[ARC5] Using BC-454 as backend

[J Mcvey]

Using a R-25  (1.5-3 Mhz) makes a whole lot more sense and would be more selective as well.Have you tried tuning the second  harmonic of the converter ( around 3.050) on the BC454? 
I don't think it's practical  to retune the IF's...
 

    On Wednesday, January 24, 2018 10:16 PM, D C _Mac_ Macdonald <k2gkk at hotmail.com> wrote:
 

 #yiv6333258060 #yiv6333258060 -- P {margin-top:0;margin-bottom:0;}#yiv6333258060 I used an R-25/ARC-5 for the fixed I.F. for a Morrow 5BR-1 converter as my primary station receiver for several years in the mid-1050s.  I believe you would be happier from a selectivity standpoint going that way instead of trying to convert your BC-454 I.F. to 1525 kHz.

73 de Mac, K2GKK/5
(Since 30 Nov '53)
Oklahoma City, OK
USAF Retired 61-81
FAA Retired 94-10

From: arc5-bounces at mailman.qth.net <arc5-bounces at mailman.qth.net> on behalf of Ian Wilson <ianmwilson73 at gmail.com>
Sent: Wednesday, January 24, 2018 20:45
To: ARC5
Subject: [ARC5] Using BC-454 as backend I am working on using a BC-454 as backend to a Morrow converter. TheMorrow produces 1525kc for a BC band car radio as backend. My planis to use the BC-454 with IF and BFO tuned up from its original 1415kc.The idea is to make 100% reversible changes only.
So far I have dug out and reanimated a BC-454. This works OK as a receiver -tested with 4MHz input. Tested all the tubes - all good except a dead 12SK7.
So the next step was to remove the RF amplifier and converter tubes andtap into the input to the first IF transformer. This appeared to be working OK.
Next step is to retune the BFO, align the IFTs to 1525kc (obviously I don'tknow whether they will pull this far. If not, have to think of a Plan B). However,came across a problem - if I retune the BFO too far it apears that the IFstrip itself starts to oscillate. Not sure whether I am diagnosing this correctly.
Perhaps a screen bypass capacitor in the IF stages? There is some sign ofleakage from some of the metal can capacitors.
Originally I left the primary of the 1st IFT floating. Bad idea. However, puttinga few kOhm (with series 0.01u cap to keep the HT happy) to ground made nodifference whatsoever.
I'm sure numerous people over the aeons have trodden this path. Interestedin any suggestions.
73, ian K3IMW
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