[Central-Electronics] The CE 20A and BC-458 VFO

Wed Jan 6 22:11:37 EST 2021

Hello Jim,

Well, I lived in Connecticut in the 1960s, and was just starting 
college. My brother was still in HS. We chased DX on 144 MHz, and our 
plan was to make a kilowatt amplifier, which we did. It had a pair of 4C 
X250Bs in a Plumber's Special circuit. It could be plate modulated back 
then with a pair of 4-125As. The modulator had a window in it so we 
could see the plates glow orange on voice peaks.  Of course AM was not a 
good DX mode, so we became interested in SSB, and bought a CE 10A with a 
set of coils for 20 meters.  We built up a transmit mixer/ up converter 
using 6360s. I don't remember much about our homebrew up converter. It 
was always in a state of flux, but we applied about 1 watt at 20 meters 
into the 6360 cathode with a tuned circuit and mixed it with a 130 MHz 
crystal controlled LO and then into another 6360 linear amp into the 
4CX250s. This was in 1965 or 66 as I recall. For receiving, we had a 
homebrew 417A converter and then another 7788 converter that also worked 
into a 20 meter IF as I recall. When I got out of school and went into 
the Army in 1968,  my brother and I were up to 31 or 32 states worked on 
144 MHz. When I left the Army in 1972, I moved to Maine and started over 
with 144 MHz states! It was a blast.

Later on, I built a better transmit mixer, which I still have. I 
graduated to an 8877 PA in about 1975 and needed more drive. I ended up 
using more 6360s and 6939s to drive a 4CX350A in class A. All the stages 
were running class A or close to it. The plate meter hardly wiggled 
anywhere! The 4CX350 put out 70 watts on CW and voice peaks. It was so 
clean. I think the 6360 driver put out about 100 mw !  When it became 
outmoded and the solid state revolution arrived, I could not bear to 
throw the old driver out, so I saved it on a shelf. In the last few 
weeks, I have dragged it out and am contemplating revising it and 
stealing LO energy out of my current transverter so I can run it in 
transceive mode. I know it will be much cleaner than the solid state 
amps I am running now! It will be a fun project, but not used regularly. 
I makes a lot of heat!  I do have the up converter working, and now I am 
figuring out how to drive it with 28 MHz energy and the LO from my 
modern transverters.

I forget what ever happened to that old 10A. I think we sold it back in 
the late 60's as we built up a homebrew filter type rig with a Golden 
Guardian McCoy filter setup. It was low power and just worked on 20 
meters as a VHF driver. One interesting thing about operating back then 
was that, when the band opened up, we had to switch from SSB to high 
level AM modulation as there were very few stations that could even copy 
SSB  on 144! The typical station was a Goonie Box Gonset rig that had no 
BFO!  Even though SSB was much more efficient and could go much farther, 
we had to go on AM to work much of the DX!  There was some fast CW on 
144, but only among the meteor scatter ops at that time.  It took awhile 
to convince them that SSB was effective on meteors. With a meteor burst, 
you could copy a set of calls much faster on SSB than on CW for the most 
part.  One of the first guys to use SSB was W0DQY. (Don't Quit Yet!)  He 
got us going back then. I think Smitty is still on the air in MIssouri!

I have a few MM2s and a 100V that will be worked on soon. Thanks for the 
info on the 458 VFO. It looks a bit different than what I have here. I 
have three tubes inside the box here, two 12AT7s and a single 6AU6.  
 From what I sketched out, it looks like the oscillator is different 
from the BAMA diagram. Not sure what is going on, but the good news is 
that my unit is working. It looks like my unit has the crystal 
oscillator between the two cathodes of a 12AT7 oscillator as in a Butler 
circuit. The BAMA diagram is different. There must be a few versions of 
this  ten meter kit!  The schematic is a big help though. No doubt about 
that. I am not sure but could not find this on the BAMA site. I must be 
doing something wrong.

