Hi

I replaced my Eagle Supra ID fishfinder head with a new Lowrance Elite 5
(came with new transducer). The present transducer is the round style glued
to the bottom hull (through hull).

Is there a way to test the transducer to see if it is 200khz compatible for
the new Elite 5? Can I simply splice it myself or is there a reason why I
shouldn't. I have spliced coax many times.

But I really don't want to replace that cable up to the flybridge through a
lot of fishing and pulling. I am wondering if I can use the old transducer
and cable (extension & old transducer with 10ft wire). I think the extension
is 15 feet or so.

Any ideas? I am hoping I can simply splice the plug of the old transducer
wire to the new head.

Thanks for any ideas

Cheers

73s

On 3/3/2015 5:10 PM, Tom wrote:
Hi

I replaced my Eagle Supra ID fishfinder head with a new Lowrance Elite 5
(came with new transducer). The present transducer is the round style
glued to the bottom hull (through hull).

Is there a way to test the transducer to see if it is 200khz compatible
for the new Elite 5? Can I simply splice it myself or is there a reason
why I shouldn't. I have spliced coax many times.

But I really don't want to replace that cable up to the flybridge
through a lot of fishing and pulling. I am wondering if I can use the
old transducer and cable (extension & old transducer with 10ft wire). I
think the extension is 15 feet or so.

Any ideas? I am hoping I can simply splice the plug of the old
transducer wire to the new head.

Thanks for any ideas

Cheers

73s


Coax can NEVER be spliced without causing a huge impedance mismatch at
the point of the splice. This is not 60hz or DC. But any ham with even
a minor bit of technical knowledge should understand this.

The only way you can effectively "splice" coax is with connectors, i.e.
two males and a double female. That will provide a splice with minimum
loss and impedance bump.

You would have to look at the specs for your new transducer to see if
its compatible or not. And I would recommend just replacing the coax;
you may not want to, but it's the best way.

--
==================
Remove the "x" from my email address
Jerry, AI0K

==================

Jerry Stuckle wrote:
On 3/3/2015 5:10 PM, Tom wrote:
Hi

I replaced my Eagle Supra ID fishfinder head with a new Lowrance Elite 5
(came with new transducer). The present transducer is the round style
glued to the bottom hull (through hull).

Is there a way to test the transducer to see if it is 200khz compatible
for the new Elite 5? Can I simply splice it myself or is there a reason
why I shouldn't. I have spliced coax many times.

But I really don't want to replace that cable up to the flybridge
through a lot of fishing and pulling. I am wondering if I can use the
old transducer and cable (extension & old transducer with 10ft wire). I
think the extension is 15 feet or so.

Any ideas? I am hoping I can simply splice the plug of the old
transducer wire to the new head.

Thanks for any ideas

Cheers

73s


Coax can NEVER be spliced without causing a huge impedance mismatch at
the point of the splice. This is not 60hz or DC. But any ham with even
a minor bit of technical knowledge should understand this.

The only way you can effectively "splice" coax is with connectors, i.e.
two males and a double female. That will provide a splice with minimum
loss and impedance bump.

Or one male cable connector and one female cable connector.


--
Jim Pennino

On 3/4/2015 2:29 AM, Jeff wrote:

Coax can NEVER be spliced without causing a huge impedance mismatch at
the point of the splice. This is not 60hz or DC. But any ham with even
a minor bit of technical knowledge should understand this.


We are talking about 200kHz here not 200MHz!! Use could join the coax
with a bit of choc-block at that frequency and not see any significant
performance degradation.

Jeff


It doesn't matter if it's 200kHz. The problem remains.

And yes, there WOULD be s"significant performance degradation" if he
used a bit of choc-block.

But if you understood ANYTHING about transmission lines, you wouldn't
make such a stupid statement.

--
==================
Remove the "x" from my email address
Jerry, AI0K

==================

On 3/4/2015 6:11 AM, Brian Morrison wrote:
On Wed, 04 Mar 2015 05:50:02 -0500
Jerry Stuckle wrote:

On 3/4/2015 2:29 AM, Jeff wrote:

Coax can NEVER be spliced without causing a huge impedance
mismatch at the point of the splice. This is not 60hz or DC. But
any ham with even a minor bit of technical knowledge should
understand this.


