[HBR] So i'm gonna build an HBR-XX

[Marvin Match]

On 18 Feb 2009 at 12:00, xjakobx at gmail.com wrote:

> Hello List!
> 
> I'm starting to gather together parts for my HBR-styled construction  
> project. It's a long way from being started, but hey, i gotta get the parts  
> together sometime, right?

---snip---

A dial mechanism will be difficult. I've been looking for some time, 
and I have a National or two, but I really want an Eddystone. At this 
point I don't expect to find one.

So, I'll be making my own slide-rule mechanism. I'll share it all 
with the list, but I don't expect to make much progress for another 
month or so. I really wanted a gear-reduction dial made with anti-
backlash gears, but the gears themselves are expensive, so I found a 
variable cap made by TRW with an integral 6:1 ball reduction built 
into the shaft and I'll put a 6:1 Jackson ball reduction drive in 
front of it. That'll get me 36:1 reduction. I'd prefer about twice 
that, or three times that with a two-speed reduction, but I won't 
live long enough to find the parts to build it that way.

BTW, the National and Jackson reduction units are not all the same 
either. Line up 10 identical Nationals and each one will feel 
different. The Jacksons are more consistant and generally feel better 
than the Nationals, but the same holds true. The best that i've found 
are the ball reduction drives that you see on some military equipment 
that have threaded parts that you can take apart. Not sure who made 
them. Next is the Jackson like found in Heathkits, last is (most) of 
the Nationals, although like I said, once in a while you find a 
National that feels really good.

Another thing that will be difficult is the power transformer. Fair 
Radio Sales has one that might work. It's their TR180 for $18 here:

http://www.fairradio.com/catalog.php?mode=view&categoryid=1545

You'll need to add another transformer for the tube heaters if you 
choose this one as 1 A. @ 6.3 V. is not enough.

Coil forms are near impossible to find for reasonable money.

**Note to list: Anybody have spare coil forms?

I've been making my own out of 5-pin tube bases and 1 1/4 inch 
acrylic tubing with 1/8 inch wall thickness (I think that a 3-foot 
remnant piece was $12 from the plastics store). I tested all of my 5-
pin tubes and any that didn't test into the "good" range on my 
Jackson tube tester were sacrificed for coil bases. I chuck the base 
in my lathe and cut them down to .6 inches in height. Then if it's a 
fat base I machine the inside to accept the 1 1/4 inch tubing. If 
it's a skinny base, I machine the 1 1/4 inch tubing to fit over it. 

**Note to list: Anybody have some 5-pin tube bases or 
weak/dead/shorted 5-pin tubes they would be willing to pass along to 
me? I still need about a dozen for the two projects I'm working on.

Then, you'll need an enclosure to put it in. They too are hard to 
find. I found a B&K 1077B TV Analyst for only a few bux and after 
gutting it and making a new front panel I have nice enclosure with a 
hinged flip-top lid! In fact I bought two... one for my HBR and one 
for a matching transmitter. I think I paid $20 for the first one 
(locally) and $35 (total including shipping off e-bay) for the 
second. Watch e-bay, check around town. These were never all that 
useful, but they're entirely useless now, so a local repair shop 
might just give one to you if you make friends with them.

There's one on e-bay now if you want to see what it looks like. It's 
auction number is 230325967. The enclosure is worth the $30 starting 
bid on this one, but maybe not after the $40 shipping is tacked on, 
at least not to me. There's also a 1076 on e-bay that could be 
another possibility for an enclosure. These come up for auction all 
the time, so don't be in a hurry. Sooner or later one will be listed 
on e-bay that's close enough for you to pick it up.

A good variable cap is essential. Most anything out of a tube-type FM 
radio will work, but they're not all the same, and actually they're 
just a tad too small anyway, an extra pf or two at the top end or a 
pf or two less on the bottom would be better. I can't speak for the 
one you've found, it might be fine, but if you ever get the chance to 
get the one Ted specified... GET IT! 

I've thought about using one of the AM-FM caps like the one you've 
found, and using the two larger sections to cover 160 with no RF amp, 
but to do this easily you'd need 6-pin coils so that there's an extra 
pin for the 160 coils to catch those big tuning cap sections, and 
I've already invested a lot of time building 5-pin coils.

WOW! Am I long-winded or what?

Keep us posted, Jake.

Marvin
KA7TPH