Please Help Me Identify this Piece of Equipment

[Don C L]

Originally Posted by Jim Cate

The proper RDF beacons were using frequencies near 500 kHz, and the broadcast band is ~600 -1600 kHz. A long way from the VHF 120 megahertz used by PLBs... no chance that the old RDFs can be used for this function.

Too bad...

Jim

Yeah I immediately thought about that... I could not remember if I had ever seen those frequencies... my old one couldn't do it ... maybe some old military ones on eBay? With vacuum tubes? I'm outta my league in that dept. (I'm outta my league in a lot of depts!) That reminds me, a bit off topic, but I remember my Air Force pilot brother commenting on the Mig jet that a defector flew to Japan many years ago. All the electronics in it were vacuum tubes. They all got a big laugh out of it till they found that the vacuum tubes would probably survive the electromagnetic pulse from a nuclear explosion, whereas the more modern electronics at the time would not....

[Wotname]

FWIW, the frequency band allocated to RDF transmitters is 200KHz to ~500KHz, the AM broadcast band then continues to ~1600KHz; thus most (all?) RDF receivers in modern times (post WWII) operate between 200KHz and ~1600 KH.

[Wotname]

Originally Posted by svHyLyte

Yes. Moreover, there are fixed broadcast antenna for AM/FM radio stations in many coastal locations that are plotted in the listing of broadcast beacons with position and broadcast frequency information. We have/use (occasionally) a Seafarer Navigation Ltd. Seafix 2000 RDF (hand held). With that one can easily generate LOP's that can give one a position or a "homing" course line. Crossed LOP's (3 preferably) can give one a reasonably accurate fix--at least as good as a star/sun site-- and I figure that if the uncertainty is less than the distance to the horizon, I'm good to go. Three LOP's generate a "cocked hat" from which the error of position is generally less than 1000 yards.

FWIW...

Originally Posted by BlueChicago

Thanks dfelsent, I will likely try to get power to the device this weekend. I imagine that Chicago has no shortage of radio stations within reach.

Everyone has been helpful. I appreciate it.

-BC

There are a couple of significant errors that can occur using RDF techniques.
The principle ones are coastal effect and night effect. Both can cause large positional errors. Particularly coastal effect which can "bend" the radio bearing by up to 20 degrees.

Coastal effect occurs when the receiver is well offshore (say >50 miles) and the transmitter is well inland. Depending on the relative bearing of the signal to the coastline, large errors can occur.

Night effect (usually most prominent at dusk and dawn IIRC) can also cause largish errors due the interaction of the skywave and goundwave components of the radio signal as they vary between night and day (due to the changing ionosphere). Again IIRC, the effects are greater when more distant from the station.

[dfelsent]

I just dragged out my Sailor RDF. It has a feature that helps reduce another source of error. The antennas in RDF units sense a null when pointed towards or away from the signal. This one has a sense button. When pressed it reduces or increases the signal when pointed towards or away from the source. I can't remember which of course.
I can't believe I have two RDFs. The sailor and a B and G. I might have an old apelco too.
No im not a hoarder but I'm a sucker for old electronics that my dad gives me.

[a64pilot]

Originally Posted by Don C L

Yeah I immediately thought about that... I could not remember if I had ever seen those frequencies... my old one couldn't do it ... maybe some old military ones on eBay? With vacuum tubes? I'm outta my league in that dept. (I'm outta my league in a lot of depts!) That reminds me, a bit off topic, but I remember my Air Force pilot brother commenting on the Mig jet that a defector flew to Japan many years ago. All the electronics in it were vacuum tubes. They all got a big laugh out of it till they found that the vacuum tubes would probably survive the electromagnetic pulse from a nuclear explosion, whereas the more modern electronics at the time would not....

The whole Soviet Command structure as far as radios and who communicated was different too. For instance only the Commander of a tank unit had a radio that could transmit, all others were listen only.
Even in the early 80's it was astonishing what could be done, special "tempest" communications equipment was devised. For instance you could detect and listen in on a communication from just the leaking RF from a regular carbon microphone from very surprising distances, not what is was connected to, but just the RF coming off of the mic.
Old school tubes have their place and are less susceptible to certain other technologies.

https://en.m.wikipedia.org/wiki/Tempest_(codename)