We are talking about 200kHz here not 200MHz!! Use could join the
coax with a bit of choc-block at that frequency and not see any
significant performance degradation.

Jeff


It doesn't matter if it's 200kHz. The problem remains.

It depends what you mean by 'problem'.


And yes, there WOULD be s"significant performance degradation" if he
used a bit of choc-block.

That is only true if the discontinuity is a significant fraction of a
wavelength, 200kHz is about a 1.5km wavelength, in coax that would be
about 1km with typical velocity factors. A choc block is about 10mm
long, so it is 1/100,000th of a wavelength. I would not expect any major
problem but it could be used to experiment and cleaned up later if
necessary.


Incorrect. It all depends on the amount of the impedance bump. The
larger the bump (and there always will be one, even if connectors are
used), the greater the effect on the signal. And while the change in
impedance has a greater effect as you get a higher proportion of a
wavelength, a bump that's even small percentages of a wavelength can
create a significant loss.

In extreme cases, a short or open (which is much less than 1/100,000 of
a wavelength) would allow no signal through.


But if you understood ANYTHING about transmission lines, you wouldn't
make such a stupid statement.


Actually it's because Jeff understands about transmission lines that he
makes the statement, it isn't a stupid statement at all in the context
of the OP's question and the technical details of the installation.


It is a stupid statement, showing how little he understand transmission
lines.

--
==================
Remove the "x" from my email address
Jerry, AI0K

==================

"Jerry Stuckle" wrote in message
...

It is a stupid statement, showing how little he understand transmission
lines.

It's a good thing this man is not a teacher. The stench of death would
pervade his classroom.

I don't usually see his disagreeable posts, since I blocked him on my home
computer over a year ago. I shall now do the same here on my travel laptop.
Enjoy his retort, if any; I will not see it.

On 4/1/2015 1:26 AM, Sal M. O'Nella wrote:

"Jerry Stuckle" wrote in message
...

It is a stupid statement, showing how little he understand transmission
lines.

It's a good thing this man is not a teacher. The stench of death would
pervade his classroom.

I don't usually see his disagreeable posts, since I blocked him on my
home computer over a year ago. I shall now do the same here on my
travel laptop. Enjoy his retort, if any; I will not see it.



Ah, another comment from the ignorant.

Change that. Another comment from the stoopid. The ignorant WANT to learn.

And FYI - I taught for corporations for a dozen years. Most were
Fortune 500 - and you would recognize virtually every one's name. They
were very happy with my results.

I got out only because I grew tired of all the traveling.

--
==================
Remove the "x" from my email address
Jerry, AI0K

==================

On 3/4/2015 6:54 AM, Brian Morrison wrote:
On Wed, 04 Mar 2015 06:39:20 -0500
Jerry Stuckle wrote:

On 3/4/2015 6:11 AM, Brian Morrison wrote:
On Wed, 04 Mar 2015 05:50:02 -0500
Jerry Stuckle wrote:

On 3/4/2015 2:29 AM, Jeff wrote:

Coax can NEVER be spliced without causing a huge impedance
mismatch at the point of the splice. This is not 60hz or DC.
But any ham with even a minor bit of technical knowledge should
understand this.


We are talking about 200kHz here not 200MHz!! Use could join the
coax with a bit of choc-block at that frequency and not see any
significant performance degradation.

Jeff


It doesn't matter if it's 200kHz. The problem remains.

It depends what you mean by 'problem'.


And yes, there WOULD be s"significant performance degradation" if
he used a bit of choc-block.

That is only true if the discontinuity is a significant fraction of
a wavelength, 200kHz is about a 1.5km wavelength, in coax that
would be about 1km with typical velocity factors. A choc block is
about 10mm long, so it is 1/100,000th of a wavelength. I would not
expect any major problem but it could be used to experiment and
cleaned up later if necessary.


Incorrect. It all depends on the amount of the impedance bump. The
larger the bump (and there always will be one, even if connectors are
used), the greater the effect on the signal.

You are correct, but in my opinion you would need a very large change
in impedance over 10mm for it to make any difference at 200kHz.


