In general, is it better to run a receiver off a good external DC power
supply, or using AC power and the built-in transformer? It would seem to me
that I might get less noise using an external DC power supply, but what is
the general concensus here? Thanks.

Jeff

Unrevealed Source wrote:

In general, is it better to run a receiver off a good external DC power
supply, or using AC power and the built-in transformer? It would seem to me
that I might get less noise using an external DC power supply, but what is
the general concensus here? Thanks.

Jeff


What do you base this on? Why do you think an external supply is
better or quieter than the one designed for the radio?

--
Former professional electron wrangler.

Michael A. Terrell
Central Florida

Michael A. Terrell wrote:
Unrevealed Source wrote:

In general, is it better to run a receiver off a good external DC power
supply, or using AC power and the built-in transformer? It would seem to me
that I might get less noise using an external DC power supply, but what is
the general concensus here? Thanks.

Jeff



What do you base this on? Why do you think an external supply is
better or quieter than the one designed for the radio?


I have to agree with Michael.

A power supply can be well designed or poorly designed. A poorly
designed supply is a pain in both internal or external form. It doesn't
matter if a well designed supply is internal or external.

Some may prefer external supplies as they can power more than one radio
at a time from a single supply.

There is also the belief that removing the heat generated by a supply by
using an external supply improves the reliability of the radio. However,
I have only seen anecdotal evidence to support this.

However, an external supply is easier to replace. Generally a plus if
you have a radio that comes with a poor supply.

If you mode the radio around a lot, an internal supply may be more
convenient.

With respect to noise, it may be easier to block powerline noise with an
external supply. This is because you can add filters to the input and
output of the supply to block noise at a short distance away from the radio.

With respect to noise generated within the power supply, excessive noise
would be an indication of a poorly design supply. That can apply to
internal and external supplies.

If the supply is internal, the manufacturer has control of the quality.
They have the ability ensure the supply is properly designed for the
application.

If the supply is external, the user is free to use a really poor supply
of their choice and possibly be unhappy with the radio's performance.

If you are considering using a third party supply with a radio, how
would you go about determining of the supply you are about to buy is
really better than the one supplied by the manufacturer? Trial and error
is an expensive method.

Fortunately, many radios with internal supplies also support use of an
external supply. The user is free to try an external supply.

With respect to your original question, you are correct, you "might get
less noise" but that really depends upon you choice of external supply.
A bad supply could be much noisier than the internal supply.

Craigm

From: craigm wrote (in part:

There is also the belief that removing the heat generated by a supply
by
using an external supply improves the reliability of the radio.
However,
I have only seen anecdotal evidence to support this.

Aside from reliabiltiy issues, the main reason I run my R2000s and
other radios from an external supply is to reduce heat, which leads
to reduced heat. The radio exceeds it specified stability when operated
from a external power source.

Many built in supplies, and most aftermarket power supplies can be
much noiser then many here would believe. With a decent battery
powered receiver, make a noise probe, I use 10' of RG174 with a 10
turn coil at the sensor end and connector to fit the radio. Please
be certain to use insulated wire and have all he solder connections
covered. I used "liquid tape".

With the radio or external power supply to be tested move the probe
around the supply, over the AC mains input an DC output. For some
reason very few companies include the very usefull ~1000pF caps
across each diode in a bridge. This cap can really help quiten a noisy
supply.

The probe is also usefull to find noise leaks from a PC/monitor.VCR
etc. I use a DX398 because A:It is a smal,sensisitve and easy to use
receiver, and B: I own one.

My main +12V DC supply is a Lambda 12V 20A linear supply, my
backup is a 12V 8A Lambda linear. Both were much quiter then the
often touted and extremly popular Astrons. After a few additions,
feritte beads on the input/output to the bridge, 100pF micas with
very short leads across the bridge, 1000pFs across the junctions
in the pass elements, some 1uF tantalums added across the 723,
the noise was gone.

