[HBR] Capacitor question - terminology

[Chris Howard w0ep]

I think I follow all of that except for your
reference to "band-imaging techniques" and how that
relates to a pre-selector control.

I'm not sure what that means.  Are you speaking of
an operator/using technique or a designer/builder technique?

I think Walt made reference to bandswitching and band-imaging
in a recent note also. (And so I kind of think your
use of the term is from a designer/builder standpoint)
I understand bandswitch just so far as it applies to the big
knob on the front and the wafer thing inside.

Can someone straighten me out?

Another term that has always been difficult for me is
"bandspread".  I understand that in such cases there
are two knobs.  One does large excursions and one
does smaller excursions, like the "fine tuning"
on the TV set I grew up with.  I can never remember
if "bandspread" means the coarse-change or the fine-change.
I usually guess wrong.





On 3/5/2012 5:50 AM, Shoppa, Tim wrote:
>> I see a wide variety of 3-section air variables on ebay these days.
>> I see a couple that have attractive gear drive systems on them.
>> (see 370590238594 for example)
>
>> I was wondering how hard it is to take plates out.  The capacitors
>> I see appear to have slots in the axle into which the plates fit
>> and have a small bakelite piece which drives all of the rotors at the
>> same time.
>
>> How hard is it to remove plates?
>
> It's straightforward but with close plate spacing and 3 sections would require a lot of care. It is a lot easier (hint hint) starting from a single-section unit with wider plate spacing.
>
> The types of caps where it's super easy: Single section. Here you disassemble the shaft and remove the unneeded sections and spacers, then reconstruct with the original spacers and put in a few handy extra spacers you have from previous cap reconstructions.
>
> For something like this, if you needed to just remove a few plates, you could go in with a Dremel or other good cutter and remove the plate or fraction of a plate you didn't need. But to turn this into a HBR tuning cap you'd have to remove 80% or more of the plates. What you picture is a nice cap suitable for a lot of homebrew uses... but is not a good cap for a carbon copy clone of the HBR-14 or -16 say.
>
> Some scandalous comments follow below:
>
> The original HBR design put a lot of attention on tracking RF and LO sections.
>
> This was back when the creme de la creme in any receiver was such tracking using a single tuning knob, it was an attempt to prove "this is as good as any commercial receiver".
>
> Unless the goal is to build a carbon copy of the HBR-14 or -16 or similar....
> I see no reason why a new construction HBR-inspired receiver would do the same. A separate "preselector peak" control, there's nothing at all wrong with that, and it lets band-imaging techniques come in too (techniques common on the good old Drake and other well-respected vintage  receivers).
>
> Tim N3QE
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