[HBR] Now I know where some of you are and Nice job Walt (again)

[Don]

It is sad about ICM but I guess that is the world economy. Cheap labor
is hard to compete against. One thing about ICM is that several local
hams still work there.

Excellent layout on your receiver Walt. The transformerless desing is
evident and makes the rig look sleek and compact. The wiring looks fine
to me. I like your enclosed speaker and the miniature meter. I built a
large 10" tuned speaker for my stations with a built in anti-hiss audio
filter. Very radical design but largely a bigger version of the enclosed
speaker you have. But it is the only thing that keeps my RX from being
self contained.

I also noticed the clean layout of your tubes and particularly the front
panel. I know how much thought you need to put into that layout. I
usually draw everything up on a full sized paper drawing before I cut
any holes. That avoids some mechanical or electrical conflicts later.
Nice knobs too. I love old bakelite knobs. They somehow make the
receiver sound better(?)

I am glad someone mentioned the cost of a receiver and why it is worth
it. I personally like to buy everthing new or make it. New means
avoiding any problems down the road (maybe). Making it means you can
repair or update it.
Sting and drum tuning mechanisms are my favorite. I have a design that
uses a bottle cap for the drum.  All the hardware is new from Hammond in
Canada. The only used items in my receiver are two of the pots used for
RF and IF gain. They came out of a stand by replacement module for some
oilfield gear so they saw little or no use. Mouser is my biggest
supplier and OnLine Metals is good source for the front and bottom
panels. They often send scratched sheets but some super fine auto
rubbing compound usually cleans that up. Angela Instrument has great
prices on Hammond items and ships fast. 

I found some pictures of the bottom of my receiver on K5DOA's, Darwin in
Texas, web site. Some other great boatanchor stuff there. I run into
Darwin and his buddy Dennis, W5FRS on 7.050MHz a lot. His site includes
some other tube guys with some very interesting stuff. The K2LMQ
warehouse full of Boatachor gear kinda makes your jaw drop. Complete
with a fire engine!

http://www.k5doa.net/Boatanchor/index.html


If you should get to my pictures. The receiver wiring is mostly RG-174
including the filaments. I actually did double wiring having to solder
both shield and center conductor. But it was worth it. The small PC
board is the two 2n2222's used for the BFO. Not being a total tube
purist, I was curious if SS and HS could be mixed and it proved an
excellent experiment. Simple 1N4007's are used to tune the crystals from
the front panel. I used several small PC board trimmers in the receiver
which helped reduce the over size of the receiver. There are actually
two power supplies on board. On the back of the chassis is a 12VDC
regulated supply for the BFO and will be used for the convertors for 20
and 15M. I have lots of room left as you can see. The HV supply uses
100uF capacitors. They were  a single 47uF but the larger caps knocked
out some hum. There is actually 200uF of filtering as I used choke
input. I just separated the two with a 150 Ohm resister. There is
another 100uF decoupling cap in the audio stage. This also contributed
to a quieter audio stage. I hate hum and hiss.

Lastly and the main reason I wanted to show my under chassis. There are
two small PC boards, one about halfway up the input tuning shaft and the
other to the left. These are the prototype input transformers for the
ladder crystal filter. Merely one inch scrap PC board squares that were
filed down to make pads. They are ugly but worked so I left them. 

http://www.k5doa.net/Boatanchor/K5UOS/RXbottom43d91c996_jpg.html


The nice thing about this technique is that the filters can be mounted
above or below chassis. They don't need to be in proximity to the IF
tubes either if RG174 is used. Relaxes the constraints in layout
somewhat. The matching networks could be assembled in the same box as
the filter and could be L or PI networks.

There is one lone shielded slug tuned can still on the receiver. I
originally used lattice filters and included a tail filter for wideband
IF noise. It actually worked too. The lattice filters were ok but the
ladder filters give much, much better skirt selectivity and provide a
little better opportunity for closer impedance matching and controlling
the shape of the filter. After going to the ladder filter the defunct
can was not used. I tried using it for peaking the IF but it didn't make
any difference so I gotta find another use for it. I may still add a
ladder type tail filter.

The large box on top contains the tuning cap and toroid VFO coil. In
front of the box is the 10:1 homebrew string and drum mechanism. I tried
an additional 6:1 panel mount Jackson brothers drive on the shaft with
the big knob but 60:1 was tedious to tune with.  I haven't figured out a
good dial plate yet and use an old knob. I just "discovered" small CD's
so I will probabaly use one of those. The coil is mounted inside on a
1.5" ceramic standoff to isolate it from heat. The VFO uses a colpitts
configuration. Mouser grain sized KEMET NPO caps were used. These are
200V caps and enamel encapsulated. They seem to compensate very very
fast and are not particularly prone to problems with heat. Many caps are
paralleled for stability. I temperature compensated with two siver mica
caps. The toughest mechanical work was aligning the ganged input tuning
shaft. I am weak on mechanical work.

I hope this way too long explanation gives someone a few alternative
approaches and ideas for receiver construction. Walt always gives me
ideas as do the schematics Kee's provides. Please excuse my irreverant
use of solid state technique on this fine tube site. It trully is out of
respect for the old timers who did the best they could with what they
had availble at the time. For me, I just didn't know any better.

Don K5UOS