BNC on RG-8/U size cable

Nickdap · Post by **Nickdap** » Sun Mar 03, 2002 1:18 am

Hello all, does anyone know of a way to attach BNC connectors to RG 8 size 10.3 mm dia cables. With out contributing to cable losses on the VHF High band.
Thanks nick

techie · Post by **techie** » Sun Mar 03, 2002 1:57 am

Use the correct connector?

try amphenol 6775

http://www.amphenolrf.com/pdf/109.pdf
http://www.amphenolrf.com/search_part.asp

What are you using it on? If it's a portable, you really do want a short pigtail of something more flexible.. the stress of the RG8 tends to flex the connector too much, leading to broken joints if the connector is mounted directly to the pc board without a internal jumper.

Will · Post by **Will** » Sun Mar 03, 2002 1:59 am

There is several connector manufactures that make BNC connectors that fit RG8 and other .400 inch cables.
RF Industries # RFB 1101 1EN
Amphenol # 6775

Nickdap · Post by **Nickdap** » Sun Mar 03, 2002 2:10 am

thanks guys, yeah ive made the assumption that the CDM series has a bnc connection on the back so basicly its for use on the cdm for a base radio. Just wanted to do better then RG58U. what do you guys think?
nick

Will · Post by **Will** » Sun Mar 03, 2002 2:20 am

The CDM like most of the Motorola radios of late have a Mini UHF connector (female).
Times Microwave makes on that fits RG8 & LMR400 cables.

Nickdap · Post by **Nickdap** » Sun Mar 03, 2002 2:26 am

Thank Techie, and thanks will. Sounds good ok well i shall check it out. What do you recommened for such an installation. about 80 ft from desk to tower. VHF hi band, 25 watts about 20 Kms from repeater.
Thanks
nick

Monty · Post by **Monty** » Sun Mar 03, 2002 2:33 am

Hi:

Although one can purchase King Connectors
that will mate with RG-8 to BNC, be advised
a more simple solution would be to use a
Type C ( N ) or suitiable connector, and then
use RG-223 Jumper to to source.

The loss is very little @ VHF Freqs unless you are dealing in micro-watts.

RG-223 is very similar to RG-58, and is double shielded and easy to work with. A
large piece of transmission line terminating
into a BNC plug directly could place undue
stress on the Jack its plugged into.
============================================

Just saw your post....What I would do is simply use a run of 1/2" Celwave ( or 7/8 )
if you can afford it, and then use a small
jumper from the end of the 1/2" line to your
repeater.

A good piece of transmission line, and a good
antenna is a valuable asset to a repeater.

Monty

Monty

<font size=-1>[ This Message was edited by: [email protected] on 2002-03-03 05:38 ]</font>

Nickdap · Post by **Nickdap** » Sun Mar 03, 2002 2:53 am

Thanks Monty. I'll check out some prices and see how things go. Yes i was worried about the losses with jumpers and extra connectors, thanks for reassuring me.
Nick

perthcom · Post by **perthcom** » Sun Mar 03, 2002 7:01 pm

Unless i completely misread your application.. you are trying to access a repeater 20kms (12.5 miles) away.. and your antenna is 80 feet from the radio.. so i'm guessing the antenna is likely 40 feet above ground.

For this application I wouldn't be that worried about line losses, you have more than enough ERP left with even RG58.. let alone 1/2" heliax.

I'd go with something like LMR240 for a couple reasons:
- Ease of installation (small size 1/4" diameter)
- Mini UHF connector required for the CDM radio is available
- This cable is light and flexible so your CDM radio will sit nicely on your desk with having to wrestle with heavier cable

So lets calculate the ERP.
LMR240 3 db/100 feet = 2.4 db for 80Ft
25W = 14dbw
less 2.4
less 0.5 (connectors)
plus 0.0 (unity gain antenna)
-----
11.1 = 12.9 watts

Industry Canada here doesn't like to see more than 10watts ERP on a repeater access station, so I'll still have to turn back the Tx power a bit

Just my 2 cents
Bruce