On Mon, 18 Apr 2005 13:33:03 GMT, "Michael A. Terrell"
wrote:



If you want to use 75 ohm cables its your choice. The patch bays are
BNC on both halves so you can use 50 or 75 ohm cables with them. These
patch bays show up used and surplus along with the plugs. I've used
them at several TV stations, a mobile production van I built and in the
telemetry package we shipped to Italy. They are a lot better quality
than "F" fittings and CATV switches. I used to run insertion loss and
other tests on samples for United Video Cablevision and there was more
junk submitted than quality parts. Even the better quality switches
only lasted a year or so when we used them to reroute video feeds in the
L.O. studio.

75 Ohm BNCs and 50 Ohm BNCs are two different connectors. You can mix
them up if you like, but it's lame.

By advancing the af gain control

"Dale Parfitt" wrote in message
news:J7O8e.18054$ox3.16766@trnddc03...

"dxAce" wrote in message
...


"Charles W. Hinkle" wrote:

I have used Mini Circut Labs ZFSC-2-1 and a 2 port passive Stridsberg.
I
obtained the MCL's at hamfests for $10 and the Stridsberg new
Presently
I
am using a MCL PSC-3-1 to feed 3 receivers. I also got this at a
hamfest.
My receivers make up the nearly 5 db loss.

How do they make up the loss? Just curious.

dxAce
Michigan
USA

Same question here.

Dale W4OP

http://www.trompeter.com/assets/prod...itary_Aero.pdf
You can get 50 ohm patchs bays too. The military uses them. Like I
said, if you buy them used, make sure you ohm out the connections.
There are so many variations that look like they are the same until you
plug them in.

Make sure you have a can of Caig DeOxit handy.

David wrote:

On Mon, 18 Apr 2005 13:33:03 GMT, "Michael A. Terrell"
wrote:


If you want to use 75 ohm cables its your choice. The patch bays are
BNC on both halves so you can use 50 or 75 ohm cables with them. These
patch bays show up used and surplus along with the plugs. I've used
them at several TV stations, a mobile production van I built and in the
telemetry package we shipped to Italy. They are a lot better quality
than "F" fittings and CATV switches. I used to run insertion loss and
other tests on samples for United Video Cablevision and there was more
junk submitted than quality parts. Even the better quality switches
only lasted a year or so when we used them to reroute video feeds in the
L.O. studio.

75 Ohm BNCs and 50 Ohm BNCs are two different connectors. You can mix
them up if you like, but it's lame.


"N" connectors are the really touchy connectors as far as pin and
collet diameters.

I would worry more about the intermod problems from worn contacts in
cheap A-B switches. I've seen it and had to track it down in places
that were too cheap to buy a video router or patch bay.

--
Former professional electron wrangler.

Michael A. Terrell
Central Florida

"Charles W. Hinkle" wrote in message
...
By advancing the af gain control

" My receivers make up the nearly 5 db loss.

How do they make up the loss? Just curious.

dxAce
Michigan
USA

Same question here.

Dale W4OP


The problem here lies in S/N ratio not loudness.
If the 5dB loss places a signal down near the noise floor- NO amount of RF
or AF gain in the receiver can restore the S/N.
If your assumption were true, there would be no need of LNA's, small signal
RF amps, active splitters etc.
It's not magic, it's math.
Dale W4OP

In article ,
dxAce wrote:

Telamon wrote:

In article ,
dxAce wrote:

"Charles W. Hinkle" wrote:

I have used Mini Circut Labs ZFSC-2-1 and a 2 port passive
Stridsberg. I obtained the MCL's at hamfests for $10 and the
Stridsberg new Presently I am using a MCL PSC-3-1 to feed 3
receivers. I also got this at a hamfest. My receivers make up
the nearly 5 db loss.

How do they make up the loss? Just curious.

Maybe his radios have pre-amps like the Drakes.

When you use a passive splitter the loss is 3dB power and 6dB
voltage. I think most radio S meters are responding to the voltage
number due to the nature of the AGC circuits. Someone can correct
me on this. Should be easy enough to take a splitter in and out of
line.

Correct me if I'm wrong... but would it not be better to run some
pre-amplification ahead of the splitter rather than try to make up
something that has already disappeared? Much the same in say VHF work
where it is better to run a receive pre-amp right at the antenna
versus running it at the receiver end of the coax?

Generally yes. An active splitter would have some matching losses on the
input, then amplification, then split the signal, then have a line
driver for each output.

