[HBR] HB-67 -- And the 'RSGB Handbooks'

[hbr@mailman.qth.net]

Jim:
> Years ago, I suggested that maybe ARRL should do "Product Reviews" on
> older gear that was made before the current lab was in operation. Wouldn't
> ya love to know how an SS-1R stacks up when tested in exactly the same
> manner as a new Ikensu?

I have always felt that the ARRL preferred to say kind words about 
new products:  Since advertising is an important part of their revenue 
they're not exactly in an ideal position to do hard-hitting product 
reviews.   I believe it's only in the last few years and only for the best 
(most expensive) sets that solid state gear outperforms the better 
receivers in vacuum tube sets.   

>> indeed, probably any decent pentode would deliver an adequate 
>> noise performance [without an RF stage.]

> A lot of that depends on what you're using for an antenna. 

The norm in ham receivers is design for use with a normal 
transmitting antenna -- in general a resonant antenna of some form.  
If you're designing for something much smaller than a dipole or non-
resonant, then some gain ahead of the mixer will help.

Gain, however, comes at a performance price.   A receiver with the 
gain to do well with a clip lead on a nail in the BNC connector will 
need an attenuator to give good results on a resonant antenna.   The 
best way to deal with short antennas is to provide a high impedence 
antenna connection right to the hot end of the antenna coil.

>> On higher bands the HB-67 adds a converter and 
>> the properties of the converter then dominate noise 
>> considerations -- but with a high gain second mixer (the 7360) 
>> you're looking at a great deal of gain prior to the filter.  

> I think a lot of that gain is lost due to impedance mismatching.

I believe those Collins mechanical filters were designed to match 
vacuum tube plate circuits.   In any case if the gain is adequate on 
75 with no RF stage, then it's excessive on 40 with a preceeding 
RF/mixer.

> Any way to get a scan of the G2DAF receiver article? My RSGB
> Handbook is of early-'60s vintage. 

I'll see what I can do about scanning this.

For those not familar, the British 'radio amateurs handbook' 
equivalent is (for the amateur constructor) far superior to our own 
product.   First published in 1938 as 'The Amateur Radio Handbook' 
by the 'Incorporated Radio Society of Great Britain', it has continued 
to be published as wholly revised editions on an infrequent basis.   
The second edition (my oldest) was published in 1939 but the first 
printing was in July 1940 -- the very scariest part of the war in 
England; the third about 1961, the fourth in 1968 (coinciding with a 
change to the current title: 'Radio Communication Handbook'), and 
the fifth in 1976.   In between, successive printings (on an irregular 
schedule) include various revisions, often adding new projects and 
deleting others.

How to appreciate the differences between what is usually called the 
'RSGB Handbook' and our Radio Amateur's Handbook?   A good 
start is the following, from the preface to the fifth edition:

"[It takes] it for granted that the radio amateur continues to be keenly 
interested in the technical aspects of the equipment he uses.

"In recent years, amateur radio has developed in Europe along rather 
different lines from North America, with perhaps a little more interest 
in *why* as well as *how*.  This ensures that this handbook is not 
just a British version of the popular American handbooks ...

"Practical, down-to-earth information -- certainly every amateur needs 
that if he is to continue to represent a balanced combination of 
designeer, constructor, purchaser, and operator of modern radio 
equipment ..."

The key word in all that is 'practical' -- this is 'how to do it' for you and 
I on a scale not conceived in Newington for more than half a century.  
Compared to the RSGB, our ARRL "just doesn't get it."  Specifically, 
the RSGB books assume that you want to know (and hams *should* 
know, as part of the justification for our existance as a service) 'how 
it works' and 'how to *make* it work.'   

Our own books assume that hams divide into 'appliance operators' 
and 'degreed and practicing electronic engineers.'   The RSGB books 
are written for that minority -- probably you, and certainly I -- who are 
in between.   

The projects are an order of magnitude better thought out.   The 
G2DAF Mk II receiver (the one I mentioned) is described as "a later 
version of an advanced design which was built by about 1000 
amateurs ..."   Saving perhaps the 6L6 crystal oscillator transmitter 
of the 1948 book has there ever been *any* project in our own 
handbooks that was so widely constructed?   And this is a 15 tube 
double conversion bandswitching receiver with switchable selectivity 
and specs (IFDR 100 db!!!!) only dreamed of on this side of the 
Atlantic in the 1970s -- except perhaps for those possessed of the 
SS-1R.

For anyone who ever might build a receiver (or anything else in 
hamdom) these books are a fun read, not to say a fine source of 
project ideas and techniques.  You cannot go wrong by simply 
buying a copy of each edition from the third through the fifth, however 
you may then want to supplement the collection with one or two 
earlier or later printings of some editions.   To get the 'feel' with the 
most nearly current information, I suggest the fifth edition first -- all 
editions turn up on eBay as well as in other places where used 
books are sold.

Returning to Jim's post:

> I think that if you take a catalog of the HBR period and add up the
> price of all new parts to build [one of the W6TC HBR's], the total
> reaches a surprising figure. 

That's an interesting exercise and I think I have a suitable catalog.  
However, I'd expect most hams who would tackle this sort of project 
to get all but major parts from the junkbox -- they'd need a chassis, 
tuning cap, coil forms, fresh electrolytics, a bunch of small parts -- 
but not the transformer, tube sockets, most tubes, hardware, IFTs 
and so on.   

> The balanced beam deflection mixer is a real headache because you
> need to balance both the level and phase of both the LO drive and the
> output circuits - AND adjust the DC voltages on the electrodes to get
> equal gain on both plates. 

This was the reputation of the 7360 and if you followed that tube's 
trajectory in the U.S. ham marketplaces, sets that were introduced 
with it in some cases reappeared a year or two later as a Mk II with it 
gone -- you are not the first to find the characteristics unstable.   I 
*believe* that this was the problem solved by the 6JH8 and 6ME8 -- 
but until I see (or test) for myself, I won't hang a hat on that.   
However, I would *never* built a 7360 design without exploring the 
later tubes.  They were developed for mass production TV sets; 
disabling instability is highly unlikely.

> The problem of the BFO signal getting into the IF front end was there
> even in highly shielded/bypassed designs. 

In my experience only as a self-inflicted wound -- the consequence of 
a design or construction error.   I guess if you don't have a fairly 
square sided filter and *do* have high IF gain, it could be nasty.

Back to the workbench -- I'm getting ready to completely remove the 
three front end tubes of the 1MHBR in order to add the heat sink 
discussed a few days back.   

Walt
KJ4KV