Re: {Collins} [Collins] 51J4 Alignment Question



Generally speaking, calibrating the IF gain to establish an overall RF/IF
target value helps establish the AGC threshold and gain curves at the
correct design levels.  Having said that 250mV vs 270mV is plenty close
enough.

Dennis AE6C


On Fri, Aug 23, 2013 at 5:56 PM, Fern <crc@xxxxxxxxxxxxxxx> wrote:

> If the I F alignment is off centre of 500 khz by a fair amount, it will
> severally affect the narrower 3 khz filter but barely noticable on 6 khz or
> wider filter.  Fern  VE7GZ
>
> ----- Original Message ----- From: "Richard Knoppow" <
> dickburk@xxxxxxxxxxxxx>
> To: <crc@xxxxxxxxxxxxxxx>
> Cc: "Collins@xxxxxxxxxxxxx" <collins@xxxxxxxxxxxxx>
> Sent: Friday, August 23, 2013 9:07 AM
>
> Subject: Re: {Collins} [Collins] 51J4 Alignment Question
>
>
>
> ----- Original Message ----- From: "Grant Youngman" <nq5t@xxxxxxxxx>
> To: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
> Cc: "Collins@xxxxxxxxxxxxx" <collins@xxxxxxxxxxxxx>
> Sent: Wednesday, August 21, 2013 10:04 AM
> Subject: Re: {Collins} [Collins] 51J4 Alignment Question
>
>
> Just to follow up on my question.  My receiver is an early
> one, and does not have the IF gain control.
>
> Finished the alignment of the receiver, and measured the
> gain from antenna terminal to IF output.  3 uV RMS in at the
> antenna terminals yields 250 mV RMS at the IF output port.
> The alignment spec for receivers with the IF gain control is
> 270mV out.  I figure that's close enough not to worry about.
> I think someone also indicated that the IF output signal was
> loaded down by the detector and was badly distorted and not
> very sinusoidal (?).  I did not find that to be the case.
>
> Which still begs the question … why did Collins feel the
> need to add the IF gain control in the first place?  I can
> only suppose it had to do with the fact that some
> contracting officer put it in a specification somewhere
> along the line.
>
> Grant NQ5T
>
>
>>  I've been reading over the alignment instructions for the 51J4 getting
>>> ready to touch mine up.  In manual section 5.3.17 (1962 manual), it gives
>>> instructions for setting IF gain.  My question is whether the input
>>> (antenna terminal) and output (IF output) voltages indicated are peak or
>>> RMS.  I presume it doesn't actually matter as long as both measurements are
>>> taken the same way, but thought I would ask.  I think I've also seen a
>>> comment in a posting somewhere that it isn't worth worrying about and that
>>> the IF gain should just be set to maximum.  Any input on this?
>>>
>>>
>     Its hard to know without having definite documented
> information. One thought is that it had to with compensating
> for losses in various mechanical filters but that doesn't
> quite hold water since there were three filters in the 51J-4
> and I don't think other receivers with mechanical filters
> had gain trimmers.  The other thought is that it was added
> to allow matching gain in receivers used in diversity
> set-ups.  The 51J-4 had the other connections for diversity;
> AVC and detector load so were evidently sometimes used for
> this.  In diversity its necessary to "best" the receivers so
> that the receiver with the highest gain does not dominate.
> The range of the trimmer is evidently pretty wide but the
> gain trimmers on the SP-600-JX17 and RCA AR-88F also have a
> lot of range. This is all speculation, perhaps someone on
> the list knows for certain.
>
>
> --
> Richard Knoppow
> Los Angeles
> WB6KBL
> dickburk@xxxxxxxxxxxxx
>
> ______________________________**_________________
> SHARE THE FUN: JOIN THE COLLINS COLLECTORS ASSOCIATION TODAY !
> http://www.collinsradio.org/?**page_id=37<http://www.collinsradio.org/?page_id=37>
>
> NETS: Tues & Thur: 3.805 MHz-2000 Central + Fri: 3.895 MHz-2000 Pacific
>  SUNDAYS: 14.263 MHz-2000 UTC  +  AM Net: 29.050 MHz-1200 Central
>  1st Wednesday AM Net 3.880 MHz-2000 local (ET, CT, MT, PT)
>
> The Collins Reflector reserves the right to refuse access to anyone.
>
> LIST HELP?  ADMIN EMAIL:  collins-owner@xxxxxxxxxxxxx
> This ONLY goes to the list admins and does not post to the group!
>
> *** You are subscribed to Collins as crc@xxxxxxxxxxxxxxx. If you wish to
> unsubscribe, or modify your preferences please visit
> http://mailman.listserve.com/**listmanager/options/collins/**
> crc%40cyberlink.bc.ca<http://mailman.listserve.com/listmanager/options/collins/crc%40cyberlink.bc.ca>or to learn more about our list visit
> http://mailman.listserve.com/**listmanager/listinfo/collins<http://mailman.listserve.com/listmanager/listinfo/collins>***
> ______________________________**_________________
> SHARE THE FUN: JOIN THE COLLINS COLLECTORS ASSOCIATION TODAY !
> http://www.collinsradio.org/?**page_id=37<http://www.collinsradio.org/?page_id=37>
>
> NETS: Tues & Thur: 3.805 MHz-2000 Central + Fri: 3.895 MHz-2000 Pacific
>  SUNDAYS: 14.263 MHz-2000 UTC  +  AM Net: 29.050 MHz-1200 Central
>  1st Wednesday AM Net 3.880 MHz-2000 local (ET, CT, MT, PT)
>
> The Collins Reflector reserves the right to refuse access to anyone.
>
> LIST HELP?  ADMIN EMAIL:  collins-owner@xxxxxxxxxxxxx
> This ONLY goes to the list admins and does not post to the group!
>
> *** You are subscribed to Collins as dennis.monticelli@xxxxxxxxx. If you
> wish to unsubscribe, or modify your preferences please visit
> http://mailman.listserve.com/**listmanager/options/collins/**
> dennis.monticelli%40gmail.com<http://mailman.listserve.com/listmanager/options/collins/dennis.monticelli%40gmail.com>or to learn more about our list visit
> http://mailman.listserve.com/**listmanager/listinfo/collins<http://mailman.listserve.com/listmanager/listinfo/collins>***
>




This archive was generated by a fusion of Pipermail (Mailman edition) and MHonArc.