New KAT500 pics from the Visalia DX convention

[Edward R Cole]

I assume all you have read this thread so not going to repeat all
prior e-mail in my post.

First off only place you will find PL259/SO239 "UHF" connectors is on
ham, CB and some marine radio equipment made today.  Commercial
radios long have gone to other connectors with N-connectors being
favored for VHF+ site located systems.  Mobiles and HT's have a
variety of connectors from BNC, TNC, mini-UHF, RCA-phono (gawd
awful), sma and a whole host of tiny specialty connectors used on
wireless stuff, smart phones, etc.

In my professional life I moved most cabling to either N or BNC vs
UHF.  This was for reliability.  BNC were normally used on RG-58
cable jumpers and lower power stuff where measurements were frequent
requiring cable removal.

The use of pliers to tighten connectors had gotten too many folks in
trouble due to "super mechanic" mentality that if tight is good
tighter is better.  Sorry these are not water or gas lines.  If you
use a plier to tighten only rotate 1/8 turn beyond finger-tight.  I
can see wanting to do this on antenna connections or mobile
installations where vibration is possible.  Use of heat-shrink over
the connector will result in longer reliability (also because it is
now wx tight).

BTW I have measured improvement of half a dB at VHF+ by proper
tightening of N connectors.  At HF this is probably not even noticed
but on receivers at UHF it will make a difference.  Sma connectors
are particularly susceptible to inadequate tightening but again
should only be tightened with a sma wrench with 1/8 turn or by proper
torque wrench according to the mfr's specs.  Sma do not like repeated
removal and installation so be careful with that.  I find the threads
in N connectors wear if removed too much and work much better the
first or few times.

Impedance match on low noise preamps is critical so many hams are
moving to use of either N or sma connectors over BNC.  I have not
seen a UHF on a preamp since the 1960's.

Finally, my highest connector failure is with UHF on RG-58 size
cable.  I really dislike the critters for that.  Crimp-style
connectors also seem to have a higher failure if they are cables that
are repeatedly removed (esp BNC).

So that is my two-cents on the topic.



73, Ed - KL7UW, WD2XSH/45
======================================
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EME: 50-1.1kw?, 144-1.4kw, 432-QRT, 1296-?, 3400-?
DUBUS Magazine USA Rep [hidden email]
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======================================
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[Jim Brown-10]

On 4/25/2012 10:50 AM, Edward R. Cole wrote:
> Impedance match on low noise preamps is critical

NO preamp is going to notice the difference between 1.000 and 1.05.  
More to the point, I suggest that you MEASURE the input Z of these
preamps and find out how close they actually are to their nominal
value.  I suspect you will find variations on the order of 25% or more.

>   so many hams are
> moving to use of either N or sma connectors over BNC.  I have not
> seen a UHF on a preamp since the 1960's.

Ed,

Everything you have cited regarding N-connectors is simply a matter of
folks having "drunk the Kool-Aid." Just because "everyone believes it"
doesn't make it true, and "everyone does it" can be a matter of "monkey
see, monkey do."  .

Two major reasons for using SMAs and BNCs is that they have a smaller
footprint on a panel, which is a big deal with today's more compact
equipment.

Your comments re: the importance of keeping connectors tight is right on
target.

Recently I've been hearing that the DIN connectors for hard line are
greatly superior, and if I were living in the UHF world and had
professional dollars to spend  I'd probably use them.

73, Jim K9YC
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[Alan Bloom]

(Changing to a more descriptive Subject line)

1.  One nice thing about female BNC connectors is that they are
compatible with male type-N connectors.  Try it - they plug right in.
Of course, there is no locking mechanism, so it wouldn't be good for
something like a mobile installation, but otherwise it works fine and
saves an adapter.

2.  One advantage that BNC and N have over UHF is that the ground
connection doesn't depend on the shell being properly tightened.

3.  I've had excellent reliability from UHF plugs as long as I pre-tin
the coax braid and solder it through the holes.  That's true both with
RG-8 type cable as well as the smaller RF-58 with the adapter.

