[ARC5] Fwd: Your cCystal Replacement Experience

[David Stinson]

Wayne kindly sent me this, which I posted back
in 2015 when I first started working with these.
Hope it's helpful.  2015- don't time fly?
Dave AB5S

-------- Forwarded Message --------
Subject: 	Your cCystal Replacement Experience
Date: 	Sat, 20 Nov 2021 19:38:21 +0000
From: 	releazer at earthlink.net
Reply-To: 	releazer at earthlink.net
To: 	arc5 at ix.netcom.com



Today's Topics:

    1. SCR-274N VHF:  More on Using Programmable Oscillators.
       (David Stinson)
    2. Re: SCR-274N VHF:  More on Using Programmable Oscillators.
       (David Stinson)
    3. P.S.  Programmable Oscillators. (David Stinson)
    4. Re: P.S.  Programmable Oscillators. (J Mcvey)
    5. Power Supplies, DC-DC inverters & co (Leslie Smith)
    6. Re: P.S.  Programmable Oscillators. (David Stinson)


----------------------------------------------------------------------

Message: 1
Date: Sat, 26 Sep 2015 15:06:48 -0500
From: "David Stinson"
To: ,,"ARC-5"

Subject: [ARC5] SCR-274N VHF:  More on Using Programmable Oscillators.
Message-ID:
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
reply-type=original

On subbing programmable oscillators for crystals:

While a real crystal from a reputable supplier like Bry,
AF4K, is always preferable, freqs are not always available
and multiple custom crystals are for people with more
money than I have. This may give you an option.

Most of you know I had success replacing unavailable
crystals in the 4-channel "ARC-5" VHF
receiver using programmable oscillators.
Was listening to aircraft on 122.8 UNICOM
carrying jumpers just this lovely morning.
The only problem with this 72-year-old receiver
is keeping the relays working.

Respectfully- I've heard all the arguments about noise
and jitter, etc. These oscillators are much better than
the ones made just a few years ago. I've used them
on-the-air at fundimental and to feed multipliers.
I have had no serious issues. Works with just about
any Pentode-based crystal osc.
Not enough drive for Triodes like the Pierce.

http://home.netcom.com/~arc5/ARC5/ProgOsc/ProgOsc.jpg 
(http://home.netcom.com/~arc5/ARC5/ProgOsc/ProgOsc.jpg)

I finally got to work on the BC-950 transmitter.
$4 Epson CMOS oscillators at the crystal frequencies
(F/18) for 122.8 and 146.52 MC. Powered at 6.25V
via one of those inexpensive (2-3 bucks) little "buck"
DC-DC converters feed by the 24V A+ buss.

http://home.netcom.com/~arc5/ARC5/ProgOsc/progosc1.jpg 
(http://home.netcom.com/~arc5/ARC5/ProgOsc/progosc1.jpg)
http://home.netcom.com/~arc5/ARC5/ProgOsc/progosc3.jpg 
(http://home.netcom.com/~arc5/ARC5/ProgOsc/progosc3.jpg)

Mounted that with some hefty double-sided tape.
The set works spendidly.
Service monitor says the carriers are on 122,7997
and 146.5200 and are clean.

http://home.netcom.com/~arc5/ARC5/ProgOsc/progosc2.jpg 
(http://home.netcom.com/~arc5/ARC5/ProgOsc/progosc2.jpg)

I even made a nice contact- Don't ask.
I'm tickled to pieces.

GL OM ES 73 DE Dave AB5S


------------------------------

Message: 2
Date: Sat, 26 Sep 201520:24:30 -0500
From: "David Stinson"
To: "ARC-5"
Subject: Re: [ARC5] SCR-274N VHF:  More on Using Programmable
Oscillators.
Message-ID:
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
reply-type=response

A couple of folks asked for more info on the chips.

I like to use the Epson 8002 series, tri-state.
There are many alternatives. Spec sheet:

http://home.netcom.com/~arc5/ARC5/ProgOsc/SG8002DB.pdf 
(http://home.netcom.com/~arc5/ARC5/ProgOsc/SG8002DB.pdf)

This time, I used the 8-pins, speced for 85 degrees C.
This is Digikey's listing. Cheap at $4 each.
Takes a couple of days via USPS First Class to get them.

http://tinyurl.com/nu3o2h6 (http://tinyurl.com/nu3o2h6)

On the page before confirming the order, at the bottom left,
you can enter "notes" for the order. This is where you
tell them the freqs you want, in Mhz. They don't know KC.

Cost comparison.
Cost of Custom Crystal: $45
Cost of completed DDS VFO kit:  $150
Cost of Programmable Osc substitute:  about $7

Next step in this project:
A simple FM detector for the receiver using an NE612 IC.

73 DE Dave AB5S


------------------------------




-- 
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/arc5/attachments/20211120/9f25761e/attachment-0001.html>