[Milsurplus] LO DF ing
Mike Feher
n4fs at eozinc.com
Thu Aug 25 15:17:29 EDT 2016
Back in the mid 80’s I worked for Melpar in VA. At that time my team of engineers were working on state of the art receivers for ECM and ECCM. The LO re-radiation specifications were very difficult to achieve. 73 – Mike
Mike B. Feher, N4FS
89 Arnold Blvd.
Howell, NJ, 07731
732-886-5960
From: Milsurplus [mailto:milsurplus-bounces at mailman.qth.net] On Behalf Of Hubert Miller
Sent: Thursday, August 25, 2016 3:09 PM
To: Milsurplus at mailman.qth.net
Subject: Re: [Milsurplus] LO DF ing
>......For those who haven't actually used RDFs there is an idea that you can get a good bearing on any signal you can hear. In practice that's not usually the case. It takes a strong signal to get a sharp reliable null. Weak signals give really broad to almost useless nulls.
Thanks for your very worthwhile input. The above point is one that many of us apparently overlooked. It’s one thing to detect a weak carrier and another thing to get a worthwhile bearing from it.
>For fun I tuned around for LO sigs from AM marine band xcvrs and never was able to even hear any at any appreciable distance from another boat much less shoot a bearing on them. I'm sure the designs were a lot less leaky than WW2 radios however.....
AF6IM
www.parachutemobile.com
I would say, not necessarily so. Very many of the 1940s-1960s marine band transceivers did not have an RF stage, went right into the pentagrid mixer. So some post-war radios were not necessarily
better in this respect than WW2 radios. From what i have seen, generally only the highpower high-seas types included an RF stage, i mean with transmitters of the 100-250 watt class and tuning range
higher than the 1.6 – 3 MHz channels. I think that the start of WW2 ended use of really simple regen receivers at least for the USA and UK. A single RF stage actually isolates receiver oscillator from the
antenna well enough to eliminate any potential DF location – though not always enough to prevent pickup from nearby receivers.
I have a two U.K. built merchant ship’s regen receivers. Both WERE used in WW2 and each has one RF stage, which was apparently found to be enough for their use – in a non-multiple receiver environment,
obviously.
Remember that story about a Brit ship that disappeared, sunk in North Atlantic in 1947. The Admiralty inquiry report listed the wireless equipment as a Marconi 730 regen and a spark transmitter ( ! ).
With this equipment it had made it thru WW2.
-H
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/milsurplus/attachments/20160825/211a3f8f/attachment-0001.html>
More information about the Milsurplus
mailing list