4.  Regarding RF loss in UHF connectors, it isn't as bad as many people
think.  I did an Internet search and found the Usenet posting I made on
the subject about 20 (!) years ago:

From: ... (Alan Bloom)
Date: Fri, 18 Sep 1992 23:03:13 GMT
Subject: The Truth about UHF Connectors
Organization: Hewlett-Packard, Santa Rosa, CA
Newsgroups: rec.radio.amateur.misc

Ya gotta feel sorry for UHF connectors. Recent strings on this notes
group lambasted them as worthless at VHF and above, and barely tolerable
at HF. One poster called them "5 dB attenuators", and many agreed that
there must be some sort of conspiracy among ham equipment manufacturers
to inflict such garbage connectors on the amateur community.

Today I finally remembered to bring some UHF adapters from home so I
could do some relative measurements of UHF versus type-N.  As expected,
the type-N showed lower insertion loss at high frequencies, but the UHF
connectors were hardly "5 dB attenuators."

For the test I connected an HP8753 RF network analyzer through two short
BNC cables into the following arrangement:
   _______    ____________    ___________    ____________    _______
  |       |  | BNC female |  | N female- |  | N male to  |  |       |
__| 10 dB |__| to N male  |__| N female  |__| BNC female |__| 10 dB |__
  | Atten.|  | adapter    |  | adapter   |  | adapter    |  | Atten.|
  |_______|  |____________|  |___________|  |____________|  |_______|

Then I repeated the measurement with the N adapters replaced with UHF.
I normalized the measurements by replacing the 3 adapters with a BNC
double-female. (That is, this was assumed to have 0 dB loss.)

Since two N or UHF adapters were used, I assume the loss per connector
is half the total. The vertical scale was .1 dB/division, so I estimated
the insertion loss to the nearest .01 dB or so:

            --------- Type N --------   ---------- UHF ----------
FREQ (MHz)  TOTAL  LOSS PER CONNECTOR   TOTAL  LOSS PER CONNECTOR
1.8         0 dB   0 dB                 0 dB   0 dB
30          0      0                    0      0
100         0      0                    0      0
150         0      0                    0.02   0.01
200         0      0                    0.03   0.015
450         0      0                    0.18   0.09
600         0      0                    0.26   0.13
900         0      0                    0.66   0.33
1000        0.05   0.025                0.8    0.4
1300        0.1    0.05                 0.86   0.43
1600        0.05   0.025                0.5    0.25
2000        0.05   0.025                0.02   0.01

Insertion loss increases until about 1300 MHz, and then starts to
decrease until it is almost zero for the UHF connector at 2 GHz!  At
that frequency, the connectors are about 1/4 wave long (1 inch,
assuming .66 velocity factor), so I assume that the two adapters are
providing a conjugate match to each other. This confirms my assumption
that the insertion loss is due to reflections (impedance mismatch), not
absorption (true power loss).

Bottom line: UHF connectors work fine through the VHF range, and are not
too bad even on the 420 MHz band if you can stand about .1 dB mismatch
loss per connector.

By the way, I did not do the full 2-port calibration on the HP8753, so
there was a couple hundredth's dB ripple in the plots. I averaged this
out by eye to come up with the numbers in the above chart.

AL N1AL

P.S. Sorry, I guess I violated the Usenet rule against posting objective
data... :=)


On Wed, 2012-04-25 at 09:50 -0800, Edward R. Cole wrote:

> I assume all you have read this thread so not going to repeat all
> prior e-mail in my post.
>
> First off only place you will find PL259/SO239 "UHF" connectors is on
> ham, CB and some marine radio equipment made today.  Commercial
> radios long have gone to other connectors with N-connectors being
> favored for VHF+ site located systems.  Mobiles and HT's have a
> variety of connectors from BNC, TNC, mini-UHF, RCA-phono (gawd
> awful), sma and a whole host of tiny specialty connectors used on
> wireless stuff, smart phones, etc.
>
> In my professional life I moved most cabling to either N or BNC vs
> UHF.  This was for reliability.  BNC were normally used on RG-58
> cable jumpers and lower power stuff where measurements were frequent
> requiring cable removal.
>
> The use of pliers to tighten connectors had gotten too many folks in
> trouble due to "super mechanic" mentality that if tight is good
> tighter is better.  Sorry these are not water or gas lines.  If you
> use a plier to tighten only rotate 1/8 turn beyond finger-tight.  I
> can see wanting to do this on antenna connections or mobile
> installations where vibration is possible.  Use of heat-shrink over
> the connector will result in longer reliability (also because it is
> now wx tight).
>
> BTW I have measured improvement of half a dB at VHF+ by proper
> tightening of N connectors.  At HF this is probably not even noticed
> but on receivers at UHF it will make a difference.  Sma connectors
> are particularly susceptible to inadequate tightening but again
> should only be tightened with a sma wrench with 1/8 turn or by proper
> torque wrench according to the mfr's specs.  Sma do not like repeated
> removal and installation so be careful with that.  I find the threads
> in N connectors wear if removed too much and work much better the
> first or few times.
>
> Impedance match on low noise preamps is critical so many hams are
> moving to use of either N or sma connectors over BNC.  I have not
> seen a UHF on a preamp since the 1960's.
>
> Finally, my highest connector failure is with UHF on RG-58 size
> cable.  I really dislike the critters for that.  Crimp-style
> connectors also seem to have a higher failure if they are cables that
> are repeatedly removed (esp BNC).
>
> So that is my two-cents on the topic.
>
>
>
> 73, Ed - KL7UW, WD2XSH/45
> ======================================
> BP40IQ   500 KHz - 10-GHz   www.kl7uw.com
> EME: 50-1.1kw?, 144-1.4kw, 432-QRT, 1296-?, 3400-?
> DUBUS Magazine USA Rep [hidden email]
> "Kits made by KL7UW" http://www.kl7uw.com/kits.htm
> ======================================

