Coaxial cable stuff

[robbage]

Here's some general information about coaxial cable if you're wondering what to run up your roof.

The table shows approximate loss for a 30 metre length of cable

Code: Select all

Cable            148-174 MHz      450-520 MHz
------           -----------      -----------
RG58C            7.1 dB           13.5 dB
RG213            2.6 dB           5.0 dB
Heliax 1/4"      1.2 dB           2.5 dB

For every 3dB of loss, half your transmitted power is lost. eg a 30 metre run of RG213 on 2 metres will lose you just under half your power before the other end.
Obviously any significant run of RG58C is gong to have a big impact. Around 13 metres will lose half your power. Add loss due to poor quality or poorly fitted connectors and you are going to have problems.
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[VK6ZMS]

That's a good point you raised Rob, coax choice and antenna gain are very important in the VHF and above frequency ranges.

This page will let you see how many watts you get at the end of your coax.
http://www.ocarc.ca/coax.htm

[robbage]

Thanks for that, Martin. Very handy.

[VK6LD]

Here's some general information about coaxial cable if you're wondering what to run up your roof.

The table shows approximate loss for a 30 metre length of cable

Code: Select all

Cable            148-174 MHz      450-520 MHz
------           -----------      -----------
RG58C            7.1 dB           13.5 dB
RG213            2.6 dB           5.0 dB
Heliax 1/4"      1.2 dB           2.5 dB

For every 3dB of loss, half your transmitted power is lost. eg a 30 metre run of RG213 on 2 metres will lose you just under half your power before the other end.
Obviously any significant run of RG58C is gong to have a big impact. Around 13 metres will lose half your power. Add loss due to poor quality or poorly fitted connectors and you are going to have problems.
This message brought to you by the letters ∀ and Σ and the number ∞

Another good affordable choice is something like CNT400 or LMR400.

30M of cable at 146MHz, gives a 1.473db loss. (25w in, approx 17.8 watts at the other end).

The same cable at 435MHz gives a 2.6db loss.

Connectors for CNT400 are also much cheaper than Heliax connectors.

[vk6hgr]

It's not all about loss though. Rope substitute (aka RG58) is the only practical cable for vehicle work

[robbage]

It's not all about loss though. Rope substitute (aka RG58) is the only practical cable for vehicle work

Heh, yeah. The heliax is a bugger to work into the cable channels

[robbage]

http://harg.org.au/images/coaxpower.pdf

A table of various coaxial cables and their maximum power ratings (at various frequencies)
I wonder if anybody has a similar table for various coaxial connectors?

[Nosferatu]

Hello all,

I'm researching about Coaxial cables ... I just had a look at this wikipedia page and there is a big list of all sorts of coax

http://en.wikipedia.org/wiki/Coaxial_cable

My question is : Can I use any coax ( say for transmitting or receiving in 2m Amateur Band ) as long as they are 50 Ω impedance ? For example ... Can I use RG-60/U for 2m band ?



Thank you

[vk6hgr]

My question is : Can I use any coax ( say for transmitting or receiving in 2m Amateur Band ) as long as they are 50 Ω impedance ? For example ... Can I use RG-60/U for 2m band ?

Yep, it will work fine.

The hard part about using the more exotic coax cables though is finding matching connectors.

[Nosferatu]

The hard part about using the more exotic coax cables though is finding matching connectors.

Aha ... ! Of course ... the connectors have to be as big as the cables themselves ... !
Imagine using an LMR-1700 Coax ... to a handheld transceiver using an SMA connector ...

[VK6ZMS]

Also some of the low loss cable can be thick and hard to bend around tight corners.
LMR 400 is a balance between thickness and loss for medium runs on VHF and UHF.

Cheers

[robbage]

http://www.qsl.net/dk3xt/cable.htm

A nice cheat sheet for various coax types. Shows loss for different VHF/UHF ham bands, coax diameter and velocity factor as well as a table for 1/4 wave and 1/2 electrical lengths (eg for stub filters, baluns etc)

Also.. does anybody know where I can buy Belden H155 in Perth?

[VK6ZMS]

Not sure but WARG will have RG213 co-ax and antennas on sale this Saturday the 11th at the Hills Amateur Radio Group Swap Meet.
5 Sanderson rd Lesmurdie, doors open to buyers at 1pm entry fee $5. The BBQ snaggers and burgers on sale from midday.