In article ,
"Tom Holden" wrote:
"Telamon" wrote in
message
gy.com.. .
In article . com,
wrote:
Telamon wrote:
Remember to terminate all ports at all times or your results
will vary.
The transformer type of splitter will have a "U" shaped response
curve so you need to be within that band for it to work right.
The resistive type is good from DC to some max frequency and you
need to be in that range.
From the transmitter value each output port should be 3 dB down
when the other output port is terminated in 50 ohms. The actual
loss will be a little larger then 3 dB by the splitters
insertion loss.
Oh yeah, and your meter is probably a through type instead of a
load type so you need to put a 50 ohm load on the far side of
the meter.
When you check each splitter also switch the meter and its load
in each leg to see how balanced the splitter is in each output
port.
Be sure to turn the transmitter off before all connections are
made or you could damage your transmitter.
-- Telamon Ventura, California
I made some measurements last night. I decided to move from ~7MHz
to 146 because 7MHz is just too close to the lower limit on my mMc
splitter.
I have an IC28A that is adjusted to give 1wt in low power. I used
a 10dB Narda 766-10 power attenuator in series with the splitter
input. I used another 766-10 attenuator in series with the output
and the sensor head on Boonton RF power meter. I used a .5% 50 ohm
terminator for the other port
The resitive splitter gave me 6dB of POWER loss. The MC
transformer based splitter gave me just over 3.2dB of loss.
I called a freshly frocked dual PHD, EE and physics, I know and
asked her what the heck is happening. The quick answer is the
resistive splitter is like any other resitive voltage divider. The
transformer unit is like a transformer step down, or step up. The
only losses in a transformer splitter are the wire losses and the
core loss. The R in the MiniCircuits dispates no power if all
ports are matched.
She invited me to "her" lab Friday afternoon and she will use the
modern equipment to verify my measurements. She suggested that I
treat the resistive network and use kichoff's (?spelling?, it has
been too long since college) law to show the dissapation of each
element. It is too late tonight and my head hurts from this stuff.
Oh, and cctual S-meter measurements show the MC splitter has half
the loss of the resitive splitter.
On a good note, I picked up a 3 section "dB Products" heavy
aluminium mast and another MC splitter like mine and a 1 in 8 out
RCA active LF/HF splitter rated for use from 100Kc to 40Mc. It
used Nuvisters and appears to have selectable MB/BCB filters. No
manual, and the only diagram is stincyled on the inside of the
lid. And no model number only an old "Signal Corp" decal. My
friend retired ATT microwave engineer and is moving to AZ because
he is sick of the winter snow here. He has a storage building full
of such junk and I get to cherry pick it and haul it to another
friend. I hope to check the RCA coupler before going to the
university lab. It would be nice to run a SN and frequency
response.
Well, that's interesting results.
I've used resistive splitters in the past and have gotten the 6dB
division. The resistive splitters I have used in the past are the T
and the delta type. I usually work with scopes so I see 1/2 the
voltage or 6dBV on the scope through the splitter and I have no
explanation why you are seeing more than that.
What is the make and model number of the resistive splitter?
-- Telamon Ventura, California
I think you are both in violent agreement - 6dB loss means the output
over the input is 1/2 for voltage (constant impedance), 1/4 for
power. A resistive 2-way minimum loss splitter has 6dB loss; a
transformer 2-way splitter is 3dB.
I just calculated it and you are right Tom. I have been a real dufus and
giving Terry a headache for nothing. I generally don't think in terms of
power since I work with small signals.
The resistive splitter is burning half the power as the T types three
16.7 ohm resistors in series are 50 ohms.
Sorry about that Terry. Looks like your transformer type is more
efficient in its bandwidth than the resistive type. Since you measured
3.2 dB on the transformer type you are very close to the ideal splitter
and your measurement on the resistive is also correct at 6 dB so you can
stop scratching you head now.
--
Telamon
Ventura, California