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HELP:VHF FRONT END

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HELP:VHF FRONT END

Postby G7LQY » Tue Sep 24, 2013 7:19 pm

Hi all.
I have got a 2m rx front end working, it use Coilcraft coils for L201 and L202 for 2m they are 146-04J08SL.

I would like to build two more, one on 70Mhz(4m) and one on 50Mhz(6m), is there a formula to work out the new
capacitor and coil values marked as a * in the circuit below.

I do have some coils from Coilcraft;
146-06J08SL - 6.5t
146-07J08SL - 7.5t
146-08J08SL - 8.5t
146-10J08SL - 10.5t
data can be found at http://www.coilcraft.com/uni7.cfm

Regards
Howard

2m rx (144 - 146Mhz).png
2m rx (144 - 146Mhz).png (17.77 KiB) Viewed 3755 times
Regards
Howard
G7LQY
 
Posts: 42
Joined: Wed Apr 29, 2009 4:21 pm
Location: Bury, Lancs UK - IO83UO

Re: HELP:VHF FRONT END

Postby mvs sarma » Sun Oct 06, 2013 4:27 pm

you might use the calculator below linked by entering a tentative capacitor and seeking inductance.
http://toroids.info/T25-6.php
But you should again use another formula to get turns for the uH you need.
example.
for 60MHz and 100pF , it gave a inductor of 0.7uH.
once this is known
you can use the formula in the same link, uH and turns calculator for a known AL value.

You might use to get the AL value of the cores you have my measuring the L value of the 10.5 turns coil.
and divide it by 10
I suppose the whole issue is manageable courtesy the calculators provided by www.kitsandparts.com
Regards
Sarma
mvs sarma
 
Posts: 637
Joined: Wed Oct 11, 2006 4:57 pm
Location: Hyderabad, India


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