[HBR] Relay switched coils?

[Shoppa, Tim]

IMHO:

What makes an HBR, be an HBR, is not just the electrical topology, but also the construction and especially the bandswitching.

For the typical (e.g. doesn't own a machine shop) homebrewer a design that allows construction by a normal guy with hardware-store-class tools (possible exception: chassis hole punch) defined the HBR's construction.

I don't think it's impossible to build a homebrew, front-panel-bandswitched multiband radio. In fact two-band mirror-image receivers (esp 80M/20M) are practical and appear in many handbook receiver projects. And there were occasional every-band-under-the-sun-incredibly-mechanically-complicated-bandswitching homebrew radios in QST and handbooks too.But those aren't HBR's.

I say all the above having done some non-HBR-homebrewing. I think the beauty of the HBR can only be realized, in fact, if you attempt and complete a non-HBR style bandswitched radio.

It's kinda like saying, you can only appreciate the simplicity of a (original of course) Volkswagon beetle, after you've done a complete overhaul on a big-block-chevy engine. The beauty of a engine that you can overhaul on your kitchen table won't be appreciated otherwise.

Tim N3QE
________________________________________
From: hbr-bounces at mailman.qth.net [hbr-bounces at mailman.qth.net] On Behalf Of Peter Bertini [radioconnection at gmail.com]
Sent: Monday, May 31, 2010 8:40 AM
To: wrcromwell at gmail.com; HBR Receiver List
Subject: Re: [HBR] Relay switched coils?

T'would be nice if someone could engineer a duplicaticable plug-in coil
system, as used in the National HRO receivers. That would solve a lot of
problems, including trying to herd cats.. errr, a huge pile of loose plug in
coil forms that could be easily damaged or lost. National's tuning system
using a right angle drive solved a lot of the mechanical layout problems.

Didn't someone come up with scheme using the RF decks from old ARC-5/Command
surplus RXs for this purpose?  I'm still wrestling with ideas for my HBR
project; and the frontend tops the list.

Pete

On Mon, May 31, 2010 at 7:31 AM, Bill Cromwell <wrcromwell at gmail.com> wrote:

> Hi Walt,
>
> For relay switching there are also issues of oxidation on the relay
> contacts. The oxidation, even minor oxidation, degrades the performance.
> A solution for that is to apply a voltage across the contacts and the
> current will clean the contacts. Reed style relays will have contact to
> contact "scrubbing" and that abrasion will scrub the oxidation off
> without resorting to the extra trouble of the aforementioned
> voltage/current.
>
> I'm a fan of plug-in coils for their simplicity, reliability, and
> uncompromised performance. For miniaturizing radios, even toroidal form
> factors on high Q cores can be plug-ins. With plug-ins we have to be
> careful to not lose them during field operation. Of course, the plugging
> action cleans the contacts.
>
> 73,
>
> Bill
>
>
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