--
Telamon
Ventura, California

In article ,
"Michael A. Terrell" wrote:

David wrote:

On Mon, 18 Apr 2005 02:43:05 GMT, "Michael A. Terrell"
wrote:

http://www.switchcraft.com/products/vpp.html &
http://www.switchcraft.com/products/561.html are examples of video patch
bays and plugs that work for HF receivers as well. They are used for
manual routing of video in some studios and transmitter sites. Western
Electric used to use them on their coaxial long lines that fed video
cross country before TV satellites were available. If you're old enough
to remember the nationwide live video feed after President Kennedy was
assassinated, the techs and engineers at ATT patched together the first
nationwide feed by connecting the different network's feeds together to
provide all network stations with live video and did the same with the
audio feeds.
75 Ohms, if that matters.

If you're going to use RG-59/U, you might as well just use
ubiquitous and cheap F-Connectors and A/B/C switches.


If you want to use 75 ohm cables its your choice. The patch bays are
BNC on both halves so you can use 50 or 75 ohm cables with them. These
patch bays show up used and surplus along with the plugs. I've used
them at several TV stations, a mobile production van I built and in the
telemetry package we shipped to Italy. They are a lot better quality
than "F" fittings and CATV switches. I used to run insertion loss and
other tests on samples for United Video Cablevision and there was more
junk submitted than quality parts. Even the better quality switches
only lasted a year or so when we used them to reroute video feeds in the
L.O. studio.

I think F connectors are just plain nasty. Pain in the butt getting them
started threading. BNC is used on practically any lab equipment in the
audio and video range. Most gear operating 1KHz to 500MHz uses BNC.

Making up the BNC connector is a little more work than a PL-259 but the
push on and twist makes changing patch board connections a snap.

Just say no to F connectors unless you are using RG-59, which they are
made for and the connections will not be changed often.

--
Telamon
Ventura, California

On Mon, 18 Apr 2005 00:12:32 GMT, Drifter wrote:

- Hide quoted text -
- Show quoted text -
************************

thanks to one and all for some great info.
i need to study on this. i found an old article
in the july/04, NASWA Journal. get my facts together
here, and move to there. would be fun to build when
i find the time. thanks again...
Drifter...


Now that the dust has settled a little bit and the belligerents are
hopefully being triaged.....

Please read the spec sheets on the prospective splitter you intend on
using or, if rolling your own, look at the design. Many splitters
claim to have "only" a 3 or 5 dB loss, but that's only "best case."
Often times, the loss will vary greatly across the operating range of
the splitter (and sometimes the impedance!). For HF and MF, the
losses are usually not too bad.

If you plan to use a preamplifier, PLEASE (!) use a low noise model.
Often times preamps will raise the noise floor by several dB, which
could wipe out some weak DX for you. Purchase (or build) the BEST
preampllifier that you can. It should be low noise, and the gain
should not be so high that it goes into oscillation (you really just
want to overcome the splitter losses). Some preamps will cause
trouble with the 3d order intercept points of your receiver by
overloading the front end. Every active component plays against
every other active component, so be mindful of your trade-offs and
gains.

Good luck!

Al in CNMI

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In article ,
Tebojockey wrote:

On Mon, 18 Apr 2005 00:12:32 GMT, Drifter wrote:

- Hide quoted text -
- Show quoted text -
************************

thanks to one and all for some great info.
i need to study on this. i found an old article
in the july/04, NASWA Journal. get my facts together
here, and move to there. would be fun to build when
i find the time. thanks again...
Drifter...


Now that the dust has settled a little bit and the belligerents are
hopefully being triaged.....

Not a chance! I have to give you a hard time.

Please read the spec sheets on the prospective splitter you intend on
using or, if rolling your own, look at the design. Many splitters
claim to have "only" a 3 or 5 dB loss, but that's only "best case."
Often times, the loss will vary greatly across the operating range of
the splitter (and sometimes the impedance!). For HF and MF, the
losses are usually not too bad.

Snip

There are passive and there are active splitters.

Passive can be transformer or resistive it does not matter. If the
splitter is one port to two ports then the power is going to divided in
half between the two output ports. It is that simple. Half the power is
3dB and half the voltage is 6 dB. That's all there is to it.

Active splitters can be anything because you can have any amount of
amplification to to make up for the division in power.

Same story with one to four ports where the power out is 1/4 the power
in. Same story with any other division splitter.

Now if you force me to I WILL resort to an analogy where you have this
bushel of apples you want to divide in half and...

--
Telamon
Ventura, California

Telamon wrote:

Another fine example of an intelligent response on Usenet.


What else is left after they get done throwing apples at each other
while they flame each other? ;-)

--
Former professional electron wrangler.

Michael A. Terrell
Central Florida