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[Don Wilhelm-4]

Al,

Great information!  Yes, I can agree that properly tightened UHF
connectors do not inflict much loss.  I think the main problem has been
with inadequate tightening - as you pointed out the shield connection
requires that that UHF connectors be tight.  How many hams wiggle the
PL-259 connector a bit to be certain it is seated in the notch of the
SO-239 - this is not a casual connector for making quick connections and
disconnections.

Where am I going with this - well, with the KPA100, we have long
recommended "disconnect the antenna when not in use" to protect the
wattmeter diodes from static damage.  While this is a good concept, the
literal interpretation of that statement may actually inflict damage
because of the way the UHF connector "connects".  With a PL-259, the
center conductor is what makes contact first - if there is a static
charge on that feedline, that charge will be transferred to your
equipment without a chance to bleed it off - the only way to prevent
that is to either short across the feedline (if there is a ground
connection for the shield) or some other means should be used to bleed
off the charge before attaching a feedline with a PL-259 connector to
any equipment.  Type N and BNC do not have this problem - the shell
makes contact first.


On 4/25/2012 7:09 PM, Alan Bloom wrote:
> (Changing to a more descriptive Subject line)
>
>
> 4.  Regarding RF loss in UHF connectors, it isn't as bad as many people
> think.  I did an Internet search and found the Usenet posting I made on
> the subject about 20 (!) years ago:
>
>
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[Tony Estep]

On Wed, Apr 25, 2012 at 6:09 PM, Alan Bloom <[hidden email]> wrote:

> ...Sorry, I guess I violated the Usenet rule against posting
> objective data...
> ============

Ah, Alan, you are a repeat offender. However, do not feel bad. Contrary to
what you may have heard, recently certain philosophers have concluded that
objective data is not always bad. They argue that it is in fact one of the
four basic categories of acceptable standards of proof:

1. proof by handwaving/buzzword invocation/TABLE-POUNDING
2. proof by appeal to authority/expertise/experience/common sense/universal
knowledge
3. proof by mathematical or other rigorous analysis
4. proof by experimental data

All the above have their adherents and detractors, all are in wide use, and
all have their moments in the sun on the internet.

73,
Tony KT0NY
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[k6dgw]

Tony, you forgot one, there's

5.  Proof by Powerpoint.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2012 Cal QSO Party 6-7 Oct 2012
- www.cqp.org

On 4/25/2012 4:55 PM, Tony Estep wrote:

> Ah, Alan, you are a repeat offender. However, do not feel bad. Contrary to
> what you may have heard, recently certain philosophers have concluded that
> objective data is not always bad. They argue that it is in fact one of the
> four basic categories of acceptable standards of proof:
>
> 1. proof by handwaving/buzzword invocation/TABLE-POUNDING
> 2. proof by appeal to authority/expertise/experience/common sense/universal
> knowledge
> 3. proof by mathematical or other rigorous analysis
> 4. proof by experimental data

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[ke9uw]

"...just because there's no data, it doesn't mean you're wrong" Einstein (probably)

