 This
RDF appears in the 1960 book, Marine
Radio and Electronics,
by Allan Lytel, Cornell Maritime Press. But I found an ad (below) which
is from a 1958 magazine. This is a loop unit with tubes, and no
transistors. While the graphics of the panel, and the design of the
knobs both point
to late 50's style, the electronics seem to reflect a late 40's origin.
In addition, the chassis has the curious statement printed on it, "This
chassis treated with chromate converison coating military spec.
QQ-Z-325 for maximum corrosion resistance". My guess would be that
Apelco was building these for the military, or had built them (with a
different, more military face), and while they were at it, they "dolled
up" some as these DFR-12 units for civilian use. The chassis is very
military all around... with complete markings for most components,
waterproofed connections, and it is completely sprayed with the
waxy/plastic waterproofing... even the glass of the tubes! The unit
is very different in other ways from most of the direction finders. For
one thing, it has no built in speaker. It also has no provision for
batteries, taking an external 12v DC power
supply. Another seemingly military aspect is the 12v/32v switch on the
back. I'm sure that 32v is not used on any civilian equipment, while
12v, 24v, 32v and others are used by the military. It also has a full
eight slots for marine band crystals, both for reception AND apparantly
for DF'ing. There is a squelch knob, too... called a "Signal Gate".
Click for larger image. |
 Here is an advertisement from a 1958 magazine. It is copied from an eBay ad. Is it wrong to copy a scan from an eBay ad? Probably not any worse than cutting up a hundreds of beautiful old magazines, then offering the ads for $6.00 or more, which is more than the entire magazine was worth to begin with. I suspect that the destroyers of these magazines have very many loose ads they took out, which never sell, and will just end up being thrown out. |
 I
was lucky in that the Marine Radio book I have just happened to choose
this very model as an example. In fact, they copied much from the
manual (which I cannot find anywhere on the net) directly into the
book. They have the complete operating procedure and explanation of all
controls. The book describes it, "The Apelco Model DFR-12... combines a
direction finder and communications receiver. It has unusual
selectivity, and it's features include a null and sense meter
indicator, a signal gate control, a best [beat] freq uency
oscillator, and AVC (automatic volume control). Provision is made for
the use of earphone; however, the equipment is normally operated with
an external loud-speaker". And, "In the design of this diection finder,
temperature-compensated IF transformaers of critical coupling design
are used." There are several pages of this. And this is really unusual,
because this seems to be a less common unit, with many unique features.
If the author had chosen a more typical, ferrite bar transistor unit of
the time, it would have been much more useful to the readers. But it
worked out for anyone who finds one today, in any case.The fact that it is 12v rather than A/B battery powered means it should be easier to get going. Should be... but I haven't been able to yet. I replaced three tubes in 2007, and still cannot get it going. I am a newbie radio repair person, and so I am limited in tracing out a circuit I do not have a schematic for. I've recently (October 2009) taken the radio out to play with again, and look forward to giving it another try. The important thing for me will be to see the performance of one of these large loops... and this is one of the largest... before the last NDB's are gone... only two to five years left! |
