"Pete KE9OA" wrote in message
...
No, what I mean is that the carrier insertion point, instead of
being -25dB down on the I.F. passband slope shifts to -35dB down on the
slope. If you play with a receiver that has passband tuning, the
description becomes apparent. I will describe the sound when the unit
malfunctions.....................the noise from the receiver becomes very
high pitched and voices become inaudible. The reason for this is that as
the BFO signal is moved out of the I.F. passband, the resultant audio is
in the supersonic region. Because of the low-pass filtering that is
prevalent in communications receiver designs, these high frequencies are
bypassed to ground, resulting in no apparent received audio.
Evidently, this failure mode is pretty rare, so it is pretty unlikely that
you will experience this condition with your receiver.
I hope this helps.

Pete

"Lucky" wrote in message
...

"Pete KE9OA" wrote in message
...
The folks at Lowe UK were nice enought to steer me in the right
direction with my carrier injection problem. Any of you Lowe folks, take
note! Apparently, Q4, the carrier generator (MC14569) is being run near
its design maximum. Out of 10,000 units, I was told that 12 of them have
failed because of this chip.
I let the receiver run for about 15 minutes and the carrier injection
problem showed up in the form of the BFO frequency being drastically
shifted. I cooled the chip and normal operation of the receiver resumed.
After 2 more minutes when the chip heated up again, the problem surfaced
again. I cooled the chip once more, and once more, the receiver resumed
normal operation.
The Digi-Key part number is: MC14569BCPOS-ND They have 1743 of them in
stock at a price of $2.47 if you order less than 25 pieces.
This receiver was a stumper, but since it is only a collection of parts,
it was inevitable that would eventually get fixed. Now, if only Radio
Shack has that part in
stock............................................. ..........

Pete



Can you explain this problem a little more? I did notice that sometimes
after I get a lock on a signal, and move out of range a little and you
get that howl, I have to move the dial quite a bit around to get another
lock. But, it then locks well below the frequency it locked at before.

Is this what you mean?

Lucky




Thanks Pete

I love the 150 and have it for like 1 month now. I'm drawn to using it. It's
extremely sensitive and holds weak signals very well. The sync actually
works.

You seem pretty knowledgable about the 150. What purpose does the double
side band serve and under what circumstances would you be applying it?

Thanks
Lucky