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Old 20-10-2013, 11:30   #31
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Re: Radio directional finder

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Originally Posted by Blue Stocking View Post
Bermuda still has some AM radio stations. Rotate a cast iron frying pan around your portable radio, and when you lose the signal, that the direction to the antenna. Gospel around here is to not go over the horizon without the frying pan.
Or, you could just follow the Longtails home.
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Old 20-10-2013, 12:53   #32
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Re: Radio directional finder

All Coast Guard and military ships have them and sword fishing boats still use them with their beacon buoys to find their gear
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Old 20-10-2013, 13:06   #33
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Re: Radio directional finder

I had one that was a dandy. It was about 6"by8" and maybe 4" tall with a metal case, it had the bar antennae and a standard telescopic antennae with a selector switch for AM-FM-Marine and a switch for the BFO (Beat frequency oscillator) so you could hear the signal from lighthouses and radio transmitting buoys. Probably the "Real Deal" of it's day but not so effective anymore.
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Old 20-10-2013, 15:14   #34
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Re: Radio directional finder

RDF for AM band direction finding were the only cheap electronic means of getting an LOP from shore up until SatNav and later GPS came on the scene. You can still use them to get direction of AM radio stations but the accuracy has always sucked, big time, if the transmitter tower isn't almost on the water. Basically, they were useful for finding North America when sailing west in the Atlantic. Never did and wouldn't trust them to do more than tell the general direction of land as a last resort measure.
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Old 20-10-2013, 16:31   #35
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Re: Radio directional finder

I'm very fond of the RDF technology. It has saved my bacon several times, including one memorable sail up the Adriatic from Corfu to Dubrovnik in thick fog. I used radio stations in Bari and Brindisi on the Italian coast to provide "back sights" and guide us with enough accuracy to get there.

Still have five RDF units. I still carry two aboard my boat (Brooks and Gatehouse Homer/Heron model....shown below...and a Raymarine unit with a digital readout). These days they get used mostly for tuning AM stations, as do the three RDFs in my house....two are shown in the second photo below....in fact, they stay tuned to ESPN radio to provide the sports news at breakfast time.

As was mentioned above, RDF units are still in use for a number of specialized applications, like zero-ing in on VHF transmissions (USCG), homing in on the 121.5 mHz signals from EPIRBs, military uses, etc., etc.

Old technology? Yes, decidedly.

Still useful in the era of GPS? Yep, I think so, as do many others who use it for specialized purposes, for entertainment, and to kick up the nostalgia pangs.

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This is the famous Brookes and Gatehouse Homer/Heron unit (upper left); the antenna with compass unit can be seen just below and to the right.

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These lovely little Japanese-built units were sold under several brand names. They are well built, have internal D batteries, have a good sound, and are often available in nearly new condition for around $50.

Re: the ambiguity of nulls and the use of the sense button, if you don't know which of two bearings 180-degrees apart is correct, you really shouldn't be out there :-)

Bill
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Old 20-10-2013, 17:23   #36
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Re: Radio directional finder

Dedicated DF beacons - normally adjacent to light houses- for use by merchant ships were phased out when GPS appeared. The 3 linked beacons in Bass Strait -Otway/Schank/Wickham(KI) were turned off in the early '90s and the transmitter at Cape Schank was then used to transmit the signal for use with DGPS... it maybe still is.

Shore stations could also fix your position using a number of coast stations , that required the R/O to hold the key down for a spell will they got a fix on you. That was also used in distress working... in a typhoon we were once given our position in very short order when east of Okinawa by US stations ashore there... I was impressed.

A danger in using Aero beacons situated inland was/is refraction of the signal if it was crossing the coast at an oblique angle.
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Old 20-10-2013, 17:29   #37
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Re: Radio directional finder

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......These days they get used mostly for tuning AM stations,....
Bill
That was also their primary use on the bridge of merchant ships during the 12 to 4 watch
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Old 20-10-2013, 19:13   #38
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Re: Radio directional finder

Jeez I haven't seen one of those since the mid 80s. Didn't know anyone still used them.
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Old 20-10-2013, 19:46   #39
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Re: Radio directional finder

I used to have a handheld RDF I used in Maine in the late 70's. It helped a lot. You can still buy one on Ebay.

