On Thu, 17 Feb 2005 23:32:36 +0000, "M. J. Powell"
wrote:

U-boats used HF for reporting back to base in Lorrient, but MF for talk
among themselves in the Wolfpack. It was this that was DFed by the
shipborne CRT DF.


By 'this', I assume you mean MF?

Thanks

--
73 for now
Buck
N4PGW

In message , Buck
writes
On Thu, 17 Feb 2005 23:32:36 +0000, "M. J. Powell"
wrote:

U-boats used HF for reporting back to base in Lorrient, but MF for talk
among themselves in the Wolfpack. It was this that was DFed by the
shipborne CRT DF.


By 'this', I assume you mean MF?

Sorry for vagueness. Yes, they used the lower frequencies for short
ranges, probably because the LF didn't travel far. (But far enough for
the RN)

Mike

Buck:

Aegean Park Press has reprinted Navy OPNAV 20 - 26 under the title "Direction Finding". It is a summary of what was
done and how as of 1947. Pretty complete summary of WW2 techniques. Aegean has a web site for descriptions and sales.
Note the spelling.

--
Crazy George
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"Buck" wrote in message ...
In WWII the allies were able to pinpoint the locations of German HF
transmissions very accurately. They were able to pinpoint the
locations of U-boats, etc. when they transmitted. (or so I have been
led to believe).

What methods did they use to do this? Is it something duplicatable
with Radio Amateurs in general or does it require some special type
equipment?


I hear lots of amateurs describing interference and other problems on
HF, but no one seems to be triangulating the offending stations. I am
guessing that the real secret was in their communications with the
'spotters' to triangulate the positions.

Any suggestions?

Thanks

--
73 for now
Buck
N4PGW

I hear lots of amateurs describing interference and other problems on
HF, but no one seems to be triangulating the offending stations. I am
guessing that the real secret was in their communications with the
'spotters' to triangulate the positions.

Adcock arrays http://www.airwaysmuseum.com/HF%20CR%20DF%201.htm
http://members.aol.com/BmgEngInc/Adcock.html
worked quite well, but they require precision in construction, as well as
the site.
For VHF/UHF, there are all sorts of things available
N0MKJ and I used to hunt with the "fox-copter", featured in the 3/94 73
magazine.

Here's some references in 73 magazine:
http://www.pejla.se/ardf_litteratur.htm

And a bunch of links to play with:
http://www.dxzone.com/catalog/Operat...ction_Finding/

On Fri, 18 Feb 2005 18:55:07 -0500, "Dave VanHorn"
wrote:


I hear lots of amateurs describing interference and other problems on
HF, but no one seems to be triangulating the offending stations. I am
guessing that the real secret was in their communications with the
'spotters' to triangulate the positions.

Adcock arrays http://www.airwaysmuseum.com/HF%20CR%20DF%201.htm
http://members.aol.com/BmgEngInc/Adcock.html
worked quite well, but they require precision in construction, as well as
the site.
For VHF/UHF, there are all sorts of things available
N0MKJ and I used to hunt with the "fox-copter", featured in the 3/94 73
magazine.

Here's some references in 73 magazine:
http://www.pejla.se/ardf_litteratur.htm

And a bunch of links to play with:
http://www.dxzone.com/catalog/Operat...ction_Finding/

Thank you,

I bookmarked the DF antenna and am reading the other articles.



--
73 for now
Buck
N4PGW

Buck:

A difficult to find but accurate book which answers your question about WW2 is "Secret Weapon" by Kathleen Broome
Williams published by Naval Institute Press. I no longer have a copy at hand, so I cannot quote figures for claimed
accuracy.

The reason Hams can't do this are two-fold:
1. Space
2. Money.

A good HF Adcock of WW2 design requires 10 or more acres to be accurate and is expensive to build because of the
mechanical accuracy involved. The 1960s vintage CDAA systems discussed typically require 40 acres, and the last
replacement cost figure I saw was over $100 million. The smaller "Pusher" systems are difficult to pin down price wise,
as they are out of production, but are still in the million dollar range for a prepared site, which for them is still
several acres. Measured sensitivity of the Pusher is 9 or 10 dB poorer than the full size CDAA, and the accuracy tends
to be less, although in both cases instantaneous accuracy is dependent on propagation and not system accuracy. Mobile
systems can be much less expensive, but to deploy one, you need to already know where the target is, more or less. By
the way, the last FCC mobile system I saw was in an unmarked Chrysler sedan with NO obvious external antennas.

And, even with the best equipment, a one degree accuracy (rare) still produces a large area of uncertainty at the target
distance. That is the key to understanding this. At a mile or a few blocks distance, a one degree accuracy will get
you to the target. At 2,000 miles, it just tells you which ocean the target is in.

--
Crazy George
the ATTGlobal.net is a SPAM trap. Use the att dot biz account.
"Buck" wrote in message ...
In WWII the allies were able to pinpoint the locations of German HF
transmissions very accurately. They were able to pinpoint the
locations of U-boats, etc. when they transmitted. (or so I have been
led to believe).

What methods did they use to do this? Is it something duplicatable
with Radio Amateurs in general or does it require some special type
equipment?


I hear lots of amateurs describing interference and other problems on
HF, but no one seems to be triangulating the offending stations. I am
guessing that the real secret was in their communications with the
'spotters' to triangulate the positions.

Any suggestions?

Thanks

--
73 for now
Buck
N4PGW

Crazy George wrote:
"The reason Hams can`t do this are two-fold:
1. Space
2. Money."

That`s usually true.

I don`e think anyone has mentioned Doppler or Quasi-Doppler DF systems
yet. I`ve seen hams using them but I have no experience with them.

Servo Corporation of America claims to have supplied over 350
Quasi-Doppler radio direction finding systems to the U.S. FAA and they
are used in airports throughout the U.S.A.

The angle at which a VHF signal wavefront passes over a small forest of
antenna elements is determined to give a bearing toward the transmitter.

It has been generally found that for radio direction finding that the
larger the antenna, the better the performance.. But, in the case of two
spaced antennas, the spacing must not exceed 1/2-wavelength to avoid
ambiguities. Peak error from an Adcocvk Array is 11.4 degrees, says
Servo Corp. Their Doppler Systems, they say, are much better.

I see what I suppose are Doppler antenna systems on the trunk lids of
police cars.

Best regards, Richard Harrison, KB5WZI

Actually, we have been skating around the real answer to all this. HF systems which are presently being deployed are
true mathematical interferometers, and if anyone has the computer expertise to write the computer programs to build one,
I can supply the RF design information. For 40 meters and down, this would require only a minimal antenna footprint,
local reradiators can be calculated out, and the rf and processing hardware would be surprisingly simple. I would be
happy to collaborate with anyone seriously interested in constructing one, but you better be ready to convince me you
can do high level programming. And based on previous designs, expect to invest about 4,000 hours in programming.

--
Crazy George
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