Tom Holden wrote:

Equal attack and release times over the entire range seems so
unconventional, at least for HF, MF, LF radios. I see the Microdyne 700 is
VHF/UHF and does not support AM. Fading at VHF/UHF line-of-sight is probably
very different than for ionospheric propagation as are the modes supported
and the fact that a human is not decoding the output.

From my readings, it seems that Fast Attack (less than 10 ms and closer to 1
ms often touted) was preferred for HF/MF/LF AM/SSB with selectable Release
speeds from a few tens of ms to over a second. After experimenting with AGC
modifications with that design objective, I'm inclined to think that the
Attack should be proportional to the Release, say, 10-20 times faster, not a
constant 10 ms. A really fast attack and really slow release combo resulted
in a single impulse of interference knocking gain down for a long time.
Equal attack and release speeds when too slow result in ear-damaging swells
of volume or unmanaged bursts of interference.

What do you think?

Any idea what the attack/release speeds are on your SW radios?

Tom


The Microdyne equipment was used all the way to KL and KU band and
for a lot of different applications including tracking space probes for
NASA. They are used mostly for long range digital data collection so
they are a very different from common receivers. One thing that was
different was that they used a fully linear AGC control system, rather
than the common logarithmic. I don't have all of the manuals. Due to
the RDAs that I signed I had to leave them all behind. All I have
manuals for is the C-band receivers they built and sold to CATV systems
and TV stations.

As far as the SW receivers at hand, I haven't tested any of them on
the bench. I lost most of my test equipment during the hurricanes over
the last few years when water got into my shop. The only receiver that
works at the moment is a DX-375 and possibly my HP 312 Frequency
Selective Voltmeter. I have a X-30 that was butchered by a hack at a TV
shop. He really messed it up trying to pick up Rush Limbaugh on SW
rather than listen to him on a local talk radio station. Another
receiver is a classic. A National NC183R that is going to be completely
restored. First, I have to finish repairing what little test equipment
that I can, and replacing the rest.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida