How much power can a BNC handle? rg58 coax, 1.3:1 swr,
say, 54mhz, indoor connection. I'm using a BNC jumper between
my amp and my antenna switch. I use BNC so I can d/c quickly
when a t-storm comes in the area.

--
73's de Ken KG0WX - Kadiddlehopper #11808,
Flying Pigs #-1055, Grid EM17io, FT-857D,
Elecraft XG2, 4SQRP Tenna Dipper, Heath GD-1B

wrote:
On Mon, 19 Jun 2006 12:11:07 -0500, "Ken Bessler"
wrote:


How much power can a BNC handle? rg58 coax, 1.3:1 swr,
say, 54mhz, indoor connection. I'm using a BNC jumper between
my amp and my antenna switch. I use BNC so I can d/c quickly
when a t-storm comes in the area.


Comfortable at 100W, I doubt more would be reasonable.

Allison


I don't know that answer either but I'm sure it is higher than that. I
have seen coaxial relays with SMA connectors that can handle 400 watts
at a higher frequency than 50 Mhz. Also get an N connector and a BNC
connector and do a close comparison of the pin and the shield inside the
connector. They look pretty close. In fact an N male will connect to a
BNC female, just no way to hold them together. The other way around
doesn't work because the BNC retention housing gets in the way.

--
Chris W
KE5GIX

Gift Giving Made Easy
Get the gifts you want &
give the gifts they want
One stop wish list for any gift,
from anywhere, for any occasion!
http://thewishzone.com

On Mon, 19 Jun 2006 19:58:13 GMT, wrote:

On Mon, 19 Jun 2006 13:17:42 -0500, Chris W wrote:

wrote:
On Mon, 19 Jun 2006 12:11:07 -0500, "Ken Bessler"
wrote:


How much power can a BNC handle? rg58 coax, 1.3:1 swr,
say, 54mhz, indoor connection. I'm using a BNC jumper between
my amp and my antenna switch. I use BNC so I can d/c quickly
when a t-storm comes in the area.


Comfortable at 100W, I doubt more would be reasonable.

Allison


I don't know that answer either but I'm sure it is higher than that. I
have seen coaxial relays with SMA connectors that can handle 400 watts
at a higher frequency than 50 Mhz. Also get an N connector and a BNC
connector and do a close comparison of the pin and the shield inside the
connector. They look pretty close. In fact an N male will connect to a
BNC female, just no way to hold them together. The other way around
doesn't work because the BNC retention housing gets in the way.

And how much power can RG58 take? You have to look at the connector
and cable as a whole not their parts.

Doesn't it fail either by flashover or exceeding its permitted
temperatures?

If so then you will need to know the frequency, SWR, loss, duty cycle
etc to work it out, won't you?

Owen
--

wrote:
On Mon, 19 Jun 2006 13:17:42 -0500, Chris W wrote:


wrote:

On Mon, 19 Jun 2006 12:11:07 -0500, "Ken Bessler"
wrote:



How much power can a BNC handle? rg58 coax, 1.3:1 swr,
say, 54mhz, indoor connection. I'm using a BNC jumper between
my amp and my antenna switch. I use BNC so I can d/c quickly
when a t-storm comes in the area.


Comfortable at 100W, I doubt more would be reasonable.

Allison


I don't know that answer either but I'm sure it is higher than that. I
have seen coaxial relays with SMA connectors that can handle 400 watts
at a higher frequency than 50 Mhz. Also get an N connector and a BNC
connector and do a close comparison of the pin and the shield inside the
connector. They look pretty close. In fact an N male will connect to a
BNC female, just no way to hold them together. The other way around
doesn't work because the BNC retention housing gets in the way.


And how much power can RG58 take?


