[TowerTalk] (Long)MFJ259B & PL-259/SO-239 Pair Losses
Jim Reid
jreid@aloha.net
Sun, 28 Jun 1998 15:45:02 -0900
Hi all,
It has been suggested here on TT, that a loss budget of about
0.1 dB per PL-239 in your antenna/transmission line system
was a good idea.
Well, that got me to thinking: I have a BUNCH of PL-239/SO-239
pairs in my complete set up between my various antennas and
the ultimate input SO-239 on the back of my transceiver! In
fact, this morning I counted them, starting out back at one
of my Gladiator vertical antennas (set up is the same on all
7 of them, and ditto for the triband beam).
SO-239 on Gladiator "output/input" unun box,
PL-239 on choke ferrite bead balun screws onto Gladiator SO-239,
PL-239 on output end of choke balun, screwed into PL-258 barrel,
PL-239 on end of LMR400 cable screws onto PL-238 barrel,
PL-239 on end of 6 foot LMR400 screws onto SO-239 on Top-Ten switch,
PL-239 on end of 220 feet of LMR400 screws onto SO-239 on Top-Ten
switch, then LMR runs into shack via window,
PL-239 on end of 220 feet of LMR400 screws onto SO-239 on AlphaDelta 2 way
switch,
PL-259 screws onto output SO-239 of AD switch and runs through 6 feet or so
of RG8 to,
PL-259 which screws onto SO-239 on hoffi 5-way switch (selects among other
unbalanced antennas besides Gladiators way out back),
PL-259 screws onto hoffi output SO-239 and RG8 runs about 4 feet to,
PL-259 which screws onto input SO-239 on the antenna terminal of
XMatch Classic Low Bander tuner,
PL-259 screws onto SO-239 output connector of XMatch tuner, RG8 runs only
about 4 feet to,
PL-259 which screws onto input SO-239 of an AlphaDelta 4-way switch
which determines if the antenna selected by the hoffi feeds
the rig set up, the MFJ259 analyzer (to tune the tuner),
or to another standby rcvr,
PL-259 screws onto output SO-239 connector of AD 4-way switch and RG8
runs only about 3 feet to,
PL-259 which screws onto an SO-239 connector on another AlphaDelta
2-way switch which selects either the antenna tuned by the
XMatch,
or other balanced antennas being tuned by the EFJohnson kW
Matchbox tuner to be routed to the rig chain,
PL-259 screws onto SO-239 on output of AD 2-way switch, and about
6 feet of RG8 runs to a PL-259 which screws onto output
terminal of a Low Pass Filter of rig chain,
PL-259 screws onto SO-239 at other end of LPF, and about 4 feet of
RG8 runs to,
PL-259 which screws onto SO-239 on Directional Coupler for the P-3000
Power/VSWR meter,
PL-259 screws onto SO239 on other side of the P-3000 Directional Coupler,
and RG8 runs about 3 feet to
PL-259 which screws onto the output/antenna connector
SO-239 on the back of the Alpha 87A linear,
PL-259 screws onto SO-239 at input/transceiver terminal of 87A,
and about 8 feet of RG8 runs to,
PL-259 which screws onto SO-239 connector on input side of an
AlphaDelta 2-way switch which determines which
of two transceivers will be used,
PL-259 screws onto SO-239 on output of AD 2-way switch, and about
8 feet of RG8 runs to,
PL-239 connector which screws onto the SO-239 connector on
the back of one of the transceivers.
That totals 23 PL-259/SO239 or PL-259/barrel connector pairs!!
If each was to be responsible for even 0.1 dB loss, would total
at least 2.3 dB loss in the connectors alone?! Maybe the losses
I measured the other day were real, oh, oh.
So, I today measure the loss through the entire chain of connectors
and coax switches, LPF, tuner(direct or by-pass switch setting), 87A,
etc., the entire chain of stuff between the input SO-239 of the
first AlphaDelta switch at the shack end of the 220 foot LMR run,
to the end of the RG8 and PL-259 on the back of one of the
two transceivers. I measured the following losses for this chain of
17 PL-s29/SO-239 pairs, switches, RG8, etc.
7.00 mHz......0.6 dB
10.00 mHz...0.6 dB
14010...........0.9 dB
18119..........0.9 dB
21020..........1.0 dB
24930..........1.2 dB
28500..........1.3 dB
Well, certainly not as bad as 0.1 dB per pair, but not great either!
Then I measured the whole thing -- all the way out to the TT switch,
but not through it to the balun of Gladiator unun input; still raining
outside today -- we are now up to 8.7 inches of rain for just June alone,
mostly slow steady dripping, with occasional downpours!! Will complete
the entire chain when the rain stops. Anyway, through the LMR to the
TT switch, these losses were measured, which, of course, include the
220 feet of LMR-400 loss at these frequencies:
7000.....1.3 dB,
10105...1.3 dB,
14020...1.7 dB, and at 14315 loss hit 2.0 dB,
18110...2.9 dB,
21020...2.2 dB (seems odd would be lower than at 18110),
24900...3.6 dB
and didn't go higher, was getting discouraged at this point, hi.
I am now seriously considering replacing the 220 feet of LMR400
with a similar length of 450 ohm twin lead, and use the EFJohnson
kW Matchbox to feed the Gladiators rather than the unbalanced
system. Only vertical I would have to have a balun in the shack
for would be the TL160 which the Matchbox cannot tune. I
would use an Amidon W2FMI-4:1-HBHT high power balun at the
far end of the 450 ohm ladder line to transform down into
the Top-Ten switch. And here in the shack, use the same Amidon
type to bring the ladder line down to 50 ohms to use the XMatch
on the 160 band in the Fall/Winters.
Such a scheme would eliminate the coax line loss; but will have to
simplify my super switching/selecting scheme here in the shack
if I want to further reduce losses.
Anyway, thought you might find all of this interesting.
73, Jim, KH7M
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