[ARC5] BC453 on 24V - screen voltage

[J Mcvey]

 Yeah, the sensitivity is terrible. 
with everything left in original screen voltage and 25V applied to the HV
A 40% modulated signal at -73 dbm (s9) is audible. but it drops off pretty quick.At -85 dbm ( 12.5 uv) it pretty much gone.
Now after I lifted the ground lug for the bottom resistor in the divider chain to float the screens to plate voltage, the result was quite a bit better .-73 dbm the 40% modulated signal was very audible and still discernible at -95 dbm (3.99 uv)
I'm surprised that the BC453 works this well on 25V. ( this one has been re-capped)
As a receiver , you would probably want to run the higher voltage. the radio got a lot happier volume-wise at 50V plate with the screen divider still in place. 
At 50V plate I was losing the signal -100dbm (2.24 uv) .I think 2uv is the lower sensitivity spec for this radio. anyway! 

The floating screen at 25V should work fine if it's used as an IF strip. In fact I will probably have to restore the screen divider to keep it from overloading. I want to use the front end as a tune-able IF for the R392 .The ouput from the bnc is sufficient to run a frequency counter. Might even need attenuation.
I'm going to solid state the 12A6 so I can get better volume at 25V. I might be able to get 400mw without doing anything drastic. 

    On Sunday, December 8, 2019, 5:44:30 PM EST, Kenneth G. Gordon <kgordon2006 at frontier.com> wrote:  
 
 On 8 Dec 2019 at 16:25, J Mcvey via ARC5 wrote:

> I remember from some time ago that David mentioned that he had run a
> command receiver B+ on 24V, so I tried it . 
> 
> Of coarse,  the audio output power is way down, but it does receive
> using only 24V on the HV. I'm going to check the impact on the
> sensitivity . It still should work fine as a tune-able IF, though. 

If you moved the screen voltage feed wire from the center-tap of the two big black resistors 
in the rear of the receiver to the "hot" end, your sensistivity would improve significantly.

Ken W7EKB
______________________________________________________________
ARC5 mailing list
Home: http://mailman.qth.net/mailman/listinfo/arc5
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:ARC5 at mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: https://www.qsl.net/donate.html  
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/arc5/attachments/20191209/4a75ed26/attachment-0001.html>