Hi Tom,

I haven't built any of the detectors but read some on them awhile ago.
I believe that if you get a null that the lock up is happening at 90
degrees out of phase. That cancels the audio. I remember reading
something about that in one of the articles and that there was a way
to adjust it but the rest is foggy.

There is an article on the Costa system in the old CQ SSB handbook.

73
Gary K4FMX

On Sun, 13 Jul 2003 21:44:18 -0400, "Tom Holden"
wrote:

Bob, thanks forcoming back. I'm delighted to connect with someone who has a
RD.

Do you not get null or minimal audio at zero beat in the centre of the
passband with your authentic RD? I thought that this would be the normal
response of a product detector on symmetrical sidebands - the negative
frequency product would be antiphase of the positive frequency product.
There is no such null on a SSB with carrier signal such as CHU.

What lock range do you get? Without the 455kHz filter in the feedback loop,
I get about 400Hz. With a ceramic resonator of unknown interelectrode
capacitance, I have been trying different values of parallel inductors and
getting lock range of 100 Hz or less.

Do you find that the RD suppresses impulse noise and static crashes?

73, Tom VE3MEO

"Bob G. Mahrenholz" wrote in message
...
I have a Reciprocating Detector that I built from a kit of parts that I
purchased
from W1SNN back in 1972. I use it at 455kHz in an AM broadcast receiver to
eliminate selective fading.

The IEEE Comm paper by Badessa lists the patent on the RD that you can
look up.
Also if you get a null in the center of the lock range you may be locking
90
degrees out of phase with the carrier.

Bob K4QQK