Its virtually impossible to tin polyethylene coax braid without softening
the dielectric. It will re-solidify. PTFE (Teflon) is better in that
If you think the braid is steel, try it with a magnet.
From a quick look at Belden specs, they, at least, don't make any RG6
types with steel braid. There are some versions with aluminum braid.
If it's aluminum, you can't. Either get some cable with tinned or silver
plated copper braid, or put a BNC socket on the PCB, and a crimp BNC on
the cable. (I don't trust crimping to aluminum, BTW, there's a
metallurgical creep problem)
100% of the RF connectors I use for mountain top radio sites that I
deal with are crimped, not soldered. Well, maybe a few soldered
abominations such as PL-259 connectors.
The losses per connector are quite low. For example, here's a string
of random adapters:
That's about 15 assorted adapters (30 connections) showing 2dB loss at
2.4 GHz or:
2dB / 30 = 0.07 dB loss per connection.
Unless you're working with high power levels, the connector loss is
not a problem.
Unless you're working with microwave frequencies, mismatch loss is
also not much of a problem. For example, if you insert a section of
75 ohm coaxial cable into your system, a TDR would certainly show an
impedance bump far larger than what might be produced by a solder
blob. However, the losses are fairly trivial. Much depends on the
frequency of operation. If you're doing microwave, then precision is
required. If you're doing lower frequencies, you can be fairly sloppy
and things will still work quite well.
Cut-n-pasted from my previous rant on the topic from
Let's pretend that I mix in a 75 ohm coax connector into a
50 ohm system. Depending on the location of this "impedance bump",
the VSWR is no more than 1.5:1 which is generally considered marginal.
That's 0.18dB of mismatch loss.
If you're doing satellite or microwave DX work, then 0.18dB might be
important. However, for most other applications, it's a trivial
You might be amused to know that most of my rooftop antennas are fed
with 75 ohm coax and that my favored antenna designs are also 75 ohm.
There are various reasons, but the main one is that coax cable losses
are less at 75 ohms, than at 50 ohms. 50 ohms can handle more power,
but 75 ohms has less loss.
The only problems I have with 75 ohms is finding the proper connectors
and dealing with the pads needed to make my 50 ohm test equipment look
like 75 ohms. (Actually the real reason is that the 75 ohm stuff is
mostly CATV surplus, which tends to be really cheap).
This is where the original short length of RG6 was soldered to the pcb
antenna. It's an inexpensive broadcast TV antenna for home.
Rather than make a male crimp plus a barrel to join the 2 mailes, just solder
the long run directly to the pcb. Or so I thought...
I crimped 1/2" of center solid conductor to the braid and soldered the solid
to the pcb. It seems to work but I have no way to measure any loss. I plan to
replace this when I find some REAL copper RG6.
get some phosphoric acid and brush it on when the surfaces are as hot as you can get them... the solder will flow and wet like a dream. you would not believe it! (BTW it's the same acid that's in coca cola). hope this helps,
Thank you for disclosing what you're trying to accomplish. Context is
You're going to have corrosion problems. Note that all the
aforementioned crimped connectors have the crimped area sealed inside
the connector. In addition, they are usually wrapped in some form of
waterproofing (i.e. PTFE tape and electrical tape) to keep out the
water. Even if you solder the connections, the capillary action is
going to force the water up the braid and under the jacket. Depending
on the outer jacket slop, corrosion will rot up to several inches of
braid. You can try to seal the braid and solder connections with RTV
silicon rubber that doesn't contain acetic acid but I haven't had much
luck with that.
Using bare wires from the end of a coax cable is about as bad an
impedance bump as you can possibly create. However, it won't matter
for a TV antenna, that has wide bandwidth, but relatively little gain.
PCB TV antennas tend to be rather small, and therefore have even less
gain. Impedance discontinuities will not have a huge effect on
overall performance. Therefore, you can probably just attach some
spade lugs onto the ends of the RG-6/u coax, and use ordinary brass
screws and nuts to make the connection.
If you have a PCB, why not use a PCB mounted F connector?
I tried to find such a coax cable from my distant past. It had a
copper clad steel center conductor, aluminum foil shield, and a very
loose braid of flash galvanized steel wire braid over the shield. The
braid was only for strength and not for shielding. The zinc plating
was for galvanic compatibility with the aluminum shield. Such a cable
was not intended to be soldered, only crimped. I saw it at STV
(subscription TV) in Smog Angeles in the 1960's. However, I couldn't
find it which suggests that it's either uncommon, not in current
production, or my memory is faulty.
It would be helpful if you could provide any markings on your cable so
that it can be identified.
Continuing disclosure: it's indoors, wall-mounted.
It was my call (based on almost no RF expertise) that any solder connection
was much better than the best crimp and that crimps are used strictly for
convenience. I'm beginning to doubt these presumptions...
PS, a police helicopter just flew over the neighborhood at a few hundred
feet. The digital channel I was watching blanked out completely. This at
about 50 miles from the broadcast site, as the crow files (Sutro Tower).
Ok. You won't need to deal with anti-corrosion precautions.
I consider crimping better than soldering mostly because soldering
requires some skill, but crimping can be learned by almost anyone.
With ratcheting crimpers, it is possible to guarantee that the degree
of compression is both sufficient and uniform. Crimp and compression
connectors also will survive the SCTE IPS-TP-401 40 lb pull test,
while soldered connectors often fail this test. In general, crimp and
compression connectors are much better at keeping water out. I've
seen much better reliability after switching to crimp type connectors.
They're also cheaper. I can't think of a single advantage to soldered
Bingo. Aluminum braid over aluminum foil shield. You can't solder to
the aluminum. Find a different cable with a copper braid (or use a
connector as I previously suggested).
Can I guess(tm)? I don't think the helicopter is large enough to
complete block out the signal unless the TV station signal strength
from Mt Sutro to your PCB antenna is rather weak. That's about what I
would expect at 50 miles with a small PCB TV indoor antenna. Digital
is ummm... digital and tends to deliver either a very good picture, or
nothing. At 50 miles, I would have recommended a bigger, better and
possibly amplified (to compensate for the coax cable losses) antenna.
You might want to check your location with:
to see if the indoor PCB antenna is adequate, and if a bigger antenna
will be of any benefit. Otherwise, the police helicopter might have
been transmitting video on some frequency to the ground which
overloaded your TV receiver front end.
** Low flying aircraft tend to do that ...
Just like a nearby metal structure causing "ghost" images, they produce
strong reflections of the transmitted signal so your antenna gets two
similar strength signals, one of them delayed by a few microseconds.
This is often enough to seriously corrupt the wanted signal so large amounts
of data are lost.
End result, the pic freezes or pixellates crazily.
Bad luck if you live near a major airport and rely on an off air signal.
Of course I agree re. connectors. In my situation the original (short) coax
was soldered to the pcb. I thought that duplicating this connection when
replacing with a longer run of coax was better (re. loss) than introducing
connectors. Soldering F (or other) connectors vs. crimps, I agree: a
The loss is horrible in copper braided coax at TV frequencies. The
cost is excessive, as well. 'Headend cable' used to be silver plated
copper braided coax, but that was abandoned for foil & drain when
headends passed 216 MHz. That silver plated coax was over a dollar a
foot, in the '70s.
The easiest way to spot good headend cable was to try to bend it. It
drapes, like mic cable; not stiff.
My ham radio antennas are all 50 Ohm designs, but I do cheat on the
receive loops and repurpose old Echostar cable around the house.
Ok, I'll bite. What's wrong with F-connectors? There are zillions
installed on indoor and outdoor CATV installations with no failures or
issues. Certainly there are connectors with better specifications,
but for the intended purpose and cost ($0.30/ea), F-connectors are
more than adequate. The only real problem I've found is the wide
variety of cables claiming to be RG-6/u. Making a connector that will
fit all these RG-6/u mutations is tricky, but T&B has done a decent
job with their "red" SNS1P6U Snap-N-Seal connectors:
So, what's wrong with F-connectors and what would you recommend the
CATV industry use instead?