Jack,
Thank you for your reply. You could have chosen a +10V internal rail - and a 10V regulator - but, no....
Yeah, you probably designed the amp with IM requirements - and high linearity, etc. Phooey! As my 12V 14+ A-Hr backup battery runs 12-13.2V, I guess I'll just have to 'try' it and see. It will be for emergency/loss of power, much less common in my newer home, anyway. Probably time to get out my collection of parts destined for my homebrew remote loops... if I could just find my soldering pencils... I did find my 200W iron... moving isn't fun!
Thanks again!
John
toggle quoted message
Show quoted text
--- In loopantennas@..., Jack Smith <Jack.Smith@...> wrote:
John:
The loop amplifier has an on-board 13.8V DC regulator. This has an
overhead of 2.2V, typical, 2.7V worst case. If you use the worst case
for regulator and overhead plus internal voltage drop in components
ahead of the regulator, the MINIMUM DC voltage measured at the output
jack on the loop amplifier is 16.8V. As a designer, I have to use the
worst case or else risk having some unacceptable level of failure to
operate.
If the supply voltage is below this value, correct operation cannot be
guaranteed. In the best case with 12V, it will sort of work, but none of
the specifications will be met. Maybe that will be OK under some
conditions, but the internal voltage regulator will drop out of
regulation. The particular regulator used will "try" to maintain the
output voltage at 13.8V, but with only 12V on the input, it will
obviously fail. When these regulators are operated with lower input
voltage than the defined output, they have a 1 to 2V drop, so the loop
amp will see 10 or 11V on the internal "regulated" supply rail and as I
said all performance data is based on 13.8V, so performance will be
degraded.
Jack K8ZOA
On 2/4/2014 9:36 AM, John wrote:
Jack,
Doug Talley of Pixel told me that the amp would work with a dedicated
12V power inserter when I contacted him re the improvements of the 1B
loop over my 1A. After sending him pictures of my late 1A and it's
amp, he determined it to be the then later variant. I guess my
question is simple - will my Pro-1A work with a dedicated 12V negative
ground power inserter for 'emergency' - or portable - use? I have
appropriately sized diecast cases, connectors, etc, and some 1-10 mH
rf chokes rated at several hundred mA, too. I should have taken him up
at the time on his free offer - at least I'd no. Perhaps, as the
designer of the preamp, Jack, you might comment on the suitability of
this. If the bias will be way off - and the gain suffers - perhaps
we'll look for a 'Plan B'!
John
--- In loopantennas@..., Jack Smith <Jack.Smith@> wrote:
Re battery backup of the Pro-1 loops ...
The power coupler supplies 20V DC (nominal) to the coax, and is
normally
powered with a 24V AC (RMS) transformer. It is possible to replace the
transformer with a floating DC source such as a battery, but it will
need around 26V DC. A pair of 12V gel-cell batteries in series should
work.
One could try a 12V-120V inverter for battery power, but from
theoretical considerations it would need to be a sine wave or at
least a
modified sine wave inverter. And, there is always the electrical noise
issue with inverters.
Jack K8ZOA
www.cliftonlaboratories.com
