[HBR] RE: Empirical Filters

[Walter A. Hutchens]

Don wondered:
> One question Walt? Where did you order your crystals from? I bet someone
> else is curious like me? International Crystal is about 10 miles from me.
> I have left an arm and a leg there before! Funny thing about the back
> customer service office at ICM. They have this big box full of thousands
> of crystals sitting in front of one of the desks. Must be either rejects
> or discontinued types. I need to ask them what they do with these. I
> suspect that ICM's days are numbered. They have moved from a large
> building into a very small one to cut costs I suspect.

As it happens I buy them from ICM.   I'm not surprised that they are having 
problems.   Part of their game has become a cheap commodity market ($0.41 
clock crystals) in which I can hardly imagine any U.S. maker competing and 
the rest (custom items) depends on service; theirs is so-so.   They mean well, 
but it takes a month or two to get a crystal from them and their web site 
barely reaches a high school project level of usability.   

> A thread on another site discussed the cost of parts to build tube
> receivers. It is getting harder to find quality vintage parts to
> reconstruct a 50's design which is the aim of many tube builders.
> Darned if a good chassis doesn't scare you off if you are 
> mechanically challenged like me and can't use a metal bender to make one.

Chassies are available from Mouser; I got a Bud CU 413 (10x12x3) in the 
mail Saturday for about $30 plus shipping.   There's really almost no modest 
receiver project for which you can't buy all the parts for under $200 
through the resources of Mouser, Antique Electronic Supply (tubes!), this 
list and eBay.   Considering that a receiver will take a few months to build 
and give you perhaps years of enjoyment, that's not an unreasonable price.   

$200 is what -- an average 20 hours take home?   The same bunch of parts 
in 1960 would have cost you more hours at work.   Crystals were $10 then, 
right?  Resistors then a 1960 dime apiece (am I remembering that right?), 
now less and in 2006 money -- and incomparably better.  100 x .01/500 disc 
ceramic capacitors = $24 now. Labor-intensive parts (chassies) are as costly 
now in constant dollars as then, rare stuff (audio and power transformers 
for vacuum tube circuits) has gone up unless you can get them as under-the-
table junk, but all the machine mass produced stuff is cheaper.   Tubes are 
almost all cheaper than in the 1960's and they're dirt cheap if you design 
around those that showed up too late to became popular.   In general these 
late tubes are better than the earlier ones, often much better.   

How much modern solid state gear can you buy for $200?   A decent FT-
101E ... maybe one step better if you have a friend.  

Hamfests are a great resource -- junk receivers and military sub-assemblies 
are a big source for me.   It's true vaccum tube construction is easier and 
cheaper if you do it regularly because you can buy in quantity and build up 
a stock over a few years.   

I think the main issue is that many parts are not off the shelf in convenient 
locations and because no two builders deal with the situation in quite the 
same way, you can't standardize a design to the extent you could 40 years 
ago.   Which means the builder needs to be able to make substitutions which 
requires judgement born of experience.   Unfortunately you can't get that 
experience as you could have in 1965 by picking up a current *Handbook* 
and ordering all the parts for the first two or three projects from Allied 
Radio or (if you happen to live in Boston where in 1965 they had their only 
three stores) going over to your nearest Radio Shack.   

But lists like this one can help, both by enabling parts sharing and as 
sources of advice.  

Lousy pictures of the 'R-8040A' are at:

www.timbreblue.com/radio31806.html

Looking at the rear view you can just see the 35W4 at the upper right next 
to the two gang antenna tuning cap.  The shielded tube closer to the camera 
than the tuning cap is the mixer.   The other two gang is the LO tuning and 
the tube just to camera left of there is the LO.    The IFs are across the 
rear; the two cans on the right are the IF input transformer and shield over 
the two crystal half lattice filter.   Detectors, BFO and audio stages on 
camera left.  

The wiring's not great -- I'll clean it up as I finish the diagram and minor 
tweeks in the next couple of weeks.  

Walt 
KJ4KV