For most of us, including me, the minor noise from a decent power
supply, either internal or external, is way below the local noise
floor,
but while these mods may be waste for operation ~50MHz, they really
helped remove some noise from my NOAA APT weather satellite
reception. But even on HF during some early morning quite times,
I think the lowered noise helps. And with the borrowed AR7030+,
it is clear that with a good (quite) enough receiver all the noise you
can reduce is well worth the extra effort.

I will only have the AR7030+ for about a month, so I will be listening
a lot more then posting.

And the stock wall wart suplied with the AR7030+ just sucks.
Very noisy.

Terry

"Michael A. Terrell" ) writes:
Unrevealed Source wrote:

In general, is it better to run a receiver off a good external DC power
supply, or using AC power and the built-in transformer? It would seem to me
that I might get less noise using an external DC power supply, but what is
the general concensus here? Thanks.

Jeff


What do you base this on? Why do you think an external supply is
better or quieter than the one designed for the radio?

The wording "external DC supply" versus "AC power" makes me think
that he thinks he's comparing apples and oranges. Unless he's
talking about running it off batteries, an "external DC supply" runs
off AC and is the same thing as "AC power".

Michael

Michael Black wrote:

The wording "external DC supply" versus "AC power" makes me think
that he thinks he's comparing apples and oranges. Unless he's
talking about running it off batteries, an "external DC supply" runs
off AC and is the same thing as "AC power".


Even then he could have more noise from batteries due to the internal
resistance of the battery causing poor regulation, and noise picked up
on the wires that connect the battery to the radio.

--
Former professional electron wrangler.

Michael A. Terrell
Central Florida

There should be some regulation in the radio itself on the DC input,
This doesn't have to be the case, but most radios provide a DC input
for use in mobile applications, and car voltages vary from a low if the
car is not running to a high if the battery is being charged. Even
worse would be spikes from a bad diode in the alternator. Generally a
device designed to work from auto power is designed to handle at least
16V. Many put the limit at 24V, which comes from some case where people
would put car batteries in series. Yeah, I know this sounds odd, but I
worked on a bid with Chrysler and they had a 24V upper limit on the
electronics at the time. The story I got was some people would jump
start cars with two batteries in series.

The DC input should be filtered a bit in the radio as well since auto
power isn't all that clean.

Jeff, I don't think there's gonna be any consensus here. Perhaps you
should just state what it is you're wanting to do and why and with
what. Do you have a receiver with the ol' "External DC In" terminals
on the back? Are you wanting to hook it up to a gel cell or something
of that sort? Perhaps you should give more particulars and the
resident IEEE community might better be able to help you.

The specifics a

I have a FRG-7, which of course runs off AC power but also has the
capability to run off batteries (internal) or a 12VDC external power supply.
I have a Staco PS-4 filtered power supply that puts out a very clean and
stable voltage, up to 4A. It seems very well shielded, and I could put it
as far away from the radio as I needed, within reason of course.

To hook it up requires me to purchase the right connectors, etc. I'm
wondering if it's worth the trouble.

Jeff


wrote in message
oups.com...
Jeff, I don't think there's gonna be any consensus here. Perhaps you
should just state what it is you're wanting to do and why and with
what. Do you have a receiver with the ol' "External DC In" terminals
on the back? Are you wanting to hook it up to a gel cell or something
of that sort? Perhaps you should give more particulars and the
resident IEEE community might better be able to help you.

In article ,
says...
In general, is it better to run a receiver off a good external DC power
supply, or using AC power and the built-in transformer? It would seem to me
that I might get less noise using an external DC power supply, but what is
the general concensus here? Thanks.

Jeff



I have run my Sat800 both from the external AC to DC brick supply
and from a car battery. The AC/DC supply is nominally 9 vdc and
notoriously full of hash. The Spec's of the Sat800 say it's OK 8 to 15
Volts Dc. The car battery, fully charged at 13.8 volts is noticably
quieter than the AC/DC brick especially when you're trying to hear a
weak one thru headphones.