[TowerTalk] In Search of 2db

[Fred Hopengarten]

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

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