Band Width

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Post by Jalex2 on Tue May 07, 2019 7:39 pm

Hi Harry 
just  follow up  
I finally got back to it and I just had it thrown together on some vector board and it worked beautiful. It could even detect when I walked near it.  I think if I build one properly in a good shielded box it would be even better.  For the input I just used  150k ohm resistor in place of the tuning transformer.
I was just looking for something that could pick up any kind of carrier up to around 400Mhz

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Post by Admin on Thu Mar 07, 2019 10:43 pm

Hi again, long time, no see, no hear, no read.

Yes, with the correct choice of semiconductors it should work well over 100MHz. BF199 or any half-decent transistor. But remember that the gain will fall with frequency, it is just a question of how much.
I presume you will use wide-band ferrite beads to make broadband transformer? Instead of the tuned circuit?

But please let me/us know how you get on. I would be very interested.

Sorry for the delay responding, but Maj-Lis came home this evening and I have been planning it for days :-)

BR Harry - SM0VPO

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Post by Jalex2 on Wed Mar 06, 2019 6:29 pm

Hi Harry 

I am looking for a wide band amp. Something like 400k to   100mh 
Would  your IF amp below work if you remove the tuned input? 

Cascode Novel IF strip for FM


Also Can you tell me a little about matching an antenna to an amp
Does a coil to ground on an input  change the band 
width if there is no cap across it?   
A simple Jfet with the antenna connected to the gate seems perfect and works good but is there a way to improve on it? 
I realize a wide band has less gain but I figure another stage will fix that.
How have you been these days 
Thanks Jim

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