[Milsurplus] LO DF ing

Hubert Miller kargo_cult at msn.com
Thu Aug 25 15:08:39 EDT 2016


>......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 <http://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 

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