[ARC5] [Milsurplus] Scott SLRM - Low BFO Injection
Christopher Bowne
aj1g at sbcglobal.net
Wed Sep 11 09:46:26 EDT 2019
From someone who used an SLRM as my Novice station receiver, the injection level is very low. Very difficult to receive strong signals on CW or SSB at any appreciable volume without overloading the detector with received signals. Re keeping the injection low to meet Navy incidental radio action requirements, not sure that is why it’s so low on the SLRM, the RCH/SLR-12B which was used as a communications receiver in the Mackay radio systems on Liberty Ships was also an SLR receiver and has a very robust BFO. Scott did not sell the Navy on the SLR concept, I have read that the Naval Research Lab (NRL) established the SLR incidental radiation requirements based on actual testing and evaluation. All shipboard radio receivers in WW2 had to meet these standards. I have seen photos of some receivers, perhaps SX-28s, that while used by the Navy, had large stickers affixed to them stating “Not for Shipboard Use”.
Chris Bowne
AJ1G Stonington CT
Sent from my iPhone
> On Sep 11, 2019, at 01:47, Richard Knoppow <1oldlens1 at ix.netcom.com> wrote:
>
> I can't find the original post. How is it being determined that the injection is low? Many receivers have minimal BFO coupling both to avoid pulling of the BFO by the signal and to avoid activating the AVC when it can be used on CW.
> My AR-88 has fairly low BFO injection but its adequate. The coupling is via stray capacitance. At some point the wiring was re-arranged. I tried it both ways and went back to the original. It works OK for SSB but, as with most receivers without product detectors, the RF gain has to be run low.
>
>> On 9/10/2019 9:44 PM, Bart Lee wrote:
>> 2 cents:
>> The SLR stood for Special Low Radiation. Scott sold the Navy on the idea that heterodyne oscillations could betray a ships position to a submarine. (That /*maybe*/ happened once in WW I as a result of a regenerative receiver ... but better safe than sorry, and rich on government contracts). Note the full copper shielding on the SLR.
>> The BFO question is */maybe/* related: another oscillator could inject RF and */maybe/* that RF could get out, /*maybe*/... So it would make sense to limit the injection. (But I've never seen this aspect discussed and don't know of any references).
>> 73 de Bart, K6VK ##
>> -- --
>> Bart LeeK6VK, CHRS Archivist, AWA, ARRL
>> Texts only to: 415 902 7168
>> www.bartlee.com <http://www.bartlee.com/>
>> {KV6LEE(at)gmail(dot)com} ##
>> <http://www.LawForHams.com>
>> On Mon, Sep 9, 2019 at 8:14 AM Hubert Miller <Kargo_cult at msn.com <mailto:Kargo_cult at msn.com>> wrote:
>> -----Original Message-----
>> From: milsurplus-bounces at mailman.qth.net
>> <mailto:milsurplus-bounces at mailman.qth.net>
>> <milsurplus-bounces at mailman.qth.net
>> <mailto:milsurplus-bounces at mailman.qth.net>> On Behalf Of
>> Kenneth G. Gordon
>> Sent: Sunday, September 8, 2019 7:44 PM
>> To: milsurplus at mailman.qth.net
>> <mailto:milsurplus at mailman.qth.net>; David Stinson
>> <arc5 at ix.netcom.com <mailto:arc5 at ix.netcom.com>>;
>> aRC5 at mailman.qth.net <mailto:aRC5 at mailman.qth.net>
>> Subject: Re: [Milsurplus] Scott SLRM - Low BFO Injection
>> I have always thought the Scott receivers were excellent.
>> One of the first such I ever had was an SLR-F....which was
>> named the RCH by the Navy.
>> The SLR-F/RCH covers some MF and lower HF frequencies, up to
>> 24 MHz.
>> I have two now, one of which is deaf, which I want to restore
>> and use.
>> They are excellent receivers, stable, reliable, not
>> particularly sensitive, but sensitive enough.
>> And I really like the flywheel tuning.
>> The dial on your SLR-M looks almost identical to that in the
>> SLR-F.
>> BTW, if you don't know, the SLR stand for Super Low Radiation.
>> Ken W7EKB
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>
> --
> Richard Knoppow
> 1oldlens1 at ix.netcom.com
> WB6KBL
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