Also on Ebay, is this great ad for RDF and radio telephone. It's a shame that so few of us wear a coat and tie anymore when using our radio...
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Old 21-10-2013, 19:18   #40
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Re: Radio directional finder

1987 was the last time I used one. On a charter boat. Couldn't afford a Loran C you know. I was quite comfortable with the RDF. It was a golly gee whiz bang hi tech gadget all right.
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Old 22-10-2013, 14:49   #41
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Re: Radio directional finder

Radio direction finding has lots of applications today, mostly tracking down interference signals.

The ferrite and loop systems for MF and HF still work of course but generally folks use pseudo-Doppler RDFs at VHF, UHF, and up. The four small vertical antennae on USCG small boats and Towboat/US boats are for pseudo-Doppler.

It's used for all kinds of things including sinking boats, EPIRBs, interferers, tracking down cell phones, LoJack, and more. You can build your own for marine VHF with a radio and about $300.
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Old 22-10-2013, 14:53   #42
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Quote:
Originally Posted by Auspicious View Post
Radio direction finding has lots of applications today, mostly tracking down interference signals.

The ferrite and loop systems for MF and HF still work of course but generally folks use pseudo-Doppler RDFs at VHF, UHF, and up. The four small vertical antennae on USCG small boats and Towboat/US boats are for pseudo-Doppler.

It's used for all kinds of things including sinking boats, EPIRBs, interferers, tracking down cell phones, LoJack, and more. You can build your own for marine VHF with a radio and about $300.
Where do I find plans?
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Old 22-10-2013, 15:10   #43
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Re: Radio directional finder

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Originally Posted by Adelie View Post
Where do I find plans?
Google psuedo-Doppler radio direction finding.
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Old 29-11-2013, 10:53   #44
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Re: Radio directional finder

Crossing the Atlantic in '83 by the trade wind route in our 48ft cutter, we had great fun zeroing in on Antigua from about 800 miles out using our tranny (transistor radio with a rod aerial ) to guide us with reggae from an island radio station. Those were the days!!!!
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Old 12-12-2013, 18:21   #45
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Quote:
Originally Posted by btrayfors View Post
I'm very fond of the RDF technology. It has saved my bacon several times, including one memorable sail up the Adriatic from Corfu to Dubrovnik in thick fog. I used radio stations in Bari and Brindisi on the Italian coast to provide "back sights" and guide us with enough accuracy to get there.

Still have five RDF units. I still carry two aboard my boat (Brooks and Gatehouse Homer/Heron model....shown below...and a Raymarine unit with a digital readout). These days they get used mostly for tuning AM stations, as do the three RDFs in my house....two are shown in the second photo below....in fact, they stay tuned to ESPN radio to provide the sports news at breakfast time.

As was mentioned above, RDF units are still in use for a number of specialized applications, like zero-ing in on VHF transmissions (USCG), homing in on the 121.5 mHz signals from EPIRBs, military uses, etc., etc.

Old technology? Yes, decidedly.

Still useful in the era of GPS? Yep, I think so, as do many others who use it for specialized purposes, for entertainment, and to kick up the nostalgia pangs.

This is the famous Brookes and Gatehouse Homer/Heron unit (upper left); the antenna with compass unit can be seen just below and to the right.

These lovely little Japanese-built units were sold under several brand names. They are well built, have internal D batteries, have a good sound, and are often available in nearly new condition for around $50.

Re: the ambiguity of nulls and the use of the sense button, if you don't know which of two bearings 180-degrees apart is correct, you really shouldn't be out there :-)

Bill
That's the one I remember late 70early 80's. I remember it being baby blue in color and the size of a full on record player with built in speakers. Minus the pennies taped to the record arm to keep it from skipping. Lol.
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