[time-nuts] 10 MHz Filters

Bob Camp kb8tq at n1k.org
Thu Nov 27 12:35:56 EST 2014


Hi

Just as you can “move” 455 KHz IF transformers down with a little padding, you can do the same thing with 10.7 MHz IF cans. They may or may not tune to 10 MHz. If you get some that don’t tune, it’s just a cap to bump them down. 

The gotcha to any filter in a distribution system is Q. High Q implies high phase slope or long delay. In the real world things are temperature sensitive. Delta temp -> delta inductance -> delta phase -> bad ADEV. The trick is to get the job done with as low a Q as practical. 

The next layer to the onion is loading. If the filter is on the output of the amp, it’s phase will change with load. Same issue as temperature, high Q -> big changes -> bad performance. 

Even with a “class C” multiplier, fixed tuned Q< 10 circuits will do the trick for 5 -> 10 MHz doubling. With more exotic multipliers, even simpler filtering will do the job. 

If you don’t *need* -200 db harmonics, and 30 db is fine — don’t go nuts with the filters.

Bob

> On Nov 26, 2014, at 10:08 PM, Perry Sandeen via time-nuts <time-nuts at febo.com> wrote:
> 
> List,
> 
> 
>  
> I have seen on the net a 10 MHz filter using 10.7 IFtransformers but have no idea how well they would work for isolation with thenew style Lucent boxes.
> 
> 
>  
> Thoughts?
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>  
> On Ebay venders are offering 10 MHz crystals for almostnothing if you buy 30.  My question wouldthese be good for making some type of simple ladder filter?
> 
> 
>  
> In his article *Modifying Lucent RFG-M-RB Rubidium FrequencyStandard* the author used a 10MHz filter that was taken from an old 10MbitEthernet LAN board. The part number he used was 20F001N and I found them onEbay for low prices. 
> 
> 
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> Now I don’t have any access to any old ethernet LAN boardsso I’d have to build from scratch.
> 
> 
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> Does anyone of these methods have an advantage over theothers on the new style Lucent boxes or in the making of a small distributionamplifier with good isolation?
> 
> 
>  
> Regards,
> 
> 
>  
> Perrier
> 
> 
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