BAP wrote:

Where is the empirical or engineering data to support this conclusion?

Collins did do the frequency sweeps -- and it out performed many of the
alternatives at that time --
if it didn't Art Collins would have never used the connector (BNC was
available at the time).

Look at it as a simple tube... look at the outside diameter of the shield
and the inside diameter of the center conductor and plug and chug using
the formulae in the ITT Radio Engineer's Handbook for coaxial conductors.
You get something around 95 ohms characteristic for the front part of the
connector (from the insulator forward). The back part of the connector
is less important but ou have an additional discontinuity from the ring
around the insulator.

Say, didn't the Heathkit "lunchbox" AM transceivers use RCA phono
connectors as an antenna conection? Those lunchboxes operated into low
impedance 50 ohm loads all the way up to 148 mcs.

Yup! And the truth is, you can away with pretty lousy connectors in
most antenna applications. But put a pulse generator and a scope in
place of the transmitter and you'll see discontinuities at the connector
points.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

COLIN LAMB wrote:
It should be stated that the PL-259, a favorite of the ham world, is not a
constant impedance, either. Some hams go nuts if they see you use one of
those on 2 meters or higher. However, it is simple enough to calculate the
impedance bump at a particular frequency simply by determining the impedance
(using the ratio of diameters and the length of the connection), then
determining what that bump is at a particular frequency.

PL-259 _is_ constant impedance, it's just not exactly 50 ohms. But it's
closer to 50 ohms than the RCA is.

I did that once, to show a friend that he should not lose sleep over the
connector. It is like inserting a 1" length of 75 ohm coax in a 50 ohm
line. Remember that 50 ohm coax is not necessarily 50 ohms. It is a
nominal impedance, which means it might be 50 ohms, or 52 ohms or even 53
ohms. So, if you are worried about the connector, you should measure the
coax to see what impedance you really want.

Not to mention measuring the antenna! But with coax, the number in the
manufacturer's catalogue is probably correct (but in a lot of cases it
is NOT the same as the number in the Radio Guide!)
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

"Scott Dorsey" wrote in message
...
BAP wrote:

Where is the empirical or engineering data to support this conclusion?

Collins did do the frequency sweeps -- and it out performed many of the
alternatives at that time --
if it didn't Art Collins would have never used the connector (BNC was
available at the time).

Look at it as a simple tube... look at the outside diameter of the shield
and the inside diameter of the center conductor and plug and chug using
the formulae in the ITT Radio Engineer's Handbook for coaxial conductors.
You get something around 95 ohms characteristic for the front part of the
connector (from the insulator forward). The back part of the connector
is less important but ou have an additional discontinuity from the ring
around the insulator.

Say, didn't the Heathkit "lunchbox" AM transceivers use RCA phono
connectors as an antenna conection? Those lunchboxes operated into low
impedance 50 ohm loads all the way up to 148 mcs.

Yup! And the truth is, you can away with pretty lousy connectors in
most antenna applications. But put a pulse generator and a scope in
place of the transmitter and you'll see discontinuities at the connector
points.
--scott

This is undubtedly true- also for type UHF or type F. But why is a contant
impedance connector important for an antenna input at HF? Or anywhere in an
HF receiver? Even in a critical mixer application optimized for 50 Ohms, the
small discontinuity at HF from an RCA plug is of no real world concern.

Dale W4OP

"Dale Parfitt" wrote in message
news:fNF8h.4412$9e.3072@trnddc02...

This is undubtedly true- also for type UHF or type F. But why is a contant
impedance connector important for an antenna input at HF? Or anywhere in
an HF receiver? Even in a critical mixer application optimized for 50
Ohms, the small discontinuity at HF from an RCA plug is of no real world
concern.

Dale W4OP
.... go up in frequency to land-mobile VHF and UHF and look at what GE and
Motorola used for the optional pre-amps -- RCA (phono) jacks and plugs.
This gets covered about every 18 months or so on the Collins list as
newcomers -- make these pronouncements.

I like the audio hobby with $ 40 Cardias caps for RCA jacks.
http://www.cardas.com/content.php?ar...&product_id=29

Now there is a method to make money totally through marketing.
http://www.cardas.com/content.php?ar...l e+Materials

w9gb

And those people actually believe this bovine effluence?

w9gb wrote:


I like the audio hobby with $ 40 Cardias caps for RCA jacks.
http://www.cardas.com/content.php?ar...&product_id=29

Now there is a method to make money totally through marketing.
http://www.cardas.com/content.php?ar...l e+Materials

w9gb

On Wed, 22 Nov 2006 07:27:09 -0500, K3HVG wrote in :
And those people actually believe this bovine effluence?

w9gb wrote:


I like the audio hobby with $ 40 Cardias caps for RCA jacks.
http://www.cardas.com/content.php?ar...&product_id=29

Now there is a method to make money totally through marketing.
http://www.cardas.com/content.php?ar...l e+Materials

Oh, _yeah_!

I'm mildly tempted to sell a 3-wire power-grade equivalent of open-wire
line, with ceramic insulators, for the betterment of my pocketbook at
the expense of the audioph00ls. Make it out of #6 AWG solid copper, with
an insulator every 6 inches or so, and market it as having carefully-
controlled impedance at power-line frequencies. Yeah, that'd work -- and
buzzwordifying the ad copy would only improve the sales.

BA relevance: #6 AWG solid copper makes _sturdy_ Moxon rectangles at
2m and 6m, though it's a bit big. At 140 cm and 70 cm,
#8 or #10 are a bit easier to work with.

--
Segovia on his hatred of routine playing:
I have to be present at every note I play.