[R-390] IF sweep alignment

[KA9EGW]

Typo either on my part or in the Y2K manual R3.  

To clarify, the following is a *direct verbatim quote* from TM 11-856,
Section 59b, page 54:

"The crystal filter has a crystal that is cut for a frequency of 455kc.  The
circuit consists basically of one half of the secondary L241 (between
terminals 3 and 4), crystal Y501, resistors R502 and R561, and capacitor
C502."

The Y2K manual, Revision 3, page 3-6 contains the following:

"3.2.9.1 The crystal filter (figure 3-4) is used to obtain selectivity's of
0.1 and 1 kHz. When the BANDWIDTH switch is set to .1 or 1, this filter is
connected between the output of third mixer V204 and the Input to first IF
amplifier V501. The 455 kHz output signal is coupled from third mixer
transformer T208 to crystal filter Z501. The crystal passes only those
signals at or very close to 455 kHz. Crystal holder and stray capacitances
are neutralized by adjusting C520. Coil L503 and capacitor C524 are tuned to
455 kHz."

If you look at the schematic, on the top of page 3-9 of the Y2K manual, it
is as plain as day, Z501 containing Y501, at the input to S501 and the input
to the first IF amp grid of V501.

So maybe, Bob, you want to look at the manuals before openly accusing me of
technical incompetence! 

73, Brian KA9EGW

-----Original Message-----
From: rbethman [mailto:rbethman at comcast.net] 
Sent: Saturday, February 26, 2011 7:18 PM
To: R-390-List
Cc: KA9EGW; rbethman
Subject: Re: [R-390] IF sweep alignment

I'd suggest re-looking at the circuitry!

Z-501 is NOT a crystal filter whatsoever!  For personal edification and
amazement - it happens to be THE 455Kc Oscillator!

The only crystal that has EVER been on/in the IF deck.

I have NO idea how you intend to "sweep align" a circuit that you apparently
do NOT know or understand.  That "can" is the HEART of the 455kc IF!  Take
it away, and there is NO 455Kc.

N0DGN

On 2/26/2011 7:47 PM, KA9EGW wrote:
> I beg to differ; reference Y2K manual, release 3, section 3.2.9.1 et al.
>
> On the 390 non-A, ref TM11-856, Section 59, on page 53.
>
> In both receivers it's Z501.
>
> Granted, the neither 390 non-A nor 390A has crystal lattice filters, 
> but
> Z501 is what it is...
>
> 73, Brian KA9EGW
>
> -----Original Message-----
> From: r-390-bounces at mailman.qth.net 
> [mailto:r-390-bounces at mailman.qth.net]
> On Behalf Of rbethman
> Sent: Saturday, February 26, 2011 5:59 PM
> To: r-390 at mailman.qth.net
> Subject: Re: [R-390] IF sweep alignment
>
> The R-390 series has NO crystal filters at all.  The R-390s used pure 
> circuitry to achieve the end, while the R-390As use the mechanical
filters.
>
> Bob - N0DGN
>
> On 2/26/2011 6:43 PM, Bill Hawkins wrote:
>> Haven't seen any mention in this thread of the mechanical filters in 
>> the A version.
>>
>> You may recall that there was a hybrid combination of the A and a 
>> non-A IF deck (R-725) because the mechanical filters prevented fine 
>> direction-finding operation. Ringing mechanical filters, IIRC.
>>
>> There was also at least one thread in the good old days of this list 
>> that strongly advised against trying sweep alignment of the IF strip, 
>> because the ringing filters distorted the wave form.
>>
>> Perhaps you could use a wide band 455 KC receiver before the filters 
>> to see the response curve of the IF transformers before the filters.
>> You can't align the filters anyway. What you do is find the center of 
>> the 100 Hz filter (does an A have that crystal
>> filter?) and use that as the base frequency of the sweep generator.
>>
>> Hope this stirs someone's memory.
>>
>> Bill Hawkins