Now that is something I can answer. Or at least I have found charts
that give me values for that. Assuming you can trust them, rg-58 can
handle 300 watts at 50 Mhz and 160 watts at 150 Mhz. Times microwave
equivalent LMR-190 says it can handle 680 watts at 50 Mhz and 390 at 150
Mhz. It also has the following foot not on those power ratings, "Power:
VSWR=1.0; Ambient = +40°C; Inner Conductor = 100°C (212°F);
Sea Level; dry air; atmospheric pressure; no solar loading"

I have yet to find anything that tells how much power a BNC connector
can take though. I found one that gave it a voltage rating of 500V and
a current rating of 3.5A DC. If you use Ohms law 500V at 50 ohms would
be 10 amps which gives 5,000 watts, I seriously doubt it can really
handle that. That calculation probably didn't help any. If you take
the 3.5A with 50 ohms you get 175 V and 612.5 watts. However that 3.5A
was DC and generally it is easier to carry the same number of amps with
AC, but not sure how that changes as the frequency goes way up.

In the end I still don't know how much power it can handle, but I still
think it is well over 100 watts. If I were using the LMR cable (which I
do) I would probably trust it up to 300 watts at 50 Mhz. With the RG-58
unless my VSWR were perfect and or the ambient temperature were pretty
low, I would probably keep it down to 200 watts.


--
Chris W
KE5GIX

Gift Giving Made Easy
Get the gifts you want &
give the gifts they want
One stop wish list for any gift,
from anywhere, for any occasion!
http://thewishzone.com

I have yet to find anything that tells how much power a BNC connector can
take though. I found one that gave it a voltage rating of 500V and a
current rating of 3.5A DC. If you use Ohms law 500V at 50 ohms would be
10 amps which gives 5,000 watts, I seriously doubt it can really handle
that. That calculation probably didn't help any. If you take the 3.5A
with 50 ohms you get 175 V and 612.5 watts. However that 3.5A was DC and
generally it is easier to carry the same number of amps with AC, but not
sure how that changes as the frequency goes way up.

I have certainly used TNC's at 1300MHz at over 1kW pulsed, in military
applications, so breakdown is not the problem!!

73
Jeff

I guess this is a case where one doesn't ask....he just does it!
I have a 20 Meter Hi-Q Halo-type loop (6' dia) hanging from a tree
limb about 40' high. I needed lighter weight so I used RG-58 about
75' long....well-matched at the antenna for very little SWR.
I have been using this with 1 Kw SSB peak for about 10 years with
no problems...this includes reasonably long tune-up with full carrier.

On Thu, 22 Jun 2006 16:16:57 +0000 (UTC), (Gene
Gardner) wrote:



I guess this is a case where one doesn't ask....he just does it!
I have a 20 Meter Hi-Q Halo-type loop (6' dia) hanging from a tree
limb about 40' high. I needed lighter weight so I used RG-58 about
75' long....well-matched at the antenna for very little SWR.
I have been using this with 1 Kw SSB peak for about 10 years with
no problems...this includes reasonably long tune-up with full carrier.

So you are dissipating about 4W per foot of cable with key down 1kW
CW. Average power of voice with compression is about 13dB lower, or
about 200mW per foot.

Explains why it has worked ok, doesn't it!

If you dig into the numbers, about 25%+ of your transmit power is lost
in the line losses, which is a compromise you acceptaed for the
lighter weight line you needed.

Owen
--

Ken Bessler wrote:
How much power can a BNC handle? rg58 coax, 1.3:1 swr,
say, 54mhz, indoor connection. I'm using a BNC jumper between
my amp and my antenna switch. I use BNC so I can d/c quickly
when a t-storm comes in the area.


Ken,

The connector itself is dimensioned almost the same as a type N
connector.

The limiting factor assuming a good quality properly installed BNC
connector is the cable, not the connector.

If you use a good high temperature cable in a dry room-temperature
environment 500 watts extended time with carrier is a reasonable amount
of power. That power increases quite a bit for shorter duty cycles.

We used BNC's on a 3500 watt 30 uS RF pulse generator at 40.68MHz, and
I've used them with CW and SSB with good Teflon cables at 1500 watts on
30 MHz as quick disconnects.

If you carefully exam the BNC you will see it is nearly identical to a
type N in air gap to ground and pin diameter and penetration depth. The
real problem is the cable, not the connector.

73 Tom