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Telamon · October 1st 06, 05:22 AM posted to rec.radio.shortwave

In article .com,
wrote:

Telamon wrote:

1. DC voltage. (DC input) This is connected to the power supply. 2.
AC voltage. (RF output) This is connected to the radio. 3. DC + AC
voltage. (RF input, DC output) This is connected to the
antenna/amplifier.

Port 3 to 2 is connected with a capacitor of very low reactance
(zero) to the signal you want to pass through these two ports.

Port 1 to 3 are connect with an inductor, which passes DC voltage
from port 1 to 3 but blocks RF (high Z) going from 3 to 1 so the RF
only sees a path from 3 to 2.

Port 3 and 2 are coax cable and port one could be two terminals.
One terminal is common grounded with the coax shield grounds. Using
a ground independent power supply to the terminals on port 1 allow
you to have either a positive or negative power supply to the
remote amplifier.

-- Telamon Ventura, California

It is clear you work in the microwave satellite part of electronics.

In the "good old days", circa 1990, most text and other refference
sources reffered to them as "power injectors" or "diplexers". Your
discription of it's function is correct. A power source is isolated
from the RF with an inductor, or strip line version, and a capacitor
blocks the DC from the receiver.

MiniCircuits has very nice, as in wide band, inductors. Since I may
use the same coax for VLF. LF, MW, HF, or VHF my power inject, bias
"T" or diplexer has different inductors in series because I couldn't
find a single inductor to cover from 10KHz through ~500MHz. I found
that by using smaller chokes that were effective at UHF, with larger
chokes for each decade decrease in frequency. One of the changes I am
making is to use the MC wide band inductors to allow a smaller
package to be used. Space is at a premium in my "shack".

My shack is the 2nd bath with the plumbing removed and covered. It is
5' by 10'. I prefer the word cozy over cramped.

Most broadband bias-Ts have several inductors in series. At the RF line
you start with the smallest value inductor and work your way up to
larger values. With several inductors in series you might run into some
problems with the inductors ringing so you may need to have resistors
across some of the larger inductors. Since you are only interested in DC
on the bias port and not modulating the carrier from that bias port you
should be able to do it. You may manage to do it with two inductors in
series and so not have any problems with ringing.

--
Telamon
Ventura, California

[email protected] · September 30th 06, 09:18 PM posted to rec.radio.shortwave

wrote:
wrote:

I use the ALA 100. The smaller loops may not be as good on MW. It is a
good idea to insure the amplifer is actually doing something. The fuse
could be blown, the wall wart bad, etc. Unplug the power connector and
make sure the signal strength drops. You will get reception from the
loop even if the amp is off since some RF will leak.

Some of the Wellbrook amps were positive ground. The unit is fused and
I would guess there is a reverse biased protection diode. If the wrong
wall wart was used, it would pop the fuse. In my portable set up, I
have red shrink wrap on the connector that goes to the Wellbrook, just
to make it clear the ground is backwards.

As far as the 1530 goes, it may not have a good resale value since they
released the "plus" version, which has response in the FM BCB.

This ALA 1530 requires a reversed, is shell positve and inner negative,
wall wart. But the center conductor of the coax was positive. I left
the
original power injector/diplexer intact and built my own. I verified
the
problem with the stock wall wart/diplexer before trying my own.

With out power I get virtually no signals. A few very strong MW and SW
at way less then S1. So the amp is working. The original owner says
it always behaved like this. OK, but clearly not the do all end all
of antennas.

Terry

If you throw it on ebay, please post the auction here.

[email protected] · September 30th 06, 09:33 PM posted to rec.radio.shortwave

wrote:

If you throw it on ebay, please post the auction here.

It is GONE. Traded it off about 3 hours ago.

While John dislikes his AD270, I have found my nearly new, as in
fairly unused, to be a very useful antenna.

Terry

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