITX20] uBITX - Sensible mods #ubitx
According to the Tune-up instructions, the uB idles in SSB at 700ma.
The B40 drew an amp in SSB with a loud HALLOW. It's not inconceivable
that the uB would draw 2A or maybe more in CW.
Vince.
On 12/28/2017 11:05 AM, N6QWHAM@... wrote:
Hi Arvo,
Actually I hate to post to these reflectors as you will get a variety of
responses that say well that never happened to me!
I can only share that the fuse went up in smoke and that my assessment
was high current draw. So a fuse and fuse holder despite what the radio
illuminati will tell you is cheap insurance when ¡°bullet proof¡± is not
good enough. But it was something that I used accidently and the
current draw did exceed 2 amps and my conclusion was high SWR. I am
keeping that power cord and fuse in my installation.
So you decide.
Pete N6QW
*From:* Arvo KD9HLC via Groups.Io <mailto:arvopl@...>
*Sent:* Thursday, December 28, 2017 7:52 AM
*To:* [email protected] <mailto:[email protected]>
*Subject:* Re: [BITX20] uBITX - Sensible mods #ubitx
Holy smokes!
I'm a bit too new at this to "know that sinking feeling of just having
smoked the rig."
Also, there was a thread about the BITX40 that suggested it was pretty
much bulletproof to high SWRs.
/g/BITX20/topic/6065942
So I was not thinking about excessive SWR potential for damaging the ?BITX.
I am now.
Thanks for the explanation!
--
Michigan VHF Corp.
