[HomeBrew] 72 MHz amp

[km1h]

First of all are you absolutely sure of the component values? Also at those 
frequencies I use nothing but quality monolithic caps and carbon film 
resistors. Mouser is my usual source.

Have you taken any voltage, current and gain measurements and swept over a 
wide range of frequencies?

Id say that the choke is a bit on the small size, try something in the 5-7 
uh range. Or better still feed the 12V thru a bifilar xfmr; 5-6 bifilar 
turns on a FT23-43 would be about right..

Also if you are trying for a clean output Id go 10 & 100 Ohms on the 
emitter. The .01 is fine if its mono.

What do you have available for test equipment?

Carl
KM1H




----- Original Message ----- 
From: "R. Blackman" <richard.blackman at sympatico.ca>
To: "HOMEBREW" <homebrew at mailman.qth.net>
Sent: Sunday, November 28, 2004 10:56 AM
Subject: [HomeBrew] 72 MHz amp


** Please do NOT cross-post messages in the TO: or CC: field of the e-mail 
message. **

Hi to the group.

I am trying to build a low power amp for 72 MHz IF in a homebrew
transceiver.
The following circuit  works great  at 25 MHz but is dead at 72 MHz.
Any advice would be appreciated.


                  |--------------|-----2uH---------12vdc+
                1000 ohm         |
                  |              |
                  |              |--------0.01uf --output
                  |              |
                  |  2N3866  b  /  c
input---0.01uf----|------------[
                  |             \--2.2 ohm----|-- 22 ohm---gnd
                  |          e                |
                  |                           |
                 470 ohm                      |--0.01 uF---gnd
                  |
                  |
                 gnd

Thanks for any comments.
Richard / VA3NDO



_______________________________________________
HomeBrew mailing list
HomeBrew at mailman.qth.net
http://mailman.qth.net/mailman/listinfo/homebrew