• Effective immediately we will be deleting, without notice, any negative threads or posts that deal with the use of encryption and streaming of scanner audio.

    We've noticed a huge increase in rants and negative posts that revolve around agencies going to encryption due to the broadcasting of scanner audio on the internet. It's now worn out and continues to be the same recycled rants. These rants hijack the threads and derail the conversation. They no longer have a place anywhere on this forum other than in the designated threads in the Rants forum in the Tavern.

    If you violate these guidelines your post will be deleted without notice and an infraction will be issued. We are not against discussion of this issue. You just need to do it in the right place. For example:
    https://forums.radioreference.com/rants/224104-official-thread-live-audio-feeds-scanners-wait-encryption.html

Coxial question

Status
Not open for further replies.

Rt169Radio

Member
Premium Subscriber
Joined
Aug 24, 2011
Messages
2,786
Location
CT
Hey everyone,I wanted to know if I would have great transmiting loss on a 70 foot long coax run? What would be a good coax for that long of a run? Would a 5 watts output be lost quickly on that long of a run?
 

n5ims

Member
Joined
Jul 25, 2004
Messages
3,676
For most types of coax (the cheap brands excluded), a 70 foot run will work fine on HF, even with less than 5 watts. RG-58 would be fine, RG-8X (aka mini-8) would be better, and the larger RG-8 even better (especially as you increase your power). I'd stay away from low quality cable, but mostly for the uneven shielding and other qualities that make it low quality. I would also avoid RG-174, because it's simply too small to work with easily and connectors are hard to find for it.

As you increase in frequency, the type (and quality) of coax gets quite important. What works fine on the lower frequencies may work really poorly as the frequency increases. For VHF-Hi (2 meters for hams) I'd avoid using RG-58 or RG-8X for runs of any real length (they're OK for short patch cables or mobile use however). The various RG-8 flavors will work fine however (remember that RG-8X isn't the same thing as RG-8, although the name looks similar, the performance isn't anywhere near the same!). These include RG-213, RG-214, Belden 9913, LMR-400, etc.

For UHF (the 440 or 70 cm band) RG-8 would be the minimum level to start with with the lower loss versions generally worth the extra cost. You may even want to consider the commercial grade heliax like Andrew LDF4-50A or something larger than RG-8 like LMR-600. Please note that the heliax can be expensive, but you can often find folks selling short runs (end-of-reel type things) for about what a dealer will charge for LMR-400 and get much lower loss and better life out of the coax.

Use a coax loss calculator (Welcome to Times Microwave | Coaxial Cable - Attenuation & Power Handling Calculator) and your dealer's on-line price chart as a guide to find what works best for you price vs performance wise. And above all, stick with quality coax!
 

LtDoc

Member
Joined
Dec 4, 2006
Messages
2,145
Location
Oklahoma
'IMS' pretty well covered it. The two biggies are the length of the run and the amount of loss per 100 feet at the -frequency of use-.
- 'Doc
 
Status
Not open for further replies.
Top