[ARC5] BC-348

Mon Dec 30 19:49:44 EST 2019

Tubular as in round is as far as they got. Other gear including ham might also include "paper"  Actually Im surprised it wasnt a bathtub cap.

> On December 30, 2019 at 6:21 PM Mark K3MSB <mark.k3msb at gmail.com> wrote:
> 
>     Several months ago at a hamfest I picked up a rat infested / urinated / gnawed to death junker BC-348Q (for $5) and I harvested what I could.   Fortunately, all 4 modules were very clean on the inside and not urinated on or even gnawed.    Yes, I used gloves and a face mask while working on it.....
> 
>     There's a 0.05 uF 400V Tubular Capacitor in the OSC compartment.  It is the Oscillator Unit Screen Bypass Cap (Part 60 -- I think, my schematic is fuzzy)     I'm not sure what they mean by "tubular" in the manual,  perhaps one of you can enlighten me.   I've always thought tubular was a shape,  not a type (like mica,  wax paper, etc).
> 
>     You can see a picture of it here (bottom row):   https://www.k3msb.com/bc348/assemblies/main.html
> 
>     Anyway,  these are the values from the leakage tests I performed:
> 
>     100V:   8 uA
>     200   36 uA
>     300    70 uA
>     400  125 uA
> 
>     125 uA at rated voltage tells me to replace it, but  there's only supposed to be 100V on it, so I suppose I might consider letting it go.   On the other hand,  If I had a 100V rated cap that shows 8 uA of leakage I'd replace it.
> 
>     Just trying to muddy the waters a bit.....
> 
>     73 Mark K3MSB 
> 
> 
> 
> 
> 
> 
>     On Mon, Dec 30, 2019 at 5:38 PM Doran Platt < jeepp at comcast.net mailto:jeepp at comcast.net > wrote:
> 
>         > >         As a matter of fact, I use two of them currently. Both have been re-capped, to include the 4 modules and the BFO and Xtal filter.  To obtain a better bandwidth, I simply use either of the LF ARC-5 or 274-N receivers tuned to 1/2 the BC-358 IF, minus 50khz.  It does wonders on 80 and 40 meters.  Coupling is done via a small loop at the base ofthe last IF in the '348.  No need for any mods of any kind.  I do the same for my ARR-15 receivers, but tuned to the IF freq. directly (500 khz).  Makes these receivers totally usable on the current bands.
> >         Jeep K3HVG
> > 
> >             > > >             On December 30, 2019 at 5:21 PM Jim Haynes < jhhaynes at earthlink.net mailto:jhhaynes at earthlink.net > wrote:
> > > 
> > > 
> > >             On Mon, 30 Dec 2019, Whitebear1122 wrote:
> > >             >
> > > 
> > >                 > > > >                 Boy those 348’s are gorgeous. Does anyone here actually use theirs on
> > > >                 the ham bands?
> > > > 
> > > >             > > >             Well I did circa 1958. Those were the favorite receivers of the late
> > >             Bob Weitbrecht, W6NRM/W9TCJ, one of the RTTY pioneers. He developed
> > >             a mod where he used the IF transformers from the LF/MF Command Set
> > >             receivers to get a narrow passband. He converted the 915 KHz IF down
> > >             to 85 KHz, put it through the transformers, and then converted it
> > >             back to 915 KHz and back into the original IF chain. A neat feature
> > >             of this is that you get passband tuning by varying the frequency of
> > >             the conversion oscillator.
> > > 
> > >             Mine was eventually extensively modified. I adopted Bob's narrow band
> > >             IF scheme, but instead of the IF transformers I used a bandpass filter
> > >             found at a surplus store in Chicago. Then I made a new rack-mount front
> > >             panel, and added a chassis on the back to hold the AC power supply and
> > >             the IF filtering and also a product detector. This was used for a few
> > >             years until Bob discovered the Drake 2-B receiver and persuaded me to get
> > >             one too. But I missed the general coverage that the BC-348 offered -
> > >             back then there was a lot of copyable RTTY outside the ham bands.
> > > 
> > >             Jim W6JVE______________________________________________________________
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