Sent from my iPad

On Apr 25, 2012, at 8:47 PM, "Fred Jensen" <[hidden email]> wrote:

> Tony, you forgot one, there's
>
> 5.  Proof by Powerpoint.
>
> 73,
>
> Fred K6DGW
> - Northern California Contest Club
> - CU in the 2012 Cal QSO Party 6-7 Oct 2012
> - www.cqp.org
>
> On 4/25/2012 4:55 PM, Tony Estep wrote:
>
>> Ah, Alan, you are a repeat offender. However, do not feel bad. Contrary to
>> what you may have heard, recently certain philosophers have concluded that
>> objective data is not always bad. They argue that it is in fact one of the
>> four basic categories of acceptable standards of proof:
>>
>> 1. proof by handwaving/buzzword invocation/TABLE-POUNDING
>> 2. proof by appeal to authority/expertise/experience/common sense/universal
>> knowledge
>> 3. proof by mathematical or other rigorous analysis
>> 4. proof by experimental data
>
> ______________________________________________________________
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[John Huggins, kx4o]

This compares well enough with my measurements...

http://www.hamradio.me/graphs/connectors/UHFConnectorGraphs/Mismatch-Loss_1000.png 

http://www.hamradio.me/graphs/connectors/UHFConnectorGraphs/Insertion-Loss_S21_1000.png 


Some of the longer UHF "barrels" show the repeating characteristic you
observed which I assume is when the "different" transmission line is
about 1/2 wavelength long.

John, kx4o

On 4/25/12 7:09 PM, Alan Bloom wrote:
Since two N or UHF adapters were used, I assume the loss per connector
is half the total. The vertical scale was .1 dB/division, so I estimated
the insertion loss to the nearest .01 dB or so:

              --------- Type N --------   ---------- UHF ----------
FREQ (MHz)  TOTAL  LOSS PER CONNECTOR   TOTAL  LOSS PER CONNECTOR
1.8         0 dB   0 dB                 0 dB   0 dB
30          0      0                    0      0
100         0      0                    0      0
150         0      0                    0.02   0.01
200         0      0                    0.03   0.015
450         0      0                    0.18   0.09
600         0      0                    0.26   0.13
900         0      0                    0.66   0.33
1000        0.05   0.025                0.8    0.4
1300        0.1    0.05                 0.86   0.43
1600        0.05   0.025                0.5    0.25
2000        0.05   0.025                0.02   0.01

Insertion loss increases until about 1300 MHz, and then starts to
decrease until it is almost zero for the UHF connector at 2 GHz!  At
that frequency, the connectors are about 1/4 wave long (1 inch,
assuming .66 velocity factor), so I assume that the two adapters are
providing a conjugate match to each other. This confirms my assumption
that the insertion loss is due to reflections (impedance mismatch), not
absorption (true power loss).
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[Jim Brown-10]

On 4/25/2012 4:09 PM, Alan Bloom wrote:
> P.S. Sorry, I guess I violated the Usenet rule against posting objective data...

It should be noted that in an earlier post, I noted that I had measured
the loss of 1300 ft of coax with characteristics like LMR400 that had
been cut into 100 ft and 200 ft lengths for a DX trip. I noted that
there were at least 25 PL259s and 13 Amphenol barrels in line, and that
the loss at every frequency up to 500 MHz was less than the mfr's spec
for the cable at that frequency.  While I did not go to the extent of
finding and measuring 1,300 ft of the same coax and subtracting out the
loss, I submit that my measurements show that the loss in those 38
connectors is negligible to at least 500 MHz.

And I also submit that not every small deviation from the ideal MATTERS
in every real world conditions. Good engineering is making good choices
for a given situation. The world does not need the $800 hammers demanded
by certain military specs.

Shouting down?  Hardly -- when completely illogical arguments were
presented as justification for a position I pointed them out.

Also -- I don't trust the precision of loss measurements for very small
losses -- there are two many factors that can pollute the measurement,
and often the accuracy of the instrumentation is a significant.fraction
of the result being measured. For example, try getting a good number for
the loss of 100 ft of LMR400 at 1.8 MHz. You'd better be measuring at
least 1,000 ft to get even 10% accuracy!  Several years ago, a VE1 (RGB,
I think) sent me data for measurements he had made of a sizable number
of UHF connectors in a string.  His numbers for loss in a single
connector were significantly less than what Alan has posted.

