[AMRadio] RE: Never ending receiver update!

[Brett Gazdzinski]

Hello all AM,ers.
In an effort to make the receiver look better,
I contacted Neil, of Almost all digital electronics to see if
I could buy a betel for the digital display.
He is sending one for free!
Very nice of him indeed.

I was not satisfied with the tuning on the receiver, the
8:1 ratio being too fast for me, after the 12:1 of the large
national slide rule dial.
So I hooked up two 8:1 vernier drives in series.
I found it tunes ridiculously slow, so I replaced the 
30 pf tuning cap with one that is about 100 pf.

The receiver now tunes almost all of the ham bands on 80 and 40,
but still tunes somewhat slowly....like a full turn of the knob
to tune through an AM signal.

I don't jump frequencies much, so this is ok with me.

Sunday, I thought something went wrong with the receiver,
as signal were way down, as was the noise.
  
I checked the antenna (outside), all the coax connections,
the receiver, and finally found it was band conditions.
Boy, things sure can change from one day to the next!

I turned on the r390a and that was dead as well.
Very little static, weak signals, qsb....

The home brew receiver is VERY quiet when there are no
signals...I have been fooled many times in the past
with these dead band conditions, checking everything out
and finding the band is dead, but its even more quiet
on the homebrew...
I have no idea why the thing is so quiet.
Listening to very weak signals on both the home brew
and the r390A yesterday, the homebrew picks up
weak signals clearly that cant be heard under the hiss
on the r390a.

So is the r390a broke, or, why would the home brew be
so darn quiet?
Everything I ever read said receiver noise should be
out of the picture at lower frequencies.
 
On a side note, Jay, (N3WWL) told me my tape playback
over the air sounded 'colored'.
Well, he has VERY good ears, as I found I had the tape deck
going through one side of the eq, (its not supposed to be),
with the highs above 4 kc rolled off. (DUH!)

I also did a goof up on Saturday.
I switched to the big rig to give it a workout, and
FORGOT to turn off the exciter for the 812 rig.
So I suppose I was driving the grids quite hard
while using the other transmitter (till I noticed).
On Sunday morning, I found the band dead, the 812 rig
tuning up odd, but the swr ok????

Although the grids in the 812a,s look ok, they take more grid
drive to get to the same current now.

I have a gassy 812, a good 812, and two odd 812A's, one has
a partly melted plate (got it that way) and the other now
needs more drive than it did.

I tried a pair of 572b tubes, and they work fine but
seem to get plenty hot.
I also tried a nice pair of 811A's, and they seem to work
fine, so I left them in.

I need to find 4 good 812A's to use and as spares.
I have some good 4-125 and 4-250 tubes to trade, sockets
for same, and some 838 triodes of unknown quality.

I remember when 811 and 812 tubes were $.50 each at fests!

Brett
N2DTS