Unsolderable wire?

On 1/19/2014 2:30 AM, Michael A. Terrell wrote:
>
> "Bob E." wrote:
>>
>>>> When it comes to broadcast TV I try to solder every connection possible.
>>>> Every crimp is one more dB lost.
>>
>> I'm no RF expert, just my impression--possibly mistaken.
>
>
>     The loss should be under .1 dB for a good F connector,
                                            ^^^^^^^^^^^^^^^^
Jumbo shrimp alert. ;)

Cheers

Phil Hobbs


-- 
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

On Sat, 18 Jan 2014 20:50:34 -0800, Bob E. <bespoke@invalid.tv> wrote:

>When it comes to broadcast TV I try to solder every connection possible. 
>Every crimp is one more dB lost.

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:
<http://www.learnbydestroying.com/jeffl/antennas/connector-loss/slides/Adapter%20Colluge.html>
<http://www.learnbydestroying.com/jeffl/antennas/connector-loss/>
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
rec.radio.amateur.antenna.

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.
<http://www.microwaves101.com/encyclopedia/calvswr.cfm>
If you're doing satellite or microwave DX work, then 0.18dB might be
important.  However, for most other applications, it's a trivial
amount.

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.
<http://www.belden.com/blog/broadcastav/50-Ohms-The-Forgotten-Impedance.cfm>
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).

More:
<http://www.qsl.net/n9zia/wireless/75_ohm_hardline.html>

-- 
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

> 100% of the RF connectors I use for mountain top radio sites that I
> deal with are crimped, not soldered.  

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.

Thanks.

"Maynard A. Philbrook Jerkoff."

> Electroplated wire, most likely nickel.



** But nickel plated stuff solders beautifully.

  Jack plugs and sockets, DC plugs etc.


....  Phil 

On Sun, 19 Jan 2014 16:01:53 -0800, Bob E. <bespoke@invalid.tv> wrote:

>> 100% of the RF connectors I use for mountain top radio sites that I
>> deal with are crimped, not soldered.  

>This is where the original short length of RG6 was soldered to the pcb 
>antenna. It's an inexpensive broadcast TV antenna for home. 

Thank you for disclosing what you're trying to accomplish.  Context is
always important.

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.

>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.

If you have a PCB, why not use a PCB mounted F connector?
<http://www.ebay.com/itm/111244951312>
<http://www.ebay.com/itm/261373960762>

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.

-- 
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

> Thank you for disclosing what you're trying to accomplish.  Context is
> always important.
> 
> You're going to have corrosion problems.

Continuing disclosure: it's indoors, wall-mounted. 

> If you have a PCB, why not use a PCB mounted F connector?
> <http://www.ebay.com/itm/111244951312>
> <http://www.ebay.com/itm/261373960762>

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...

> It would be helpful if you could provide any markings on your cable so
> that it can be identified.

<http://www.cables.com/Products/92003.aspx> 

Thanks.

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). 

On Sun, 19 Jan 2014 20:35:10 -0800, Bob E. <bespoke@invalid.tv> wrote:

>> Thank you for disclosing what you're trying to accomplish.  Context is
>> always important.
>> 
>> You're going to have corrosion problems.
>
>Continuing disclosure: it's indoors, wall-mounted. 

Ok.  You won't need to deal with anti-corrosion precautions.

>> If you have a PCB, why not use a PCB mounted F connector?
>> <http://www.ebay.com/itm/111244951312>
>> <http://www.ebay.com/itm/261373960762>
>
>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...

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
RF connectors.

>> It would be helpful if you could provide any markings on your cable so
>> that it can be identified.
>
><http://www.cables.com/Products/92003.aspx> 

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).

>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). 

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:
<http://www.tvfool.com>
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.  





-- 
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

"Bob E."
>
> 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).


** 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.


...  Phil

> 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
> RF connectors.

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 
nightmare. 

Thanks.

> Bad luck if you live near a major airport and rely on an off air signal.
> ...  Phil

Just the PD "serving and protecting".

Thanks.