73, Jim K9YC
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[Jim Wiley-2]

It's nice to have some fresh air amongst the smoke.  Thanks Jim.  


I have been using UHF connectors for decades without a single problem,
with the caveat that I purchase ONLY brand name (e.g.: Amphenol)
connectors, take care to install them properly, and use them only once
(reuse of connectors removed from other cables is not permitted in my
station) .


And yes, I do use "type N" fittings and other less common types (type C,
7/8 flange, etc.) for some work where appropriate.


- Jim, KL7CC



Jim Brown wrote:

> On 4/25/2012 4:09 PM, Alan Bloom wrote:
>  
>> P.S. Sorry, I guess I violated the Usenet rule against posting objective data...
>>    
>
> It should be noted that in an earlier post, I noted that I had measured
> the loss of 1300 ft of coax with characteristics like LMR400 that had
> been cut into 100 ft and 200 ft lengths for a DX trip. I noted that
> there were at least 25 PL259s and 13 Amphenol barrels in line, and that
> the loss at every frequency up to 500 MHz was less than the mfr's spec
> for the cable at that frequency.  While I did not go to the extent of
> finding and measuring 1,300 ft of the same coax and subtracting out the
> loss, I submit that my measurements show that the loss in those 38
> connectors is negligible to at least 500 MHz.
>
> And I also submit that not every small deviation from the ideal MATTERS
> in every real world conditions. Good engineering is making good choices
> for a given situation. The world does not need the $800 hammers demanded
> by certain military specs.
>
> Shouting down?  Hardly -- when completely illogical arguments were
> presented as justification for a position I pointed them out.
>
> Also -- I don't trust the precision of loss measurements for very small
> losses -- there are two many factors that can pollute the measurement,
> and often the accuracy of the instrumentation is a significant.fraction
> of the result being measured. For example, try getting a good number for
> the loss of 100 ft of LMR400 at 1.8 MHz. You'd better be measuring at
> least 1,000 ft to get even 10% accuracy!  Several years ago, a VE1 (RGB,
> I think) sent me data for measurements he had made of a sizable number
> of UHF connectors in a string.  His numbers for loss in a single
> connector were significantly less than what Alan has posted.
>
> 73, Jim K9YC
> ______________________________________________________________
> Elecraft mailing list
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>
>  

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[Hisashi T Fujinaka]

Just a quick question:

> On 4/25/12 7:09 PM, Alan Bloom wrote:
> Since two N or UHF adapters were used, I assume the loss per connector
> is half the total. The vertical scale was .1 dB/division, so I estimated
> the insertion loss to the nearest .01 dB or so:
>
>              --------- Type N --------   ---------- UHF ----------
> FREQ (MHz)  TOTAL  LOSS PER CONNECTOR   TOTAL  LOSS PER CONNECTOR
> 1.8         0 dB   0 dB                 0 dB   0 dB
> 30          0      0                    0      0

What are the measurements below this? I'm not sure I can work any
DX at those frequencies. I always tell my microwave experimenter buddies
that if I can walk there and talk to the guy, I'll do that and not worry
about my radio. :)

> 100         0      0                    0      0
> 150         0      0                    0.02   0.01
> 200         0      0                    0.03   0.015
> 450         0      0                    0.18   0.09
> 600         0      0                    0.26   0.13
> 900         0      0                    0.66   0.33
> 1000        0.05   0.025                0.8    0.4
> 1300        0.1    0.05                 0.86   0.43
> 1600        0.05   0.025                0.5    0.25
> 2000        0.05   0.025                0.02   0.01

Oh, and for technical content: even though you get an impedance
mismatch, at the frequencies I care about the mismatch is so short that
you don't make it far around the Smith chart (easier than doing the
calculations). It doesn't really matter that a UHF connector isn't
exactly 50 ohms when it's << a wavelength, 1/10 the wavelength.

So if a UHF connector is about an inch, 10 times that is about 10
inches, or about what I think is a nanosecond is (about a foot) which is
10^9Hz or about a gigahertz.

So back-of-the-envelope, UHF connectors impedance mismatch only matters
around a gigahertz. This would horrify my engineering profs because
MIT back-of-the-envelope calculations would require Maxwell's equations.

--
Hisashi T Fujinaka - [hidden email]
BSEE(6/86) + BSChem(3/95) + BAEnglish(8/95) + MSCS(8/03) + $2.50 = latte
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