And just how big is the change being proposed?

And while the change in
impedance has a greater effect as you get a higher proportion of a
wavelength, a bump that's even small percentages of a wavelength can
create a significant loss.

Shouldn't be too difficult to calculate the impedance of the choc
block, it's pretty much a balanced line.


And a coax is an unbalanced line - which complicates the calculations.


In extreme cases, a short or open (which is much less than 1/100,000
of a wavelength) would allow no signal through.

We were not discussing either a short or an open.


As I said it is an extreme - but it shows that even a small percentage
of a wavelength can have an effect, contrary to your previous statement.



But if you understood ANYTHING about transmission lines, you
wouldn't make such a stupid statement.


Actually it's because Jeff understands about transmission lines
that he makes the statement, it isn't a stupid statement at all in
the context of the OP's question and the technical details of the
installation.


It is a stupid statement, showing how little he understand
transmission lines.


I don't agree, there is plenty of latitude using imperfect connectors
at low frequencies. People have been using PL259/SO239 connectors for
frequencies as high as 500MHz for decades and yet on the VNA they most
certainly are not 50 ohm connectors above 10MHz or so. A VSWR of 2:1
creates a mismatch loss of 0.5dB, at 3:1 it's still only 1.2dB.


Connector impedance doesn't change with frequency, just as coax
impedance doesn't change with frequency. Loss will increase as
frequency increases, however.

And yes, PL259/SO239 was never meant to be an "all purpose connector"
and has greater loss than many other connectors - at any frequency.

--
==================
Remove the "x" from my email address
Jerry, AI0K

==================

On 3/4/2015 7:49 AM, Jeff wrote:

Connector impedance doesn't change with frequency, just as coax
impedance doesn't change with frequency. Loss will increase as
frequency increases, however.

Coax impedance certainly does change with frequency. Below about 500kHz
there is a significant slope with frequency.

At 200kHz a 50ohm cable may well look more like 100ohms and by the time
that you get to 1kHz it could be as high as 1kohm.

200kHz is in what is called the transition region and the impedance is
given by:

SQRT((R+j2pifL)/(C+j2pifC))

as opposed to the high frequency region where it is merely:

sqrt(L/C)

Below about 20kHz it changes again to SQRT(R/(j2pifC)

There are also other variables due to changes in the dielectric with
frequency and other losses.

Can you explain the above equations? In general it doesn't make sense
that the same effect would have different equations for different
frequencies. It does make sense though that the equations involved are
all simplifications of a single, more complex equation, optimized to
discount small effects over a given frequency range.

That said, I'm not sure I can see how these three equations can morph
into each other as f changes. The equation for the middle frequency
range seems to be the more encompassing so starting with that - if
frequency goes up enough the terms j2pifL and j2pifC dominate the R and
C terms and the equation simplifies to sqrt(L/C) appropriately.

But when f goes down enough, both terms shrink compared to R and C and
the equation would seem to simplify to sqrt(R/C) rather than
sqrt(R/j2pifC).

Is there possibly a typo in there somewhere?

--

Rick

"Jeff" wrote in message
...

Connector impedance doesn't change with frequency, just as coax
impedance doesn't change with frequency. Loss will increase as
frequency increases, however.

Coax impedance certainly does change with frequency. Below about 500kHz
there is a significant slope with frequency.

At 200kHz a 50ohm cable may well look more like 100ohms and by the time
that you get to 1kHz it could be as high as 1kohm.

200kHz is in what is called the transition region and the impedance is
given by:

SQRT((R+j2pifL)/(C+j2pifC))

as opposed to the high frequency region where it is merely:

sqrt(L/C)

Below about 20kHz it changes again to SQRT(R/(j2pifC)

There are also other variables due to changes in the dielectric with
frequency and other losses.


Thanks for this Jeff. That is the first time I have seen anything about the
impedance other than formulars that just compair the diameters of the
conductors and modified by the dielectric. There was never a mention of
frequency affecting the impedance.

I guess that it is like many other electrical/electronic formulars. They
leave out some of the 'small change' . Sort of like what I always referr to
as putting one extra brick on a truck load . Just too small to worry about
in most cases, but it is still there.