Crystal frequency calculation for Air Band

[JJH0906]

Many thanks to those who have responded to my other threads regarding crystals for the Realistic PRO-48 scanner. However, the quest continues!

I was referred to this link of the formula used to calculate the frequency crystal needed to get a monitor frequency (which I still don't quite get):

Scanner Crystals - The RadioReference Wiki

wiki.radioreference.com

When looking at the manual for this particular scanner, the frequency bands show this:



So! I guess I'm a little confused on how to calculate the airband frequencies, as they don't seem to fit in the VHF Lo or VHF Hi range.

Any thoughts?

 

[mass-man]

what are you trying to do? If you need a crystal of a specific frequency, you inform the manufacturer of the model of the radio and the frequency desired....they should do the rest.

 

[JJH0906]

what are you trying to do? If you need a crystal of a specific frequency, you inform the manufacturer of the model of the radio and the frequency desired....they should do the rest.

I just want to buy some damn crystals to listen the airplanes near my house, it's that simple! Seems like finding the specific frequencies I'm looking for is harder than finding a pot of gold at the end of the rainbow, however!

That's how I got introduced to needing formulas and holder types and all the rest. I'm appreciating the education but also getting frustrated with the amount of effort it's taking to just get a half dozen crystals for this lil' hobby.

 

[gmclam]

I believe that receiver is only double conversion for VHF Hi and employs a 10.7MHz IF, similar to many radios I still run today. The crystal is likely 3rd overtone. So desired frequency minus 10.7E6 divided by 3. Let's try 110.7E6 as the desired receive (110.7 - 10.7 = 100) / 3 = 33.33MHz.

 

[KevinC]

I believe that receiver is only double conversion for VHF Hi and employs a 10.7MHz IF, similar to many radios I still run today. The crystal is likely 3rd overtone. So desired frequency minus 10.7E6 divided by 3. Let's try 110.7E6 as the desired receive (110.7 - 10.7 = 100) / 3 = 33.33MHz.

Which is what I told him here...

Uniden radio crystal specifications

I recently got nostalgic and purchased a Uniden 20-143 scanner. My intention was to install crystals to listen to the aircraft band, especially since I live near one of the busiest airports in the US, and also the world! Much to my surprise and disappointment, the frequencies this airport uses...

forums.radioreference.com

But for $50 per channel after 3 crystals he could buy a brand new BC125AT and have 500 alpha-tagged, synthesized channels.

 

[mass-man]

KevinC beat me to it! Crystals are silly expensive now. The BC125AT is an excellent air scanner! You might try looking around for one!

 

[mass-man]

Trust me I’m all for nostalgia and radios! My original Besrcst 101 still sits in the shack and happily scans away! I do remember as a kid being overjoyed that I no longer had to buy crystals!

 

[ramal121]

I believe that receiver is only double conversion for VHF Hi and employs a 10.7MHz IF, similar to many radios I still run today. The crystal is likely 3rd overtone. So desired frequency minus 10.7E6 divided by 3. Let's try 110.7E6 as the desired receive (110.7 - 10.7 = 100) / 3 = 33.33MHz.

Unless air band uses high side injection. If that's the case your crystal example would be 40.67 MHz. The wiki link doesn't show the air band so you would need to confirm first before spending precious $$$ on crystals.

 

[gmclam]

Unless air band uses high side injection. If that's the case your crystal example would be 40.67 MHz. The wiki link doesn't show the air band so you would need to confirm first before spending precious $$$ on crystals.

Yeah agree. My thinking was to just get a "junk crystal" at a given frequency and see what you can hear. Even if it's high side, rather than low side; he'd be likely to pick up the desired frequency as an image (frequency).

 

[RMason]

You may want to also refer to:

Police Scanner Crystals Stocked at Ken's Electronics, (Wholesale & Retail Electronic Parts) Kalamazoo, Michigan

Police Scanner crystals, accessories, repair parts, schematics and modification & repair manuals are available from Ken's Electronics, (Wholesale & Retail Electronic Parts) Kalamazoo, Michigan at reasonable prices

www.kenselectronics.com

Police Scanner Crystal Interchangability Information Reference from Ken's Electronics, (Wholesale & Retail Electronic Parts) Kalamazoo, Michigan

Police Scanner crystals and accessories and repair parts and schematics and modification and repair manuals available from Ken's Electronics, (Wholesale & Retail Electronic Parts) Kalamazoo, Michigan at reasonable prices

www.kenselectronics.com