73

Dave K1WHS

On 1/6/2021 8:53 PM, Jim Candela wrote:
> David,
>
>    I loved your story! I attach a copy of the BC-458-10 option.
>
> For the group, please elaborate how you got a 10A equipped station on 
> 2 meters!
>
> The Best,
> Jim
> Wd5JKO
>
> On Wednesday, January 6, 2021, 5:56:38 PM CST, David Olean 
> <k1whs at metrocast.net> wrote:
>
>
> Hello CEers
>
> I am new to this e mail list. I have been a ham for a long time and used
> a Central Electronics 10A on 144 MHz back in 1965, I loved that rig. It
> was great rig that my brother and I could afford and it sure made DXing
> on 144 MHz a lot easier. We were both early proponents of SSB meteor
> scatter on VHF.  On 50 MHz, SSB was instrumental in popularizing
> ionospheric scatter for ham use in1965 as well. So fast forward a few
> decades and I found a derelict 20A at a flea market, and restored it in
> 2017 to use as a January 1st SKN rig. I was disappointed in that the CW
> keying was almost perfect. I was hoping to get a little bit of chirp or
> whoop on the signal.  I used a DDS VFO.
>
> I have since scrounged up a Central Electronics 458 VFO and have been
> working on it with pretty good results.  My unit has the 458-10  option
> but I am unable to find a schematic of this add-on kit on the internet.
> Can anyone point me to a good schematic?  I tried to reverse engineer
> it, but my shaky hands make schematic drawing somewhat problematic. My
> first pass was illegible!  It looks like the kit had a 48.4 MHz Butler
> oscillator that mixed with an 11-10 MHz signal from the 458 VFO to
> generate a 37.4-38.4 MHz signal for ten meter SSB operation.  I did get
> the 458-10 to work, but I sure would like a schematic of the ten meter
> kit for my records.
>
> I was a bit disappointed at how the ten meter assembly attached to the
> chassis in the BC-458. It used one screw on the VFO can to hold it
> down.  Coax cables were flopping around near the 1626 VFO tube and the
> 1625 buffer amp, causing frequency shifts depending on where the cable
> was! The VFO can that covered the VFO coil did not have all the screws
> for holding it down. This made for a distinct frequency "burble" on 5
> MHz.  I found a few more screws to fix that! I re engineered the
> 458-10  chassis, fitting a 1/8" aluminum plate to the bottom so that I
> could drill and tap some mounting holes and make a more secure mounting
> arrangement. The plate also was countersunk to make flush the mounting
> screws and the BC458 capacitor screws, so the kit assembly was securely
> flush and adequately fastened to the BC-458 chassis. It is now much
> better looking and seems quite rugged.
>
> One problem I noted was that the 10-11 MHz signal from the BC-458 was
> routed thru an RG-58 coax with the ground attached to the 458 chassis,
> but the center conductor was connected to the ten meter sub assembly
> which was not well grounded to the unit.  All this made for instability
> of the VFO. If anything moved, the frequency would jump a bit.  In
> addition to securely fastening the 10 meter sub assembly down tight, I
> added a ground lug on it to eliminate any ground inductance for the 10
> MHz coax cable.
>
> Anyway, I am rambling on here, but I wonder if anyone has a decent
> schematic for that ten meter CE option for the VFO?  It is referred to
> as a 458-10, and was available as a kit or factory wired.
>
> 73
>
> Dave K1WHS
>
> ______________________________________________________________
> Central-Electronics mailing list
> Home: http://mailman.qth.net/mailman/listinfo/central-electronics 
> <http://mailman.qth.net/mailman/listinfo/central-electronics>
> Help: http://mailman.qth.net/mmfaq.htm <http://mailman.qth.net/mmfaq.htm>
> Post: mailto:Central-Electronics at mailman.qth.net 
> <mailto:Central-Electronics at mailman.qth.net>
>
> This list hosted by: http://www.qsl.net <http://www.qsl.net>
> Please help support this email list: http://www.qsl.net/donate.html 
> <http://www.qsl.net/donate.html>