[R-390] R-390 IF Deck

[Les Locklear]

Woooosh right over your head!


----- Original Message -----
From: Jim Whartenby via R-390 <r-390 at mailman.qth.net>
Reply-To: Jim Whartenby <old_radio at aol.com>
To: 'R-390 Mailing List' <r-390 at mailman.qth.net>
Sent: 1/12/2025 3:33:27 PM
Subject: Re: [R-390] R-390 IF Deck
________________________________________________________________________________

> Les
> No, I meant the R-725/URR, see:  https://sv7apq.blogspot.com/2019/03/the-
> r725urr-and-tropicon-project.html
> 
> The story was that the phase distortion caused by mechanical filters when the R-
> 390A was used for direction finding caused errors in the DF circuits.  Using 
> the R-390 IF in the R-390A chassis and a few mods to make it work eliminated 
> these location errors.  There are other stories in the above article but one 
> comment supports the DF story.
> Jim
> 
> Logic: Method used to arrive at the wrong conclusion, with confidence.  Murphy 
> 
>     On Sunday, January 12, 2025 at 03:08:42 PM CST, Les Locklear 
> <leslocklear at hotmail.com> wrote:   
> 
>  The R-390/URR predates the R-725/URR. you’re thinking about the R-390A/URR…
> 
> Sent from my iPadFrom: r-390-bounces at mailman.qth.net <r-390-
> bounces at mailman.qth.net> on behalf of Jim Whartenby via R-390 <r-
> 390 at mailman.qth.net>
> Sent: Sunday, January 12, 2025 2:57:26 PM
> To: 'R-390 Mailing List' <r-390 at mailman.qth.net>
> Subject: Re: [R-390] R-390 IF Deck OH, so it is an R-725 wannabe?
> Logic: Method used to arrive at the wrong conclusion, with confidence.  Murphy 
> 
>     On Sunday, January 12, 2025 at 01:12:01 PM CST, Jacques Fortin 
> <jacques.f at videotron.ca> wrote:  
> 
>  Jim, with all due respect, Byron is asking about the IF deck of a R-390 (a non-
> A, if you prefer).
> No mechanical filter in there, but a 6 stages IF strip....
> 
> 73, Jacques, VE2JFE in Montreal
> 
> -----Message d'origine-----
> De : r-390-bounces at mailman.qth.net <r-390-bounces at mailman.qth.net> De la part 
> de Jim Whartenby via R-390
> Envoyé : 12 janvier 2025 13:56
> À : 'R-390 Mailing List' <r-390 at mailman.qth.net>
> Objet : Re: [R-390] R-390 IF Deck
> 
> Where is S504?  I see S501, S502 and S503 but no S504 in the schematic or parts 
> list.
> I personally think that the 8kc mechanical filter now has a high insertion loss 
> due to the internal "rubber" isolator turning into goo or perhaps a weld 
> connecting a wire to a disk has failed.  I have seen both.  If one has any 
> mechanical skill and patients, the filter can be repaired by careful 
> disassembly and replacing the "rubber" isolator.  If it is a broken weld, the 
> filter is toast.  The filter repair info is in the Pearls of Wisdom, 
> IIRC.Regards,Jim
> Logic: Method used to arrive at the wrong conclusion, with confidence.  Murphy 
> 
>     
> 
>   
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