In article ,
says...


On Sat, 6 Nov 2004 11:30:55 -0600, "Ken Bessler"
wrote:

I'm aware that the PL-259 has loss but what I'd
like to find out is how much loss at 146 & 450 mHz?

Anyone know?

Looking at my Wirebook IV, pages 3.2 and 3.3

Alan Bloom, n1al, used an HP8753 RF network analyzer to compare losses
of UHF vs. N connectors.

Both connectors measured 0 db loss up to 100 mhz.

At 150 mhz, the N has 0 db loss, the UHF has .01 db loss.

At 450 mhz, the N has 0 db loss, the UHF has .09 db loss.

That's it...

Bob
k5qwg

For those who want to see Al's original USENET post from 1992:

From: (Alan Bloom)
Date: Fri, 18 Sep 1992 23:03:13 GMT
Subject: The Truth about UHF Connectors
Message-ID:
Organization: Hewlett-Packard, Santa Rosa, CA
Path:
dxis!batman!cs.widener.edu!eff!sol.ctr.columbia.ed u!spool.mu.edu!sdd.hp.c
om!scd.hp.com!hplextra!hpl-opus!hpnmdla!alanb
Newsgroups: rec.radio.amateur.misc
Lines: 64

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 .02 .01
200 0 0 .03 .015
450 0 0 .18 .09
600 0 0 .26 .13
900 0 0 .66 .33
1000 .05 .025 .8 .4
1300 .1 .05 .86 .43
1600 .05 .025 .5 .25
2000 .05 .025 .02 .01

Insertion loss increases until about 1200 MHz, and then starts to
decrease until it is almost zero for the UHF connector at 2 GHz!
At this 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 is 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... :=)

--
+----------------------------------------------+
| Bob Schreibmaier K3PH | E-mail: |
| Kresgeville, PA 18333 | http://www.dxis.org |
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