why TRF?

[Peter Ferrand]

Hi John:
I've had the exact same model for some years. For a Navy set
it's not all that massive.

It's also not really considered a TRF but a regenerative
receiver, although regens are TRFs if adjusted so the
detector doesn't oscillate.

This set was designed in the late 30's and the regens
offered several advantages. The oscillating detector is
isolated by several stages of rf amplification which may
have been easier to keep from radiating, since the Navy was
primarily concerned about receivers giving away their
location.

Total absence of images, except of course the one on the
other side of zero beat like all regens or direct conversion
sets. 

No AVC nonsense to deal with as there isn't any...the one
referred to on the panel is a level limiter, which works
fine but isn't an AVC in the more modern sense.

No local oscillator means no tracking or dial calibration
nonlinearities. There isn't a calibrated dial in the normal
sense just a turns counter on the tuning cap and the hand
done chart.

No S-meter calibration issues as there isn't one, the meter
just reads audio.

This receiver was mated with the LF version, the RAK, very
similar. Regens have extreme sensitivity and extremely low
internal noise, since there's no mixer noise and mixer
artifacts to deal with. This can be a huge problem in close
proximity to a transmitter, common on shipboard.

Regens also have continuously variable selectivity, which
has a shape factor which is poor by today's standards, is
preferred by some operators as it's very narrow at the top
and broadens out, somewhat like a Lamb type crystal filter
but without the ringing. The result is you can hear the
station you want but also hear the rest of the band, which
if you think of how shipboard ops work, is ideal. A lot of
cw ops prefer the sound of regens as they have an inherent
noise immunity and a sort of squelch effect that makes the
signals stand out better than the constant noise of a
superhet.

Although the design of this set is extremely well thought
out and a totally successful design, the concept is simple
and so maintenance would be simple, something also useful
for a shipboard RO. 

IMHO, this is set represents the peak of regen design. There
are two separate audio filters, one setting the broad-narrow
bandwidth and the other a sharp peaking filter, and its very
stable sounds good. Oddly it works well for sideband,
something the designers never anticipated. Haven't tried it
on PSK31. Regens weren't really developed beyond this and
the ones made in more recent times were basically sold as
toys for neophytes.

This sample looks extraordinarily clean, the gearing is very
nice. The cabinet is tightly closed so these units are
rarely dirty. Looks like the power cable has been replaced,
a good looking job. I see the auction makes no mention of
the power supply, which is nothing special but required to
run the set.  

All I can think of.
-Pete
WB2QLL
Somers, WI

> From: Boat Anchor Owners and Collectors List
> [mailto:BOATANCHORS at LISTSERV.TEMPE.GOV] On Behalf Of
> John N. Ritter
> Sent: Sunday, July 09, 2006 12:16 PM
> To: BOATANCHORS at LISTSERV.TEMPE.GOV
> Subject: [BOATANCHORS-TEMPE] why TRF?
> 
> Was just looking at this massive boatanchor:

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