[TowerTalk] In Search of 2db

Fri, 26 May 2000 13:14:13 -0400

Fred, That's a great post and a great question. I don't have the answer per
se, but KC1XX did help me with exactly this. You mention in your post how
good his construction is. I thought I made quality jumpers, but Matt laughed
and after telling me that's how little girls made them, he showed me the
right way. He enlarges the 3 solder drip holes in the pl259 with a tool we
could only find at Home Depot, a slightly better cup-shaped hole holds the
solder better and he was right. I do this all the time and for some reason
it just works faster and better when you're filling the holes with solder.
He also coats the coax braid with solder and a coat of flux, puts the pl-259
over it, and then heats the connector with a very large, very hot soldering
wand (got it at McKitrick in Lowell). You just heat it long enough to make
the flux do it's job so you don't melt the coax. The result is a killer
connection. You may do this already. Just those little changes, but what a
difference. Matt's point to me was that a mediocre patch cord won't kill
you, but it's the combination of all the lossy mediocre patch cords and
devices that cumulatively rob you of db.

-----Original Message-----
From: owner-towertalk@contesting.com
[mailto:owner-towertalk@contesting.com]On Behalf Of Fred Hopengarten
Sent: Friday, May 26, 2000 11:58 AM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] In Search of 2db

TowerTalkers:

        With all this talk about the value of 2 dB, I thought I'd contribute
an
anecdote and ask a real world question.

        Anecdote. A few years back we (AD1C, KM3T and I) entered the M/S
category of ARRL DX CW and came in #2 USA to W3BGN. We lost by EITHER 4
QSO's OR 1 multiplier, after 48 hours. He who says that a dB or two makes
only a tiny difference must deal with the fact that in that contest, for
us, a tiny difference would have made the difference between hardwood and
paper.  I'm telling you that I believe that, had we had another 2 dB,
we'd have won.

        Query. I have a two radio station with a lot of 50 ohm jumpers. It
works, honest. But some jumpers were assembled in the middle of the night
by tired operators. Some are 30 years old.  I doubt any of them was done
as well as W0UN or KC1XX would do it at his work bench. No jumper is
longer than 10 feet. See configuration below (which should look similar
to a lot of stations). What method do you recommend to test RG-213 or
RG-58 jumpers? Any chance I can pick up 1 dB by finding a "bad" jumper?

Jumpers

Radio to band pass filters (RG-58)
Band pass filters to input of Heath Monitorscope (speeds up tuning,
guarantees linearity, reduces complaints about splatter) (RG-58)
Heath Monitorscope to amplifier (RG-58)
Amplifier to low pass filter (RG-213)
Low pass filter to Drake wattmeter (if I look up and see no output, I
know the transceiver and amp are not on the same band) (RG-213)
Drake wattmeter to Six band Top Ten Devices automatic antenna selector
(RG-213)
Top Ten Devices antenna selector to A/B station ("run" and "mult") manual
switch (RG-213)
A/B switch to hardline (RG-213 for 50 ohm hardline or asymmetric coax
balun if the hardline is 75 ohm)

Total:
        RG-58 jumpers           3
        RG-213 jumpers          5

[Actually, that's the "run" station. The "mult" station has one more
RG-58 jumper (because the relays and band pass filters are not an
integral unit) and one more RG-213 jumper (because that station can
switch between two amplifiers to reduce tuning up). "Mult" station
totals: RG-58 jumpers 4, RG-213 jumpers 6.]

The questions again:
1. How test for loss?
2. Likelihood of finding 2 dB, or some dB at all, at frequencies below
28.8 MHz?

Fred Hopengarten K1VR
hopengarten@post.harvard.edu
Six Willarch Road * Lincoln, MA 01773-5105
781/259-0088 *eFax 419/858-2421

.
.
.
.
.
.
.

.
.
..
.

________________________________________________________________
YOU'RE PAYING TOO MUCH FOR THE INTERNET!
Juno now offers FREE Internet Access!
Try it today - there's no risk!  For your FREE software, visit:
http://dl.www.juno.com/get/tagj.

--
FAQ on WWW:               http://www.contesting.com/towertalkfaq.html
Submissions:              towertalk@contesting.com
Administrative requests:  towertalk-REQUEST@contesting.com
Problems:                 owner-towertalk@contesting.com
Search:                   http://www.contesting.com/km9p/search.htm

--
FAQ on WWW:               http://www.contesting.com/towertalkfaq.html
Submissions:              towertalk@contesting.com
Administrative requests:  towertalk-REQUEST@contesting.com
Problems:                 owner-towertalk@contesting.com
Search:                   http://www.contesting.com/km9p/search.htm