[ARC5] 10 meter BC-454 - yet more

[tbs50a at aol.com]

Hey Ken seems like your have a load of fun with old set!! I think the tube # you where looking a while back to replace the 12SG7 was a 717A. Keep us posted as to it performance, think it should be a hot performer.
GL
Terry N3GTE

 

 

 

-----Original Message-----
From: Kenneth G. Gordon <kgordon2006 at frontier.com>
To: ARC-5 List <arc5 at mailman.qth.net>
Sent: Mon, Feb 4, 2013 2:05 pm
Subject: [ARC5] 10 meter BC-454 - yet more


Well, the old article that this thing was based on mentioned coverage from 27 - 
30 MHz. 
Sorry, Jack, no way.

Coverage is a good steady 28 - 30 MHz with the tuning capacitor/inductor 
combination as it 
is.

Since I rebuilt the coils with the "proper" number of turns, and have glued them 
down solidly, 
stability has vastly improved.

The front-panel antenna trim control is "about" centered, instead of at one end 
or the other 
(fully meshed), and the oscillator calibration capacitors are no longer at their 
limits.

However, C-4F and C-4D. associated with L-3, the RF amp plate and mixer input 
grid 
network exhibit a very low, broad, but clear peak.

I am not sure that this is OK, or not OK.

I may learn whether this is OK or needs to be "adjusted" when I check S+N/N 
ratio. I do know 
the coils are now correct according to the article, at least.

As it is, there is no direct connection to the signal generator: the antenna is 
a clip lead 
connected to the input to the RCA jack.

There is, to my mind, a bit more AC hum on the DC supply than I prefer. I may 
fix that.

Backing both the RF gain and the IF gain to minimum still results in ample 
signal output.

Gotta go get the HP-8640B for a definitive test. I am using an Eico Model 324 
signal 
generator I was given, then refurbished, calibrating it with a Heathkit 
frequency counter. The 
324 is very stable...once you get it on frequency...which is difficult. I really 
would rather use 
my pair of BC-221s, but there are over in the storage shed.

So far, this has been an interesting experiment.

Ken W7EKB
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